The DENX U-Boot and Linux Guide (DULG) for canyonlands - Lysator

The DENX U-Boot and Linux Guide (DULG) for 

canyonlands 

Table of contents: 

• 1. Abstract 

• 2. Introduction 

♦ 2.1. Copyright 

♦ 2.2. Disclaimer 

♦ 2.3. Availability 

♦ 2.4. Credits 

♦ 2.5. Translations 

♦ 2.6. Feedback 

♦ 2.7. Conventions 

• 3. Embedded Linux Development Kit 

♦ 3.1. ELDK Availability 

♦ 3.2. ELDK Getting Help 

♦ 3.3. Supported Host Systems 

♦ 3.4. Supported Target Architectures 

♦ 3.5. Installation 

◊ 3.5.1. Product Packaging 

◊ 3.5.2. Downloading the ELDK 

◊ 3.5.3. Initial Installation 

◊ 3.5.4. Installation and Removal of Individual Packages 

◊ 3.5.5. Removal of the Entire Installation 

♦ 3.6. Working with ELDK 

◊ 3.6.1. Switching Between Multiple Installations 

♦ 3.7. Mounting Target Components via NFS 

♦ 3.8. Rebuilding ELDK Components 

◊ 3.8.1. ELDK Source Distribution 

◊ 3.8.2. Rebuilding Target Packages 

◊ 3.8.3. Rebuilding ELDT Packages 

♦ 3.9. ELDK Packages 

◊ 3.9.1. List of ELDT Packages 

◊ 3.9.2. List of Target Packages 

♦ 3.10. Rebuilding the ELDK from Scratch 

◊ 3.10.1. ELDK Build Process Overview 

◊ 3.10.2. Setting Up ELDK Build Environment 

◊ 3.10.3. build.sh Usage 

◊ 3.10.4. Format of the cpkgs.lst and tpkgs.lst Files 

♦ 3.11. Notes for Solaris 2.x Host Environment 

• 4. System Setup 

♦ 4.1. Serial Console Access 

♦ 4.2. Configuring the "cu" command 

♦ 4.3. Configuring the "kermit" command 

♦ 4.4. Using the "minicom" program 

♦ 4.5. Permission Denied Problems 

♦ 4.6. Configuration of a TFTP Server 

♦ 4.7. Configuration of a BOOTP / DHCP Server 

♦ 4.8. Configuring a NFS Server 

• 5. Das U-Boot 

♦ 5.1. Current Versions 

♦ 5.2. Unpacking the Source Code 

The DENX U-Boot and Linux Guide (DULG) for canyonlands 1

♦ 5.3. Configuration 


◊ 5.4.1. Before You Begin 

⋅ 5.4.1.1. Installation Requirements 

⋅ 5.4.1.2. Board Identification Data 

◊ 5.4.2. Installation Using a BDM/JTAG Debugger 

◊ 5.4.3. Installation using U-Boot 

♦ 5.5. Tool Installation 

♦ 5.6. Initialization 

♦ 5.7. Initial Steps 

♦ 5.8. The First Power-On 

♦ 5.9. U-Boot Command Line Interface 

◊ 5.9.1. Information Commands 

⋅ 5.9.1.1. bdinfo - print Board Info structure 

⋅ 5.9.1.2. coninfo - print console devices and informations 

⋅ 5.9.1.3. flinfo - print FLASH memory information 

⋅ 5.9.1.4. iminfo - print header information for application image 

⋅ 5.9.1.5. help - print online help 

◊ 5.9.2. Memory Commands 

⋅ 5.9.2.1. base - print or set address offset 

⋅ 5.9.2.2. crc32 - checksum calculation 

⋅ 5.9.2.3. cmp - memory compare 

⋅ 5.9.2.4. cp - memory copy 

⋅ 5.9.2.5. md - memory display 

⋅ 5.9.2.6. mm - memory modify (auto-incrementing) 

⋅ 5.9.2.7. mtest - simple RAM test 

⋅ 5.9.2.8. mw - memory write (fill) 

⋅ 5.9.2.9. nm - memory modify (constant address) 

⋅ 5.9.2.10. loop - infinite loop on address range 

◊ 5.9.3. Flash Memory Commands 



⋅ 5.9.3.3. erase - erase FLASH memory 

⋅ 5.9.3.4. protect - enable or disable FLASH write protection 

⋅ 5.9.3.5. mtdparts - define a Linux compatible MTD partition scheme 

◊ 5.9.4. Execution Control Commands 

⋅ 5.9.4.1. autoscr - run script from memory 

⋅ 5.9.4.2. bootm - boot application image from memory 

⋅ 5.9.4.3. go - start application at address 'addr' 

◊ 5.9.5. Download Commands 

⋅ 5.9.5.1. bootp - boot image via network using BOOTP/TFTP protocol 

⋅ 5.9.5.2. dhcp - invoke DHCP client to obtain IP/boot params 

⋅ 5.9.5.3. loadb - load binary file over serial line (kermit mode) 

⋅ 5.9.5.4. loads - load S-Record file over serial line 

⋅ 5.9.5.5. rarpboot- boot image via network using RARP/TFTP protocol 

⋅ 5.9.5.6. tftpboot- boot image via network using TFTP protocol 

◊ 5.9.6. Environment Variables Commands 

⋅ 5.9.6.1. printenv- print environment variables 

⋅ 5.9.6.2. saveenv - save environment variables to persistent storage 

⋅ 5.9.6.3. setenv - set environment variables 

⋅ 5.9.6.4. run - run commands in an environment variable 

⋅ 5.9.6.5. bootd - boot default, i.e., run 'bootcmd' 

◊ 5.9.7. Flattened Device Tree support 

⋅ 5.9.7.1. fdt addr - select FDT to work on 


⋅ 5.9.7.2. fdt list - print one level 

⋅ 5.9.7.3. fdt print - recursive print 

⋅ 5.9.7.4. fdt mknode - create new nodes 

⋅ 5.9.7.5. fdt set - set node properties 

⋅ 5.9.7.6. fdt rm - remove nodes or properties 

⋅ 5.9.7.7. fdt move - move FDT blob to new address 

⋅ 5.9.7.8. fdt chosen - fixup dynamic info 

◊ 5.9.8. Special Commands 

⋅ 5.9.8.1. i2c - I2C sub-system 

◊ 5.9.9. Storage devices 

◊ 5.9.10. Miscellaneous Commands 

⋅ 5.9.10.1. echo - echo args to console 

⋅ 5.9.10.2. reset - Perform RESET of the CPU 

⋅ 5.9.10.3. sleep - delay execution for some time 

⋅ 5.9.10.4. version - print monitor version 

⋅ 5.9.10.5. - alias for 'help' 

♦ 5.10. U-Boot Environment Variables 

♦ 5.11. U-Boot Scripting Capabilities 

♦ 5.12. U-Boot Standalone Applications 

◊ 5.12.1. "Hello World" Demo 

◊ 5.12.2. Timer Demo 

♦ 5.13. U-Boot Image Formats 

♦ 5.14. U-Boot Advanced Features 

◊ 5.14.1. Boot Count Limit 

◊ 5.14.2. Bitmap Support 

◊ 5.14.3. Splash Screen Support 

• 6. Embedded Linux Configuration 

♦ 6.1. Download and Unpack the Linux Kernel Sources 

♦ 6.2. Kernel Configuration and Compilation 


• 7. Booting Embedded Linux 

♦ 7.1. Introduction 

♦ 7.2. Flattened Device Tree Blob 

♦ 7.3. Passing Kernel Arguments 

♦ 7.4. Boot Arguments Unleashed 

♦ 7.5. Networked Operation with Root Filesystem over NFS 

◊ 7.5.1. Bootlog of Linux kernel with Root Filesystem over NFS 

♦ 7.6. Boot from Flash Memory 

♦ 7.7. Standalone Operation with Ramdisk Image 

• 8. Building and Using Modules 

• 9. Advanced Topics 

♦ 9.1. Flash Filesystems 

◊ 9.1.1. Memory Technology Devices 

◊ 9.1.2. Journalling Flash File System 

◊ 9.1.3. Second Version of JFFS 

◊ 9.1.4. Compressed ROM Filesystem 

♦ 9.2. The TMPFS Virtual Memory Filesystem 

◊ 9.2.1. Mount Parameters 

◊ 9.2.2. Kernel Support for tmpfs 

◊ 9.2.3. Usage of tmpfs in Embedded Systems 

♦ 9.3. Adding Swap Space 

♦ 9.4. Splash Screen Support in Linux 

♦ 9.5. Root File System: Design and Building 

◊ 9.5.1. Root File System on a Ramdisk 


◊ 9.5.2. Root File System on a JFFS2 File System 

◊ 9.5.3. Root File System on a cramfs File System 

◊ 9.5.4. Root File System on a Read-Only ext2 File System 

◊ 9.5.5. Root File System on a Flash Card 

◊ 9.5.6. Root File System in a Read-Only File in a FAT File System 

♦ 9.6. Root File System Selection 

♦ 9.7. Overlay File Systems 

♦ 9.8. The Persistent RAM File system (PRAMFS) 


◊ 9.8.2. Example 

• 10. Debugging 

♦ 

♦ 

10.1. Debugging of U-Boot 

◊ 10.1.1. Debugging of U-Boot Before Relocation 

◊ 10.1.2. Debugging of U-Boot After Relocation 

10.2. Linux Kernel Debugging 

◊ 10.2.1. Linux Kernel and Statically Linked Device Drivers 

◊ 10.2.2. Dynamically Loaded Device Drivers (Modules) 

◊ 10.2.3. GDB Macros to Simplify Module Loading 

♦ 10.3. GDB Startup File and Utility Scripts 

♦ 10.4. Tips and Tricks 

♦ 10.5. Application Debugging 

◊ 10.5.1. Local Debugging 

◊ 10.5.2. Remote Debugging 

♦ 10.6. Debugging with Graphical User Interfaces 

• 11. Simple Embedded Linux Framework 

• 12. Books, Mailing Lists, Links, etc. 

♦ 12.1. Application Notes 

♦ 12.2. Further Reading 

◊ 12.2.1. Linux kernel 

◊ 12.2.2. General Linux / Unix programming 

◊ 12.2.3. Network Programming 

◊ 12.2.4. C++ programming 

◊ 12.2.5. Java programming 

◊ 12.2.6. PowerPC Programming 

◊ 12.2.7. Embedded Topics 

• 

♦ 12.3. Mailing Lists 

♦ 12.4. Links 

♦ 12.5. Tools 

13. Appendix 

♦ 13.1. Flat Device Tree 

♦ 13.2. BDI2000 Configuration file 

• 14. FAQ - Frequently Asked Questions 

♦ 

♦ 

14.1. ELDK 

◊ 14.1.1. ELDK Installation under FreeBSD 

◊ 14.1.2. ELDK Installation Hangs 

◊ 14.1.3. .gvfs: Permission Denied 

◊ 14.1.4. Installation on Local Harddisk 

◊ 14.1.5. ELDK Include Files Missing 

◊ 14.1.6. Using the ELDK on a 64 bit platform 

◊ 14.1.7. GDB Problems with BDI2000/BDI3000 on e500 Cores 

◊ 14.1.8. [[ELDK Installation Aborts][ELDK 2.x Installation Aborts]] 

14.2. U-Boot 

◊ 14.2.1. Can U-Boot be configured such that it can be started in RAM 

◊ 14.2.2. Relocation cannot be done when using -mrelocatable 


◊ 14.2.3. U-Boot crashes after relocation to RAM 

◊ 14.2.4. Warning - bad CRC, using default environment 

◊ 14.2.5. Wrong debug symbols after relocation 

◊ 14.2.6. Decoding U-Boot Crash Dumps 

◊ 14.2.7. Porting Problem: cannot move location counter backwards 

◊ 14.2.8. U-Boot Doesn't Run after Upgrading my Compiler 

◊ 14.2.9. How Can I Reduce The Image Size 

◊ 14.2.10. Erasing Flash Fails 

◊ 14.2.11. Ethernet Does Not Work 

◊ 14.2.12. Where Can I Get a Valid MAC Address from 

◊ 14.2.13. Why do I get TFTP timeouts 

◊ 14.2.14. Why is my Ethernet operation not reliable 

◊ 14.2.15. How the Command Line Parsing Works 

⋅ 14.2.15.1. Old, simple command line parser 

⋅ 14.2.15.2. Hush shell 

⋅ 14.2.15.3. Hush shell scripts 

⋅ 14.2.15.4. General rules 

◊ 14.2.16. How can I load and uncompress a compressed image 

◊ 14.2.17. My standalone program does not work 

◊ 14.2.18. Linux hangs after uncompressing the kernel 

♦ 14.3. Linux 

◊ 14.3.1. Linux crashes randomly 

◊ 14.3.2. Linux crashes when uncompressing the kernel 

◊ 14.3.3. Linux Post Mortem Analysis 

◊ 14.3.4. Linux kernel register usage 

◊ 14.3.5. Linux Kernel Ignores my bootargs 

◊ 14.3.6. Cannot configure Root Filesystem over NFS 

◊ 14.3.7. Linux Kernel Panics because "init" process dies 

◊ 14.3.8. Unable to open an initial console 

◊ 14.3.9. Mounting a Filesystem over NFS hangs forever 

◊ 14.3.10. Ethernet does not work in Linux 

◊ 14.3.11. Loopback interface does not work 

◊ 14.3.12. Linux kernel messages are not printed on the console 

◊ 14.3.13. Linux ignores input when using the framebuffer driver 

◊ 14.3.14. How to switch off the screen saver and the blinking cursor 

◊ 14.3.15. BogoMIPS Value too low 

◊ 14.3.16. Linux Kernel crashes when using a ramdisk image 

◊ 14.3.17. Ramdisk Greater than 4 MB Causes Problems 

◊ 14.3.18. Combining a Kernel and a Ramdisk into a Multi-File Image 

◊ 14.3.19. Adding Files to Ramdisk is Non Persistent 

◊ 14.3.20. Kernel Configuration for PCMCIA 

◊ 14.3.21. Configure Linux for PCMCIA Cards using the Card Services package 

◊ 14.3.22. Configure Linux for PCMCIA Cards without the Card Services package 

⋅ 14.3.22.1. Using a MacOS Partition Table 

⋅ 14.3.22.2. Using a MS-DOS Partition Table 

◊ 14.3.23. Boot-Time Configuration of MTD Partitions 

◊ 14.3.24. Use NTP to synchronize system time against RTC 

◊ 14.3.25. Configure Linux for XIP (Execution In Place) 

⋅ 14.3.25.1. XIP Kernel 

⋅ 14.3.25.2. Cramfs Filesystem 

⋅ 14.3.25.3. Hints and Notes 

⋅ 14.3.25.4. Space requirements and RAM saving, an example 

◊ 14.3.26. Use SCC UART with Hardware Handshake 

◊ 14.3.27. How can I access U-Boot environment variables in Linux 


◊ 14.3.28. The =appWeb= server hangs *OR* /dev/random hangs 

◊ 14.3.29. Swapping over NFS 

♦ 14.4. Self 

◊ 14.4.1. How to Add Files to a SELF Ramdisk 

◊ 14.4.2. How to Increase the Size of the Ramdisk 

♦ 14.5. RTAI 

◊ 14.5.1. Conflicts with asm clobber list 

♦ 14.6. BDI2000 

◊ 14.6.1. Where can I find BDI2000 Configuration Files 

◊ 14.6.2. How to Debug Linux Exceptions 

◊ 14.6.3. How to single step through "RFI" instruction 

◊ 14.6.4. Setting a breakpoint doesn't work 

♦ 14.7. Motorola LITE5200 Board 

◊ 14.7.1. LITE5200 Installation Howto 

◊ 14.7.2. USB does not work on Lite5200 board 

• 15. Glossary 

1. Abstract 

This is the DENX U-Boot and Linux Guide to Embedded PowerPC, ARM and MIPS Systems. 

The document describes how to configure, build and use the firmware Das U-Boot (typically abbreviated as 

just "U-Boot") and the operating system Linux for Embedded PowerPC, ARM and MIPS Systems. 

The focus of this version of the document is on canyonlands boards. 

This document was generated at 22 May 2009 - 10:15. 

• 2. Introduction 

♦ 2.1. Copyright 

♦ 2.2. Disclaimer 

♦ 2.3. Availability 

♦ 2.4. Credits 

♦ 2.5. Translations 

♦ 2.6. Feedback 

♦ 2.7. Conventions 

2. Introduction 

This document describes how to use the firmware U-Boot and the operating system Linux in Embedded 

PowerPC, ARM and MIPS Systems. 

There are many steps along the way, and it is nearly impossible to cover them all in depth, but we will try to 

provide all necessary information to get an embedded system running from scratch. This includes all the tools 

you will probably need to configure, build and run U-Boot and Linux. 

First, we describe how to install the Cross Development Tools Embedded Linux Development Kit which you 

probably need - at least when you use a standard x86 PC running Linux or a Sun Solaris 2.6 system as build 

environment. 

Then we describe what needs to be done to connect to the serial console port of your target: you will have to 

configure a terminal emulation program like cu or kermit. 

2. Introduction 6

In most cases you will want to load images into your target using ethernet; for this purpose you need TFTP 

and DHCP / BOOTP servers. A short description of their configuration is given. 

A description follows of what needs to be done to configure and build the U-Boot for a specific board, and 

how to install it and get it working on that board. 

The configuration, building and installing of Linux in an embedded configuration is the next step. We use 

SELF, our Simple Embedded Linux Framework, to demonstrate how to set up both a development system 

(with the root filesystem mounted over NFS) and an embedded target configuration (running from a ramdisk 

image based on busybox). 

This document does not describe what needs to be done to port U-Boot or Linux to a new hardware platform. 

Instead, it is silently assumed that your board is already supported by U-Boot and Linux. 

The focus of this document is on canyonlands boards. 

2.1. Copyright 

Copyright (C) 2001 - 2009 by Wolfgang Denk, DENX Software Engineering. 

Copyright (C) 2003 - 2009 by Detlev Zundel, DENX Software Engineering. 

Copyright (C) 2003 - 2009 by contributing authors 

You have the freedom to distribute copies of this document in any format or to create a derivative work of it 

and distribute it provided that you: 

• Distribute this document or the derivative work at no charge at all. It is not permitted to sell this 

document or the derivative work or to include it into any package or distribution that is not freely 

available to everybody. 

• Send your derivative work (in the most suitable format such as sgml) to the author. 

• License the derivative work with this same license or use GPL. Include a copyright notice and at least 

a pointer to the license used. 

• Give due credit to previous authors and major contributors. 

It is requested that corrections and/or comments be forwarded to the author. 

If you are considering to create a derived work other than a translation, it is requested that you discuss your 

plans with the author. 

2.2. Disclaimer 

Use the information in this document at your own risk. DENX disavows any potential liability for the contents 

of this document. Use of the concepts, examples, and/or other content of this document is entirely at your own 

risk. All copyrights are owned by their owners, unless specifically noted otherwise. Use of a term in this 

document should not be regarded as affecting the validity of any trademark or service mark. Naming of 

particular products or brands should not be seen as endorsements. 

2.3. Availability 

The latest version of this document is available in a number of formats: 

2.1. Copyright 7

• HTML http://www.denx.de/wiki/publish/DULG/DULG-canyonlands.html 

• plain ASCII text http://www.denx.de/wiki/publish/DULG/DULG-canyonlands.txt 

• PostScript European A4 format http://www.denx.de/wiki/publish/DULG/DULG-canyonlands.ps 

• PDF European A4 format http://www.denx.de/wiki/publish/DULG/DULG-canyonlands.pdf 

2.4. Credits 

A lot of the information contained in this document was collected from several mailing lists. Thanks to 

anybody who contributed in one form or another. 

2.5. Translations 

None yet. 

2.6. Feedback 

Any comments or suggestions can be mailed to the author: Wolfgang Denk at wd@denx.de. 

2.7. Conventions 

Descriptions 

Appearance 

Warnings 

Hint 

Notes 

Note. 

Information requiring special attention 

Warning 

File Names 

file.extension 

Directory Names 

directory 

Commands to be typed 

a command 

Applications Names 

another 

application 

Prompt of users command under bash shell 

bash$ 

Prompt of root users command under bash shell bash# 

Prompt of users command under tcsh shell 

tcsh$ 

Environment Variables 

VARIABLE 

Emphasized word 

word 

Code Example ls -l 

• 3. Embedded Linux Development Kit 

♦ 3.1. ELDK Availability 

♦ 3.2. ELDK Getting Help 

♦ 3.3. Supported Host Systems 

♦ 3.4. Supported Target Architectures 


◊ 3.5.1. Product Packaging 

◊ 3.5.2. Downloading the ELDK 

◊ 3.5.3. Initial Installation 

◊ 3.5.4. Installation and Removal of Individual Packages 

◊ 3.5.5. Removal of the Entire Installation 

♦ 3.6. Working with ELDK 

◊ 3.6.1. Switching Between Multiple Installations 

2.3. Availability 8

♦ 3.7. Mounting Target Components via NFS 

♦ 3.8. Rebuilding ELDK Components 

◊ 3.8.1. ELDK Source Distribution 

◊ 3.8.2. Rebuilding Target Packages 

◊ 3.8.3. Rebuilding ELDT Packages 

♦ 3.9. ELDK Packages 

◊ 3.9.1. List of ELDT Packages 

◊ 3.9.2. List of Target Packages 

♦ 3.10. Rebuilding the ELDK from Scratch 

◊ 3.10.1. ELDK Build Process Overview 

◊ 3.10.2. Setting Up ELDK Build Environment 

◊ 3.10.3. build.sh Usage 

◊ 3.10.4. Format of the cpkgs.lst and tpkgs.lst Files 

♦ 3.11. Notes for Solaris 2.x Host Environment 

3. Embedded Linux Development Kit 

The Embedded Linux Development Kit (ELDK) includes the GNU cross development tools, such as the 

compilers, binutils, gdb, etc., and a number of pre-built target tools and libraries necessary to provide some 

functionality on the target system. 

It is provided for free with full source code, including all patches, extensions, programs and scripts used to 

build the tools. 

Some versions of ELDK (4.1) are available in two versions, which use Glibc resp. uClibc as the main C 

library for the target packages. 

Packaging and installation is based on the RPM package manager. 

3.1. ELDK Availability 

The ELDK is available 

• on DVD-ROM from DENX Computer Systems 

• for download on the following server: 

FTP 

HTTP 

ftp://ftp.denx.de/pub/eldk/ http://www.denx.de/ftp/pub/eldk/ 

• for download on the following mirrors: 

FTP 

ftp://ftp-stud.hs-esslingen.de/pub/Mirrors/eldk/ 

ftp://mirror.switch.ch/mirror/eldk/ 

ftp://sunsite.utk.edu/pub/linux/eldk/ 

ftp://ftp.sunet.se/pub/Linux/distributions/eldk/ 

HTTP 

http://ftp-stud.hs-esslingen.de/pub/Mirrors/eldk/ 

http://mirror.switch.ch/ftp/mirror/eldk/ 

http://sunsite.utk.edu/ftp/pub/linux/eldk/ 

http://ftp.sunet.se/pub/Linux/distributions/eldk/ 

3.1. ELDK Availability 9

3.2. ELDK Getting Help 

Community support for the ELDK is available through the ELDK Mailing List. 

Previous postings to this mailing list are available from the ELDK archives. 

Commercial support is also available; please feel free to contact DENX Software Engineering GmbH. 

3.3. Supported Host Systems 

The ELDK can be installed onto and operate with the following operating systems: 

• Fedora Core 4, 5, 6 Fedora 7, 8, 9 

• Red Hat Linux 7.3, 8.0, 9 

• SuSE Linux 8.x, 9.0, 9.1, 9.2, 9.3 

• OpenSUSE 10.2, 10.3 (32 Bit); OpenSUSE 11.0 (32 and 64 Bit) 

• Debian 3.0 (Woody), 3.1 (Sarge) and 4.0 (Etch) 

• Ubuntu 4.10, 5.04, 6.10, 8.04 

• FreeBSD 5.0 

Users also reported successful installation and use of the ELDK on the following host systems: 

• Suse Linux 7.2, 7.3 

• Mandrake 8.2 

• Slackware 8.1beta2 

• Gentoo Linux 2006.1 

Note: It may be necessary, and is usually recommended, to install the latest available software updates on 

your host system. For example, on Fedora Core systems, you can use one of yum, apt-get or up2date to 

keep your systems current. 

3.4. Supported Target Architectures 

The ELDK includes target components and supports code generation for the following PowerPC types of 

processors: 

• ppc_4xx = AMCC 4xx processors without FPU 

• ppc_4xxFP = AMCC 4xx processors with FPU (440EP, 440EPx) 

• ppc_6xx = PowerPC processors based on 60x cores 

(This includes support for MPC5xxx, 7xx, 82xx and 83xx processors). 

• ppc_74xx = 74xx processors 

(This includes support for MPC86xx processors). 

• ppc_8xx = MPC8xx processors 

• ppc_85xx = MPC85xx processors 

There is also an ELDK for ARM and MIPS systems. 

3.5. Installation 

3.5. Installation 10

3.5.1. Product Packaging 

Stable versions of the ELDK are distributed in the form of an ISO image, which can be either burned onto a 

DVD or mounted directly, using the loopback Linux device driver (Linux host only). 

For the PowerPC target, the ELDK distribution was split into three independent ISO images: one targeting the 

4xx family of processors (AMCC), one targeting the ppc64 family of processors and another one for the 8xx, 

6xx, 74xx and 85xx families (Freescale). This makes the ISO images fit on standard DVDROM media. 

If you are not bound by the DVDROM size limitiation there is still a single image containing all 32-bit targets 

(AMCC and Freescale). 

Development versions of the ELDK are available as directory trees so it is easy to update individual packages; 

instructions for download of these trees and creation of ISO images from it is described in section 3.5.2. 

Downloading the ELDK. 

The ELDK contains an installation utility and a number of RPM packages, which are installed onto the hard 

disk of the cross development host by the installation procedure. The RPM packages can be logically divided 

into two parts: 

• Embedded Linux Development Tools (ELDT) 

• Target components 

The first part contains the cross development tools that are executed on the host system. Most notably, these 

are the GNU cross compiler, binutils, and gdb. For a full list of the provided ELDT packages, refer to section 

3.9.1. List of ELDT Packages below. 

The target components are pre-built tools and libraries which are executed on the target system. The ELDK 

includes necessary target components to provide a minimal working NFS-based environment for the target 

system. For a list of the target packages included in the ELDK, refer to section 3.9.2. List of Target Packages 

below. 

The ELDK contains several independent sets of the target packages, one for each supported target architecture 

CPU family. Each set has been built using compiler code generation and optimization options specific to the 

respective target CPU family. 

3.5.2. Downloading the ELDK 

You can either download the ready-to-burn ISO-images from one of the mirror sites (see 3.1. ELDK 

Availability), or you can download the individual files of the ELDK from the development directory tree and 

either use these directly for installation or create an ISO image that can be burned on DVD-ROM. 

Change to a directory with sufficient free disk space; for the PowerPC version of the ELDK you need about 

1.6 GiB, or twice as much (3.2 GiB) if you also want to create an ISO image in this directory. 

To download the ISO image from the ppc-linux-x86/iso directory of one of the mirror sites you can use 

standard tools like wget or ncftpget, for example: 

bash$ wget ftp://ftp.sunet.se/pub/Linux/distributions/eldk/4.2/ppc-linux-x86/iso/ppc-2007-01-19.i 

If you want to download the whole ELDK directory tree instead you can - for example - use the ncftp FTP 

client: 

3.5.2. Downloading the ELDK 11

ash$ ncftp ftp.sunet.se 

... 

ncftp / > cd /pub/Linux/distributions/eldk/4.2 

ncftp /pub/Linux/distributions/eldk/4.2 > bin 

ncftp /pub/Linux/distributions/eldk/4.2 > get -R ppc-linux-x86/distribution 

... 

ncftp /pub/Linux/distributions/eldk/4.2 > bye 

If you don't find the ncftp tool on your system you can download the NcFTP client from 

http://www.ncftp.com/download/ 

There are a few executable files (binaries and scripts) in the ELDK tree. Make sure they have the execute 

permissions set in your local copy: 

bash$ for file in \ 

> tools/bin/rpm \ 

> tools/usr/lib/rpm/rpmd \ 

> install \ 

> ELDK_MAKEDEV \ 

> ELDK_FIXOWNER 

> do 

> chmod +x ppc-linux-x86/distribution/$file 

> done 

Now create an ISO image from the directory tree: 

bash$ mkisofs \ 

> -A "ELDK-4.2 -- Target: PowerPC -- Host: x86 Linux" \ 

> -publisher "(C) `date "+%Y"` DENX Software Engineering, www.denx.de" \ 

> -p "ìd -nu`@`hostname` -- `date`" \ 

> -V ppc-linux-x86 \ 

> -l -J -R -o eldk-ppc-linux-x86.iso ppc-linux-x86/distribution 

This will create an ISO image eldk-ppc-linux-x86.iso in your local directory that can be burned on DVD or 

mounted using the loopback device and used for installation as described above. Of course you can use the 

local copy of the directory tree directly for the installation, too. 

Please refer to section 3.10.2. Setting Up ELDK Build Environment for instructions on obtaining the build 

environment needed to re-build the ELDK from scratch. 

3.5.3. Initial Installation 

The initial installation is performed using the install utility located in the root of the ELDK ISO image 

directory tree. The install utility has the following syntax: 

$ ./install [-d ] [] [] ... 

-d Specifies the root directory of the ELDK being installed. If omitted, the ELDK goes into 

the current directory. 

Specifies the target CPU family the user desires to install. If one or more 

parameters are specified, only the target components specific to the 

respective CPU families are installed onto the host. If omitted, the target components for 

all supported target architecture CPU families are installed. 

Note: Make sure that the "exec" option to the mount command is in effect when mounting the ELDK ISO 

image. Otherwise the install program cannot be executed. On some distributions, it may be necessary to 

modify the /etc/fstab file, adding the "exec" mount option to the cdrom entry - it may also be the case that 

other existing mount options, such as "user" prevent a particular configuration from mounting the ELDK 

DVD with appropriate "exec" permission. In such cases, consult your distribution documentation or mount the 

3.5.3. Initial Installation 12

DVD explicitly using a command such as "sudo mount -o exec /dev/cdrom /mnt/cdrom" (sudo allows regular 

users to run certain privileged commands but may not be configured - run the previous command as root 

without "sudo" in the case that "sudo" has not been setup for use on your particular GNU/Linux system). 

You can install the ELDK to any empty directory you wish, the only requirement being that you have to have 

write and execute permissions on the directory. The installation process does not require superuser privileges. 

Depending on the parameters the install utility is invoked with, it installs one or more sets of target 

components. The ELDT packages are installed in any case. 

Refer to section 3.6. Working with ELDK for a sample usage of the ELDK. 

Note: If you intend to use the installation as a root filesystem exported over NFS, then you now have to 

finish the configuration of the ELDK following the instructions in 3.7. Mounting Target Components via 

NFS. 

Note: Installation of the Glibc- and uClibc-based ELDK versions into one directory is not yet supported. 

Note: Installation of the 32-bit and 64-bit ELDK versions into one directory is not yet supported. 

3.5.4. Installation and Removal of Individual 

Packages 

The ELDK has an RPM-based structure. This means that on the ISO image, individual components of the 

ELDK are in the form of RPM packages, and after installation, the ELDK maintains its own database which 

contains information about installed packages. The RPM database is kept local to the specific ELDK 

installation, which allows you to have multiple independent ELDK installations on your host system. (That is, 

you can install several instances of ELDK under different directories and work with them independently). 

Also, this provides for easy installation and management of individual ELDK packages. 

To list the installed ELDK RPM packages, use the following command: 

bash$ ${CROSS_COMPILE}rpm -qa 

To remove an ELDK package, use the following command: 

bash$ ${CROSS_COMPILE}rpm -e 

To install a package, use the following command: 

bash$ ${CROSS_COMPILE}rpm -i 

To update a package, use the following command: 

bash$ ${CROSS_COMPILE}rpm -U 

For the above commands to work correctly, it is crucial that the correct rpm binary gets invoked. In case of 

multiple ELDK installations and RedHat-based host system, there may well be several rpm tools installed on 

the host system. 

You must make sure, either by using an explicit path or by having set an appropriate PATH environment 

variable, that when you invoke rpm to install/remove components of a ELDK installation, it is the ELDK's 

rpm utility that gets actually invoked. The rpm utility is located in the bin subdirectory relative to the ELDK 

root installation directory. 

3.5.4. Installation and Removal of Individual Packages 13

To avoid confusion with the host OS (RedHat) rpm utility, the ELDK creates symlinks to its rpm binary with 

the names such that it could be invoked using the ${CROSS_COMPILE}rpm notation, for all supported 

$CROSS_COMPILE values. 

The standard (host OS) rpm utility allows various macros and configuration parameters to specified in 

user-specific ~/.rpmrc and ~/.rpmmacros files. The ELDK rpm tool also has this capability, but the names of 

the user-specific configuration files are ~/.eldk_rpmrc and ~/.eldk_rpmmacros, respectively. 

3.5.5. Removal of the Entire Installation 

To remove the entire ELDK installation, use the following command while in the ELDK root directory: 

bash$ rm -rf 

where specifies the root directory of the ELDK to be removed. 

3.6. Working with ELDK 

After the initial installation is complete, all you have to do to start working with the ELDK is to set and export 

the CROSS_COMPILE environment variable. Optionally, you may wish to add the bin and usr/bin 

directories of your ELDK installation to the value of your PATH environment variable. For instance, a sample 

ELDK installation and usage scenario looks as follows: 

• Create a new directory where the ELDK is to be installed, say: 

bash$ mkdir /opt/eldk 

• Mount a CD or an ISO image with the distribution: 

bash$ mount /dev/cdrom /mnt/cdrom 

• Run the installation utility included on the distribution to install into that specified directory: 

bash$ /mnt/cdrom/install -d /opt/eldk 

• After the installation utility completes, export the CROSS_COMPILE variable: 

bash$ export CROSS_COMPILE=ppc_4xx- 

• The trailing '-' character in the CROSS_COMPILE variable value is optional and has no effect on 

the cross tools behavior. However, it is required when building Linux kernel and U-Boot images. 

• Add the directories /opt/eldk/usr/bin and /opt/eldk/bin to PATH: 

bash$ PATH=$PATH:/opt/eldk/usr/bin:/opt/eldk/bin 

• Compile a file: 

bash$ ${CROSS_COMPILE}gcc -o hello_world hello_world.c 

You can also call the cross tools using the generic prefix ppc-linux- for example: 

bash$ ppc-linux-gcc -o hello_world hello_world.c 

• or, equivalently: 

bash$ /opt/eldk/usr/ppc-linux/bin/gcc -o hello_world hello_world.c 

3.6. Working with ELDK 14

The value of the CROSS_COMPILE variable must correspond to the target CPU family you want the cross 

tools to work for. Refer to the table below for the supported CROSS_COMPILE variable values: 

3.6.A Table of possible values for $CROSS_COMPILE 

CROSS_COMPILE Value Predefined Compiler Flag 

FPU present 

or not 

ppc_4xx- -mcpu=403 No 

ppc_4xxFP- -mcpu=405fp Yes 

ppc_6xx- -mcpu=603 Yes 


ppc_8xx- -mcpu=860 No 


ppc64-linux- -mcpu=powerpc64 Yes 

For compatibility with older versions of the ELDK and with other toolkits the following values for 

$CROSS_COMPILE can be used, too: ppc_7xx- and ppc_82xx-. These are synonyms for ppc_6xx. 

3.6.1. Switching Between Multiple Installations 

No special actions are required from the user to switch between multiple ELDK installations on the same host 

system. Which ELDK installation is used is determined entirely by the filesystem location of the binary that is 

being invoked. This approach can be illustrated using the following example. 

Assume the directory /work/denx_tools/usr/bin, where the ppc-linux-gcc compiler binary has been 

installed, is a part of the PATH environment variable. The user types the command as follows: 

$ ppc_8xx-gcc -c myfile.c 

To load the correct include files, find the correct libraries, spec files, etc., the compiler needs to know the 

ELDK root directory. The compiler determines this information by analyzing the shell command it was 

invoked with ( ppc_8xx-gcc - without specifying the explicit path in this example) and, if needed, the 

value of the PATH environment variable. Thus, the compiler knows that it has been executed from the 

/work/denx_tools/usr/bin directory. 

Then, it knows that the compiler is installed in the usr/bin subdirectory of the root installation directory, so the 

ELDK, the compiler is a part of, has been installed in the subdirectories of the /work/denx_tools directory. 

This means that the target include files are in /work/denx_tools//usr/include, and so on. 

3.7. Mounting Target Components via NFS 

The target components of the ELDK can be mounted via NFS as the root file system for your target machine. 

For instance, for an 8xx-based target, and assuming the ELDK has been installed into the /opt/eldk directory, 

you can use the following directory as the NFS-based root file system: 

/opt/eldk/ppc_8xx 

Before the NFS-mounted root file system can work, you must create necessary device nodes in the 

//dev directory. This process requires superuser privileges and thus 

cannot be done by the installation procedure (which typically runs as non-root). To facilitate creation of the 

device nodes, the ELDK provides a script named ELDK_MAKEDEV, which is located in the root of the ELDK 

distribution ISO image. The script acccepts the following optional arguments: 

3.7. Mounting Target Components via NFS 15

-d Specifies the root directory of the ELDK being installed. If omitted, then the current 

directory is assumed. 

-a Specifies the target CPU family directory. If omitted, all installed target architecture 

directories will be populated with the device nodes. 

-h Prints usage. 

# /mnt/cdrom/ELDK_MAKEDEV -d /opt/eldk 

NOTE: Compared to older versions of the ELDK, options and behaviour of this command have been changed 

significantly. Please read the documentation. 

Some of the target utilities included in the ELDK, such as mount and su, have the SUID bit set. This 

means that when run, they will have privileges of the file owner of these utilities. That is, normally, they will 

have the privileges of the user who installed the ELDK on the host system. However, for these utilities to 

work properly, they must have superuser privileges. This means that if the ELDK was not installed by the 

superuser, the file owner of the target ELDK utilities that have the SUID bit set must be changed to root 

before a target component may be mounted as the root file system. The ELDK distribution image contains an 

ELDK_FIXOWNER script, which you can use to change file owners of all the appropriate files of the ELDK 

installation to root. The script accepts the same arguments as the ELDK_MAKEDEV script above. Please note 

that you must have superuser privileges to run this script. For instance, if you have installed the ELDK in the 

/opt/eldk directory, you can use the following commands: 

# cd /opt/eldk 

# /mnt/cdrom/ELDK_FIXOWNER 

Please note, that in the case that the installation directory, where the new ELDK distribution is being installed, 

is already populated with other ELDK distributions, the execution of the ELDK_FIXOWNER script without 

arguments will make the script work with all installed ELDK target architecture directories. This could take 

some time. To save the time, please use the -a argument to specify the appropriate target architecture. For 

instance: 

# cd /opt/eldk 

# /mnt/cdrom/ELDK_FIXOWNER -a ppc_8xx 

3.8. Rebuilding ELDK Components 

3.8.1. ELDK Source Distribution 

The ELDK is distributed with the full sources of all the components, so you may rebuild any ELDK package. 

The sources are provided in the form of SRPM packages, distributed as a separate ISO image. 

To rebuild a target or ELDT package, you must first install the appropriate source RPM package from the ISO 

image into the ELDK environment. This can be done using the following command: 

$ ${CROSS_COMPILE}rpm -i /mnt/cdrom/SRPMS/.src.rpm 

After an ELDK source RPM is installed using the above command, its spec file and sources can be found in 

the subdirectories of the /usr/src/denx subdirectory. 

The sections that follow provide detailed instructions on rebuilding ELDT and target components of the 

ELDK. 

3.8. Rebuilding ELDK Components 16

3.8.2. Rebuilding Target Packages 

All the target packages can be rebuilt from the provided source RPM packages. At first you have to install the 

Source RPM itself: 

bash$ ${CROSS_COMPILE}rpm -iv .src.rpm 

Then you can rebuild the binary target RPM using the following command from the ELDK environment: 

bash$ ${CROSS_COMPILE}rpmbuild -ba .spec 

In order for the rebuilding process to work correctly, the following conditions must be true: 

• The $CROSS_COMPILE environment variable must be set as appropriate for the target CPU family. 

• The /usr/ppc-linux/bin directory must be in PATH before the /usr/bin directory. This is 

to make sure that the command gcc results in the fact that the ELDK cross compiler is invoked, 

rather than the host gcc. 

3.8.3. Rebuilding ELDT Packages 

All the ELDT packages allow for rebuilding from the provided source RPM packages using the following 

command from the ELDK environment: 

$ unset CROSS_COMPILE 

$ /usr/bin/rpmbuild -ba 

In order for the rebuilding process to work correctly, make sure all of the following is true: 

• The $CROSS_COMPILE environment variable must NOT be set. 

• Do NOT use the $CROSS_COMPILE command prefix. 

• The /usr/ppc-linux/bin directory must NOT be in PATH. This is to make sure that the 

command gcc causes invokation of the host gcc, rather than the ELDK cross compiler. 

3.9. ELDK Packages 

3.9.1. List of ELDT Packages 

Package Name 

Package 

Version 

autoconf 2.61-8 

automake 1.10-5 

bison 2.3-3 

crosstool-devel 0.43-3 

dtc 20070802-1 

elocaledef 1-1 

3.9. ELDK Packages 17

ftdump 20070802-1 

gdb 6.7-2 

genext2fs 1.4.1-1 

info 4.8-15 

ldd 0.1-1 

libtool 1.5.22-11 

make 3.81-6 

mkcramfs 1.1-1 

mkimage 1.3.1-1 

mtd-utils 1.0.1-2 

rpm 

rpm-build 

4.4.2-46_2 

4.4.2-46_2 

sed 4.1.4-1 

texinfo 4.8-15 

Note: The crosstool 0.43 ELDT package provides the following packages: gcc 4.2.2, gcc-c++ 

4.2.2, gcc-java 4.2.2, cpp 4.2.2 and binutils 2.17.90. For more information about the 

crosstool package please refer to http://kegel.com/crosstool. 

3.9.2. List of Target Packages 

Package Name 

Package Version 

acl 2.2.39-3.1 

appweb 2.2.2-5 

attr 2.4.32-2 

autoconf 2.61-8 

bash 3.2-9 

bc 1.06-26 

bind 

9.4.1-8.P1 

binutils 2.17.90-1 

binutils-devel 2.17.90-1 

boa 

0.94.14-0.5.rc21 

busybox 1.7.1-2 

byacc 1.9.20050813-1 

bzip2 1.0.4-10 

bzip2-devel 1.0.4-10 

bzip2-libs 1.0.4-10 

3.9.1. List of ELDT Packages 18

ccid 1.2.1-10 

chkconfig 1.3.34-1 

coreutils 6.9-3 

cpio 2.6-27 

cpp 4.2.2-2 

cracklib 2.8.9-11 

cracklib-dicts 2.8.9-11 

crosstool-targetcomponents 0.43-3 

curl 7.16.2-1 

cyrus-sasl 2.1.22-6 

cyrus-sasl-devel 2.1.22-6 

cyrus-sasl-lib 2.1.22-6 

db4 

db4-devel 

db4-utils 

4.5.20-5_2 

4.5.20-5_2 

4.5.20-5_2 

device-mapper 1.02.17-7 

device-mapper-devel 1.02.17-7 

device-mapper-libs 1.02.17-7 

dhclient 3.0.5-38 

dhcp 3.0.5-38 

diffutils 2.8.1-16 

directfb 1.0.0-1 

dosfstools 2.11-8 

dropbear 0.50-1 

dtc 20070802-1 

duma 2.5.8-2 

e2fsprogs 1.39-11 

e2fsprogs-devel 1.39-11 

e2fsprogs-libs 1.39-11 

ethtool 5-1 

expat 1.95.8-9 

expat-devel 1.95.8-9 

file 4.21-1 

file-libs 4.21-1 

3.9.2. List of Target Packages 19

findutils 4.2.29-2 

flex 2.5.33-9 

freetype 2.3.4-3 

freetype-devel 2.3.4-3 

ftdump 20070802-1 

ftp 0.17-40 

gawk 3.1.5-15 

gcc 4.2.2-2 

gcc-c++ 4.2.2-2 

gcc-java 4.2.2-2 

gdb 6.7-1 

glib 1.2.10-26 

glib2 2.12.13-1 

glib2-devel 2.12.13-1 

glib-devel 1.2.10-26 

gmp 4.1.4-12.3 

grep 2.5.1-57 

groff 1.18.1.4-2 

gzip 1.3.11-2 

hdparm 6.9-3 

httpd 2.2.4-4.1 

httpd-devel 2.2.4-4.1 

httpd-manual 2.2.4-4.1 

initscripts 8.54.1-1 

iproute 2.6.20-2 

iptables 1.3.8-2 

iputils 20070202-3 

iscsitarget 0.4.15-1 

kbd 1.12-22 

kernel-headers 2.6.24-1 

kernel-source 2.6.24-1 

krb5-devel 1.6.1-2.1 

krb5-libs 1.6.1-2.1 

less 394-9 


libattr 2.4.32-2 

libattr-devel 2.4.32-2 

libcap 1.10-29 

libcap-devel 1.10-29 

libpng 1.2.16-1 

libpng-devel 1.2.16-1 

libsysfs 2.1.0-1 

libsysfs-devel 2.1.0-1 

libtermcap 2.0.8-46.1 

libtermcap-devel 2.0.8-46.1 

libtirpc 

libtirpc-devel 

0.1.7-7_2 

0.1.7-7_2 

libtool 1.5.22-11 

libtool-ltdl 1.5.22-11 

libtool-ltdl-devel 1.5.22-11 

libusb 0.1.12-7 

libusb-devel 0.1.12-7 

libuser 0.56.2-1 

libuser-devel 0.56.2-1 

libxml2 2.6.29-1 

logrotate 3.7.5-3.1 

lrzsz 0.12.20-22.1 

lsof 4.78-5 

ltp 

20080131-eldk2 

lvm2 2.02.24-1 

m4 1.4.8-2 

mailcap 2.1.23-1 

make 3.81-6 

MAKEDEV 3.23-1.2 

man 

1.6e-3 

mdadm 2.6.2-4 

microwindows 0.91-2 

microwindows-fonts 0.91-1 

mingetty 1.07-5.2.2 


mktemp 1.5-25 

module-init-tools 

3.3-0.pre11.1.0 

mtd-utils 1.0.1-2 

ncompress 4.2.4-49 

ncurses 5.6-17 

ncurses-devel 5.6-17 

net-snmp 5.4-14 

net-snmp-devel 5.4-14 

net-snmp-libs 5.4-14 

net-snmp-utils 5.4-14 

net-tools 1.60-82 

newt 0.52.6-30 

newt-devel 0.52.6-30 

nfs-utils 1.1.0-1 

ntp 

4.2.4p2-1 

open-iscsi 2.0-865.15 

openldap 2.3.34-3 

openldap-devel 2.3.34-3 

openssl 

openssl-devel 

oprofile 

0.9.8b-12_2 

0.9.8b-12_2 

0.9.2-8_2 

pam 0.99.7.1-5.1 

pam-devel 0.99.7.1-5.1 

passwd 0.74-3 

patch 2.5.4-29.2.2 

pciutils 

pciutils-devel 

pcmciautils 

2.2.4-3_2 

2.2.4-3_2 

014-9_2 

pcre 7.0-2 

pcsc-lite 1.3.3-1.0 

pcsc-lite-devel 1.3.3-1.0 

pcsc-lite-libs 1.3.3-1.0 

perl 

perl-libs 

5.8.8-18_2 

5.8.8-18_2 


popt 1.12-1 

portmap 

postgresql 

postgresql-devel 

postgresql-libs 

4.0-65_2 

8.2.4-1_2 

8.2.4-1_2 

8.2.4-1_2 

ppp 2.4.4-7 

procps 3.2.7-14 

psmisc 22.3-2 

python 2.5.1-1 

rdate 1.4-6 

readline 5.2-4 

readline-devel 5.2-4 

routed 

0.17-12_1 

rpcbind 0.1.4-6 

rpm 

rpm-build 

rpm-devel 

rpm-libs 

4.4.2-46_2 

4.4.2-46_2 

4.4.2-46_2 

4.4.2-46_2 

rsh 0.17-40 

rsh-server 0.17-40 

screen 4.0.3-50 

sed 4.1.5-7 

SELF 1.0-13 

setup 

2.6.4-1_2 

shadow-utils 4.0.18.1-15 

slang 2.0.7-17 

slang-devel 2.0.7-17 

smartmontools 5.38-2 

strace 4.5.15-1 

sysfsutils 2.1.0-1 

sysklogd 1.4.2-9 

sysvinit 2.86-17 

tar 1.15.1-26 

tcp_wrappers 7.6-48 


tcp_wrappers-devel 7.6-48 

tcp_wrappers-libs 7.6-48 

telnet 0.17-38 

telnet-server 0.17-38 

termcap 5.5-1.20060701.1 

tftp 0.42-4 

tftp-server 0.42-4 

thttpd 

2.25b-13 

time 1.7-29 

u-boot 1.3.1-1 

udev 106-4.1 

unixODBC 2.2.12-2 

unzip 5.52-4 

util-linux 

2.13-0.52_2 

vim-common 7.1.12-1 

vim-minimal 7.1.12-1 

vixie-cron 4.1-82 

vsftpd 

2.0.5-16_2 

which 2.16-8 

wireless-tools 28-4 

wpa_supplicant 0.5.7-3 

wu-ftpd 2.6.2-1 

xdd 65.013007-1 

xenomai 2.4.2-1 

xinetd 2.3.14-12 

zip 2.31-3 

zlib 1.2.3-10 

zlib-devel 1.2.3-10 

Note 1: Not all packages will be installed automatically; for example the boa and thttpd web servers 

are mutually exclusive - you will have to remove one package before you can (manually) install the other one. 

Note 2: The crosstool 0.43 target package provides the following packages: glibc 2.6, 

glibc-common 2.6, glibc-devel 2.6, libstdc++ 4.2.2, libgcj 4.2.2, libgcj-devel 

4.2.2 and libstdc++-devel 4.2.2. For more information about the crosstool package please 

refer to http://kegel.com/crosstool 

Note 3: The Xenomai and gcc-java packages are unavailable in ARM ELDK version. 


3.10. Rebuilding the ELDK from Scratch 

In this section, you will find instructions on how to build the ELDK from scratch, using the pristine package 

sources available on the Internet, and patches, spec files, and build scripts provided on the ELDK source 

CD-ROM. 

3.10.1. ELDK Build Process Overview 

The ELDK uses the Fedora 7 Linux distribution as source code reference. Any modifications to Fedora's 

sources the ELDK has introduced are in the form of patches applied by the RPM tool while building the 

packages. Also, the ELDK uses modified spec files for its RPM packages. So, the sources of almost every 

ELDK package consist of the following parts: 

• Fedora pristine sources or 

• ELDK source tarball, 

• ELDK patches, 

• ELDK spec file. 

The Fedora pristine sources may be obtained from the Internet, see 

http://download.fedora.redhat.com/pub/fedora/linux/core. 

The ELDK patches and spec files are available on the ELDK source CD-ROM and from the DENX GIT 

repositories. Also, for convenience, the pristine Fedora sources are available here, too. 

Please use the following commands to check out a copy of one of the modules: 

git-clone git://www.denx.de/git/eldk/module 

The following ELDK modules are available: 

Module Name 

tarballs 

build 

Contents 

Source tarballs 

Build tools, patches, and spec files 

SRPMS 

Fedora 7 sources 

Then you may switch to a specific release of the ELDK using the "git-checkout" command; for example, to 

get the files for ELDK release 4.1, please do the following from the module directory: 

git-checkout ELDK_4_2 

It must be noted that some of the packages which are included in the ELDK are not included in Fedora. 

Examples of such packages are appWeb, microwindows, and wu-ftpd. For these packages tarballs are 

provided in the DENX GIT repository. 

To facilitate building of the ELDK, a build infrastructure has been developed. The infrastructure is composed 

of the following components: 

• ELDK_BUILD script 

• build.sh script 

• cpkgs.lst file 

• tpkgs.lst file 

• SRPMS.lst file 

3.10. Rebuilding the ELDK from Scratch 25

• tarballs.lst file 

The ELDK_BUILD script is the main script of the ELDK build procedure. It is the tool that you would 

normally use to build the ELDK from scratch. In the simplest case, the script may be invoked without 

arguments, and it will perform all necessary steps to build the ELDK in a fully automated way. You may pass 

the following optional arguments to the ELDK_BUILD script: 

-a target architecture: "arm", "ppc" or "ppc64", defaults to "ppc". 

-n 

-v ELDK version string 

-u 

-p 

an identification string for the build. Defaults to the value based on the build 

architecture and current date, and has the following format: -YYYY-MM-DD 

build the uClibc-based ELDK version (on the platforms and versions where this is 

available). 

Optional build directory. By default, build will place the work files and results in the 

current directory. 

Warning: The ELDK build scripts rely on standard behaviour of the RPM tool. Make sure you don't use 

non-standard settings in your personal ~/.rpmmacros file that might cause conflicts. 

build.sh is a supplementary script that is called by ELDK_BUILD to accomplish certain steps of the build. 

Refer to section 3.10.3. build.sh Usage below for more details. 

The cpkgs.lst and tpkgs.lst files are read by build.sh and must contain lines describing sub-steps of the eldt 

and trg build procedure steps. Essentially, the files contain the list of the ELDT and target packages to be 

included in the ELDK. The SRPMS.lst file contains the list of the Fedora source RPM packages used during 

the ELDK build. The tarballs.lst file contains the list of source tarballs of the packages that are included in the 

ELDK but are not present in Fedora 7. 

For the ELDK_BUILD script to work correctly, it must be invoked from a certain build environment created 

on the host system. The build environment can be either checked out from the DENX GIT repository (see 

section 3.10.2. Setting Up ELDK Build Environment below for details) or copied from the ELDK build 

environment CD-ROM. 

To be more specific, the following diagram outlines the build environment needed for correct operation of the 

ELDK_BUILD script: 

/ 

build/cross_rpms//SPECS/... 

SOURCES/... 

target_rpms//SPECS/... 

SOURCES/... 

install/install.c 

Makefile 

misc/ELDK_MAKEDEV 

ELDK_FIXOWNER 

README.html 

cpkgs.lst 

tpkgs.lst 

build.sh 

ELDK_BUILD 

SRPMS.lst 

tarballs.lst 

tarballs/.... 

3.10.1. ELDK Build Process Overview 26

SRPMS/.... 

SRPMS-updates/.... 

In subdirectories of the cross_rpms and target_rpms directories, the sources and RPM spec files of, 

respectively, the ELDT and target packages are stored. The install subdirectory contains the sources of the 

installation utility which will be built and placed in the root of the ISO image. tarballs directory contains the 

source tarballs of the packages that are included in the ELDK but are not present in Fedora 7. 

The SRPMS and SRPMS-updates directories may contain the source RPM packages of Fedora 7. The 

ELDK_BUILD script looks for a package in the SRPMS directory and then, if the package is not found, in the 

SRPMS-updates directory. If some (or all) of the Fedora SRPMs needed for the build are missing in the 

directories, the ELDK_BUILD script will download the source RPMs automatically from the Internet. 

The ELDK build environment CD-ROM provides a ready-to-use ELDK build environment. Please refer to 

section 3.10.2. Setting Up ELDK Build Environment below for detailed instructions on setting up the build 

environment. 

The ELDK_BUILD script examines the contents of the ELDK_PREFIX environment variable to determine 

the root directory of the ELDK build environment. If the variable is not set when the script is invoked, it is 

assumed that the root directory of the ELDK build environment is /opt/eldk. To build the ELDK in the 

example directory layout given above, you must set and export the ELDK_PREFIX variable 

prior to invoking ELDK_BUILD. 

After all the build steps are complete, the following subdirectories are created in the ELDK build 

environment: 

build//work/ 

- full ELDK environment 

build//logs/ 

- build procedure log files 

build//results/b_cdrom/ - binary cdrom tree, ready for mkisofs 

results/s_cdrom/ - source cdrom tree, ready for mkisofs 

results/d_cdrom/ - debuginfo cdrom tree, ready for mkisofs 

On Linux hosts, the binary and source ISO images are created automatically by the ELDK_BUILD script and 

placed in the results directory. On Solaris hosts, creating the ISO images is a manual step. Use the contents of 

the b_cdrom and s_cdrom directories for the contents of the ISO images. 

3.10.2. Setting Up ELDK Build Environment 

For your convenience, the ELDK build environment CD-ROM provides full ELDK build environment. All 

you need to do is copy the contents of the CD-ROM to an empty directory on your host system. Assuming the 

ELDK build environment CD-ROM is mounted at /mnt/cdrom, and the empty directory where you want to 

create the build environment is named /opt/eldk, use the following commands to create the build environment: 

bash$ cd /opt/eldk 

bash$ cp -r /mnt/cdrom/* . 

These commands will create the directory structure as described in section 3.10.1. ELDK Build Process 

Overview above. All necessary scripts and ELDK specific source files will be placed in the build 

subdirectory, and the required tarballs can be found in the tarballs subdirectory. In the SRPMS subdirectory, 

you will find all the Fedora 7 SRPMS needed to build the ELDK. 

Alternatively, you can obtain the ELDK build environment from the DENX GIT repository. Two modules are 

provided for check out: build and tarballs. The first one contains the files for the build subdirectory in the 

build environment, and the second one contains source tarballs of the packages that are included in the ELDK 

but are not present in Fedora 7. To create the ELDK build environment from the DENX GIT repository, use 

3.10.2. Setting Up ELDK Build Environment 27

the following commands (the example below assumes that the root directory of the build environment is 

/opt/eldk): 

bash$ cd /opt/eldk 

bash$ git-clone git://www.denx.de/git/eldk/build 

bash$ git-clone git://www.denx.de/git/eldk/tarballs 

bash$ git-clone git://www.denx.de/git/eldk/SRPMS 

Note: To allow to install the ELDK on as many as possible Linux distributions (including old systems), we 

use a Red Hat 7.3 host system for building. Also, Fedora Core 5 is known to work as a build environment. 

Other, especially more recent Linux distributions, will most likely have problems. We therefor provide a Red 

Hat 7.3 based root file system image than can run in some virtualization environment (like qemu etc.). Here is 

an application note with detailed instructions: 

http://www.denx.de/wiki/DULG/AN2009_02_EldkReleaseBuildEnvironment 

3.10.3. build.sh Usage 

If you wish to perform only a part of the ELDK build procedure, for instance to re-build or update a certain 

package, it may sometimes be convenient to invoke the build.sh script manually, without the aid of the 

ELDK_BUILD script. Please note, however, that this approach is in general discouraged. 

The whole build procedure is logically divided into six steps, and the build.sh must be told which of the 

build steps to perform. The build steps are defined as follows: 

• rpm - build RPM 

• eldt - build ELDT packages 

• seldt - save ELDT SRPM packages to create a source ISO image later on 

• trg - build target packages 

• biso - prepare the file tree to create the binary ISO image 

• siso - prepare the file tree to create the source ISO image 

• diso - prepare the file tree to create the debuginfo ISO image 

Further, the eldt and trg build steps are devided into sub-steps, as defined in the cpkgs.lst and tpkgs.lst 

files (see below for details). You may specify which sub-steps of the build step are to be performed. 

The formal syntax for the usage of build.sh is as follows: 

bash$ ./build.sh [-a ] [-n ] [-p ] [-r ] \ 

[-w ] [] 

-a target architecture: "ppc", "ppc64", "arm" or "mips", defaults to "ppc". 

-n an identification string for the build. It is used as a name for some directories 

created during the build. You may use for example the current date as the build 

name. 

-p is the name of the directory that contains the build environment. Refer to build 

overview above for description of the build environment. 

-r is the name of the directory where the resulting RPMs and SRPMs created on this 

step will be placed. 

-w is the name of the directory where the build is performed. 

 

is the name of the build step that is to be performed. Refer to the list of the build 

procedure steps above. 

3.10.3. build.sh Usage 28

is an optional parameter which identifies sub-steps of the step which are to be 

performed. This is useful when you want to re-build only some specific packages. 

The numbers are defined in the cpkgs.lst and tpkgs.lst files discussed below. You 

can specify a range of numbers here. For instance, "2 5" means do steps from 2 to 

5, while simply "2" means do all steps starting at 2. 

Please note that you must never use build.sh to build the ELDK from scratch. For build.sh to work 

correctly, the script must be invoked from the build environment after a successful build using the 

ELDK_BUILD script. A possible scenario of build.sh usage is such that you have a build environment 

with results of a build performed using the ELDK_BUILD script and want to re-build certain ELDT and target 

packages, for instance, because you have updated sources of a package or added a new package to the build. 

When building the target packages (during the trg buildstep), build.sh examines the contents of the 

TARGET_CPU_FAMILY_LIST environment variable, which may contain a list indicating which target CPU 

variants the packages must be built for. Possible CPU variants are 4xx, 4xxFP, 6xx, 74xx, 8xx, 85xx and 

ppc64. For example, the command below rebuilds the target RPM listed in the tpckgs.lst file under the number 

of 47 (see section 3.10.4. Format of the cpkgs.lst and tpkgs.lst Files for description of the tpckgs.lst and 

cpkgs.lst files), for the 8xx and 85xx CPUs: 

bash$ TARGET_CPU_FAMILY_LIST="8xx 85xx" \ 

> /opt/eldk/build.sh -a ppc \ 

> -n 2007-01-19 \ 

> -p /opt/eldk/build/ppc-2007-01-19 \ 

> -r /opt/eldk/build/ppc-2007-01-19/results \ 

> -w /opt/eldk/build/ppc-2007-01-19/work \ 

> trg 47 47 

Note: If you are going to invoke build.sh to re-build a package that has already been built in the build 

environment by the ELDK_BUILD script, then you must first manually uninstall the package from ELDK 

installation created by the build procedure under the work directory of the build environment. 

Note: It is recommended that you use the build.sh script only at the final stage of adding/updating a 

package to the ELDK. For debugging purposes, it is much more convenient and efficient to build both ELDT 

and target packages using a working ELDK installation, as described in the sections 3.8.2. Rebuilding Target 

Packages and 3.8.3. Rebuilding ELDT Packages above. 

3.10.4. Format of the cpkgs.lst and tpkgs.lst Files 

Each line of these files has the following format: 

\ 

 

The ELDK source CD-ROM contains the cpkgs.lst and tpkgs.lst files used to build this version of the ELDK 

distribution. Use them as reference if you want to include any additional packages into the ELDK, or remove 

unneeded packages. 

To add a package to the ELDK you must add a line to either the cpkgs.lst file, if you are adding a ELDT 

package, or to the tpkgs.lst file, if it is a target package. Keep in mind that the relative positions of packages in 

the cpkgs.lst and tpkgs.lst files (the sub-step numbers) are very important. The build procedure builds the 

packages sequentially as defined in the *.lst files and installs the packages in the "work" environment as they 

are built. This implies that if a package depends on other packages, those packages must be specified earlier 

(with smaller sub-step numbers) in the *.lst files. 

Note: For cpkgs.lst, the package_version may be replaced by the special keyword "RHAUX". Such packages 

are used as auxiliary when building ELDK 4.2 on non-Fedora hosts. These packages will be built and used 

3.10.4. Format of the cpkgs.lst and tpkgs.lst Files 29

during the build process, but will not be put into the ELDK 4.2 distribution ISO images. 

3.11. Notes for Solaris 2.x Host Environment 

If you use a Solaris 2.x host environment, you need additional freeware packages (mostly GNU tools) to 

install and especially to build the ELDK packages. The following table lists all required packages that must be 

installed on the Solaris host system before attempting to build and/or install the ELDK. All these files except 

those marked with (**) (and the RPM and zlib-1.1.2 packages, which are available at 

ftp://rpmfind.net/linux/solaris are available for free download at 

ftp://ftp.sunfreeware.com/pub/freeware/sparc/2.6/ 

Necessary Freeware Packages: 

Package Version Instance File Name 

autoconf(**) 2.13 SMCautoc autoconf-2.13-sol26-sparc-local.gz 

automake(**) 1.4 SMCautom automake-1.4-sol26-sparc-local.gz 

bash 2.05 SMCbash bash-2.05-sol26-sparc-local.gz 

binutils 2.11.2 SMCbinut binutils-2.11.2-sol26-sparc-local.gz 

bison 1.28 SMCbison bison-1.28-sol26-sparc-local.gz 

bzip2 1.0.1 SMCbzip2 bzip2-1.0.1-sol26-sparc-local.gz 

ddd(*) 3.0 TUBddd ddd-3.0-sol26-sparc-local.gz 

diffutils 2.7 GNUdiffut diffutils-2.7-sol26-sparc-local.gz 

expect(*) 5.25 NTexpect expect-5.25-sol26-sparc-local.gz 

fileutils 4.0 SMCfileu fileutils-4.0-sol26-sparc-local.gz 

flex 2.5.4a FSFflex flex-2.5.4a-sol26-sparc-local.gz 

gawk 3.1.0 SMCgawk gawk-3.1.0-sol26-sparc-local.gz 

gcc 2.95.3 SMCgcc gcc-2.95.3-sol26-sparc-local.gz 

gettext 0.10.37 SMCgtext gettext-0.10.37-sol26-sparc-local.gz 

gzip 1.3 SMCgzip gzip-1.3-sol26-sparc-local 

libiconv 1.6.1 SMClibi libiconv-1.6.1-sol26-sparc-local.gz 

libtool 1.4 SMClibt libtool-1.4-sol26-sparc-local.gz 

m4 1.4 SMCm4 m4-1.4-sol26-sparc-local.gz 

make(**) 3.79.1 SMCmake make-3.79.1-sol26-sparc-local.gz 

ncurses 5.2 SMCncurs ncurses-5.2-sol26-sparc-local.gz 

patch 2.5 FSFpatch patch-2.5-sol26-sparc-local.gz 

perl(**) 5.005_03 SMCperl perl-5.005_03-sol26-sparc-local.gz 

python 1.5.2 SMCpython python-1.5.2-sol26-sparc-local.gz 

rpm 2.5.2 RPM rpm-2.5.2.pkg 

sed 3.02 SMCsed sed-3.02-sol26-sparc-local.gz 

tar 1.13.19 SMCtar tar-1.13.19-sol26-sparc-local.gz 

tcl(*) 8.3.3 SMCtcl tcl-8.3.3-sol26-sparc-local.gz 

texinfo 4.0 SMCtexi texinfo-4.0-sol26-sparc-local.gz 

textutils 2.0 SMCtextu textutils-2.0-sol26-sparc-local.gz 

unzip 5.32 IZunzip unzip-5.32-sol26-sparc-local.gz 

wget 1.7 SMCwget wget-1.7-sol26-sparc-local.gz 

zlib(**) 1.0.4 SMCzlib zlib-1.0.4-sol26-sparc-local.gz 

zlib 1.1.2 - zlib-1.1.2.tar.gz 

3.11. Notes for Solaris 2.x Host Environment 30

The packages marked "(*)" are not absolutely required, but sooner or later you will need them anyway so we 

recommend to install them. 

The packages marked "(**)" are older versions of the ones currently available at 

ftp://ftp.sunfreeware.com/pub/freeware/sparc/2.6/. You can obtain them from the DENX public FTP server. 

The following symbolic links must be created in order to be able to build the ELDK on a Solaris machine: 

/usr/local/bin/cc --> /usr/local/bin/gcc 

/usr/lib/libiconv.so.2 --> /usr/local/lib/libiconv.so.2 

/usr/lib/libncurses.so.5 --> /usr/local/lib/libncurses.so.5 

Additionally, to be able to build the ELDK on Solaris, you must place newer GNU gettext macros to the 

/usr/local/share/aclocal directory. This can be accomplished as follows: 

• Download the 

http://www.ibiblio.org/pub/packages/solaris/sparc/GNUgettext.0.10.40.SPARC.32bit.Solaris.8.pkg.tgz 

package. 

• Untar the package to a temporary directory and copy the macros to the /usr/local/share/aclocal 

directory: 

$ cp GNUgettext/root/usr/local/share/aclocal/*.m4 /usr/local/share/aclocal 

• 4. System Setup 

♦ 4.1. Serial Console Access 

♦ 4.2. Configuring the "cu" command 

♦ 4.3. Configuring the "kermit" command 

♦ 4.4. Using the "minicom" program 

♦ 4.5. Permission Denied Problems 

♦ 4.6. Configuration of a TFTP Server 

♦ 4.7. Configuration of a BOOTP / DHCP Server 

♦ 4.8. Configuring a NFS Server 

4. System Setup 

Some tools are needed to install and configure U-Boot and Linux on the target system. Also, especially during 

development, you will want to be able to interact with the target system. This section describes how to 

configure your host system for this purpose. 

4.1. Serial Console Access 

To use U-Boot and Linux as a development system and to make full use of all their capabilities you will need 

access to a serial console port on your target system. Later, U-Boot and Linux can be configured to allow for 

automatic execution without any user interaction. 

There are several ways to access the serial console port on your target system, such as using a terminal server, 

but the most common way is to attach it to a serial port on your host. Additionally, you will need a terminal 

emulation program on your host system, such as cu or kermit. 

4. System Setup 31

4.2. Configuring the "cu" command 

The cu command is part of the UUCP package and can be used to act as a dial-in terminal. It can also do 

simple file transfers, which can be used in U-Boot for image download. 

On RedHat systems you can check if the UUCP package is installed as follows: 

$ rpm -q uucp 

If necessary, install the UUCP package from your distribution media. 

To configure cu for use with U-Boot and Linux please make sure that the following entries are present in the 

UUCP configuration files; depending on your target configuration the serial port and/or the console baudrate 

may be different from the values used in this example: (/dev/ttyS0, 115200 bps, 8N1): 

• /etc/uucp/sys: 

# 

# /dev/ttyS0 at 115200 bps: 

# 

system 

S0@115200 

port 

serial0_115200 

time 

any 

• /etc/uucp/port: 

# 

# /dev/ttyS0 at 115200 bps: 

# 

port 

serial0_115200 

type 

direct 

device 

/dev/ttyS0 

speed 115200 

hardflow false 

You can then connect to the serial line using the command 

$ cu S0@115200 

Connected. 

To disconnect, type the escape character '~' followed by '.' at the beginning of a line. 

See also: cu(1), info uucp. 

4.3. Configuring the "kermit" command 

The name kermit stands for a whole family of communications software for serial and network connections. 

The fact that it is available for most computers and operating systems makes it especially well suited for our 

purposes. 

kermit executes the commands in its initialization file, .kermrc, in your home directory before it executes 

any other commands, so this can be easily used to customize its behaviour using appropriate initialization 

commands. The following settings are recommended for use with U-Boot and Linux: 

4.2. Configuring the "cu" command 32

• ~/.kermrc: 

set line /dev/ttyS0 

set speed 115200 

set carrier-watch off 

set handshake none 

set flow-control none 

robust 

set file type bin 

set file name lit 

set rec pack 1000 

set send pack 1000 

set window 5 

This example assumes that you use the first serial port of your host system (/dev/ttyS0) at a baudrate of 

115200 to connect to the target's serial console port. 

You can then connect to the serial line: 

$ kermit -c 

Connecting to /dev/ttyS0, speed 115200. 

The escape character is Ctrl-\ (ASCII 28, FS) 

Type the escape character followed by C to get back, 

or followed by to see other options. 

---------------------------------------------------- 

Due to licensing conditions you will often find two kermit packages in your GNU/Linux distribution. In 

this case you will want to install the ckermit package. The gkermit package is only a command line tool 

implementing the kermit transfer protocol. 

If you cannot find kermit on the distribution media for your Linux host system, you can download it 

from the kermit project home page: http://www.columbia.edu/kermit/ 

4.4. Using the "minicom" program 

minicom is another popular serial communication program. Unfortunately, many users have reported 

problems using it with U-Boot and Linux, especially when trying to use it for serial image download. It's use 

is therefore discouraged. 

4.5. Permission Denied Problems 

The terminal emulation program must have write access to the serial port and to any locking files that are used 

to prevent concurrent access from other applications. Depending on the used Linux distribution you may have 

to make sure that: 

• the serial device belongs to the same group as the cu command, and that the permissions of cu have 

the setgid bit set 

• the kermit belongs to the same group as cu and has the setgid bit set 

• the /var/lock directory belongs to the same group as the cu command, and that the write permissions 

for the group are set 

4.3. Configuring the "kermit" command 33

4.6. Configuration of a TFTP Server 

The fastest way to use U-Boot to load a Linux kernel or an application image is file transfer over Ethernet. For 

this purpose, U-Boot implements the TFTP protocol (see the tftpboot command in U-Boot). 

To enable TFTP support on your host system you must make sure that the TFTP daemon program 

/usr/sbin/in.tftpd is installed. On RedHat systems you can verify this by running: 

$ rpm -q tftp-server 

If necessary, install the TFTP daemon program from your distribution media. 

Most Linux distributions disable the TFTP service by default. To enable it for example on RedHat systems, 

edit the file /etc/xinetd.d/tftp and remove the line 

disable = yes 

or change it into a comment line by putting a hash character in front of it: 

# default: off 

# description: The tftp server serves files using the trivial file transfer 

# protocol. The tftp protocol is often used to boot diskless 

# workstations, download configuration files to network-aware printers, 

# and to start the installation process for some operating systems. 

service tftp 

{ 

socket_type 

= dgram 

protocol 

= udp 

wait 

= yes 

user 

= root 

server 

= /usr/sbin/in.tftpd 

server_args 

= -s /tftpboot 

# disable = yes 

per_source = 11 

cps = 100 2 

} 

Also, make sure that the /tftpboot directory exists and is world-readable (permissions at least "dr-xr-xr-x"). 

4.7. Configuration of a BOOTP / DHCP Server 

BOOTP resp. DHCP can be used to automatically pass configuration information to the target. The only 

thing the target must "know" about itself is its own Ethernet hardware (MAC) address. The following 

command can be used to check if DHCP support is available on your host system: 

$ rpm -q dhcp 

If necessary, install the DHCP package from your distribution media. 

Then you have to create the DHCP configuration file /etc/dhcpd.conf that matches your network setup. The 

following example gives you an idea what to do: 

subnet 192.168.0.0 netmask 255.255.0.0 { 

option routers 192.168.1.1; 

option subnet-mask 255.255.0.0; 

option domain-name 

"local.net"; 

4.6. Configuration of a TFTP Server 34

option domain-name-servers ns.local.net; 

} 

host trgt { hardware ethernet 00:30:BF:01:02:D0; 

fixed-address 192.168.100.6; 

option root-path "/opt/eldk-4.2/ppc_4xx"; 

option host-name "canyonlands"; 

next-server 192.168.1.1; 

filename 

"/tftpboot/canyonlands/uImage"; 

} 

With this configuration, the DHCP server will reply to a request from the target with the ethernet address 

00:30:BF:01:02:D0 with the following information: 

• The target is located in the subnet 192.168.0.0 which uses the netmask 255.255.0.0. 

• The target has the hostname canyonlands and the IP address 192.168.100.6. 

• The host with the IP address 192.168.1.1 will provide the boot image for the target and provide 

NFS server function in cases when the target mounts it's root filesystem over NFS. 

The host listed with the next-server option can be different from the host that is running the 

DHCP server. 

• The host provides the file /tftpboot/canyonlands/uImage as boot image for the target. 

• The target can mount the directory /opt/eldk-4.2/ppc_4xx on the NFS server as root filesystem. 

4.8. Configuring a NFS Server 

For a development environment it is very convenient when the host and the target can share the same files 

over the network. The easiest way for such a setup is when the host provides NFS server functionality and 

exports a directory that can be mounted from the target as the root filesystem. 

Assuming NFS server functionality is already provided by your host, the only configuration that needs to be 

added is an entry for your target root directory to your /etc/exports file, for instance like this: 

/opt/eldk-4.2/ppc_4xx 

192.168.0.0/255.255.0.0(rw,no_root_squash,sync) 

This line exports the /opt/eldk-4.2/ppc_4xx directory with read and write permissions to all hosts on the 

192.168.0.0 subnet. 

After modifying the /etc/exports file you must make sure the NFS system is notified about the change, for 

instance by issuing the command: 

# /sbin/service nfs restart 

• 5. Das U-Boot 

♦ 5.1. Current Versions 

♦ 5.2. Unpacking the Source Code 

♦ 5.3. Configuration 


◊ 

5.4.1. Before You Begin 

⋅ 5.4.1.1. Installation Requirements 

⋅ 5.4.1.2. Board Identification Data 

4.7. Configuration of a BOOTP / DHCP Server 35

◊ 5.4.2. Installation Using a BDM/JTAG Debugger 

◊ 5.4.3. Installation using U-Boot 

♦ 5.5. Tool Installation 

♦ 5.6. Initialization 

♦ 5.7. Initial Steps 

♦ 5.8. The First Power-On 

♦ 5.9. U-Boot Command Line Interface 

◊ 

◊ 

◊ 

◊ 

◊ 

◊ 

◊ 

5.9.1. Information Commands 

⋅ 5.9.1.1. bdinfo - print Board Info structure 

⋅ 5.9.1.2. coninfo - print console devices and informations 


⋅ 5.9.1.4. iminfo - print header information for application image 

⋅ 5.9.1.5. help - print online help 

5.9.2. Memory Commands 

⋅ 5.9.2.1. base - print or set address offset 

⋅ 5.9.2.2. crc32 - checksum calculation 

⋅ 5.9.2.3. cmp - memory compare 


⋅ 5.9.2.5. md - memory display 

⋅ 5.9.2.6. mm - memory modify (auto-incrementing) 

⋅ 5.9.2.7. mtest - simple RAM test 

⋅ 5.9.2.8. mw - memory write (fill) 

⋅ 5.9.2.9. nm - memory modify (constant address) 

⋅ 5.9.2.10. loop - infinite loop on address range 

5.9.3. Flash Memory Commands 



⋅ 5.9.3.3. erase - erase FLASH memory 

⋅ 5.9.3.4. protect - enable or disable FLASH write protection 

⋅ 5.9.3.5. mtdparts - define a Linux compatible MTD partition scheme 

5.9.4. Execution Control Commands 

⋅ 5.9.4.1. autoscr - run script from memory 

⋅ 5.9.4.2. bootm - boot application image from memory 

⋅ 5.9.4.3. go - start application at address 'addr' 

5.9.5. Download Commands 

⋅ 5.9.5.1. bootp - boot image via network using BOOTP/TFTP protocol 

⋅ 5.9.5.2. dhcp - invoke DHCP client to obtain IP/boot params 

⋅ 5.9.5.3. loadb - load binary file over serial line (kermit mode) 

⋅ 5.9.5.4. loads - load S-Record file over serial line 

⋅ 5.9.5.5. rarpboot- boot image via network using RARP/TFTP protocol 

⋅ 5.9.5.6. tftpboot- boot image via network using TFTP protocol 

5.9.6. Environment Variables Commands 

⋅ 5.9.6.1. printenv- print environment variables 

⋅ 5.9.6.2. saveenv - save environment variables to persistent storage 

⋅ 5.9.6.3. setenv - set environment variables 

⋅ 5.9.6.4. run - run commands in an environment variable 

⋅ 5.9.6.5. bootd - boot default, i.e., run 'bootcmd' 

5.9.7. Flattened Device Tree support 

⋅ 5.9.7.1. fdt addr - select FDT to work on 

⋅ 5.9.7.2. fdt list - print one level 

⋅ 5.9.7.3. fdt print - recursive print 

⋅ 5.9.7.4. fdt mknode - create new nodes 

⋅ 5.9.7.5. fdt set - set node properties 

⋅ 5.9.7.6. fdt rm - remove nodes or properties 

4.8. Configuring a NFS Server 36

⋅ 5.9.7.7. fdt move - move FDT blob to new address 

⋅ 5.9.7.8. fdt chosen - fixup dynamic info 

◊ 5.9.8. Special Commands 

⋅ 5.9.8.1. i2c - I2C sub-system 

◊ 5.9.9. Storage devices 

◊ 5.9.10. Miscellaneous Commands 

⋅ 5.9.10.1. echo - echo args to console 

⋅ 5.9.10.2. reset - Perform RESET of the CPU 

⋅ 5.9.10.3. sleep - delay execution for some time 

⋅ 5.9.10.4. version - print monitor version 

⋅ 5.9.10.5. - alias for 'help' 

♦ 5.10. U-Boot Environment Variables 

♦ 5.11. U-Boot Scripting Capabilities 

♦ 5.12. U-Boot Standalone Applications 

◊ 5.12.1. "Hello World" Demo 

◊ 5.12.2. Timer Demo 

♦ 5.13. U-Boot Image Formats 

♦ 5.14. U-Boot Advanced Features 

◊ 5.14.1. Boot Count Limit 

◊ 5.14.2. Bitmap Support 

◊ 5.14.3. Splash Screen Support 

5. Das U-Boot 

5.1. Current Versions 

Das U-Boot (or just "U-Boot" for short) is Open Source Firmware for Embedded PowerPC, ARM, MIPS, x86 

and other processors. The U-Boot project is hosted by DENX, where you can also find the project home page: 

http://www.denx.de/wiki/U-Boot/ 

The current version of the U-Boot source code can be retrieved from the DENX "git" repository. 

You can browse the "git" repositories at http://git.denx.de/ 

The trees can be accessed through the git, HTTP, and rsync protocols. For example you can use one of the 

following commands to create a local clone of one of the source trees: 

git clone git://git.denx.de/u-boot.git u-boot/ 

git clone http://git.denx.de/u-boot.git u-boot/ 

git clone rsync://git.denx.de/u-boot.git u-boot/ 

For details please see here. 

Official releases of U-Boot are also available through FTP. Compressed tar archives can downloaded from 

the directory ftp://ftp.denx.de/pub/u-boot/. 

5.2. Unpacking the Source Code 

If you used GIT to get a copy of the U-Boot sources, then you can skip this next step since you already have 

an unpacked directory tree. If you downloaded a compressed tarball from the DENX FTP server, you can 

unpack it as follows: 

5.2. Unpacking the Source Code 37

$ cd /opt/eldk/usr/src 

$ wget ftp://ftp.denx.de/pub/u-boot/u-boot-1.3.2.tar.bz2 

$ rm -f u-boot 

$ bunzip2 < u-boot-1.3.2.tar.bz2 | tar xf - 

$ ln -s u-boot-1.3.2 u-boot 

$ cd u-boot 

5.3. Configuration 

After changing to the directory with the U-Boot source code you should make sure that there are no build 

results from any previous configurations left: 

$ make distclean 

The following (model) command configures U-Boot for the canyonlands board: 

$ make canyonlands_config 

And finally we can compile the tools and U-Boot itself: 

$ make all 

By default the build is performed locally and the objects are saved in the source directory. One of the two 

methods can be used to change this behaviour and build U-Boot to some external directory: 

1. Add O= to the make command line invocations: 

make O=/tmp/build distclean 

make O=/tmp/build canyonlands_config 

make O=/tmp/build all 

Note that if the 'O=output/dir' option is used then it must be used for all invocations of make. 

2. Set environment variable BUILD_DIR to point to the desired location: 

export BUILD_DIR=/tmp/build 

make distclean 

make canyonlands_config 

make all 

Note that the command line "O=" setting overrides the BUILD_DIR environment variable. 


5.4.1. Before You Begin 

5.4.1.1. Installation Requirements 

The following section assumes that flash memory is used as the storage device for the firmware on your 

board. If this is not the case, the following instructions will not work - you will probably have to replace the 

storage device (probably ROM or EPROM) on such systems to install or update U-Boot. 

5.4.1. Before You Begin 38

5.4.1.2. Board Identification Data 

All %BOARDNAME% boards use a serial number for identification 

purposes. Also, all boards have at least one ethernet (MAC) address 

assigned. You may lose your warranty on the board if this data gets 

lost. Before installing U-Boot or otherwise changing the software 

configuration of a board (like erasing some flash memory) you should 

make sure that you have all necessary information about such data. 

5.4.2. Installation Using a BDM/JTAG Debugger 

A fast and simple way to write new data to flash memory is via the use of a debugger or flash programmer 

with a BDM or JTAG interface. In cases where there is no running firmware at all (for instance on new 

hardware), this is usually the only way to install any software at all. 

We use (and highly recommend) the BDI2000 by Abatron . 

Other BDM / JTAG debuggers may work too, but how to use them is beyond the scope of this document. 

Please see the documentation for the tool you want to use. 

Before you can use the BDI2000 you have to configure it. A configuration file that can be used with 

canyonlands boards is included in section 13.2. BDI2000 Configuration file 

To install a new U-Boot image on your canyonlands board using a BDI2000, proceed as follows: 

Note: Included topic DULGData_canyonlands.InstallUBootUsingBDI2000 does not exist yet 

5.4.3. Installation using U-Boot 

If U-Boot is already installed and running on your board, you can use these instructions to download another 

U-Boot image to replace the current one. 

Warning: Before you can install the new image, you have to erase the current one. If anything goes wrong 

your board will be dead. It is strongly recommended that: 

• you have a backup of the old, working U-Boot image 

• you know how to install an image on a virgin system 

Proceed as follows: 

Note: Included topic DULGData_canyonlands.InstallUBootUsingUBoot does not exist yet 

5.5. Tool Installation 

U-Boot uses a special image format when loading the Linux kernel or ramdisk or other images. This image 

contains (among other things) information about the time of creation, operating system, compression type, 

image type, image name and CRC32 checksums. 

The tool mkimage is used to create such images or to display the information they contain. When using the 

ELDK, the mkimage command is already included with the other ELDK tools. 

5.5. Tool Installation 39

If you don't use the ELDK then you should install mkimage in some directory that is in your command 

search PATH, for instance: 

$ cp tools/mkimage /usr/local/bin/ 

5.6. Initialization 

To initialize the U-Boot firmware running on your canyonlands board, you have to connect a terminal to the 

board's serial console port. 

The default configuration of the console port on the canyonlands board uses a baudrate of 115200/8N1 

(115200 bps, 8 Bit per character, no parity, 1 stop bit, no handshake). 

If you are running Linux on your host system we recommend either kermit or cu as terminal emulation 

programs. Do not use minicom, since this has caused problems for many users, especially for software 

download over the serial port. 

For the configuration of your terminal program see section 4.1. Serial Console Access 

Make sure that both hardware and software flow control are disabled. 

5.7. Initial Steps 

In the default configuration, U-Boot operates in an interactive mode which provides a simple command 

line-oriented user interface using a serial console on port UART1. 

In the simplest case, this means that U-Boot shows a prompt (default: =>) when it is ready to receive user 

input. You then type a command, and press enter. U-Boot will try to run the required action(s), and then 

prompt for another command. 

To see a list of the available U-Boot commands, you can type help (or simply ). This will print a list of all 

commands that are available in your current configuration. [Please note that U-Boot provides a lot of 

configuration options; not all options are available for all processors and boards, and some options might be 

simply not selected for your configuration.] 

=> help 

- alias for 'help' 

askenv - get environment variables from stdin 

autoscr - run script from memory 

base - print or set address offset 

bdinfo - print Board Info structure 

boot - boot default, i.e., run 'bootcmd' 

bootd - boot default, i.e., run 'bootcmd' 

bootelf - Boot from an ELF image in memory 

bootm - boot application image from memory 

bootp - boot image via network using BootP/TFTP protocol 

bootstrap - program the I2C bootstrap EEPROM 

bootvx - Boot vxWorks from an ELF image 

cmp - memory compare 

coninfo - print console devices and information 

cp - memory copy 

crc32 - checksum calculation 

date - get/set/reset date & time 

dhcp - invoke DHCP client to obtain IP/boot params 

dtt - Digital Thermometer and Thermostat 

5.7. Initial Steps 40

echo - echo args to console 

eeprom - EEPROM sub-system 

erase - erase FLASH memory 

exit - exit script 

ext2load- load binary file from a Ext2 filesystem 

ext2ls - list files in a directory (default /) 

fatinfo - print information about filesystem 

fatload - load binary file from a dos filesystem 

fatls - list files in a directory (default /) 

fdt - flattened device tree utility commands 

flinfo - print FLASH memory information 

getdcr - Get an AMCC PPC 4xx DCR's value 

getidcr - Get a register value via indirect DCR addressing 

go - start application at address 'addr' 

help - print online help 

icrc32 - checksum calculation 

iloop - infinite loop on address range 

imd - i2c memory display 

iminfo - print header information for application image 

imls - list all images found in flash 

imm - i2c memory modify (auto-incrementing) 

imw - memory write (fill) 

imxtract- extract a part of a multi-image 

inm - memory modify (constant address) 

iprobe - probe to discover valid I2C chip addresses 

irqinfo - print information about IRQs 

isdram - print SDRAM configuration information 

itest - return true/false on integer compare 

loadb - load binary file over serial line (kermit mode) 

loads - load S-Record file over serial line 

loady - load binary file over serial line (ymodem mode) 

loop - infinite loop on address range 

loopw - infinite write loop on address range 

md - memory display 

mdc - memory display cyclic 

mii - MII utility commands 

mm - memory modify (auto-incrementing) 

mtest - simple RAM test 

mw - memory write (fill) 

mwc - memory write cyclic 

nand - NAND sub-system 

nboot - boot from NAND device 

nfs - boot image via network using NFS protocol 

nm - memory modify (constant address) 

pci - list and access PCI Configuration Space 

ping - send ICMP ECHO_REQUEST to network host 

printenv- print environment variables 

protect - enable or disable FLASH write protection 

rarpboot- boot image via network using RARP/TFTP protocol 

reginfo - print register information 

reset - Perform RESET of the CPU 

run - run commands in an environment variable 

saveenv - save environment variables to persistent storage 

setdcr - Set an AMCC PPC 4xx DCR's value 

setenv - set environment variables 

setidcr - Set a register value via indirect DCR addressing 

sleep - delay execution for some time 

test - minimal test like /bin/sh 

tftpboot- boot image via network using TFTP protocol 

usb - USB sub-system 

usbboot - boot from USB device 

version - print monitor version 

=> 

With the command help you can get additional information about most commands: 

5.7. Initial Steps 41

=> help tftpboot 

tftpboot [loadAddress] [[hostIPaddr:]bootfilename] 

=> 

=> help setenv printenv 

setenv name value ... 

- set environment variable 'name' to 'value ...' 

setenv name 

- delete environment variable 'name' 

printenv 

- print values of all environment variables 

printenv name ... 

- print value of environment variable 'name' 

=> 

Most commands can be abbreviated as long as the string remains unambiguous: 

=> help fli tftp 

flinfo 

- print information for all FLASH memory banks 

flinfo N 

- print information for FLASH memory bank # N 


=> 

5.8. The First Power-On 

Note: If you bought your canyonlands board with U-Boot already installed, you can skip this section since 

the manufacturer probably has already performed these steps. 

Connect the port labeled UART1 on your canyonlands board to the designated serial port of your host, start 

the terminal program, and connect the power supply of your canyonlands board. You should see messages like 

this: 

=> reset 

U-Boot 1.3.3-rc2-01466-g4f27098 (May 1 2008 - 13:57:57) 

CPU: AMCC PowerPC 460EX Rev. A at 600 MHz (PLB=200, OPB=100, EBC=100 MHz) 

Security/Kasumi support 

Bootstrap Option H - Boot ROM Location I2C (Addr 0x52) 

Internal PCI arbiter disabled 

32 kB I-Cache 32 kB D-Cache 

Board: Canyonlands - AMCC PPC460EX Evaluation Board, 2*PCIe, Rev. 13 

I2C: ready 

DTT: 1 is 48 C 

DRAM: 256 MB (ECC not enabled, 400 MHz, CL3) 

FLASH: 64 MB 

NAND: 32 MiB 

PCI: Bus Dev VenId DevId Class Int 

PCIE0: link is not up. 

PCIE0: initialization as root-complex failed 

PCIE1: link is not up. 

PCIE1: initialization as root-complex failed 

5.8. The First Power-On 42

Net: 

ppc_4xx_eth0, ppc_4xx_eth1 

Type run flash_nfs to mount root filesystem over NFS 

Hit any key to stop autoboot: 0 

=> 

=> 

You can interrupt the "Count-Down" by pressing any key. If you don't you will probably see some (harmless) 

error messages because the system has not been initialized yet. 

In some cases you may see a message 

*** Warning - bad CRC, using default environment 

This is harmless and will go away as soon as you have initialized and saved the environment variables. 

At first you have to enter the serial number and the ethernet address of your board. Pay special attention here 

since these parameters are write protected and cannot be changed once saved (usually this is done by the 

manufacturer of the board). To enter the data you have to use the U-Boot command setenv, followed by the 

variable name and the data, all separated by white space (blank and/or TAB characters). Use the variable 

name serial# for the board ID and/or serial number, and ethaddr for the ethernet address, for instance: 

=> setenv ethaddr !!!!!!FILL_THIS!!!!!! 

=> setenv serial# CF56-216F-400A 

Use the printenv command to verify that you have entered the correct values: 

=> printenv serial# ethaddr 

## Error: "serial#" not defined 

ethaddr=5e:ed:18:38:81:85 

=> 

Please double check that the printed values are correct! You will not be able to correct any errors later! If 

there is something wrong, reset the board and restart from the beginning; otherwise you can store the 

parameters permanently using the saveenv command: 

=> saveenv 

Saving Environment to Flash... 

Un-Protected 1 sectors 


Erasing Flash... 

. done 

Erased 1 sectors 

Writing to Flash... done 

Protected 1 sectors 


=> 

5.9. U-Boot Command Line Interface 

The following section describes the most important commands available in U-Boot. Please note that U-Boot is 

highly configurable, so not all of these commands may be available in the configuration of U-Boot installed 

on your hardware, or additional commands may exist. You can use the help command to print a list of all 

available commands for your configuration. 

5.9. U-Boot Command Line Interface 43

For most commands, you do not need to type in the full command name; instead it is sufficient to type a few 

characters. For instance, help can be abbreviated as h. 

The behaviour of some commands depends of the configuration of U-Boot and on the definition of some 

variables in your U-Boot environment. 

All U-Boot commands expect numbers to be entered in hexadecimal input format. 

Be careful not to use edit keys besides 'Backspace', as hidden characters in things like environment 

variables can be very difficult to find. 

5.9.1. Information Commands 

5.9.1.1. bdinfo - print Board Info structure 

=> help bdinfo 

bdinfo - No help available. 

=> 

The bdinfo command (short: bdi) prints the information that U-Boot passes about the board such as 

memory addresses and sizes, clock frequencies, MAC address, etc. This information is mainly needed to be 

passed to the Linux kernel. 

=> bdi 

memstart = 0x00000000 

memsize = 0x10000000 

flashstart = 0xFC000000 

flashsize = 0x04000000 

flashoffset = 0x00000000 

sramstart = 0x00000000 

sramsize = 0x00000000 

bootflags = 0xFFFDFC84 

intfreq = 600 MHz 

busfreq = 200 MHz 

ethaddr = 5E:ED:18:38:81:85 

eth1addr = 5E:ED:18:38:81:86 

IP addr = 192.168.100.6 

baudrate = 115200 bps 

=> 

5.9.1.2. coninfo - print console devices and informations 

=> help conin 

coninfo 

=> 

The coninfo command (short: conin) displays information about the available console I/O devices. 

=> conin 

List of available devices: 

serial 80000003 SIO stdin stdout stderr 

serial1 00000003 .IO 

serial0 00000003 .IO 

=> 

5.9.1. Information Commands 44

The output contains the device name, flags, and the current usage. For example, the output 

serial 

80000003 SIO stdin stdout stderr 

means that the serial device is a system device (flag 'S') which provides input (flag 'I') and output 

(flag 'O') functionality and is currently assigned to the 3 standard I/O streams stdin, stdout and 

stderr. 

5.9.1.3. flinfo - print FLASH memory information 

=> help flinfo 

flinfo 

- print information for all FLASH memory banks 

flinfo N 

- print information for FLASH memory bank # N 

=> 

The command flinfo (short: fli) can be used to get information about the available flash memory (see 

Flash Memory Commands below). 

=> fli 

Bank # 1: CFI conformant FLASH (16 x 16) Size: 64 MB in 512 Sectors 

AMD Standard command set, Manufacturer ID: 0x01, Device ID: 0x227E 

Erase timeout: 16384 ms, write timeout: 2 ms 

Buffer write timeout: 5 ms, buffer size: 32 bytes 

Sector Start Addresses: 

FC000000 E FC020000 E FC040000 E FC060000 E FC080000 E 

FC0A0000 E FC0C0000 E FC0E0000 E FC100000 E FC120000 E 

FC140000 E FC160000 E FC180000 E FC1A0000 E FC1C0000 E 

FC1E0000 E FC200000 E FC220000 E FC240000 E FC260000 E 

FC280000 E FC2A0000 E FC2C0000 E FC2E0000 E FC300000 E 

FC320000 E FC340000 E FC360000 E FC380000 E FC3A0000 E 

FC3C0000 E FC3E0000 E FC400000 E FC420000 E FC440000 E 

FC460000 E FC480000 E FC4A0000 E FC4C0000 E FC4E0000 E 









FCA00000 E FCA20000 E FCA40000 E FCA60000 E FCA80000 E 

FCAA0000 E FCAC0000 E FCAE0000 E FCB00000 E FCB20000 E 

FCB40000 E FCB60000 E FCB80000 E FCBA0000 E FCBC0000 E 

FCBE0000 E FCC00000 E FCC20000 E FCC40000 E FCC60000 E 

FCC80000 E FCCA0000 E FCCC0000 E FCCE0000 E FCD00000 E 

FCD20000 E FCD40000 E FCD60000 E FCD80000 E FCDA0000 E 

FCDC0000 E FCDE0000 E FCE00000 E FCE20000 E FCE40000 E 

FCE60000 E FCE80000 E FCEA0000 E FCEC0000 E FCEE0000 E 

FCF00000 E FCF20000 E FCF40000 E FCF60000 E FCF80000 E 

FCFA0000 E FCFC0000 E FCFE0000 E FD000000 E FD020000 E 

FD040000 E FD060000 E FD080000 E FD0A0000 E FD0C0000 E 

FD0E0000 E FD100000 E FD120000 E FD140000 E FD160000 E 

FD180000 E FD1A0000 E FD1C0000 E FD1E0000 E FD200000 E 

FD220000 E FD240000 E FD260000 E FD280000 E FD2A0000 E 

FD2C0000 E FD2E0000 E FD300000 E FD320000 E FD340000 E 

FD360000 E FD380000 E FD3A0000 E FD3C0000 E FD3E0000 E 

5.9.1.2. coninfo - print console devices and informations 45

FD400000 E FD420000 E FD440000 E FD460000 E FD480000 E 

FD4A0000 E FD4C0000 E FD4E0000 E FD500000 E FD520000 E 








FD9A0000 E FD9C0000 E FD9E0000 E FDA00000 E FDA20000 E 

FDA40000 E FDA60000 E FDA80000 E FDAA0000 E FDAC0000 E 

FDAE0000 E FDB00000 E FDB20000 E FDB40000 E FDB60000 E 

FDB80000 E FDBA0000 E FDBC0000 E FDBE0000 E FDC00000 E 

FDC20000 E FDC40000 E FDC60000 E FDC80000 E FDCA0000 E 

FDCC0000 E FDCE0000 E FDD00000 E FDD20000 E FDD40000 E 

FDD60000 E FDD80000 E FDDA0000 E FDDC0000 E FDDE0000 E 

FDE00000 E FDE20000 E FDE40000 E FDE60000 E FDE80000 E 

FDEA0000 E FDEC0000 E FDEE0000 E FDF00000 E FDF20000 E 

FDF40000 E FDF60000 E FDF80000 E FDFA0000 E FDFC0000 E 

FDFE0000 E FE000000 E FE020000 E FE040000 E FE060000 E 

FE080000 E FE0A0000 E FE0C0000 E FE0E0000 E FE100000 E 

FE120000 E FE140000 E FE160000 E FE180000 E FE1A0000 E 

FE1C0000 E FE1E0000 E FE200000 E FE220000 E FE240000 E 

FE260000 E FE280000 E FE2A0000 E FE2C0000 E FE2E0000 E 

FE300000 E FE320000 E FE340000 E FE360000 E FE380000 E 

FE3A0000 E FE3C0000 E FE3E0000 E FE400000 E FE420000 E 

FE440000 E FE460000 E FE480000 E FE4A0000 E FE4C0000 E 

FE4E0000 E FE500000 E FE520000 E FE540000 E FE560000 E 








FE9E0000 E FEA00000 E FEA20000 E FEA40000 E FEA60000 E 

FEA80000 E FEAA0000 E FEAC0000 E FEAE0000 E FEB00000 E 

FEB20000 E FEB40000 E FEB60000 E FEB80000 E FEBA0000 E 

FEBC0000 E FEBE0000 E FEC00000 E FEC20000 E FEC40000 E 

FEC60000 E FEC80000 E FECA0000 E FECC0000 E FECE0000 E 

FED00000 E FED20000 E FED40000 E FED60000 E FED80000 E 

FEDA0000 E FEDC0000 E FEDE0000 E FEE00000 E FEE20000 E 

FEE40000 E FEE60000 E FEE80000 E FEEA0000 E FEEC0000 E 

FEEE0000 E FEF00000 E FEF20000 E FEF40000 E FEF60000 E 

FEF80000 E FEFA0000 E FEFC0000 E FEFE0000 E FF000000 E 

FF020000 E FF040000 E FF060000 E FF080000 E FF0A0000 E 

FF0C0000 E FF0E0000 E FF100000 E FF120000 E FF140000 E 

FF160000 E FF180000 E FF1A0000 E FF1C0000 E FF1E0000 E 

FF200000 E FF220000 E FF240000 E FF260000 E FF280000 E 

FF2A0000 E FF2C0000 E FF2E0000 E FF300000 E FF320000 E 

FF340000 E FF360000 E FF380000 E FF3A0000 E FF3C0000 E 

FF3E0000 E FF400000 E FF420000 E FF440000 E FF460000 E 

FF480000 E FF4A0000 E FF4C0000 E FF4E0000 E FF500000 E 








FF980000 E FF9A0000 E FF9C0000 E FF9E0000 E FFA00000 E 

FFA20000 E FFA40000 E FFA60000 E FFA80000 E FFAA0000 E 

FFAC0000 E FFAE0000 E FFB00000 E FFB20000 E FFB40000 E 

FFB60000 E FFB80000 E FFBA0000 E FFBC0000 E FFBE0000 E 

FFC00000 E FFC20000 E FFC40000 E FFC60000 E FFC80000 E 

FFCA0000 E FFCC0000 E FFCE0000 E FFD00000 E FFD20000 E 

FFD40000 E FFD60000 E FFD80000 E FFDA0000 E FFDC0000 E 

5.9.1.3. flinfo - print FLASH memory information 46

FFDE0000 E FFE00000 E FFE20000 E FFE40000 E FFE60000 E 

FFE80000 E FFEA0000 E FFEC0000 E FFEE0000 E FFF00000 E 

FFF20000 E FFF40000 E FFF60000 RO FFF80000 RO FFFA0000 RO 

FFFC0000 RO FFFE0000 RO 

=> 

5.9.1.4. iminfo - print header information for application 

image 

=> help iminfo 

iminfo addr [addr ...] 

- print header information for application image starting at 

address 'addr' in memory; this includes verification of the 

image contents (magic number, header and payload checksums) 

=> 

iminfo (short: imi) is used to print the header information for images like Linux kernels or ramdisks. It 

prints (among other information) the image name, type and size and verifies that the CRC32 checksums stored 

within the image are OK. 

/tftpboot/canyonlands/uImage-duts: u-boot/PPCBoot image 

=> setenv bootfile /tftpboot/canyonlands/uImage-duts 

=> 

=> setenv ram_ws 100000 

=> tftp ${ram_ws} ${bootfile} 

Waiting for PHY auto negotiation to complete... done 

ENET Speed is 1000 Mbps - FULL duplex connection (EMAC0) 

Using ppc_4xx_eth0 device 

TFTP from server 192.168.1.1; our IP address is 192.168.100.6 

Filename '/tftpboot/canyonlands/uImage-duts'. 

Load address: 0x100000 

Loading: *T ################################################################# 

###################################################### 

done 

Bytes transferred = 1744326 (1a9dc6 hex) 

=> 

=> imi 100000 

## Checking Image at 00100000 ... 

Legacy image found 

Image Name: Linux-2.6.25-rc8-01016-g94bf13b- 

Created: 2008-04-10 9:50:08 UTC 

Image Type: PowerPC Linux Kernel Image (gzip compressed) 

Data Size: 1744262 Bytes = 1.7 MB 

Load Address: 00000000 

Entry Point: 00000000 

Verifying Checksum ... OK 

=> 

Like with many other commands, the exact operation of this command can be controlled by the settings of 

some U-Boot environment variables (here: the verify variable). See below for details. 

5.9.1.5. help - print online help 

=> help help 

help [command ...] 

- show help information (for 'command') 

'help' prints online help for the monitor commands. 

5.9.1.4. iminfo - print header information for application image 47

Without arguments, it prints a short usage message for all commands. 

To get detailed help information for specific commands you can type 

'help' with one or more command names as arguments. 

=> 

The help command (short: h or ) prints online help. Without any arguments, it prints a list of all U-Boot 

commands that are available in your configuration of U-Boot. You can get detailed information for a specific 

command by typing its name as argument to the help command: 

=> help protect 

protect on start end 

- protect FLASH from addr 'start' to addr 'end' 

protect on start +len 

- protect FLASH from addr 'start' to end of sect w/addr 'start'+'len'-1 

protect on N:SF[-SL] 

- protect sectors SF-SL in FLASH bank # N 

protect on bank N 

- protect FLASH bank # N 

protect on all 

- protect all FLASH banks 

protect off start end 

- make FLASH from addr 'start' to addr 'end' writable 

protect off start +len 

- make FLASH from addr 'start' to end of sect w/addr 'start'+'len'-1 wrtable 

protect off N:SF[-SL] 

- make sectors SF-SL writable in FLASH bank # N 

protect off bank N 

- make FLASH bank # N writable 

protect off all 

- make all FLASH banks writable 

=> 

5.9.2. Memory Commands 

5.9.2.1. base - print or set address offset 

=> help base 

base 

- print address offset for memory commands 

base off 

- set address offset for memory commands to 'off' 

=> 

You can use the base command (short: ba) to print or set a "base address" that is used as address offset for 

all memory commands; the default value of the base address is 0, so all addresses you enter are used 

unmodified. However, when you repeatedly have to access a certain memory region (like the internal memory 

of some embedded PowerPC processors) it can be very convenient to set the base address to the start of this 

area and then use only the offsets: 

=> base 

Base Address: 0x00000000 

=> 

5.9.2. Memory Commands 48

=> md 0 c 

00000000: ffff0000 00000000 ffffffff ffffffff ................ 

00000010: ffff0000 00000000 ffffffff ffffffff ................ 

00000020: 7c8000a6 70840020 41820008 64630001 |...p.. A...dc.. 

=> 

=> base 100000 

Base Address: 0x00100000 

=> 

=> md 0 c 

00100000: 27051956 6aa09851 47f3731e 0000009e '..Vj..QG.s..... 

00100010: 00000000 00000000 f54c21db 05070600 .........L!..... 

00100020: 6175746f 73637220 6578616d 706c6520 autoscr example 

=> 

5.9.2.2. crc32 - checksum calculation 

The crc32 command (short: crc) can be used to caculate a CRC32 checksum over a range of memory: 

=> crc 100004 3FC 

CRC32 for 00100004 ... 001003ff ==> 3c82ba9d 

=> 

When used with 3 arguments, the command stores the calculated checksum at the given address: 

=> crc 100004 3FC 100000 

CRC32 for 00100004 ... 001003ff ==> 3c82ba9d 

=> 

=> md 100000 4 

00100000: 3c82ba9d 6aa09851 47f3731e 0000009e 

As you can see, the CRC32 checksum was not only printed, but also stored at address 0x100000. 

5.9.2.3. cmp - memory compare 

=> help cmp 

cmp [.b, .w, .l] addr1 addr2 count 

- compare memory 

=> 

With the cmp command you can test of the contents of two memory areas is identical or not. The command 

will either test the whole area as specified by the 3rd (length) argument, or stop at the first difference. 

=> cmp 100000 200000 400 

word at 0x00100000 (0x3c82ba9d) != word at 0x00200000 (0xfda7aec5) 

Total of 0 words were the same 

=> 

=> md 100000 C 

00100000: 3c82ba9d 6aa09851 47f3731e 0000009e 

=> md 200000 C 

00200000: fda7aec5 7c42d757 e4bd86f8 e0f1e5c8 ....|B.W........ 

00200010: 4b74f157 a82c74b8 ea13e792 faec767f Kt.W.,t.......v. 

00200020: 74e3cb5d f4dc3a04 1e65bc42 4bf7bfc0 t..]..:..e.BK... 

=> 

5.9.2.1. base - print or set address offset 49

Like most memory commands the cmp can access the memory in different sizes: as 32 bit (long word), 16 bit 

(word) or 8 bit (byte) data. If invoked just as cmp the default size (32 bit or long words) is used; the same can 

be selected explicitely by typing cmp.l instead. If you want to access memory as 16 bit or word data, you 

can use the variant cmp.w instead; and to access memory as 8 bit or byte data please use cmp.b. 

Please note that the count argument specifies the number of data items to process, i. e. the number of long 

words or words or bytes to compare. 

=> cmp.l 100000 200000 400 

word at 0x00100000 (0x3c82ba9d) != word at 0x00200000 (0xfda7aec5) 

Total of 0 words were the same 

=> 

=> cmp.w 100000 200000 800 

halfword at 0x00100000 (0x3c82) != halfword at 0x00200000 (0xfda7) 

Total of 0 halfwords were the same 

=> 

=> cmp.b 100000 200000 1000 

byte at 0x00100000 (0x3c) != byte at 0x00200000 (0xfd) 

Total of 0 bytes were the same 

=> 

5.9.2.4. cp - memory copy 

=> help cp 

cp [.b, .w, .l] source target count 

- copy memory 

=> 

The cp is used to copy memory areas. 

=> cp 200000 100000 10000 

=> 

The cp understands the type extensions .l, .w and .b : 

=> cp.l 200000 100000 10000 

=> 

=> cp.w 200000 100000 20000 

=> 

=> cp.b 200000 100000 40000 

=> 

5.9.2.5. md - memory display 

=> help md 

md [.b, .w, .l] address [# of objects] 

- memory display 

=> 

The md can be used to display memory contents both as hexadecimal and ASCII data. 

=> md 100000 

5.9.2.3. cmp - memory compare 50




=> 

=> 

=> 

=> 

This command, too, can be used with the type extensions .l, .w and .b : 

=> md.w 100000 

00100000: fda7 aec5 7c42 d757 e4bd 86f8 e0f1 e5c8 ....|B.W........ 

00100010: 4b74 f157 a82c 74b8 Kt.W.,t. 

=> 

=> md.b 100000 

00100000: fd a7 ae c5 7c 42 d7 57 e4 bd 86 f8 ....|B.W.... 

=> 

The last displayed memory address and the value of the count argument are remembered, so when you enter 

md again without arguments it will automatically continue at the next address, and use the same count again. 

=> md.b 100000 20 

00100000: fd a7 ae c5 7c 42 d7 57 e4 bd 86 f8 e0 f1 e5 c8 ....|B.W........ 

00100010: 4b 74 f1 57 a8 2c 74 b8 ea 13 e7 92 fa ec 76 7f Kt.W.,t.......v. 

=> 

=> md.w 100000 

00100000: fda7 aec5 7c42 d757 e4bd 86f8 e0f1 e5c8 ....|B.W........ 

00100010: 4b74 f157 a82c 74b8 ea13 e792 faec 767f Kt.W.,t.......v. 

00100020: 74e3 cb5d f4dc 3a04 1e65 bc42 4bf7 bfc0 t..]..:..e.BK... 

00100030: c744 e937 9da0 3af3 f9f9 7902 bc74 f4a4 .D.7..:...y..t.. 

=> 

=> md 100000 




00100030: c744e937 9da03af3 f9f97902 bc74f4a4 .D.7..:...y..t.. 

00100040: 260fb31b 749b7b0c baadbd0d fa52fadf &...t.{......R.. 

00100050: 2c6cbbf5 ae5613d7 9fdea1bc 45382c8d ,l...V......E8,. 

00100060: 95b49da0 3d5d437b f33686b8 2616d8f9 ....=]C{.6..&... 

00100070: c1f68fdb f849d974 0fe5eb2d 807dae8e .....I.t...-.}.. 

=> 

5.9.2.6. mm - memory modify (auto-incrementing) 

=> help mm 

mm [.b, .w, .l] address 

- memory modify, auto increment address 

=> 

The mm is a method to interactively modify memory contents. It will display the address and current contents 

and then prompt for user input. If you enter a legal hexadecimal number, this new value will be written to the 

address. Then the next address will be prompted. If you don't enter any value and just press ENTER, then the 

contents of this address will remain unchanged. The command stops as soon as you enter any data that is not a 

hex number (like .): 

=> mm 100000 

00100000: fda7aec5 0 

5.9.2.5. md - memory display 51

00100004: 7c42d757 aabbccdd 

00100008: e4bd86f8 01234567 

0010000c: e0f1e5c8 . 

=> 

=> md 100000 10 

00100000: 00000000 aabbccdd 01234567 e0f1e5c8 .........#Eg.... 




=> 

Again this command can be used with the type extensions .l, .w and .b : 

=> mm.w 100000 

00100000: 0000 0101 

00100002: 0000 0202 

00100004: aabb 4321 

00100006: ccdd 8765 

00100008: 0123 . 

=> 

=> md 100000 10 

00100000: 01010202 43218765 01234567 e0f1e5c8 ....C!.e.#Eg.... 




=> 

=> mm.b 100000 

00100000: 01 48 

00100001: 01 65 

00100002: 02 6c 

00100003: 02 6c 

00100004: 43 6f 

00100005: 21 20 

00100006: 87 20 

00100007: 65 20 

00100008: 01 . 

=> 

=> md 100000 10 

00100000: 48656c6c 6f202020 01234567 e0f1e5c8 Hello .#Eg.... 




=> 

5.9.2.7. mtest - simple RAM test 

=> help mtest 

mtest [start [end [pattern]]] 

- simple RAM read/write test 

=> 

The mtest provides a simple memory test. 

=> mtest 100000 200000 

Pattern 00000000 Writing... 

=> 

Reading...Pattern FFFFFFFF Writing... 

5.9.2.6. mm - memory modify (auto-incrementing) 52

This tests writes to memory, thus modifying the memory contents. It will fail when applied to ROM or 

flash memory. 

This command may crash the system when the tested memory range includes areas that are needed for the 

operation of the U-Boot firnware (like exception vector code, or U-Boot's internal program code, stack or 

heap memory areas). 

5.9.2.8. mw - memory write (fill) 

=> help mw 

mw [.b, .w, .l] address value [count] 

- write memory 

=> 

The mw is a way to initialize (fill) memory with some value. When called without a count argument, the value 

will be written only to the specified address. When used with a count, then a whole memory areas will be 

initialized with this value: 

=> md 100000 10 

00100000: 0000000f 00000010 00000011 00000012 ................ 

00100010: 00000013 00000014 00000015 00000016 ................ 

00100020: 00000017 00000018 00000019 0000001a ................ 

00100030: 0000001b 0000001c 0000001d 0000001e ................ 

=> 

=> mw 100000 aabbccdd 

=> 

=> md 100000 10 

00100000: aabbccdd 00000010 00000011 00000012 ................ 

00100010: 00000013 00000014 00000015 00000016 ................ 

00100020: 00000017 00000018 00000019 0000001a ................ 

00100030: 0000001b 0000001c 0000001d 0000001e ................ 

=> 

=> mw 100000 0 6 

=> 

=> md 100000 10 

00100000: 00000000 00000000 00000000 00000000 ................ 

00100010: 00000000 00000000 00000015 00000016 ................ 

00100020: 00000017 00000018 00000019 0000001a ................ 

00100030: 0000001b 0000001c 0000001d 0000001e ................ 

=> 

This is another command that accepts the type extensions .l, .w and .b : 

=> mw.w 100004 1155 6 

=> 

=> md 100000 10 

00100000: 00000000 11551155 11551155 11551155 .....U.U.U.U.U.U 

00100010: 00000000 00000000 00000015 00000016 ................ 

00100020: 00000017 00000018 00000019 0000001a ................ 

00100030: 0000001b 0000001c 0000001d 0000001e ................ 

=> 

=> mw.b 100007 ff 7 

=> 

=> md 100000 10 

00100000: 00000000 115511ff ffffffff ffff1155 .....U.........U 

00100010: 00000000 00000000 00000015 00000016 ................ 

00100020: 00000017 00000018 00000019 0000001a ................ 

00100030: 0000001b 0000001c 0000001d 0000001e ................ 

5.9.2.7. mtest - simple RAM test 53

=> 

5.9.2.9. nm - memory modify (constant address) 

=> help nm 

nm [.b, .w, .l] address 

- memory modify, read and keep address 

=> 

The nm command (non-incrementing memory modify) can be used to interactively write different data several 

times to the same address. This can be useful for instance to access and modify device registers: 

=> nm.b 100000 

00100000: 00 48 

00100000: 48 65 

00100000: 65 6c 

00100000: 6c 6c 

00100000: 6c 6f 

00100000: 6f . 

=> 

=> md 100000 8 

00100000: 6f000000 115511ff ffffffff ffff1155 o....U.........U 

00100010: 00000000 00000000 00000015 00000016 ................ 

=> 

The nm command too accepts the type extensions .l, .w and .b. 

5.9.2.10. loop - infinite loop on address range 

=> help loop 

loop [.b, .w, .l] address number_of_objects 

- loop on a set of addresses 

=> 

The loop command reads in a tight loop from a range of memory. This is intended as a special form of a 

memory test, since this command tries to read the memory as fast as possible. 

This command will never terminate. There is no way to stop it but to reset the board! 

=> loop 100000 8 

5.9.3. Flash Memory Commands 

5.9.3.1. cp - memory copy 

=> help cp 

cp [.b, .w, .l] source target count 

- copy memory 

=> 

5.9.3. Flash Memory Commands 54

The cp command "knows" about flash memory areas and will automatically invoke the necessary flash 

programming algorithm when the target area is in flash memory. 

=> cp.b 100000 FF900000 40000 

Copy to Flash... done 

=> 

Writing to flash memory may fail when the target area has not been erased (see erase below), or if it is 

write-protected (see protect below). 

=> cp.b 100000 FF900000 40000 

Copy to Flash... Can't write to protected Flash sectors 

=> 

Remember that the count argument specifies the number of items to copy. If you have a "length" instead (= 

byte count) you should use cp.b or you will have to calculate the correct number of items. 

5.9.3.2. flinfo - print FLASH memory information 

The command flinfo (short: fli) can be used to get information about the available flash memory. The 

number of flash banks is printed with information about the size and organization into flash "sectors" or erase 

units. For all sectors the start addresses are printed; write-protected sectors are marked as read-only (RO). 

Some configurations of U-Boot also mark empty sectors with an (E). 

=> fli 

































5.9.3.1. cp - memory copy 55




































































5.9.3.2. flinfo - print FLASH memory information 56










=> 

5.9.3.3. erase - erase FLASH memory 

=> help era 

erase start end 

- erase FLASH from addr 'start' to addr 'end' 

erase start +len 

- erase FLASH from addr 'start' to the end of sect w/addr 'start'+'len'-1 

erase N:SF[-SL] 

- erase sectors SF-SL in FLASH bank # N 

erase bank N 

- erase FLASH bank # N 

erase all 

- erase all FLASH banks 

=> 

The erase command (short: era) is used to erase the contents of one or more sectors of the flash memory. It 

is one of the more complex commands; the help output shows this. 

Probably the most frequent usage of this command is to pass the start and end addresses of the area to be 

erased: 

=> era FF900000 FF95FFFF 

... done 


=> 

Note that both the start and end addresses for this command must point exactly at the start resp. end 

addresses of flash sectors. Otherwise the command will not be executed. 

Another way to select certain areas of the flash memory for the erase command uses the notation of flash 

banks and sectors: 

Technically speaking, a bank is an area of memory implemented by one or more memory chips that are 

connected to the same chip select signal of the CPU, and a flash sector or erase unit is the smallest area that 

can be erased in one operation. 

For practical purposes it is sufficient to remember that with flash memory a bank is something that eventually 

may be erased as a whole in a single operation. This may be more efficient (faster) than erasing the same area 

sector by sector. 

[It depends on the actual type of flash chips used on the board if such a fast bank erase algorithm exists, and 

on the implementation of the flash device driver if is actually used.] 

In U-Boot, flash banks are numbered starting with 1, while flash sectors start with 0. 

5.9.3.3. erase - erase FLASH memory 57

To erase the same flash area as specified using start and end addresses in the example above you could also 

type: 

=> era 1:455-456 

Erase Flash Sectors 455-456 in Bank # 1 

.. done 

=> 

To erase a whole bank of flash memory you can use a command like this one: 

=> era bank 1 

Erase Flash Bank # 1 - Warning: 5 protected sectors will not be erased! 

................................................................................................. 

=> 

Note that a warning message is printed because some write protected sectors exist in this flash bank which 

were not erased. 

With the command: 

=> era all 

Erase Flash Bank # 1 - Warning: 5 protected sectors will not be erased! 

................................................................................................. 

=> 

the whole flash memory (except for the write-protected sectors) can be erased. 

5.9.3.4. protect - enable or disable FLASH write protection 

=> help protect 

protect on start end 

- protect FLASH from addr 'start' to addr 'end' 

protect on start +len 

- protect FLASH from addr 'start' to end of sect w/addr 'start'+'len'-1 

protect on N:SF[-SL] 

- protect sectors SF-SL in FLASH bank # N 

protect on bank N 

- protect FLASH bank # N 

protect on all 

- protect all FLASH banks 

protect off start end 

- make FLASH from addr 'start' to addr 'end' writable 

protect off start +len 

- make FLASH from addr 'start' to end of sect w/addr 'start'+'len'-1 wrtable 

protect off N:SF[-SL] 

- make sectors SF-SL writable in FLASH bank # N 

protect off bank N 

- make FLASH bank # N writable 

protect off all 

- make all FLASH banks writable 

=> 

The protect command is another complex one. It is used to set certain parts of the flash memory to 

read-only mode or to make them writable again. Flash memory that is "protected" (= read-only) cannot be 

written (with the cp command) or erased (with the erase command). Protected areas are marked as (RO) 

(for "read-only") in the output of the flinfo command: 

5.9.3.4. protect - enable or disable FLASH write protection 58

=> fli 














































































































=> 

=> prot on FF900000 FF97FFFF 


=> 

=> fli 



































































































FF8E0000 E FF900000 E RO FF920000 E RO FF940000 E RO FF960000 E RO 












=> 

=> era FF900000 FF97FFFF 

- Warning: 4 protected sectors will not be erased! 

done 


=> 

=> prot off 1:455 

Un-Protect Flash Sectors 455-455 in Bank # 1 

=> 

=> fli 



































































































FF8E0000 E FF900000 E RO FF920000 E RO FF940000 E RO FF960000 E RO 












=> 

=> era 1:455 

Erase Flash Sectors 455-455 in Bank # 1 

. done 

=> 

The actual level of protection depends on the flash chips used on your hardware, and on the 

implementation of the flash device driver for this board. In most cases U-Boot provides just a simple 

software-protection, i. e. it prevents you from erasing or overwriting important stuff by accident (like the 

U-Boot code itself or U-Boot's environment variables), but it cannot prevent you from circumventing these 

restrictions - a nasty user who is loading and running his own flash driver code cannot and will not be stopped 

by this mechanism. Also, in most cases this protection is only effective while running U-Boot, i. e. any 

operating system will not know about "protected" flash areas and will happily erase these if requested to do 

so. 

5.9.3.5. mtdparts - define a Linux compatible MTD partition 

scheme 

U-Boot implements two different approaches to define a MTD partition scheme that can be shared easily with 

the linux kernel. 

The first one is to define a single, static partition in your board config file, for example: 

#undef CONFIG_JFFS2_CMDLINE 

#define CONFIG_JFFS2_DEV 

"nor0" 

#define CONFIG_JFFS2_PART_SIZE 0xFFFFFFFF /* use whole device */ 

#define CONFIG_JFFS2_PART_SIZE 0x00100000 /* use 1MB */ 

#define CONFIG_JFFS2_PART_OFFSET 0x00000000 

The second method uses the Linux kernel's mtdparts command line option and dynamic partitioning: 

#define CONFIG_JFFS2_CMDLINE 

#define MTDIDS_DEFAULT "nor1=zuma-1,nor2=zuma-2" 

#define MTDPARTS_DEFAULT "mtdparts=zuma-1:-(jffs2),zuma-2:-(user)" 

Command line of course produces bigger images, and may be inappropriate for some targets, so by default it's 

off. 

The mtdparts command offers an easy to use and powerful interface to define the contents of the 

environment variable of the same name that can be passed as boot argument to the Linux kernel: 

=> help mtdparts 

mtdparts 

- list partition table 

mtdparts delall 

- delete all partitions 

mtdparts del part-id 

5.9.3.5. mtdparts - define a Linux compatible MTD partition scheme 64

- delete partition (e.g. part-id = nand0,1) 

mtdparts add [@] [] [ro] 

- add partition 

mtdparts default 

- reset partition table to defaults 

----- 

this command uses three environment variables: 

'partition' - keeps current partition identifier 

partition := 

:= ,part_num 

'mtdids' - linux kernel mtd device id u-boot device id mapping 

mtdids=[,,...] 

:= = 

:= 'nand'|'nor' 

:= mtd device number, 0... 

:= unique device tag used by linux kernel to find mtd device (mtd->name) 

'mtdparts' - partition list 

mtdparts=mtdparts=[;...] 

:= :[,...] 

:= unique device tag used by linux kernel to find mtd device (mtd->name) 

:= [@][][] 

:= standard linux memsize OR '-' to denote all remaining space 

:= partition start offset within the device 

:= '(' NAME ')' 

:= when set to 'ro' makes partition read-only (not used, passed to kernel) 

For example, on some target system the mtdparts command might display this information: 

=> mtdparts 

device nor0 , # parts = 4 

#: name size offset mask_flags 

0: firmware 0x00100000 0x00000000 1 

1: kernel 0x00180000 0x00100000 0 

2: small-fs 0x00d80000 0x00280000 0 

3: big-fs 0x01000000 0x01000000 0 

active partition: nor0,0 - (firmware) 0x00100000 @ 0x00000000 

defaults: 

mtdids : nor0=TQM5200-0 

mtdparts: mtdparts=TQM5200-0:1m(firmware),1536k(kernel),3584k(small-fs),2m(initrd),8m(misc),16m(b 

The partition table printed here obviously differs from the default value for the mtdparts variable printed in 

the last line. To verify this, we can check the current content of this variable: 

=> print mtdparts 

mtdparts=mtdparts=TQM5200-0:1024k(firmware)ro,1536k(kernel),13824k(small-fs),16m(big-fs) 

and we can see that it exactly matches the partition table printed above. 

Now let's switch back to the default settings: 

5.9.3.5. mtdparts - define a Linux compatible MTD partition scheme 65

=> mtdparts default 

=> mtdparts 



0: firmware 0x00100000 0x00000000 0 

1: kernel 0x00180000 0x00100000 0 

2: small-fs 0x00380000 0x00280000 0 

3: initrd 0x00200000 0x00600000 0 

4: misc 0x00800000 0x00800000 0 

5: big-fs 0x01000000 0x01000000 0 


defaults: 




mtdparts=mtdparts=TQM5200-0:1m(firmware),1536k(kernel),3584k(small-fs),2m(initrd),8m(misc),16m(bi 

Then we delete the last 4 partitions ("small-fs", "initrd", "misc" and "big-fs") ... 

=> mtdparts del small-fs 

=> mtdparts del initrd 

=> mtdparts del misc 

=> mtdparts del big-fs 

=> mtdparts 



0: firmware 0x00100000 0x00000000 0 

1: kernel 0x00180000 0x00100000 0 


defaults: 



... and combine the free space into a singe big partition: 

=> mtdparts add nor0 - new-part 

=> mtdparts 



0: firmware 0x00100000 0x00000000 0 

1: kernel 0x00180000 0x00100000 0 

2: new-part 0x01d80000 0x00280000 0 


defaults: 




mtdparts=mtdparts=TQM5200-0:1m(firmware),1536k(kernel),30208k(new-part) 

5.9.4. Execution Control Commands 

5.9.4. Execution Control Commands 66

5.9.4.1. autoscr - run script from memory 

=> help autoscr 

autoscr [addr] - run script starting at addr - A valid autoscr header must be present 

=> 

With the autoscr command you can run "shell" scripts under U-Boot: You create a U-Boot script image by 

simply writing the commands you want to run into a text file; then you will have to use the mkimage tool to 

convert this text file into a U-Boot image (using the image type script). 

This image can be loaded like any other image file, and with autoscr you can run the commands in such an 

image. For instance, the following text file: 

echo 

echo Network Configuration: 

echo ---------------------- 

echo Target: 

printenv ipaddr hostname 

echo 

echo Server: 

printenv serverip rootpath 

echo 

can be converted into a U-Boot script image using the mkimage command like this: 

Now you can load and execute this script image in U-Boot: 

=> tftp 100000 /tftpboot/canyonlands/example.img 




Filename '/tftpboot/canyonlands/example.img'. 


Loading: *# 

done 

Bytes transferred = 222 (de hex) 

=> 

=> imi 



Image Name: autoscr example script 

Created: 2008-04-02 11:50:54 UTC 

Image Type: PowerPC Linux Script (uncompressed) 

Data Size: 158 Bytes = 0.2 kB 



Contents: 

Image 0: 150 Bytes = 0.1 kB 


=> 

=> autoscr 100000 

## Executing script at 00100000 

Network Configuration: 

---------------------- 

5.9.4.1. autoscr - run script from memory 67

Target: 

ipaddr=192.168.100.6 

hostname=canyonlands 

Server: 

serverip=192.168.1.1 

rootpath=/opt/eldk/ppc_4xxFP 

=> 

5.9.4.2. bootm - boot application image from memory 

=> help bootm 

bootm [addr [arg ...]] 

- boot application image stored in memory 

passing arguments 'arg ...'; when booting a Linux kernel, 

'arg' can be the address of an initrd image 

When booting a Linux kernel which requires a flat device-tree 

a third argument is required which is the address of the 

device-tree blob. To boot that kernel without an initrd image, 

use a '-' for the second argument. If you do not pass a third 

a bd_info struct will be passed instead 

=> 

The bootm command is used to start operating system images. From the image header it gets information 

about the type of the operating system, the file compression method used (if any), the load and entry point 

addresses, etc. The command will then load the image to the required memory address, uncompressing it on 

the fly if necessary. Depending on the OS it will pass the required boot arguments and start the OS at it's entry 

point. 

The first argument to bootm is the memory address (in RAM, ROM or flash memory) where the image is 

stored, followed by optional arguments that depend on the OS. 

Linux requires the flattened device tree blob to be passed at boot time, and bootm expects its third 

argument to be the address of the blob in memory. Second argument to bootm depens on whether an 

initrd initial ramdisk image is to be used. If the kernel should be booted without the initial ramdisk, the 

second argument should be given as "-", otherwise it is interpreted as the start address of initrd (in RAM, 

ROM or flash memory). 

To boot a Linux kernel image without a initrd ramdisk image, the following command can be used: 

=> bootm ${kernel_addr} - ${fdt_addr} 

If a ramdisk image shall be used, you can type: 

=> bootm ${kernel_addr} ${ramdisk_addr} ${fdt_addr} 

Both examples of course imply that the variables used are set to correct addresses for a kernel, fdt blob and a 

initrd ramdisk image. 

When booting images that have been loaded to RAM (for instance using TFTP download) you have to be 

careful that the locations where the (compressed) images were stored do not overlap with the memory needed 

to load the uncompressed kernel. For instance, if you load a ramdisk image at a location in low memory, it 

may be overwritten when the Linux kernel gets loaded. This will cause undefined system crashes. 

5.9.4.2. bootm - boot application image from memory 68

5.9.4.3. go - start application at address 'addr' 

=> help go 

go addr [arg ...] 

- start application at address 'addr' 

passing 'arg' as arguments 

=> 

U-Boot has support for so-called standalone applications. These are programs that do not require the complex 

environment of an operating system to run. Instead they can be loaded and executed by U-Boot directly, 

utilizing U-Boot's service functions like console I/O or malloc() and free(). 

This can be used to dynamically load and run special extensions to U-Boot like special hardware test routines 

or bootstrap code to load an OS image from some filesystem. 

The go command is used to start such standalone applications. The optional arguments are passed to the 

application without modification. For more informatoin see 5.12. U-Boot Standalone Applications. 

5.9.5. Download Commands 

5.9.5.1. bootp - boot image via network using BOOTP/TFTP 

protocol 

=> help bootp 

bootp [loadAddress] [bootfilename] 

=> 

5.9.5.2. dhcp - invoke DHCP client to obtain IP/boot params 

=> help dhcp 

dhcp 

=> 

5.9.5.3. loadb - load binary file over serial line (kermit mode) 

=> help loadb 

loadb [ off ] [ baud ] 

- load binary file over serial line with offset 'off' and baudrate 'baud' 

=> 

With kermit you can download binary data via the serial line. Here we show how to download uImage, the 

Linux kernel image. Please make sure, that you have set up kermit as described in section 4.3. Configuring 

the "kermit" command and then type: 

=> loadb 100000 

## Ready for binary (kermit) download ... 

Ctrl-\c 

(Back at denx.denx.de) 

5.9.5. Download Commands 69

---------------------------------------------------- 

C-Kermit 7.0.197, 8 Feb 2000, for Linux 

Copyright (C) 1985, 2000, 

Trustees of Columbia University in the City of New York. 

Type or HELP for help. 

Kermit> send /bin /tftpboot/pImage 

... 

Kermit> connect 

Connecting to /dev/ttyS0, speed 115200. 

The escape character is Ctrl-\ (ASCII 28, FS) 

Type the escape character followed by C to get back, 

or followed by to see other options. 

---------------------------------------------------- 

= 550260 Bytes 

## Start Addr = 0x00100000 

=> iminfo 100000 


Image Name: Linux-2.4.4 

Created: 2002-07-02 22:10:11 UTC 


Data Size: 550196 Bytes = 537 kB = 0 MB 




5.9.5.4. loads - load S-Record file over serial line 

=> help loads 

loads [ off ] [ baud ] 

- load S-Record file over serial line with offset 'off' and baudrate 'baud' 

=> 

5.9.5.5. rarpboot- boot image via network using RARP/TFTP 

protocol 

=> help rarp 

rarpboot [loadAddress] [bootfilename] 

=> 

5.9.5.6. tftpboot- boot image via network using TFTP 

protocol 

=> help tftp 


=> 

5.9.6. Environment Variables Commands 

5.9.6. Environment Variables Commands 70

5.9.6.1. printenv- print environment variables 

=> help printenv 

printenv 

- print values of all environment variables 

printenv name ... 

- print value of environment variable 'name' 

=> 

The printenv command prints one, several or all variables of the U-Boot environment. When arguments 

are given, these are interpreted as the names of environment variables which will be printed with their values: 

=> printenv ipaddr hostname netmask 

ipaddr=192.168.100.6 


netmask=255.255.0.0 

=> 

Without arguments, printenv prints all a list with all variables in the environment and their values, plus 

some statistics about the current usage and the total size of the memory available for the environment. 

=> printenv 

bootcmd=run flash_self 

bootdelay=5 

baudrate=115200 

loads_echo=1 

preboot=echo;echo Type "run flash_nfs" to mount root filesystem over NFS;echo 


rootpath=/opt/eldk/ppc_4xxFP 

netdev=eth0 

nfsargs=setenv bootargs root=/dev/nfs rw nfsroot=${serverip}:${rootpath} 

ramargs=setenv bootargs root=/dev/ram rw 

addip=setenv bootargs ${bootargs} ip=${ipaddr}:${serverip}:${gatewayip}:${netmask}:${hostname}:${ 

addtty=setenv bootargs ${bootargs} console=ttyS0,${baudrate} 

flash_self=run ramargs addip addtty;bootm ${kernel_addr} ${ramdisk_addr} ${fdt_addr} 

flash_nfs=run nfsargs addip addtty;bootm ${kernel_addr} - ${fdt_addr} 

net_nfs=tftp ${kernel_addr_r} ${bootfile}; tftp ${fdt_addr_r} ${fdt_file}; run nfsargs addip addt 

kernel_addr_r=400000 

initrd_high=30000000 

load=tftp 200000 ${hostname}/u-boot.bin 

update=protect off fffa0000 ffffffff;era fffa0000 ffffffff;cp.b ${fileaddr} fffa0000 ${filesize}; 

upd=run load update 

nload=tftp 200000 ${hostname}/u-boot-nand.bin 

nupdate=nand erase 0 100000;nand write 200000 0 100000;setenv filesize;saveenv 

nupd=run nload nupdate 

pciconfighost=1 

pcie_mode=RP:RP 

ethaddr=5e:ed:18:38:81:85 

eth1addr=5e:ed:18:38:81:86 

ethact=ppc_4xx_eth0 

fdt_addr=FC1E0000 

fdt_addr_r=00b00000 

fdt_file=/tftpboot/canyonlands/canyonlands.dtb 

kernel_addr=FC000000 

ramdisk_addr=FC200000 

stdin=serial 

stdout=serial 

stderr=serial 

ver=U-Boot 1.3.3-rc2-01466-g4f27098 (May 1 2008 - 13:57:57) 

bootfile=/tftpboot/canyonlands/uImage-duts 

5.9.6.1. printenv- print environment variables 71

am_ws=100000 

filesize=1A9DC6 

fileaddr=100000 

netmask=255.255.0.0 

ipaddr=192.168.100.6 

serverip=192.168.1.1 

Environment size: 1647/16379 bytes 

=> 

5.9.6.2. saveenv - save environment variables to persistent 

storage 

=> help saveenv 

saveenv - No help available. 

=> 

All changes you make to the U-Boot environment are made in RAM only. They are lost as soon as you reboot 

the system. If you want to make your changes permanent you have to use the saveenv command to write a 

copy of the environment settings to persistent storage, from where they are automatically loaded during 

startup: 

=> saveenv 





. done 





=> 

5.9.6.3. setenv - set environment variables 

=> help setenv 

setenv name value ... 

- set environment variable 'name' to 'value ...' 

setenv name 

- delete environment variable 'name' 

=> 

To modify the U-Boot environment you have to use the setenv command. When called with exactly one 

argument, it will delete any variable of that name from U-Boot's environment, if such a variable exists. Any 

storage occupied for such a variable will be automatically reclaimed: 

=> setenv foo This is an example value. 

=> 

=> printenv foo 

foo=This is an example value. 

=> 

=> setenv foo 

=> 

=> printenv foo 

5.9.6.2. saveenv - save environment variables to persistent storage 72

## Error: "foo" not defined 

=> 

When called with more arguments, the first one will again be the name of the variable, and all following 

arguments will (concatenated by single space characters) form the value that gets stored for this variable. New 

variables will be automatically created, existing ones overwritten. 

=> printenv bar 

## Error: "bar" not defined 

=> 

=> setenv bar This is a new example. 

=> 

=> printenv bar 

bar=This is a new example. 

=> 

Remember standard shell quoting rules when the value of a variable shall contain characters that have a 

special meaning to the command line parser (like the $ character that is used for variable substitution or the 

semicolon which separates commands). Use the backslash (\) character to escape such special characters, or 

enclose the whole phrase in apstrophes ('). Use "${name}" for variable expansion (see 14.2.15. How the 

Command Line Parsing Works for details). 

=> setenv cons_opts 'console=tty0 console=ttyS0,${baudrate}' 

=> 

=> printenv cons_opts 

cons_opts=console=tty0 console=ttyS0,${baudrate} 

=> 

There is no restriction on the characters that can be used in a variable name except the restrictions imposed 

by the command line parser (like using backslash for quoting, space and tab characters to separate arguments, 

or semicolon and newline to separate commands). Even strange input like "=-/|()+=" is a perfectly legal 

variable name in U-Boot. 

A common mistake is to write 

setenv name=value 

instead of 

setenv name value 

There will be no error message, which lets you believe everything went OK, but it didn't: instead of setting the 

variable name to the value value you tried to delete a variable with the name name=value - this is probably 

not what you intended! Always remember that name and value have to be separated by space and/or tab 

characters! 

5.9.6.4. run - run commands in an environment variable 

=> help run 

run var [...] 

- run the commands in the environment variable(s) 'var' 

=> 

You can use U-Boot environment variables to store commands and even sequences of commands. To execute 

5.9.6.3. setenv - set environment variables 73

such a command, you use the run command: 

=> setenv test echo This is a test;printenv ipaddr;echo Done. 

ipaddr=192.168.100.6 

Done. 

=> 

=> printenv test 

test=echo This is a test 

=> 

=> run test 

This is a test 

=> 

You can call run with several variables as arguments, in which case these commands will be executed in 

sequence: 

=> setenv test2 echo This is another Test;printenv hostname;echo Done. 


Done. 

=> 

=> printenv test test2 

test=echo This is a test 

test2=echo This is another Test 

=> 

=> run test test2 

This is a test 

This is another Test 

=> 

If a U-Boot variable contains several commands (separated by semicolon), and one of these commands 

fails when you "run" this variable, the remaining commands will be executed anyway. 

If you execute several variables with one call to run, any failing command will cause "run" to terminate, i. 

e. the remaining variables are not executed. 

5.9.6.5. bootd - boot default, i.e., run 'bootcmd' 

=> help boot 

boot - No help available. 

=> 

The bootd (short: boot) executes the default boot command, i. e. what happens when you don't interrupt 

the initial countdown. This is a synonym for the run bootcmd command. 

5.9.7. Flattened Device Tree support 

U-Boot is capable of quite comprehensive handling of the flattened device tree blob, implemented by the fdt 

family of commands: 

=> help fdt 

fdt addr [] - Set the fdt location to 

fdt boardsetup 

- Do board-specific set up 

fdt move - Copy the fdt to and make it active 

fdt print [] 

- Recursive print starting at 

fdt list [] - Print one level starting at 

5.9.7. Flattened Device Tree support 74

fdt set [] - Set [to ] 

fdt mknode 

- Create a new node after 

fdt rm [] - Delete the node or 

fdt header 

- Display header info 

fdt bootcpu 

- Set boot cpuid 

fdt memory 

- Add/Update memory node 

fdt rsvmem print 

- Show current mem reserves 

fdt rsvmem add - Add a mem reserve 

fdt rsvmem delete 

- Delete a mem reserves 

fdt chosen - Add/update the /chosen branch in the tree 

NOTE: If the path or property you are setting/printing has a '#' character 

or spaces, you MUST escape it with a \ character or quote it with ". 

=> 

5.9.7.1. fdt addr - select FDT to work on 

First, the blob that is to be operated on should be stored in memory, and U-Boot has to be informed about its 

location by the fdt addr command. Once this command has been issued, all subsequent fdt handling 

commands will use the blob stored at the given address. This address can be changed later on by issuing fdt 

addr or fdt move command. Here's how to load the blob into memory and tell U-Boot its location: 

=> print fdt_addr_r 

fdt_addr_r=00b00000 

=> 

=> print fdt_file 

fdt_file=/tftpboot/canyonlands/canyonlands.dtb 

=> 

=> tftp ${fdt_addr_r} ${fdt_file} 




Filename '/tftpboot/canyonlands/canyonlands.dtb'. 

Load address: 0xb00000 

Loading: *# 

done 

Bytes transferred = 10000 (2710 hex) 

=> 

=> fdt addr ${fdt_addr_r} 

=> 

5.9.7.2. fdt list - print one level 

Having selected the device tree stored in the blob just loaded, we can inspect its contents. As an FDT usually 

is quite extensive, it is easier to get information about the structure by looking at selected levels rather than 

full hierarchies. fdt list allows us to do exactly this. Let's have a look at the hierarchy one level below the 

cpus node: 

Note: Included topic DULGData_canyonlands.UBootFDTCmdList does not exist yet 

5.9.7.3. fdt print - recursive print 

To print a complete subtree we use fdt print. In comparison to the previous example it is obvious that the 

whole subtree is printed: 

=> fdt print / 

/ { 

#address-cells = ; 

5.9.7.1. fdt addr - select FDT to work on 75

#size-cells = ; 

model = "amcc,canyonlands"; 

compatible = "amcc,canyonlands"; 

dcr-parent = ; 

aliases { 

ethernet0 = "/plb/opb/ethernet@ef600e00"; 

ethernet1 = "/plb/opb/ethernet@ef600f00"; 

serial0 = "/plb/opb/serial@ef600300"; 

serial1 = "/plb/opb/serial@ef600400"; 

}; 

cpus { 



cpu@0 { 

device_type = "cpu"; 

model = "PowerPC,460EX"; 

reg = ; 

clock-frequency = ; 

timebase-frequency = ; 

i-cache-line-size = ; 

d-cache-line-size = ; 

i-cache-size = ; 

d-cache-size = ; 

dcr-controller; 

dcr-access-method = "native"; 

linux,phandle = ; 

}; 

}; 

memory { 

device_type = "memory"; 

reg = ; 

}; 

interrupt-controller0 { 

compatible = "ibm,uic-460ex", "ibm,uic"; 

interrupt-controller; 

cell-index = ; 

dcr-reg = ; 



#interrupt-cells = ; 


}; 





dcr-reg = ; 




interrupts = ; 

interrupt-parent = ; 


}; 





dcr-reg = ; 







}; 


5.9.7.3. fdt print - recursive print 76




dcr-reg = ; 







}; 

sdr { 

compatible = "ibm,sdr-460ex"; 

dcr-reg = ; 

}; 

cpr { 

compatible = "ibm,cpr-460ex"; 

dcr-reg = ; 

}; 

plb { 

compatible = "ibm,plb-460ex", "ibm,plb4"; 



ranges; 


sdram { 

compatible = "ibm,sdram-460ex", "ibm,sdram-405gp"; 

dcr-reg = ; 

}; 

mcmal { 

compatible = "ibm,mcmal-460ex", "ibm,mcmal2"; 

dcr-reg = ; 

num-tx-chans = ; 

num-rx-chans = ; 






}; 

ehci@bffd0400 { 

compatible = "ibm,usb-ehci-460ex", "usb-ehci"; 



reg = ; 

}; 

usb@bffd0000 { 

compatible = "ohci-le"; 

reg = ; 



}; 

usbotg@bff80000 { 

compatible = "amcc,usb-otg-460ex"; 

reg = ; 






interrupt-map = ; 

interrupt-map-mask = ; 


}; 

sata@bffd1000 { 

compatible = "amcc,sata-460ex"; 

reg = ; 




}; 

opb { 

compatible = "ibm,opb-460ex", "ibm,opb"; 



ranges = ; 


ebc { 

compatible = "ibm,ebc-460ex", "ibm,ebc"; 

dcr-reg = ; 






nor_flash@0,0 { 

compatible = "amd,s29gl512n", "cfi-flash"; 

bank-width = ; 

reg = ; 



partition@0 { 

label = "kernel"; 

reg = ; 

}; 

partition@1e0000 { 

label = "dtb"; 

reg = ; 

}; 

partition@200000 { 

label = "root"; 

reg = ; 

}; 


label = "user"; 

reg = ; 

}; 

partition@3f60000 { 

label = "env"; 

reg = ; 

}; 

partition@3fa0000 { 

label = "u-boot"; 

reg = ; 

}; 

}; 

}; 

serial@ef600300 { 

device_type = "serial"; 

compatible = "ns16550"; 

reg = ; 

virtual-reg = ; 


current-speed = ; 



}; 




reg = ; 







}; 




reg = ; 






}; 




reg = ; 






}; 

i2c@ef600700 { 

compatible = "ibm,iic-460ex", "ibm,iic"; 

reg = ; 



}; 

i2c@ef600800 { 


reg = ; 



}; 

emac-zmii@ef600d00 { 

compatible = "ibm,zmii-460ex", "ibm,zmii"; 

reg = ; 

}; 

emac-rgmii@ef601500 { 

compatible = "ibm,rgmii-460ex", "ibm,rgmii"; 

reg = ; 

has-mdio; 


}; 

emac-tah@ef601350 { 

compatible = "ibm,tah-460ex", "ibm,tah"; 

reg = ; 


}; 

emac-tah@ef601450 { 


reg = ; 


}; 

ethernet@ef600e00 { 

device_type = "network"; 

compatible = "ibm,emac-460ex", "ibm,emac4"; 







reg = ; 

local-mac-address = [00 00 00 00 00 00]; 

mal-device = ; 

mal-tx-channel = ; 


mal-rx-channel = ; 


max-frame-size = ; 

rx-fifo-size = ; 

tx-fifo-size = ; 

phy-mode = "rgmii"; 

phy-map = ; 

rgmii-device = ; 

rgmii-channel = ; 

tah-device = ; 

tah-channel = ; 

has-inverted-stacr-oc; 

has-new-stacr-staopc; 


}; 

ethernet@ef600f00 { 









reg = ; 

local-mac-address = [00 00 00 00 00 00]; 









phy-map = ; 







mdio-device = ; 


}; 

}; 

pci@c0ec00000 { 

device_type = "pci"; 




compatible = "ibm,plb-pcix-460ex", "ibm,plb-pcix"; 

primary; 

large-inbound-windows; 

enable-msi-hole; 

reg =

}; 

=> 

}; 

}; 

primary; 

port = ; 

reg = ; 

dcr-reg = ; 

sdr-base = ; 

ranges = 

=> fdt mknode / testnode 

=> 

=> fdt list / 

/ { 






testnode { 

}; 

aliases { 

}; 

cpus { 

}; 

5.9.7.4. fdt mknode - create new nodes 81

memory { 

}; 


}; 


}; 


}; 


}; 

sdr { 

}; 

cpr { 

}; 

plb { 

}; 

}; 

=> 

=> fdt list /testnode 

testnode { 

}; 

=> 

5.9.7.5. fdt set - set node properties 

Now, let's create a property at the newly created node; again we'll use fdt list for verification: 

=> fdt set /testnode testprop testvalue 

=> 


testnode { 

testprop = "testvalue"; 

}; 

=> 

5.9.7.6. fdt rm - remove nodes or properties 

The fdt rm command is used to remove nodes and properties. Let's delete the test property created in the 

previous paragraph and verify the results: 

=> fdt rm /testnode testprop 

=> 


testnode { 

}; 

=> 

=> fdt rm /testnode 

=> 

=> fdt list / 

/ { 






aliases { 

}; 

cpus { 

}; 

memory { 

}; 

5.9.7.5. fdt set - set node properties 82

}; 

=> 


}; 


}; 


}; 


}; 

sdr { 

}; 

cpr { 

}; 

plb { 

}; 

5.9.7.7. fdt move - move FDT blob to new address 

To move the blob from one memory location to another we will use the fdt move command. Besides 

moving the blob, it makes the new address the "active" one - similar to fdt addr: 

=> fdt move ${fdt_addr_r} 200000 

=> 

=> fdt list / 

/ { 






aliases { 

}; 

cpus { 

}; 

memory { 

}; 


}; 


}; 


}; 


}; 

sdr { 

}; 

cpr { 

}; 

plb { 

}; 

}; 

=> 

=> fdt mknod / foobar 

=> 

=> fdt list / 

/ { 






foobar { 

}; 

5.9.7.6. fdt rm - remove nodes or properties 83

aliases { 

}; 

cpus { 

}; 

memory { 

}; 


}; 


}; 


}; 


}; 

sdr { 

}; 

cpr { 

}; 

plb { 

}; 

}; 

=> 

=> fdt addr ${fdt_addr_r} 

=> 

=> fdt list / 

/ { 






aliases { 

}; 

cpus { 

}; 

memory { 

}; 


}; 


}; 


}; 


}; 

sdr { 

}; 

cpr { 

}; 

plb { 

}; 

}; 

=> 

5.9.7.8. fdt chosen - fixup dynamic info 

One of the modifications made by U-Boot to the blob before passing it to the kernel is the addition of the 

/chosen node. Linux 2.6 Documentation/powerpc/booting-without-of.txt says that this node is used to store 

"some variable environment information, like the arguments, or the default input/output devices." To force 

U-Boot to add the /chosen node to the current blob, fdt chosen command can be used. Let's now verify 

its operation: 

=> fdt list / 

5.9.7.7. fdt move - move FDT blob to new address 84

{ 






aliases { 

}; 

cpus { 

}; 

memory { 

}; 


}; 


}; 


}; 


}; 

sdr { 

}; 

cpr { 

}; 

plb { 

}; 

}; 

=> 

=> fdt chosen 

=> 

=> fdt list / 

/ { 






chosen { 

}; 

aliases { 

}; 

cpus { 

}; 

memory { 

}; 


}; 


}; 


}; 


}; 

sdr { 

}; 

cpr { 

}; 

plb { 

}; 

}; 

=> 

=> fdt list /chosen 

chosen { 

}; 

=> 

5.9.7.8. fdt chosen - fixup dynamic info 85

Note: fdt boardsetup performs board-specific blob updates, most commonly setting clock frequencies, 

etc. Discovering its operation is left as an excercise for the reader. 

5.9.8. Special Commands 

5.9.8.1. i2c - I2C sub-system 

=> help iprobe 

iprobe 

-discover valid I2C chip addresses 

=> 

=> help icrc32 

icrc32 chip address[.0, .1, .2] count 

- compute CRC32 checksum 

=> 

=> help imw 

imw chip address[.0, .1, .2] value [count] 

- memory write (fill) 

=> 

=> help inm 

inm chip address[.0, .1, .2] 

- memory modify, read and keep address 

=> 

=> help imm 

imm chip address[.0, .1, .2] 

- memory modify, auto increment address 

=> 

=> help imd 

imd chip address[.0, .1, .2] [# of objects] 

- i2c memory display 

=> 

=> help iloop 

iloop chip address[.0, .1, .2] [# of objects] 

- loop, reading a set of addresses 

=> 

5.9.9. Storage devices 

This chapter introduces commands to work with storage devices, i.e. ATA, CF, SATA, SCSI, USB, NAND, 

etc. connected to the board. 

5.9.10. Miscellaneous Commands 

5.9.10.1. echo - echo args to console 

=> help echo 

echo [args..] 

- echo args to console; \c suppresses newline 

5.9.10. Miscellaneous Commands 86

=> 

The echo command echoes the arguments to the console: 

=> echo The quick brown fox jumped over the lazy dog. 

The quick brown fox jumped over the lazy dog. 

=> 

5.9.10.2. reset - Perform RESET of the CPU 

=> help reset 

reset - No help available. 

=> 

The reset command reboots the system. 

5.9.10.3. sleep - delay execution for some time 

=> help sleep 

sleep N 

- delay execution for N seconds (N is _decimal_ !!!) 

=> 

The sleep command pauses execution for the number of seconds given as the argument: 

=> date ; sleep 5 ; date 

Date: 2061-22-03 (Wednesday) Time: 11:25:33 

Date: 2061-22-03 (Wednesday) Time: 11:25:38 

=> 

5.9.10.4. version - print monitor version 

=> help version 

version - No help available. 

=> 

You can print the version and build date of the U-Boot image running on your system using the version 

command (short: vers): 

=> version 

U-Boot 1.3.3-rc2-01466-g4f27098 (May 1 2008 - 13:57:57) 

=> 

5.9.10.5. - alias for 'help' 

You can use as a short form for the help command (see description above). 

5.9.10.1. echo - echo args to console 87

5.10. U-Boot Environment Variables 

The U-Boot environment is a block of memory that is kept on persistent storage and copied to RAM when 

U-Boot starts. It is used to store environment variables which can be used to configure the system. The 

environment is protected by a CRC32 checksum. 

This section lists the most important environment variables, some of which have a special meaning to U-Boot. 

You can use these variables to configure the behaviour of U-Boot to your liking. 

• autoload: if set to "no" (or any string beginning with 'n'), the rarpb, bootp or dhcp commands 

will perform only a configuration lookup from the BOOTP / DHCP server, but not try to load any 

image using TFTP. 

• autostart: if set to "yes", an image loaded using the rarpb, bootp, dhcp, tftp, disk, or 

docb commands will be automatically started (by internally calling the bootm command). 

• baudrate: a decimal number that selects the console baudrate (in bps). Only a predefined list of 

baudrate settings is available. 

When you change the baudrate (using the "setenv baudrate ..." command), U-Boot will switch the 

baudrate of the console terminal and wait for a newline which must be entered with the new speed 

setting. This is to make sure you can actually type at the new speed. If this fails, you have to reset the 

board (which will operate at the old speed since you were not able to saveenv the new settings.) 

If no "baudrate" variable is defined, the default baudrate of 115200 is used. 

• bootargs: The contents of this variable are passed to the Linux kernel as boot arguments (aka 

"command line"). 

• bootcmd: This variable defines a command string that is automatically executed when the initial 

countdown is not interrupted. 

This command is only executed when the variable bootdelay is also defined! 

• bootdelay: After reset, U-Boot will wait this number of seconds before it executes the contents of 

the bootcmd variable. During this time a countdown is printed, which can be interrupted by pressing 

any key. 

Set this variable to 0 boot without delay. Be careful: depending on the contents of your bootcmd 

variable, this can prevent you from entering interactive commands again forever! 

Set this variable to -1 to disable autoboot. 

• bootfile: name of the default image to load with TFTP 

• cpuclk: (Only with MPC859 / MPC866 / MPC885 processors) On some processors, the CPU clock 

frequency can be adjusted by the user (for example to optimize performance versus power 

dissipation). On such systems the cpuclk variable can be set to the desired CPU clock value, in 

MHz. If the cpuclk variable exists and its value is within the compile-time defined limits 

(CFG_866_CPUCLK_MIN and CFG_866_CPUCLK_MAX = minimum resp. maximum allowed CPU 

clock), then the specified value is used. Otherwise, the default CPU clock value is set. 

• ethaddr: Ethernet MAC address for first/only ethernet interface (= eth0 in Linux). 

This variable can be set only once (usually during manufacturing of the board). U-Boot refuses to 

delete or overwrite this variable once it has been set. 

• eth1addr: Ethernet MAC address for second ethernet interface (= eth1 in Linux). 

5.10. U-Boot Environment Variables 88

• eth2addr: Ethernet MAC address for third ethernet interface (= eth2 in Linux). 

... 

• initrd_high: used to restrict positioning of initrd ramdisk images: 

If this variable is not set, initrd images will be copied to the highest possible address in RAM; this is 

usually what you want since it allows for maximum initrd size. If for some reason you want to make 

sure that the initrd image is loaded below the CFG_BOOTMAPSZ limit, you can set this environment 

variable to a value of "no" or "off" or "0". Alternatively, you can set it to a maximum upper address to 

use (U-Boot will still check that it does not overwrite the U-Boot stack and data). 

For instance, when you have a system with 16 MB RAM, and want to reserve 4 MB from use by 

Linux, you can do this by adding "mem=12M" to the value of the "bootargs" variable. However, now 

you must make sure that the initrd image is placed in the first 12 MB as well - this can be done with 

=> setenv initrd_high 00c00000 

Setting initrd_high to the highest possible address in your system (0xFFFFFFFF) prevents U-Boot from 

copying the image to RAM at all. This allows for faster boot times, but requires a Linux kernel with zero-copy 

ramdisk support. 

• ipaddr: IP address; needed for tftp command 

• loadaddr: Default load address for commands like tftp or loads. 

• loads_echo: If set to 1, all characters received during a serial download (using the loads 

command) are echoed back. This might be needed by some terminal emulations (like cu), but may as 

well just take time on others. 

• mtdparts: This variable (usually defined using the mtdparts command) allows to share a common 

MTD partition scheme between U-Boot and the Linux kernel. 

• pram: If the "Protected RAM" feature is enabled in your board's configuration, this variable can be 

defined to enable the reservation of such "protected RAM", i. e. RAM which is not overwritten by 

U-Boot. Define this variable to hold the number of kB you want to reserve for pRAM. Note that the 

board info structure will still show the full amount of RAM. If pRAM is reserved, a new environment 

variable "mem" will automatically be defined to hold the amount of remaining RAM in a form that 

can be passed as boot argument to Linux, for instance like that: 

=> setenv bootargs ${bootargs} mem=\${mem} 

=> saveenv 

This way you can tell Linux not to use this memory, either, which results in a memory region that will not be 

affected by reboots. 

• serverip: TFTP server IP address; needed for tftp command. 

• serial#: contains hardware identification information such as type string and/or serial number. 

This variable can be set only once (usually during manufacturing of the board). U-Boot refuses to 

delete or overwrite this variable once it hass been set. 

• silent: If the configuration option CONFIG_SILENT_CONSOLE has been enabled for your board, 

setting this variable to any value will suppress all console messages. Please see 

doc/README.silent for details. 

5.10. U-Boot Environment Variables 89

• verify: If set to n or no disables the checksum calculation over the complete image in the bootm 

command to trade speed for safety in the boot process. Note that the header checksum is still verified. 

The following environment variables may be used and automatically updated by the network boot commands 

(bootp, dhcp, or tftp), depending the information provided by your boot server: 

• bootfile: see above 

• dnsip: IP address of your Domain Name Server 

• gatewayip: IP address of the Gateway (Router) to use 

• hostname: Target hostname 

• ipaddr: see above 

• netmask: Subnet Mask 

• rootpath: Pathname of the root filesystem on the NFS server 

• serverip: see above 

• filesize: Size (as hex number in bytes) of the file downloaded using the last bootp, dhcp, or 

tftp command. 

5.11. U-Boot Scripting Capabilities 

U-Boot allows to store commands or command sequences in a plain text file. Using the mkimage tool you 

can then convert this file into a script image which can be executed using U-Boot's autoscr command. 

For example, assume that you will have to run the following sequence of commands on many boards, so you 

store them in a text file, say "setenv-commands": 

bash$ cat setenv-commands 

setenv loadaddr 00200000 

echo ===== U-Boot settings ===== 

setenv u-boot /tftpboot/TQM860L/u-boot.bin 

setenv u-boot_addr 40000000 

setenv load_u-boot 'tftp ${loadaddr} ${u-boot}' 

setenv install_u-boot 'protect off ${u-boot_addr} +${filesize};era ${u-boot_addr} +${filesize};cp 

setenv update_u-boot run load_u-boot install_u-boot 

echo ===== Linux Kernel settings ===== 

setenv bootfile /tftpboot/TQM860L/uImage 

setenv kernel_addr 40040000 

setenv load_kernel 'tftp ${loadaddr} ${bootfile};' 

setenv install_kernel 'era ${kernel_addr} +${filesize};cp.b ${loadaddr} ${kernel_addr} ${filesize 

setenv update_kernel run load_kernel install_kernel 

echo ===== Ramdisk settings ===== 

setenv ramdisk /tftpboot/TQM860L/uRamdisk 

setenv ramdisk_addr 40100000 

setenv load_ramdisk 'tftp ${loadaddr} ${ramdisk};' 

setenv install_ramdisk 'era ${ramdisk_addr} +${filesize};cp.b ${loadaddr} ${ramdisk_addr} ${files 

setenv update_ramdisk run load_ramdisk install_ramdisk 

echo ===== Save new definitions ===== 

saveenv 

bash$ 

To convert the text file into a script image for U-Boot, you have to use the mkimage tool as follows: 

bash$ mkimage -T script -C none -n 'Demo Script File' -d setenv-commands setenv.img 

Image Name: Demo Script File 

Created: Mon Jun 6 13:33:14 2005 


Data Size: 1147 Bytes = 1.12 kB = 0.00 MB 

Load Address: 0x00000000 

Entry Point: 0x00000000 

5.11. U-Boot Scripting Capabilities 90

Contents: 

Image 0: 1139 Bytes = 1 kB = 0 MB 

bash$ 

On the target, you can download this image as usual (for example, using the "tftp" command). Use the 

"autoscr" command to execute it: 

=> tftp 100000 /tftpboot/TQM860L/setenv.img 

Using FEC ETHERNET device 


Filename '/tftpboot/TQM860L/setenv.img'. 


Loading: # 

done 

Bytes transferred = 1211 (4bb hex) 

=> imi 100000 


Image Name: Demo Script File 

Created: 2005-06-06 11:33:14 UTC 






=> autoscr 100000 

## Executing script at 00100000 

===== U-Boot settings ===== 

===== Linux Kernel settings ===== 

===== Ramdisk settings ===== 

===== Save new definitions ===== 





. done 





=> 

Hint: maximum flexibility can be achieved if you are using the Hush shell as command interpreter in 

U-Boot; see section 14.2.15. How the Command Line Parsing Works 

5.12. U-Boot Standalone Applications 

U-Boot supports "standalone" applications, which are loaded dynamically; these applications can have access 

to the U-Boot console I/O functions, memory allocation and interrupt services. 

A couple of simple examples are included with the U-Boot source code: 

5.12.1. "Hello World" Demo 

examples/hello_world.c contains a small "Hello World" Demo application; it is automatically compiled when 

you build U-Boot. It's configured to run at address 0x00040004, so you can play with it like that: 

=> loads 

## Ready for S-Record download ... 

~>examples/hello_world.srec 

1 2 3 4 5 6 7 8 9 10 11 ... 

5.12. U-Boot Standalone Applications 91

[file transfer complete] 

[connected] 

## Start Addr = 0x00040004 

=> go 40004 Hello World! This is a test. 

## Starting application at 0x00040004 ... 

Hello World 

argc = 7 

argv[0] = "40004" 

argv[1] = "Hello" 

argv[2] = "World!" 

argv[3] = "This" 

argv[4] = "is" 

argv[5] = "a" 

argv[6] = "test." 

argv[7] = "" 

Hit any key to exit ... 

## Application terminated, rc = 0x0 

Alternatively, you can of course use TFTP to download the image over the network. In this case the binary 

image (hello_world.bin) is used. 

Note that the entry point of the program is at offset 0x0004 from the start of file, i. e. the download address 

and the entry point address differ by four bytes. 

=> tftp 40000 /tftpboot/hello_world.bin 

... 

=> go 40004 This is another test. 


Hello World 

argc = 5 

argv[0] = "40004" 

argv[1] = "This" 

argv[2] = "is" 

argv[3] = "another" 

argv[4] = "test." 

argv[5] = "" 

Hit any key to exit ... 

## Application terminated, rc = 0x0 

5.12.2. Timer Demo 

This example is only available on MPC8xx CPUs. 

This example, which demonstrates how to register a CPM interrupt handler with the U-Boot code, can be 

found in examples/timer.c. Here, a CPM timer is set up to generate an interrupt every second. The interrupt 

service routine is trivial, just printing a '.' character, but this is just a demo program. The application can be 

controlled by the following keys: 

- print current values og the CPM Timer registers 

b - enable interrupts and start timer 

e - stop timer and disable interrupts 

q - quit application 

=> loads 

## Ready for S-Record download ... 

~>examples/timer.srec 

1 2 3 4 5 6 7 8 9 10 11 ... 

[file transfer complete] 

5.12.1. "Hello World" Demo 92

[connected] 

## Start Addr = 0x00040004 

=> go 40004 


TIMERS=0xfff00980 

Using timer 1 

tgcr @ 0xfff00980, tmr @ 0xfff00990, trr @ 0xfff00994, tcr @ 0xfff00998, tcn @ 0xfff0099c, t 

Hit 'b': 

[q, b, e, ] Set interval 1000000 us 

Enabling timer 

Hit '': 

[q, b, e, ] ........ 

tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0xef6, ter=0x0 

Hit '': 

[q, b, e, ] . 

tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x2ad4, ter=0x0 

Hit '': 

[q, b, e, ] . 

tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x1efc, ter=0x0 

Hit '': 

[q, b, e, ] . 

tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x169d, ter=0x0 

Hit 'e': 

[q, b, e, ] ...Stopping timer 

Hit 'q': 

[q, b, e, ] ## Application terminated, rc = 0x0 

5.13. U-Boot Image Formats 

U-Boot operates on "image" files which can be basically anything, preceeded by a special header; see the 

definitions in include/image.h for details; basically, the header defines the following image properties: 

• Target Operating System (Provisions for OpenBSD, NetBSD, FreeBSD, 4.4BSD, Linux, SVR4, Esix, 

Solaris, Irix, SCO, Dell, NCR, LynxOS, pSOS, QNX, RTEMS, ARTOS, Unity OS; Currently 

supported: Linux, NetBSD, VxWorks, QNX, RTEMS, ARTOS, Unity OS). 

• Target CPU Architecture (Provisions for Alpha, ARM, Intel x86, IA64, MIPS, MIPS, PowerPC, IBM 

S390, SuperH, Sparc, Sparc 64 Bit, M68K, NIOS; Currently supported: ARM, PowerPC, MIPS, 

MIPS64, M68K, NIOS). 

• Compression Type (Provisions for uncompressed, gzip, bzip2; Currently supported: uncompressed, 

gzip, bzip2). 

• Load Address 

• Entry Point 

• Image Name 

• Image Timestamp 

The header is marked by a special Magic Number, and both the header and the data portions of the image are 

secured against corruption by CRC32 checksums. 

5.13. U-Boot Image Formats 93

5.14. U-Boot Advanced Features 

5.14.1. Boot Count Limit 

The Open Source Development Labs Carrier Grade Linux Requirements Definition version 2.0 

(http://www.osdl.org/docs/carrier_grade_linux_requirements_definition___version_20_final_public_draft.pdf) 

contains the following requirement definition (ID PLT.4.0, p. 44): 

CGL shall provide support for detecting a repeating reboot cycle due to recurring failures and will go to an 

offline state if this occurs. 

This feature is available in U-Boot if you enable the CONFIG_BOOTCOUNT_LIMIT configuration option. 

The implementation uses the following environment variables: 

bootcount: 

This variable will be automatically created if it does not exist, and it will be updated at each reset of 

the processor. After a power-on reset, it will be initialized with 1, and each reboot will increment the 

value by 1. 

bootlimit: 

If this variable exists, its contents are taken as the maximum number of reboot cycles allowed. 

altbootcmd: 

If, after a reboot, the new value of bootcount exceeds the value of bootlimit, then instead of 

the standard boot action (executing the contents of bootcmd) an alternate boot action will be 

performed, and the contents of altbootcmd will be executed. 

If the variable bootlimit is not defined in the environment, the Boot Count Limit feature is disabled. If it is 

enabled, but altbootcmd is not defined, then U-Boot will drop into interactive mode and remain there. 

It is the responsibility of some application code (typically a Linux application) to reset the variable 

bootcount, thus allowing for more boot cycles. 

At the moment, the Boot Count Limit feature is available only for MPC8xx and MPC82xx PowerPC 

processors. 

• ubootBootcountAccess.c: C-source: bootcount access through /proc file system 

5.14.2. Bitmap Support 

By adding the CFG_CMD_BMP option to your CONFIG_COMMANDS command selections you can enable 

support for bitmap images in U-Boot. This will add bmp to the list of commands in your configuration of 

U-Boot: 

=> help bmp 

bmp info - display image info 

bmp display - display image 

This command can be used to show information about bitmap images or to display the images on your screen. 

Example: 

5.14.2. Bitmap Support 94

=> tftp 100000 /tftpboot/LWMON/denk_startup.bmp 


Filename '/tftpboot/LWMON/denk_startup.bmp'. 


Loading: ############################################################# 

done 

Bytes transferred = 308278 (4b436 hex) 

=> bmp info 100000 

Image size : 640 x 480 

Bits per pixel: 8 

Compression : 0 

=> bmp display 100000 

To keep the code in U-Boot simple and as fast as possible, the bitmap images must match the color depth of 

your framebuffer device. For example, if your display is configured for a color depth of 8 bpp (bit per pixel) 

then the bmp command will complain if you try to load images with a different color depth: 

=> tftp 100000 /tftpboot/LWMON/Bergkirchen.bmp 


Filename '/tftpboot/LWMON/Bergkirchen.bmp'. 


Loading: ################################################################# 

################################################################# 

################################################### 

done 

Bytes transferred = 921654 (e1036 hex) 

=> bmp i 100000 




=> bmp d 100000 

Error: 8 bit/pixel mode, but BMP has 24 bit/pixel 

(As you can see above, the sub-commands "info" and "display" can be abbreviated as "i" resp. "d" .) 

Images that are bigger than your framebuffer device will be clipped on the top and right hand side. 

Images that are smaller than the display will be loaded into the top left corner. 

Since loading an image will define a new color map, the remainder of the display will appear with 

incorrect colors. It is therefore recommended that all images match exactly the size of the current display 

device. We accepted these restrictions since speed was top priority, and all attempts to implement scaling or 

optimizing the color maps would slow down the display too much. It is much easier to perform the necessary 

transformations on the development host, where a plethora of tools is available. 

For example, to convert existing images to bitmap files with the required color depth (here: 8 bpp), the 

"PBM" -Tools can be used (PBM = portable pix map - see "man 5 ppm" ): 

bash$ jpegtopnm Bergkirchen.jpg | \ 

> ppmquant 256 | \ 

> ppmtobmp -bpp 8 >Bergkirchen-8bit.bmp 

jpegtopnm: WRITING PPM FILE 

ppmquant: making histogram... 

ppmquant: too many colors! 

ppmquant: scaling colors from maxval=255 to maxval=127 to improve clustering... 


ppmquant: too many colors! 

ppmquant: scaling colors from maxval=127 to maxval=63 to improve clustering... 


ppmquant: 9760 colors found 

ppmquant: choosing 256 colors... 

ppmquant: mapping image to new colors... 

5.14.2. Bitmap Support 95

ppmtobmp: analyzing colors... 

ppmtobmp: 231 colors found 

ppmtobmp: Writing 8 bits per pixel with a color pallette 

This gives the following results on the target: 

=> tftp 100000 /tftpboot/LWMON/Bergkirchen-8bit.bmp 


Filename '/tftpboot/LWMON/Bergkirchen-8bit.bmp'. 


Loading: ############################################################# 

done 


=> bmp i 100000 




=> bmp d 100000 

5.14.3. Splash Screen Support 

Even if you manage to boot U-Boot and Linux into a graphical user application within 5 or 6 seconds of 

power-on (which is not difficult), many customers expect to see "something" immediately. U-Boot supports 

the concept of a splash screen for such purposes. 

To enable splash screen support, you have to add a "#define CONFIG_SPLASH_SCREEN" to your board 

configuration file. This will also implicitly enable U-Boot Bitmap Support. 

After power-on, U-Boot will test if the environment variable "splashimage" is defined, and if it contains 

the address of a valid bitmap image. If this is the case, the normal startup messages will be suppressed and the 

defined splash screen will be displayed instead. Also, all output (devices stdout and stderr ) will be 

suppressed (redirected to the "nulldev" device). 

For example, to install this feature on a system, proceed as follows: 

=> tftp 100000 /tftpboot/denx_startup.bmp 


Filename '/tftpboot/denx_startup.bmp'. 


Loading: ############################################################# 

done 


=> cp.b 100000 41F80000 $filesize 


=> setenv splashimage 41F80000 

=> saveenv 




. done 




=> bmp info $splashimage 




Note that, for perfect operation, this option has to be complemented by matching Splash Screen Support in 

5.14.3. Splash Screen Support 96

Linux. 

• 6. Embedded Linux Configuration 

♦ 6.1. Download and Unpack the Linux Kernel Sources 

♦ 6.2. Kernel Configuration and Compilation 


6. Embedded Linux Configuration 

6.1. Download and Unpack the Linux Kernel Sources 

You can download the Linux Kernel Sources from our anonymous git server at http://git.denx.de/. To 

checkout the module for the first time, proceed as follows: 

bash$ cd /opt/eldk/usr/src 

bash$ git clone git://git.denx.de/linux-2.6-denx.git linux-2.6-denx 

bash$ cd linux-2.6-denx 

6.2. Kernel Configuration and Compilation 

The canyonlands board is fully supported by DENX Software Engineering. This means that you will always 

be able to build a working default configuration with just minimal interaction. 

Please be aware that you will need the "powerpc" cross development tools for the following steps. Make sure 

that the directory which contains the binaries of your ELDK are in your PATH. 

To be sure that no intermediate results of previous builds are left in your Linux kernel source tree you can 

clean it up as follows: 

bash$ make mrproper 

The following command selects a standard configuration for the canyonlands board that has been extensively 

tested. It is recommended to use this as a starting point for other, customized configurations: 

bash$ make ARCH=powerpc CROSS_COMPILE=ppc_4xx- canyonlands_defconfig 

Note: The name of this default configuration file is arch/powerpc/configs/XXX_defconfig . By 

listing the contents of the arch/powerpc/configs/ directory you can easily find out which other default 

configurations are available. 

If you don't want to change the default configuration you can now continue to use it to build a kernel image: 

bash$ make ARCH=powerpc CROSS_COMPILE=ppc_4xx- uImage 

Otherwise you can modify the kernel configuration as follows: 

bash$ make ARCH=powerpc CROSS_COMPILE=ppc_4xx- config 

or 

bash$ make ARCH=powerpc CROSS_COMPILE=ppc_4xx- menuconfig 

6. Embedded Linux Configuration 97

Note: Because of problems (especially with some older Linux kernel versions) the use of "make xconfig" 

is not recommended. 

bash$ make ARCH=powerpc CROSS_COMPILE=ppc_4xx- uImage 

The make target uImage uses the tool mkimage (from the U-Boot package) to create a Linux kernel image in 

arch/powerpc/boot/uImage 

which is immediately usable for download and booting with U-Boot. 

In case you configured modules you will also need to compile the modules: 

make ARCH=powerpc CROSS_COMPILE=ppc_4xx- modules 

add install the modules (make sure to pass the correct root path for module installation): 

bash$ make ARCH=powerpc CROSS_COMPILE=ppc_4xx- INSTALL_MOD_PATH=/opt/eldk-4.2/ppc_4xx modules_ins 


For now it is sufficient to copy the Linux kernel image into the directory used by your TFTP server: 

bash$ cp arch/powerpc/boot/uImage /tftpboot/uImage 

• 7. Booting Embedded Linux 

♦ 7.1. Introduction 

♦ 7.2. Flattened Device Tree Blob 

♦ 7.3. Passing Kernel Arguments 

♦ 7.4. Boot Arguments Unleashed 

♦ 7.5. Networked Operation with Root Filesystem over NFS 

◊ 7.5.1. Bootlog of Linux kernel with Root Filesystem over NFS 

♦ 7.6. Boot from Flash Memory 

♦ 7.7. Standalone Operation with Ramdisk Image 

7. Booting Embedded Linux 

7.1. Introduction 

In principle, if you have a Linux kernel image and the flattened device tree blob somewhere in system 

memory (RAM, ROM, flash...), then all you need to boot the system is the bootm command. Assume a 

Linux kernel image has been stored at address 0xFC000000 and the flattened device tree blob has been stored 

at address 0xFC1E0000 - then you can boot this image with the following command: 

=> bootm FC000000 - FC1E0000 

7.2. Flattened Device Tree Blob 

Linux kernel expects certain information on the hardware that it runs on. For kernels compiled with 

ARCH=powerpc, this information has the form of a device tree, which is based on the Open Firmware 

7.2. Flattened Device Tree Blob 98

specification. Bootloaders like U-Boot that do not implement the Open Firmware API, are expected to pass to 

the kernel a binary form of the flattened device tree, commonly referred to as FDT blob or simply the blob. 

Device trees are defined in human-readable text files, which are part of the Linux 2.6 source tree. Device tree 

source for the canyonlands board is found in arch/powerpc/boot/dts/canyonlands.dts file. 

Before the device tree can be passed to the kernel, it has to be compiled to the binary form by the dtc 

compiler. Current version of the dtc compiler is maintained at, and can be downloaded from, 

http://www.jdl.com/. It is also included with ELDK 4.2. Here's how to compile the blob for canyonlands: 

dtc -b 0 -V 17 -p 0x1000 -I dts -O dtb -f arch/powerpc/boot/dts/canyonlands.dts > /tftpboot/canyo 

After the blob has been compiled, it has to be transferred to target's memory, for example over the TFTP 

protocol using U-Boot's tftp command. Then, the blob is passed to the kernel by the bootm command, and 

its address in memory is one of the arguments to bootm - refer to the description of this command in 

UBootCmdGroupExec for more details. Note that U-Boot makes some automatic modifications to the blob 

before passing it to the kernel - mainly adding and modifying information that is learnt at run-time. 

U-Boot also has provisions to alter a flattened device tree in arbitrary ways from the command line, refer to 

the description of the fdt commands found in UBootCmdGroupMisc. 

Notes: 

• Flattened Device Tree custodian's page at http://www.denx.de/wiki/U-Boot/UBootFdtInfo contains 

useful information, and a number of references. 

• At the time of this writing (September 2007) blob handling is still a very fresh feature and undergonig 

frequent changes. Reader is encouraged to watch the u-boot-users and linuxppc-dev mailing 

lists for important news (required version of the dtc compiler, blob compilation options, flattened 

device tree source file structure, etc.). 

7.3. Passing Kernel Arguments 

In nearly all cases, you will want to pass additional information to the Linux kernel; for instance, information 

about the root device or network configuration. 

In U-Boot, this is supported using the bootargs environment variable. Its contents are automatically passed 

to the Linux kernel as boot arguments (or "command line" arguments). This allows the use of the same Linux 

kernel image in a wide range of configurations. For instance, by just changing the contents of the bootargs 

variable you can use the very same Linux kernel image to boot with an initrd ramdisk image, with a root 

filesystem over NFS, with a CompactFlash disk or from a flash filesystem. 

As one example, to boot the Linux kernel image at address 0x200000 using the initrd ramdisk image at 

address 0x400000 as root filesystem, and with the flattened device tree blob at address 0x600000, you can use 

the following commands: 

=> setenv bootargs root=/dev/ram rw 

=> bootm 200000 400000 600000 

To boot the same kernel image with a root filesystem over NFS, the following command sequence can be 

used. This example assumes that your NFS server has the IP address "192.168.1.1" and exports the directory 

"/opt/eldk-4.2/ppc_4xx" as root filesystem for the target. The target has been assigned the IP address 

"192.168.100.6" and the hostname "canyonlands". A netmask of "255.255.0.0" is used: 

=> setenv bootargs root=/dev/nfs rw nfsroot=192.168.1.1:/opt/eldk-4.2/ppc_4xx ip=192.168.100.6:19 

=> bootm 200000 - 600000 

7.3. Passing Kernel Arguments 99

Please see also the files Documentation/initrd.txt and Documentation/nfsroot.txt in your 

Linux kernel source directory for more information about which options can be passed to the Linux kernel. 

Note: Once your system is up and running, if you have a simple shell login, you can normally examine the 

boot arguments that were used by the kernel for the most recent boot with the command: 

$ cat /proc/cmdline 

7.4. Boot Arguments Unleashed 

Passing command line arguments to the Linux kernel allows for very flexible and efficient configuration 

which is especially important in Embedded Systems. It is somewhat strange that these features are nearly 

undocumented everywhere else. One reason for that is certainly the very limited capabilities of other boot 

loaders. 

It is especially U-Boot's capability to easily define, store, and use environment variables that makes it such a 

powerful tool in this area. In the examples above we have already seen how we can use for instance the root 

and ip boot arguments to pass information about the root filesystem or network configuration. The ip 

argument is not only useful in configurations with root filesystem over NFS; if the Linux kernel has the 

CONFIG_IP_PNP configuration enabled (IP kernel level autoconfiguration), this can be used to enable 

automatic configuration of IP addresses of devices and of the routing table during kernel boot, based on either 

information supplied on the kernel command line or by BOOTP or RARP protocols. 

The advantage of this mechanism is that you don't have to spend precious system memory (RAM and flash) 

for network configuration tools like ifconfig or route - especially in Embedded Systems where you 

seldom have to change the network configuration while the system is running. 

We can use U-Boot environment variables to store all necessary configuration parameters: 

=> setenv ipaddr 192.168.100.6 

=> setenv serverip 192.168.1.1 

=> setenv netmask 255.255.0.0 

=> setenv hostname canyonlands 

=> setenv rootpath /opt/eldk-4.2/ppc_4xx 

=> saveenv 

Then you can use these variables to build the boot arguments to be passed to the Linux kernel: 

=> setenv nfsargs 'root=/dev/nfs rw nfsroot=${serverip}:${rootpath}' 

Note how apostrophes are used to delay the substitution of the referenced environment variables. This way, 

the current values of these variables get inserted when assigning values to the "bootargs" variable itself 

later, i. e. when it gets assembled from the given parts before passing it to the kernel. This allows us to simply 

redefine any of the variables (say, the value of "ipaddr" if it has to be changed), and the changes will 

automatically propagate to the Linux kernel. 

Note: You cannot use this method directly to define for example the "bootargs" environment variable, 

as the implicit usage of this variable by the "bootm" command will not trigger variable expansion - this 

happens only when using the "setenv" command. 

In the next step, this can be used for a flexible method to define the "bootargs" environment variable by 

using a function-like approach to build the boot arguments step by step: 

=> setenv ramargs setenv bootargs root=/dev/ram rw 

=> setenv nfsargs 'setenv bootargs root=/dev/nfs rw nfsroot=${serverip}:${rootpath}' 

7.4. Boot Arguments Unleashed 100

=> setenv addip 'setenv bootargs ${bootargs} ip=${ipaddr}:${serverip}:${gatewayip}:${netmask}:${h 

=> setenv ram_root 'run ramargs addip;bootm ${kernel_addr} ${ramdisk_addr} ${fdt_addr} ' 

=> setenv nfs_root 'run nfsargs addip;bootm ${kernel_addr} - ${fdt_addr} ' 

In this setup we define two variables, ram_root and nfs_root, to boot with root filesystem from a 

ramdisk image or over NFS, respecively. The variables can be executed using U-Boot's run command. These 

variables make use of the run command itself: 

• First, either run ramargs or run nfsargs is used to initialize the bootargs environment 

variable as needed to boot with ramdisk image or with root over NFS. 

• Then, in both cases, run addip is used to append the ip parameter to use the Linux kernel IP 

autoconfiguration mechanism for configuration of the network settings. 

• Finally, the bootm command is used with three resp. two address arguments to boot the Linux kernel 

image with resp. without a ramdisk image. (We assume here that the variables kernel_addr , 

ramdisk_addr and fdt_addr have already been set.) 

This method can be easily extended to add more customization options when needed. 

If you have used U-Boot's network commands before (and/or read the documentation), you will probably have 

recognized that the names of the U-Boot environment variables we used in the examples above are exactly the 

same as those used with the U-Boot commands to boot over a network using DHCP or BOOTP. That means 

that, instead of manually setting network configuration parameters like IP address, etc., these variables will be 

set automatically to the values retrieved with the network boot protocols. This will be explained in detail in 

the examples below. 

7.5. Networked Operation with Root Filesystem 

over NFS 

You can use the printenv command on the Target to find out which commands get executed by U-Boot to 

load and boot the Linux kernel: 

=> printenv 

bootcmd=bootp %MIF_KIB_ADDR_R%; setenv bootargs root=/dev/nfs rw nfsroot=${serverip}:${rootpath} 

bootdelay=5 


stdin=serial 

stdout=serial 

stderr=serial 

... 

After Power-On or reset the system will initialize and then wait for a key-press on the console port. The 

duration of this countdown is determined by the contents of the bootdelay environment variable (default: 5 

seconds). 

If no key is pressed, the command (or the list of commands) stored in the environment variable bootcmd is 

executed. If you press a key, you get a prompt at the console port which allows for interactive command input. 

In the example above the following commands are executed sequentially: 

bootp %MIF_KIB_ADDR_R% 

setenv bootargs root=/dev/nfs nfsroot=${serverip}:${rootpath} ip=${ipaddr}:${serverip}:${gatewayi 

bootm %MIF_KIB_ADDR_R% - 

7.5. Networked Operation with Root Filesystem over NFS 101

These commands take the following effect (pay attention for the modification of environment variables by 

these commands): 

• bootp: This command uses the BOOTP protocol to ask a boot server for information about our 

system and to load a boot image (which will usually be a multi-image file containing a Linux kernel 

and a flattened device tree blob). The command will use passed address of %MIF_KIB_ADDR_R% 

to load the file. 

=> bootp %MIF_KIB_ADDR_R% 

BOOTP broadcast 1 

ARP broadcast 0 


Filename '%MIF_KIB%' 

Load address: 0x%MIF_KIB_ADDR_R% 

Loading: ######################################################################################## 

done 

=> printenv 

bootcmd=bootp %MIF_KIB_ADDR_R%; setenv bootargs root=/dev/nfs rw nfsroot=${serverip}:${rootpath} 

bootdelay=5 


stdin=serial 

stdout=serial 

stderr=serial 

bootfile=%MIF_KIB% 

gatewayip=192.168.1.1 

netmask=255.255.0.0 


rootpath=/opt/eldk-4.2/ppc_4xx 

ipaddr=192.168.100.6 

serverip=192.168.1.1 

dnsip=192.168.1.1 

... 

The Target sends a BOOTP request on the network, and (assuming there is a BOOTP server available) 

receives a reply that contains the IP address (ipaddr=192.168.100.6) and other network information 

for the target (hostname=canyonlands, serverip=192.168.1.1, gatewayip=192.168.1.1, 

netmask=255.255.0.0). 

Also, the name of the boot image (bootfile= %MIF_KIB% ) and the root directory on a NFS server 

(rootpath=/opt/eldk-4.2/ppc_4xx) was transmitted. 

U-Boot then automatically downloaded the bootimage from the server using TFTP. 

You can use the command iminfo (Image Info, or short imi) to verify the contents of the loaded image: 

/tftpboot/canyonlands/uImage-duts: u-boot/PPCBoot image 

=> setenv bootfile /tftpboot/canyonlands/uImage-duts 

=> 


=> tftp ${ram_ws} ${bootfile} 







Loading: *T ################################################################# 

###################################################### 


done 


=> 

=> imi 100000 




Created: 2008-04-10 9:50:08 UTC 






=> 

This tells you that we loaded a compressed Linux kernel image, and that the file was not corrupted, since the 

CRC32 checksum is OK. 

setenv bootargs root=/dev/nfs rw nfsroot=${serverip}:${rootpath} \ 

ip=${ipaddr}:${serverip}:${gatewayip}:${netmask}:${hostname}::off 

This command defines the environment variable bootargs. (If an old definition exists, it is deleted first). 

The contents of this variable is passed as command line to the LInux kernel when it is booted (hence the 

name). Note how U-Boot uses variable substitution to dynamically modify the boot arguments depending on 

the information we got from the BOOTP server. 

To verify, you can run this command manually: 

=> setenv bootargs root=/dev/nfs rw nfsroot=${serverip}:${rootpath} ip=${ipaddr}:${serverip}:${ga 

=> printenv 

... 

bootargs=root=/dev/nfs rw nfsroot=192.168.1.1:/opt/eldk-4.2/ppc_4xx ip=192.168.100.6:192.168.1.1: 

... 

This command line passes the following information to the Linux kernel: 

• root=/dev/nfs rw: the root filesystem will be mounted using NFS, and it will be writable. 

• nfsroot=192.168.1.1:/opt/eldk-4.2/ppc_4xx: the NFS server has the IP address 

192.168.1.1, and exports the directory /opt/eldk-4.2/ppc_4xx for our system to use as root filesystem. 

• ip=192.168.100.6:192.168.1.1:192.168.1.1:255.255.0.0:canyonlands::off: 

the target has the IP address 192.168.100.6; the NFS server is 192.168.1.1; there is a 

gateway at IP address 192.168.1.1; the netmask is 255.255.0.0 and our hostname is 

canyonlands. The first ethernet interface (eth0) willbe used, and the Linux kernel will 

immediately use this network configuration and not try to re-negotiate it (IP autoconfiguration is 

off). 

See Documentation/nfsroot.txt in you Linux kernel source directory for more information about these 

parameters and other options. 

• bootm: This command boots an operating system image that resides somewhere in the system 

memory (RAM or flash - the m in the name is for memory). In this case we passed 

%MIF_KIB_ADDR_R% as the address of the multi-image file. 


7.5.1. Bootlog of Linux kernel with Root Filesystem over 

NFS 

=> 

=> setenv rootpath /opt/eldk/ppc_4xx/ 

=> run flash_nfs 

## Booting kernel from Legacy Image at fc000000 ... 


Created: 2008-04-10 9:50:08 UTC 






Uncompressing Kernel Image ... OK 

## Flattened Device Tree blob at fc1e0000 

Booting using the fdt blob at 0xfc1e0000 

Loading Device Tree to 007fd000, end 007ff70f ... OK 

Using Canyonlands machine description 

Linux version 2.6.25-rc8-01016-g94bf13b-dirty (stefan@ubuntu) (gcc version 4.2.2) #54 Thu Apr 10 

Zone PFN ranges: 

DMA 0 -> 65536 

Normal 65536 -> 65536 

Movable zone start PFN for each node 

early_node_map[1] active PFN ranges 

0: 0 -> 65536 

Built 1 zonelists in Zone order, mobility grouping on. Total pages: 65024 

Kernel command line: root=/dev/nfs rw nfsroot=192.168.1.1:/opt/eldk/ppc_4xx/ ip=192.168.100.6:192 

UIC0 (32 IRQ sources) at DCR 0xc0 

UIC1 (32 IRQ sources) at DCR 0xd0 

UIC2 (32 IRQ sources) at DCR 0xe0 

UIC3 (32 IRQ sources) at DCR 0xf0 

PID hash table entries: 1024 (order: 10, 4096 bytes) 

clocksource: timebase mult[6aaaab] shift[22] registered 

Dentry cache hash table entries: 32768 (order: 5, 131072 bytes) 

Inode-cache hash table entries: 16384 (order: 4, 65536 bytes) 

Memory: 255872k/262144k available (3464k kernel code, 6028k reserved, 124k data, 132k bss, 156k i 

SLUB: Genslabs=10, HWalign=32, Order=0-1, MinObjects=4, CPUs=1, Nodes=1 

Mount-cache hash table entries: 512 

net_namespace: 152 bytes 

NET: Registered protocol family 16 

PCIE1: Checking link... 

PCIE1: No device detected. 

PCI host bridge /plb/pciex@d20000000 (primary) ranges: 

MEM 0x0000000e80000000..0x0000000effffffff -> 0x0000000080000000 

IO 0x0000000f80010000..0x0000000f8001ffff -> 0x0000000000000000 

4xx PCI DMA offset set to 0x00000000 

PCIE1: successfully set as root-complex 

PCI host bridge /plb/pci@c0ec00000 (primary) ranges: 

MEM 0x0000000d80000000..0x0000000dffffffff -> 0x0000000080000000 

IO 0x0000000c08000000..0x0000000c0800ffff -> 0x0000000000000000 


PCI: Probing PCI hardware 

PCI: Hiding 4xx host bridge resources 0000:80:00.0 

PCI: Bridge: 0000:80:00.0 

IO window: disabled. 

MEM window: disabled. 

PREFETCH window: disabled. 

SCSI subsystem initialized 

usbcore: registered new interface driver usbfs 

usbcore: registered new interface driver hub 

usbcore: registered new device driver usb 


IP route cache hash table entries: 2048 (order: 1, 8192 bytes) 

7.5.1. Bootlog of Linux kernel with Root Filesystem over NFS 104

TCP established hash table entries: 8192 (order: 4, 65536 bytes) 

TCP bind hash table entries: 8192 (order: 3, 32768 bytes) 

TCP: Hash tables configured (established 8192 bind 8192) 

TCP reno registered 

io scheduler noop registered 

io scheduler anticipatory registered (default) 

io scheduler deadline registered 

io scheduler cfq registered 

Serial: 8250/16550 driver $Revision: 1.2 $ 4 ports, IRQ sharing enabled 

serial8250.0: ttyS0 at MMIO 0x4ef600300 (irq = 18) is a 16550A 

console [ttyS0] enabled 




4ef600300.serial: ttyS0 at MMIO 0x4ef600300 (irq = 18) is a 16550A 




brd: module loaded 

Intel(R) PRO/1000 Network Driver - version 7.3.20-k2-NAPI 

Copyright (c) 1999-2006 Intel Corporation. 

PPC 4xx OCP EMAC driver, version 3.54 

MAL v2 /plb/mcmal, 2 TX channels, 16 RX channels 

ZMII /plb/opb/emac-zmii@ef600d00 initialized 

RGMII /plb/opb/emac-rgmii@ef601500 initialized with MDIO support 

TAH /plb/opb/emac-tah@ef601350 initialized 


/plb/opb/emac-rgmii@ef601500: input 0 in RGMII mode 

eth0: EMAC-0 /plb/opb/ethernet@ef600e00, MAC 5e:ed:18:38:81:85 

eth0: found Generic MII PHY (0x00) 


eth1: EMAC-1 /plb/opb/ethernet@ef600f00, MAC 5e:ed:18:38:81:86 


Driver 'sd' needs updating - please use bus_type methods 

sata_dwc: DW SATA host Id=0x00000000, Version=0x3138322a 

dw_ahb_dma_init: start=4bffd0800 size=400 

sata_dwc: SATA DMA initialized registers=0xd1054800 

scsi0 : sata-dwc 

ata1: SATA max UDMA/133 irq 22 

sata_dwc_error_handler 

ata_eh_recover: line 2646 

ata_eh_reset: line 2127 






ata1: SATA link down (SStatus 0 SControl 300) 




4cc000000.nor_flash: Found 1 x16 devices at 0x0 in 16-bit bank 

Amd/Fujitsu Extended Query Table at 0x0040 

4cc000000.nor_flash: CFI does not contain boot bank location. Assuming top. 

number of CFI chips: 1 

cfi_cmdset_0002: Disabling erase-suspend-program due to code brokenness. 

RedBoot partition parsing not available 

Creating 6 MTD partitions on "4cc000000.nor_flash": 

0x00000000-0x001e0000 : "kernel" 

0x001e0000-0x00200000 : "dtb" 

0x00200000-0x00400000 : "root" 

0x00400000-0x03f60000 : "user" 

0x03f60000-0x03fa0000 : "env" 

0x03fa0000-0x04000000 : "u-boot" 

NDFC NAND Driver initialized. Chip-Rev: 0x00000111 

NAND device: Manufacturer ID: 0x20, Chip ID: 0x75 (ST Micro NAND 32MiB 3,3V 8-bit) 

Scanning device for bad blocks 


Bad eraseblock 1011 at 0x00fcc000 

Number of partitions 3 

Creating 3 MTD partitions on "NAND 32MiB 3,3V 8-bit": 

0x00000000-0x00060000 : "u-boot" 

0x00060000-0x00068000 : "env" 

0x00068000-0x02000000 : "content" 

ppc-of-ohci 4bffd0000.usb: OF OHCI 

ppc-of-ohci 4bffd0000.usb: new USB bus registered, assigned bus number 1 

ppc-of-ohci 4bffd0000.usb: irq 37, io mem 0x4bffd0000 

usb usb1: configuration #1 chosen from 1 choice 

hub 1-0:1.0: USB hub found 

hub 1-0:1.0: 1 port detected 

usb usb1: New USB device found, idVendor=1d6b, idProduct=0001 

usb usb1: New USB device strings: Mfr=3, Product=2, SerialNumber=1 

usb usb1: Product: OF OHCI 

usb usb1: Manufacturer: Linux 2.6.25-rc8-01016-g94bf13b-dirty ohci_hcd 

usb usb1: SerialNumber: PPC-OF USB 

Initializing USB Mass Storage driver... 

usbcore: registered new interface driver usb-storage 

USB Mass Storage support registered. 

dwc_otg: version 2.60a 22-NOV-2006 

dwc_otg: Shared Tx FIFO mode 

dwc_otg: Using Slave mode 

dwc_otg dwc_otg.0: DWC OTG Controller 

dwc_otg dwc_otg.0: new USB bus registered, assigned bus number 2 

dwc_otg dwc_otg.0: irq 28, io mem 0x00000000 

dwc_otg: dwc_otg_core_host_init: Unable to clear halt on channel 1 

dwc_otg: Init: Port Power op_state=4 






usb usb2: Product: DWC OTG Controller 

usb usb2: Manufacturer: Linux 2.6.25-rc8-01016-g94bf13b-dirty dwc_otg_hcd 

usb usb2: SerialNumber: dwc_otg.0 

i2c /dev entries driver 

IBM IIC driver v2.1 

TCP cubic registered 



RPC: Registered udp transport module. 

RPC: Registered tcp transport module. 

/home/stefan/git/linux-2.6/denx-merge-sr/drivers/rtc/hctosys.c: unable to open rtc device (rtc0) 

eth0: link is down 

IP-Config: Complete: 

device=eth0, addr=192.168.100.6, mask=255.255.0.0, gw=255.255.255.255, 

host=canyonlands, domain=, nis-domain=(none), 

bootserver=192.168.1.1, rootserver=192.168.1.1, rootpath= 

Looking up port of RPC 100003/2 on 192.168.1.1 

eth0: link is up, 1000 FDX, pause enabled 

Looking up port of RPC 100005/1 on 192.168.1.1 

VFS: Mounted root (nfs filesystem). 

Freeing unused kernel memory: 156k init 

modprobe: FATAL: Could not load /lib/modules/2.6.25-rc8-01016-g94bf13b-dirty/modules.dep: No such 


INIT: version 2.86 booting 

Welcome to DENX Embedded Linux Environment 

Press 'I' to enter interactive startup. 



Cannot access the Hardware Clock via any known method. 

Use the --debug option to see the details of our search for an access method. 


Setting clock : Thu Jan 1 01:00:07 CET 1970 [ OK ] 

Building the cache [ OK ] 

Setting hostname canyonlands: [ OK ] 

Mounting local filesystems: [ OK ] 

Enabling /etc/fstab swaps: [ OK ] 

INIT: Entering runlevel: 3 

Entering non-interactive startup 

FATAL: Could not load /lib/modules/2.6.25-rc8-01016-g94bf13b-dirty/modules.dep: No such file or d 

Bringing up loopback interface: [ OK ] 

FATAL: Could not load /lib/modules/2.6.25-rc8-01016-g94bf13b-dirty/modules.dep: No such file or d 

Starting system logger: [ OK ] 

Starting kernel logger: [ OK ] 

Starting rpcbind: [ OK ] 

Mounting NFS filesystems: [ OK ] 

Mounting other filesystems: [ OK ] 

Starting xinetd: [ OK ] 

DENX ELDK version 4.2 build 2008-03-27 

Linux 2.6.25-rc8-01016-g94bf13b-dirty on a ppc 

canyonlands login: root 

Last login: Thu Jan 1 01:00:31 on console 

-bash-3.2# 

7.6. Boot from Flash Memory 

The previous section described how to load the Linux kernel image over ethernet using TFTP. This is 

especially well suited for your development and test environment, when the kernel image is still undergoing 

frequent changes, for instance because you are modifying kernel code or configuration. 

Later in your development cycle you will work on application code or device drivers, which can be loaded 

dynamically as modules. If the Linux kernel remains the same then you can save the time needed for the 

TFTP download and put the kernel image into the flash memory of your canyonlands board. 

The U-Boot command flinfo can be used to display information about the available on-board flash on your 

system: 

=> fli 






















7.6. Boot from Flash Memory 107

























































































=> 

From this output you can see the total amount of flash memory, and how it is divided in blocks (Erase Units 

or Sectors). The RO markers show blocks of flash memory that are write protected (by software) - this is the 

area where U-Boot is stored. The remaining flash memory is available for other use. 

For instance, we can store the Linux kernel image in flash starting at the start address of the next free flash 

sector. Before we can do this we must make sure that the flash memory in that region is empty - a Linux 

kernel image is typically around 600...700 kB, so to be on the safe side we dedicate the whole area from 

0xFC000000 to 0xFC17FFFF for the kernel image. Keep in mind that with flash memory only whole erase 

units can be cleared. 

After having deleted the target flash area, you can download the Linux image and write it to flash. Below is a 

transcript of the complete operation with a final iminfo command to check the newly placed Linux kernel 

image in the flash memory. 

=> 

=> setenv kernel_addr FC000000 

=> 

=> prot off FC000000 FC17FFFF 


=> 

=> era FC000000 FC17FFFF 

............ done 


=> 

=> tftp 100000 /tftpboot/canyonlands/uImage-duts 






Loading: *################################################################# 

###################################################### 

done 


=> 

=> imi 100000 





Created: 2008-04-10 9:50:08 UTC 






=> 


=> 

=> cp.b ${ram_ws} ${kernel_addr} ${filesize} 


=> 

=> iminfo ${kernel_addr} 

## Checking Image at fc000000 ... 



Created: 2008-04-10 9:50:08 UTC 






=> 

=> saveenv 





. done 





=> 

Note how the filesize variable (which gets set by the TFTP transfer) is used to automatically adjust for 

the actual image size. 

Since kernel requires the flattened device tree blob to be passed at boot time, you have to also write the blob 

to the flash memory. Below is a transcript of this operation. 

=> 

=> setenv fdt_addr FC1E0000 

=> 

=> prot off FC1E0000 FC1FFFFF 


=> 

=> era FC1E0000 FC1FFFFF 

. done 


=> 

=> tftp 100000 /tftpboot/canyonlands/canyonlands.dtb 





Filename '/tftpboot/canyonlands/canyonlands.dtb'. 


Loading: *T # 

done 

Bytes transferred = 10000 (2710 hex) 

=> 


=> md 100000 

00100000: d00dfeed 00002710 000000b8 00001b08 ......'......... 

00100010: 00000028 00000011 00000010 00000000 ...(............ 

00100020: 000002f5 00001a50 00000000 00000000 .......P........ 

00100030: 00000000 00000000 00000000 00000000 ................ 

00100040: 00000000 00000000 00000000 00000000 ................ 

00100050: 00000000 00000000 00000000 00000000 ................ 

00100060: 00000000 00000000 00000000 00000000 ................ 

00100070: 00000000 00000000 00000000 00000000 ................ 

00100080: 00000000 00000000 00000000 00000000 ................ 

00100090: 00000000 00000000 00000000 00000000 ................ 

001000a0: 00000000 00000000 00000000 00000000 ................ 

001000b0: 00000000 00000000 00000001 00000000 ................ 

001000c0: 00000003 00000004 00000000 00000002 ................ 

001000d0: 00000003 00000004 0000000f 00000001 ................ 

001000e0: 00000003 00000011 0000001b 616d6363 ............amcc 

001000f0: 2c63616e 796f6e6c 616e6473 00000000 ,canyonlands.... 

=> 


=> 

=> cp.b ${ram_ws} ${fdt_addr} ${filesize} 


=> 

=> md ${fdt_addr} 

fc1e0000: d00dfeed 00002710 000000b8 00001b08 ......'......... 

fc1e0010: 00000028 00000011 00000010 00000000 ...(............ 

fc1e0020: 000002f5 00001a50 00000000 00000000 .......P........ 

fc1e0030: 00000000 00000000 00000000 00000000 ................ 

fc1e0040: 00000000 00000000 00000000 00000000 ................ 

fc1e0050: 00000000 00000000 00000000 00000000 ................ 

fc1e0060: 00000000 00000000 00000000 00000000 ................ 

fc1e0070: 00000000 00000000 00000000 00000000 ................ 

fc1e0080: 00000000 00000000 00000000 00000000 ................ 

fc1e0090: 00000000 00000000 00000000 00000000 ................ 

fc1e00a0: 00000000 00000000 00000000 00000000 ................ 

fc1e00b0: 00000000 00000000 00000001 00000000 ................ 

fc1e00c0: 00000003 00000004 00000000 00000002 ................ 

fc1e00d0: 00000003 00000004 0000000f 00000001 ................ 

fc1e00e0: 00000003 00000011 0000001b 616d6363 ............amcc 

fc1e00f0: 2c63616e 796f6e6c 616e6473 00000000 ,canyonlands.... 

=> 

=> setenv filesize 

=> 

=> saveenv 





. done 





=> 

Now we can boot directly from flash. All we need to do is passing the in-flash address of the image 

(FC000000) and the in-flash address of the flattened device tree (FC1E0000) with the bootm command; we 

also make the definition of the bootargs variable permanent now: 

=> setenv bootcmd bootm FC000000 - FC1E0000 

=> setenv bootargs root=/dev/nfs rw nfsroot=${serverip}:${rootpath} ip=${ipaddr}:${serverip}:${ga 

Use printenv to verify that everything is OK before you save the environment settings: 

=> printenv 


ootdelay=5 


stdin=serial 

stdout=serial 

stderr=serial 

bootcmd=bootm FC000000 - FC1E0000 

bootargs=root=/dev/nfs rw nfsroot=192.168.1.1:/opt/eldk-4.2/ppc_4xx 

ip=192.168.100.6:192.168.1.1:192.168.1.1:255.255.0.0:canyonlands::off 

.... 

=> saveenv 

To test booting from flash you can now reset the board (either by power-cycling it, or using the U-Boot 

command reset), or you can manually call the boot command which will run the commands in the 

bootcmd variable: 


=> run flash_self 



Created: 2008-04-10 9:50:08 UTC 









## Loading init Ramdisk from Legacy Image at fc200000 ... 

Image Name: Simple Embedded Linux Framework 

Created: 2008-03-27 17:13:20 UTC 

Image Type: PowerPC Linux RAMDisk Image (gzip compressed) 






Loading Ramdisk to 0fd11000, end 0fed61bc ... OK 


Found initrd at 0xcfd11000:0xcfed61bc 


DMA 0 -> 65536 

Normal 65536 -> 65536 



0: 0 -> 65536 


7.7. Standalone Operation with Ramdisk Image 

When your application development is completed, you usually will want to run your Embedded System 

standalone, i. e. independent from external resources like NFS filesystems. Instead of mounting the root 

filesystem from a remote server you can use a compressed ramdisk image, which is stored in flash memory 

and loaded into RAM when the system boots. 

Ramdisk images for tests can be found in the ftp://ftp.denx.de/pub/LinuxPPC/usr/src/SELF/images/ 

directories. 

Load the ramdisk image into RAM and write it to flash as follows: 

7.7. Standalone Operation with Ramdisk Image 112

=> setenv ramdisk_addr FC200000 

=> 


=> 

=> prot off FC200000 FC3FFFFF 


=> 

=> era FC200000 FC3FFFFF 

................ done 


=> 

=> tftp 100000 /tftpboot/canyonlands/uRamdisk 




Filename '/tftpboot/canyonlands/uRamdisk'. 


Loading: *################################################################# 

############################################################## 

done 

Bytes transferred = 1855996 (1c51fc hex) 

=> 

=> imi 100000 




Created: 2008-03-27 17:13:20 UTC 






=> 

=> cp.b ${ram_ws} ${ramdisk_addr} ${filesize} 


=> 

=> imi ${ramdisk_addr} 

## Checking Image at fc200000 ... 



Created: 2008-03-27 17:13:20 UTC 






=> 

=> saveenv 





. done 





=> 

To tell the Linux kernel to use the ramdisk image as root filesystem you have to modify the command line 

arguments passed to the kernel, and pass ramdisk image address as the second argument to the bootm 

command (first argument is the memory address of the Linux kernel image, the third one is the memory 


address of the flattened device tree blob): 

=> run flash_self 



Created: 2008-04-10 9:50:08 UTC 









## Loading init Ramdisk from Legacy Image at fc200000 ... 


Created: 2008-03-27 17:13:20 UTC 







Loading Ramdisk to 0fd11000, end 0fed61bc ... OK 



Found initrd at 0xcfd11000:0xcfed61bc 


DMA 0 -> 65536 

Normal 65536 -> 65536 



0: 0 -> 65536 


Kernel command line: root=/dev/ram rw ip=192.168.100.6:192.168.1.1::255.255.0.0:canyonlands:eth0: 

UIC0 (32 IRQ sources) at DCR 0xc0 

UIC1 (32 IRQ sources) at DCR 0xd0 

UIC2 (32 IRQ sources) at DCR 0xe0 

UIC3 (32 IRQ sources) at DCR 0xf0 

PID hash table entries: 1024 (order: 10, 4096 bytes) 

clocksource: timebase mult[6aaaab] shift[22] registered 

Dentry cache hash table entries: 32768 (order: 5, 131072 bytes) 

Inode-cache hash table entries: 16384 (order: 4, 65536 bytes) 

Memory: 253952k/262144k available (3464k kernel code, 7844k reserved, 124k data, 132k bss, 156k i 

SLUB: Genslabs=10, HWalign=32, Order=0-1, MinObjects=4, CPUs=1, Nodes=1 

Mount-cache hash table entries: 512 

net_namespace: 152 bytes 


PCIE1: Checking link... 

PCIE1: No device detected. 

PCI host bridge /plb/pciex@d20000000 (primary) ranges: 

MEM 0x0000000e80000000..0x0000000effffffff -> 0x0000000080000000 

IO 0x0000000f80010000..0x0000000f8001ffff -> 0x0000000000000000 


PCIE1: successfully set as root-complex 

PCI host bridge /plb/pci@c0ec00000 (primary) ranges: 

MEM 0x0000000d80000000..0x0000000dffffffff -> 0x0000000080000000 

IO 0x0000000c08000000..0x0000000c0800ffff -> 0x0000000000000000 


PCI: Probing PCI hardware 

PCI: Hiding 4xx host bridge resources 0000:80:00.0 

PCI: Bridge: 0000:80:00.0 

IO window: disabled. 

MEM window: disabled. 

PREFETCH window: disabled. 


SCSI subsystem initialized 

usbcore: registered new interface driver usbfs 

usbcore: registered new interface driver hub 

usbcore: registered new device driver usb 


IP route cache hash table entries: 2048 (order: 1, 8192 bytes) 

TCP established hash table entries: 8192 (order: 4, 65536 bytes) 

TCP bind hash table entries: 8192 (order: 3, 32768 bytes) 

TCP: Hash tables configured (established 8192 bind 8192) 

TCP reno registered 

checking if image is initramfs...it isn't (no cpio magic); looks like an initrd 

Freeing initrd memory: 1812k freed 

io scheduler noop registered 

io scheduler anticipatory registered (default) 

io scheduler deadline registered 

io scheduler cfq registered 

Serial: 8250/16550 driver $Revision: 1.2 $ 4 ports, IRQ sharing enabled 


console [ttyS0] enabled 








brd: module loaded 

Intel(R) PRO/1000 Network Driver - version 7.3.20-k2-NAPI 

Copyright (c) 1999-2006 Intel Corporation. 

PPC 4xx OCP EMAC driver, version 3.54 

MAL v2 /plb/mcmal, 2 TX channels, 16 RX channels 

ZMII /plb/opb/emac-zmii@ef600d00 initialized 

RGMII /plb/opb/emac-rgmii@ef601500 initialized with MDIO support 




eth0: EMAC-0 /plb/opb/ethernet@ef600e00, MAC 5e:ed:18:38:81:85 



eth1: EMAC-1 /plb/opb/ethernet@ef600f00, MAC 5e:ed:18:38:81:86 


Driver 'sd' needs updating - please use bus_type methods 

sata_dwc: DW SATA host Id=0x00000000, Version=0x3138322a 

dw_ahb_dma_init: start=4bffd0800 size=400 

sata_dwc: SATA DMA initialized registers=0xd1054800 

scsi0 : sata-dwc 

ata1: SATA max UDMA/133 irq 22 









ata1: SATA link down (SStatus 0 SControl 300) 




4cc000000.nor_flash: Found 1 x16 devices at 0x0 in 16-bit bank 

Amd/Fujitsu Extended Query Table at 0x0040 

4cc000000.nor_flash: CFI does not contain boot bank location. Assuming top. 

number of CFI chips: 1 

cfi_cmdset_0002: Disabling erase-suspend-program due to code brokenness. 

RedBoot partition parsing not available 

Creating 6 MTD partitions on "4cc000000.nor_flash": 

0x00000000-0x001e0000 : "kernel" 


0x001e0000-0x00200000 : "dtb" 

0x00200000-0x00400000 : "root" 

0x00400000-0x03f60000 : "user" 

0x03f60000-0x03fa0000 : "env" 

0x03fa0000-0x04000000 : "u-boot" 

NDFC NAND Driver initialized. Chip-Rev: 0x00000111 

NAND device: Manufacturer ID: 0x20, Chip ID: 0x75 (ST Micro NAND 32MiB 3,3V 8-bit) 

Scanning device for bad blocks 

Bad eraseblock 1011 at 0x00fcc000 

Number of partitions 3 

Creating 3 MTD partitions on "NAND 32MiB 3,3V 8-bit": 

0x00000000-0x00060000 : "u-boot" 

0x00060000-0x00068000 : "env" 

0x00068000-0x02000000 : "content" 

ppc-of-ohci 4bffd0000.usb: OF OHCI 

ppc-of-ohci 4bffd0000.usb: new USB bus registered, assigned bus number 1 

ppc-of-ohci 4bffd0000.usb: irq 37, io mem 0x4bffd0000 






usb usb1: Product: OF OHCI 

usb usb1: Manufacturer: Linux 2.6.25-rc8-01016-g94bf13b-dirty ohci_hcd 

usb usb1: SerialNumber: PPC-OF USB 

Initializing USB Mass Storage driver... 

usbcore: registered new interface driver usb-storage 

USB Mass Storage support registered. 

dwc_otg: version 2.60a 22-NOV-2006 

dwc_otg: Shared Tx FIFO mode 

dwc_otg: Using Slave mode 

dwc_otg dwc_otg.0: DWC OTG Controller 

dwc_otg dwc_otg.0: new USB bus registered, assigned bus number 2 

dwc_otg dwc_otg.0: irq 28, io mem 0x00000000 

dwc_otg: dwc_otg_core_host_init: Unable to clear halt on channel 1 

dwc_otg: Init: Port Power op_state=4 






usb usb2: Product: DWC OTG Controller 

usb usb2: Manufacturer: Linux 2.6.25-rc8-01016-g94bf13b-dirty dwc_otg_hcd 

usb usb2: SerialNumber: dwc_otg.0 

i2c /dev entries driver 

IBM IIC driver v2.1 

TCP cubic registered 



RPC: Registered udp transport module. 

RPC: Registered tcp transport module. 

/home/stefan/git/linux-2.6/denx-merge-sr/drivers/rtc/hctosys.c: unable to open rtc device (rtc0) 

eth0: link is down 

IP-Config: Complete: 

device=eth0, addr=192.168.100.6, mask=255.255.0.0, gw=255.255.255.255, 

host=canyonlands, domain=, nis-domain=(none), 

bootserver=192.168.1.1, rootserver=192.168.1.1, rootpath= 

RAMDISK: Compressed image found at block 0 

VFS: Mounted root (ext2 filesystem). 


eth0: link is up, 1000 FDX, pause enabled 

init started: BusyBox v1.7.1 (2008-03-27 18:07:38 MET) 

starting pid 810, tty '': '/etc/rc.sh' 

starting pid 815, tty '': '/bin/application' 

### Application running ... 

starting pid 821, tty '': '/bin/sh' 

~ # 


~ # 

• 9. Advanced Topics 

♦ 9.1. Flash Filesystems 

◊ 9.1.1. Memory Technology Devices 

◊ 9.1.2. Journalling Flash File System 

◊ 9.1.3. Second Version of JFFS 

◊ 9.1.4. Compressed ROM Filesystem 

♦ 9.2. The TMPFS Virtual Memory Filesystem 


◊ 9.2.2. Kernel Support for tmpfs 

◊ 9.2.3. Usage of tmpfs in Embedded Systems 

♦ 9.3. Adding Swap Space 

♦ 9.4. Splash Screen Support in Linux 

♦ 9.5. Root File System: Design and Building 

◊ 9.5.1. Root File System on a Ramdisk 

◊ 9.5.2. Root File System on a JFFS2 File System 

◊ 9.5.3. Root File System on a cramfs File System 

◊ 9.5.4. Root File System on a Read-Only ext2 File System 

◊ 9.5.5. Root File System on a Flash Card 

◊ 9.5.6. Root File System in a Read-Only File in a FAT File System 

♦ 9.6. Root File System Selection 

♦ 9.7. Overlay File Systems 

♦ 9.8. The Persistent RAM File system (PRAMFS) 


◊ 9.8.2. Example 

9. Advanced Topics 

This section lists some advanced topics of interest to users of U-Boot and Linux. 

9.1. Flash Filesystems 

9.1.1. Memory Technology Devices 

All currently available flash filesystems are based on the Memory Technology Devices MTD layer, so you 

must enable (at least) the following configuration options to get flash filesystem support in your system: 

CONFIG_MTD=y 

CONFIG_MTD_PARTITIONS=y 

CONFIG_MTD_CHAR=y 

CONFIG_MTD_BLOCK=y 

CONFIG_MTD_CFI=y 

CONFIG_MTD_GEN_PROBE=y 

CONFIG_MTD_CFI_AMDSTD=y 

CONFIG_MTD_ROM=y 

CONFIG_MTD_canyonlands=y 

Note: this configuration uses CFI conformant AMD flash chips; you may need to adjust these settings on 

other boards. 

9.1.1. Memory Technology Devices 117

The partition layout of the flash devices is contained in the flat device tree for the system (see 13.1. Flat 

Device Tree). 

Informational messages of the MTD subsystem can be found in the Linux bootlog, i.e. see section 7.5.1. 

Bootlog of Linux kernel with Root Filesystem over NFS. 

One can discover this information in a running system using the proc filesystem: 

-bash-3.2# cat /proc/mtd 

dev: size erasesize name 

mtd0: 001e0000 00020000 "kernel" 

mtd1: 00020000 00020000 "dtb" 

mtd2: 00200000 00020000 "root" 

mtd3: 03b60000 00020000 "user" 

mtd4: 00040000 00020000 "env" 

mtd5: 00060000 00020000 "u-boot" 

mtd6: 02000000 00004000 "NAND 32MiB 3,3V 8-bit" 

mtd7: 00060000 00004000 "u-boot" 

mtd8: 00008000 00004000 "env" 

mtd9: 01f98000 00004000 "content" 

-bash-3.2# 

Now we can run some basic tests to verify that the flash driver routines and the partitioning works as 

expected: 

-bash-3.2# xxd /dev/mtd3 | head -4 

0000000: 5468 7520 4a61 6e20 2031 2030 313a 3034 Thu Jan 1 01:04 

0000010: 3a35 3120 4345 5420 3139 3730 0aff ffff :51 CET 1970.... 

0000020: ffff ffff ffff ffff ffff ffff ffff ffff ................ 

0000030: ffff ffff ffff ffff ffff ffff ffff ffff ................ 

-bash-3.2# 

In the hex-dumps of the MTD devices you can identify some strings that verify that we indeed see an U-Boot 

environment, a Linux kernel, a ramdisk image and an empty partition to play wih. 

The last output shows the partition to be empty. We can try write some data into it: 

-bash-3.2# date > /dev/mtd3 

-bash-3.2# 

-bash-3.2# head -1 /dev/mtd3 

Thu Jan 1 01:04:51 CET 1970 

-bash-3.2# 


-bash-3.2# 

As you can see it worked the first time. When we tried to write the (new date) again, we got an error. The 

reason is that the date has changed (probably at least the seconds) and flash memory cannot be simply 

overwritten - it has to be erased first. 

You can use the eraseall Linux commands to erase a whole MTD partition: 

-bash-3.2# flash_eraseall /dev/mtd3 

Erasing 128 Kibyte @ 0 -- 0 % complete.Erasing 128 Kibyte @ 20000 -- 0 % complete.Erasing 128 K 

-bash-3.2# 


-bash-3.2# 

-bash-3.2# head -1 /dev/mtd3 

9.1.1. Memory Technology Devices 118

Thu Jan 1 01:04:51 CET 1970 

-bash-3.2# 

We have now sufficient proof that the MTD layer is working as expected, so we can try creating a flash 

filesystem. 

9.1.2. Journalling Flash File System 

At the moment it seems that the Journalling Flash File System JFFS is the best choice for filesystems in flash 

memory of embedded devices. You must enable the following configuration options to get JFFS support in 

your system: 

CONFIG_JFFS_FS=y 

CONFIG_JFFS_FS_VERBOSE=0 

If the flash device is erased, we can simply mount it, and the creation of the JFFS filesystem is performed 

automagically. 

Note: For simple accesses like direct read or write operations or erasing you use the character device 

interface (/dev/mtd*) of the MTD layer, while for filesystem operations like mounting we must use the block 

device interface (/dev/mtdblock*). 

# eraseall /dev/mtd2 

Erased 4096 Kibyte @ 0 -- 100% complete. 

# mount -t jffs /dev/mtdblock2 /mnt 

# mount 

/dev/root on / type nfs (rw,v2,rsize=4096,wsize=4096,hard,udp,nolock,addr=10.0.0.2) 

proc on /proc type proc (rw) 

devpts on /dev/pts type devpts (rw) 

/dev/mtdblock2 on /mnt type jffs (rw) 

# df 

Filesystem 1k-blocks Used Available Use% Mounted on 

/dev/root 2087212 1232060 855152 60% / 

/dev/mtdblock2 3584 0 3584 0% /mnt 

Now you can access the files in the JFFS filesystem in the /mnt directory. 

9.1.3. Second Version of JFFS 

Probably even more interesting for embedded systems is the second version of JFFS, JFFS2, since it not only 

fixes a few design issues with JFFS, but also adds transparent compression, so that you can save a lot of 

precious flash memory. 

The mkfs.jffs2 tool is used to create a JFFS2 filesystem image; it populates the image with files from a 

given directory. For instance, to create a JFFS2 image for a flash partition of 3 MB total size and to populate it 

with the files from the /tmp/flashtools directory you would use: 

# mkfs.jffs2 --pad=3145728 --eraseblock=262144 \ 

--root=/tmp/flashtools/ --output image.jffs2 

# eraseall /dev/mtd4 

Erased 3072 Kibyte @ 0 -- 100% complete. 

\# dd if=image.jffs2 of=/dev/mtd4 bs=256k 

12+0 records in 

12+0 records out 

# mount -t jffs2 /dev/mtdblock4 /mnt 

# df /mnt 


/dev/mtdblock4 3072 2488 584 81% /mnt 

9.1.3. Second Version of JFFS 119

Note: Especially when you are running time-critical applications on your system you should carefully 

study if the behaviour of the flash filesystem might have any negative impact on your application. After all, a 

flash device is not a normal harddisk. This is especially important when your flash filesystem gets full; JFFS2 

acts a bit weird then: 

• You will note that an increasing amount of CPU time is spent by the filesystem's garbage collection 

kernel thread. 

• Access times to the files on the flash filesystem may increase drastically. 

• Attempts to truncate a file (to free space) or to rename it may fail: 

... 

# cp /bin/bash file 

cp: writing `file': No space left on device 

# >file 

bash: file: No space left on device 

# mv file foo 

mv: cannot create regular file `foo': No space left on device 

You will have to use rm to actually delete a file in this situation. 

This is especially critical when you are using the flash filesystem to store log files: when your application 

detects some abnormal condition and produces lots of log messages (which usually are especially important in 

this situation) the filesystem may fill up and cause extreme long delays - if your system crashes, the most 

important messages may never be logged at all. 

9.1.4. Compressed ROM Filesystem 

In some cases it is sufficent to have read-only access to some files, and if the files are big enough it becomes 

desirable to use some method of compression. The Compressed ROM Filesystem CramFs might be a 

solution here. 

Please note that CramFs has - beside the fact that it is a read-only filesystem - some severe limitations (like 

missing support for timestamps, hard links, and 16/32 bit uid/gids), but there are many situations in Embedded 

Systems where it's still useful. 

To create a CramFs filesystem a special tool mkcramfs is used to create a file which contains the CramFs 

image. Note that the CramFs filesystem can be written and read only by kernels with PAGE_CACHE_SIZE 

== 4096, and some versions of the mkcramfs program may have other restrictions like that the filesystem 

must be written and read with architectures of the same endianness. Especially the endianness requirement 

makes it impossible to build the CramFs image on x86 PC host when you want to use it on a PowerPC target. 

The endianness problem has been fixed in the version of mkcramfs that comes with the ELDK. 

In some cases you can use a target system running with root filesystem mounted over NFS to create the 

CramFs image on the native system and store it to flash for further use. 

Note: The normal version of the mkcramfs program tries to initialize some entries in the filesystem's 

superblock with random numbers by reading /dev/random; this may hang permanently on your target because 

there is not enough input (like mouse movement) to the entropy pool. You may want to use a modified 

version of mkcramfs which does not depend on /dev/random. 

To create a CramFs image, you put all files you want in the filesystem into one directory, and then use the 

mkcramfs= program as follows: 

9.1.4. Compressed ROM Filesystem 120

$ mkdir /tmp/test 

$ cp ... /tmp/test 

$ du -sk /tmp/test 

64 /tmp/test 

$ mkcramfs /tmp/test test.cramfs.img 

Super block: 76 bytes 

erase 

eraseall 

mkfs.jffs 

lock 

unlock 

Directory data: 176 bytes 

-54.96% (-4784 bytes) erase 

-55.46% (-5010 bytes) eraseall 

-51.94% (-8863 bytes) mkfs.jffs 

-58.76% (-4383 bytes) lock 

-59.68% (-4215 bytes) unlock 

Everything: 24 kilobytes 

$ ls -l test.cramfs.img 

-rw-r--r-- 1 wd users 24576 Nov 10 23:44 test.cramfs.img 

As you can see, the CramFs image test.cramfs.img takes just 24 kB, while the input directory contained 64 kB 

of data. Savings of some 60% like in this case are typical CramFs. 

Now we write the CramFs image to a partition in flash and test it: 

# cp test.cramfs.img /dev/mtd3 

# mount -t cramfs /dev/mtdblock3 /mnt 

# mount 

/dev/root on / type nfs (rw,v2,rsize=4096,wsize=4096,hard,udp,nolock,addr=10.0.0.2) 


devpts on /dev/pts type devpts (rw) 

/dev/mtdblock3 on /mnt type cramfs (rw) 

# ls -l /mnt 

total 54 

-rwxr-xr-x 1 wd users 8704 Jan 9 16:32 erase 

-rwxr-xr-x 1 wd users 9034 Jan 1 01:00 eraseall 

-rwxr-xr-x 1 wd users 7459 Jan 1 01:00 lock 

-rwxr-xr-x 1 wd users 17063 Jan 1 01:00 mkfs.jffs 

-rwxr-xr-x 1 wd users 7063 Jan 1 01:00 unlock 

Note that all the timestamps in the CramFs filesyste are bogus, and so is for instance the output of the df 

command for such filesystems: 

# df /mnt 


/dev/mtdblock3 0 0 0 - /mnt 

9.2. The TMPFS Virtual Memory Filesystem 

The tmpfs filesystem, formerly known as shmfs, is a filesystem keeping all files in virtual memory. 

Everything in tmpfs is temporary in the sense that no files will be created on any device. If you unmount a 

tmpfs instance, everything stored therein is lost. 

tmpfs puts everything into the kernel internal caches and grows and shrinks to accommodate the files it 

contains and is able to swap unneeded pages out to swap space. It has maximum size limits which can be 

adjusted on the fly via 'mount -o remount ...' 

9.2. The TMPFS Virtual Memory Filesystem 121

If you compare it to ramfs (which was the template to create tmpfs) you gain swapping and limit checking. 

Another similar thing is the RAM disk (/dev/ram*), which simulates a fixed size hard disk in physical RAM, 

where you have to create an ordinary filesystem on top. Ramdisks cannot swap and you do not have the 

possibility to resize them. 

9.2.1. Mount Parameters 

tmpfs has a couple of mount options: 

• size: The limit of allocated bytes for this tmpfs instance. The default is half of your physical RAM 

without swap. If you oversize your tmpfs instances the machine will deadlock since the OOM handler 

will not be able to free that memory. 

• nr_blocks: The same as size, but in blocks of PAGECACHE_SIZE. 

• nr_inodes: The maximum number of inodes for this instance. The default is half of the number of 

your physical RAM pages. 

These parameters accept a suffix k, m or g for kilo, mega and giga and can be changed on remount. 

To specify the initial root directory you can use the following mount options: 

• mode: The permissions as an octal number 

• uid: The user id 

• gid: The group id 

These options do not have any effect on remount. You can change these parameters with chmod(1), 

chown(1) and chgrp(1) on a mounted filesystem. 

So the following mount command will give you a tmpfs instance on /mytmpfs which can allocate 12MB of 

RAM/SWAP and it is only accessible by root. 

mount -t tmpfs -o size=12M,mode=700 tmpfs /mytmpfs 

9.2.2. Kernel Support for tmpfs 

In order to use a tmpfs filesystem, the CONFIG_TMPFS option has to be enabled for your kernel 

configuration. It can be found in the Filesystems configuration group. You can simply check if a running 

kernel supports tmpfs by searching the contents of /proc/fileysystems: 

bash# grep tmpfs /proc/filesystems 

nodev tmpfs 

bash# 

9.2.3. Usage of tmpfs in Embedded Systems 

In embedded systems tmpfs is very well suited to provide read and write space (e.g. /tmp and /var) for a 

read-only root file system such as CramFs described in section 9.1.4. Compressed ROM Filesystem. One way 

to achieve this is to use symbolic links. The following code could be part of the startup file /etc/rc.sh of the 

read-only ramdisk: 

#!/bin/sh 

... 

# Won't work on read-only root: mkdir /tmpfs 

mount -t tmpfs tmpfs /tmpfs 

mkdir /tmpfs/tmp /tmpfs/var 

# Won't work on read-only root: ln -sf /tmpfs/tmp /tmpfs/var / 

9.2.1. Mount Parameters 122

... 

The commented out sections will of course fail on a read-only root filesystem, so you have to create the 

/tmpfs mount-point and the symbolic links in your root filesystem beforehand in order to successfully use 

this setup. 

9.3. Adding Swap Space 

If you are running out of system RAM, you can add virtual memory by using swap space. If you reserved a 

swap partition on your disk drive, you have to initialize it once using the mkswap command: 

# fdisk -l /dev/hda 

Disk /dev/hda: 16 heads, 63 sectors, 1575 cylinders 

Units = cylinders of 1008 * 512 bytes 

Device Boot Start End Blocks Id System 

/dev/hda1 1 5 2488+ 83 Linux 

/dev/hda2 6 10 2520 83 Linux 

/dev/hda3 11 141 66024 82 Linux swap 


# mkswap /dev/hda3 

Setting up swapspace version 1, size = 67604480 bytes 

Then, to activate it, you use the swapon command like this: 

# free 

total used free shared buffers cached 

Mem: 14628 14060 568 8056 100 11664 

-/+ buffers/cache: 2296 12332 

Swap: 0 0 0 

# free 


Mem: 14628 14060 568 8056 100 11664 


Swap: 0 0 0 

# swapon /dev/hda3 

Adding Swap: 66016k swap-space (priority -2) 

# free 


Mem: 14628 14084 544 8056 100 11648 


Swap: 66016 0 66016 

If you forgot to reserve (sufficient) space in a separate partition on your disk, you can still use an ordinary file 

for swap space. You only have to create a file of appropriate size, and initialize it as follows: 

# mount /dev/hda4 /mnt 

# df 


/dev/root 2087212 1378824 708388 67% / 

/dev/hda4 711352 20 675196 1% /mnt 

# dd if=/dev/zero of=/mnt/swapfile bs=1024k count=64 



# mkswap /mnt/swapfile 


Then activate it: 

# free 

9.3. Adding Swap Space 123


Mem: 14628 14084 544 6200 96 11788 


Swap: 0 0 0 

# swapon /mnt/swapfile 

Adding Swap: 65528k swap-space (priority -3) 

# free 


Mem: 14628 14084 544 6200 96 11752 


Swap: 65528 0 65528 

9.4. Splash Screen Support in Linux 

To complement the U-Boot Splash Screen feature the new configuration option 

"CONFIG_FB_PRE_INIT_FB" was added to the Linux kernel. This allows the Linux kernel to skip certain 

parts of the framebuffer initialization and to reuse the framebuffer contents that was set up by the U-Boot 

firmware. This allows to have an image displayed nearly immediately after power-on, so the delay needed to 

boot the Linux kernel is masked to the user. 

The current implementation has some limitations: 

• We did not succeed in reusing the previously allocated framebuffer contents directly. Instead, Linux 

will allocate a new framebuffer, copy the contents, and then switch the display. This adds a minimal 

delay to the boot time, but is otherwise invisible to the user. 

• Linux manages its own colormap, and we considered it too much effort to keep the same settings as 

used by U-Boot. Instead we use the "trick" that U-Boot will fill the color map table backwards (top 

down). This works pretty well for images which use no more than 200...255 colors. If the images uses 

more colors, a bad color mapping may result. 

We strongly recommend to convert all images that will be loaded as Linux splash screens to use no 

more than 225 colors. The "ppmquant" tool can be used for this purpose (see Bitmap Support in 

U-Boot for details). 

• Usually there will be a Linux device driver that is used to adjust the brightness and contrast of the 

display. When this driver starts, a visible change of brightness will happen if the default settings as 

used by U-Boot differ. 

We recommend to store settings of brightness and contrast in U-Boot environment variables that 

can be shared between U-Boot and Linux. This way it is possible (assuming adequate driver support) 

to adjust the display settings correctly already in U-Boot and thus to avoid any flicker of the display 

when Linux takes over control. 

9.5. Root File System: Design and Building 

It is not an easy task to design the root file system for an embedded system. There are three major problems to 

be solved: 

1. what to put in it 

2. which file system type to use 

3. where to store and how to boot it 

For now we will assume that the contents of the root file system is aready known; for example, it is given to 

us as a directory tree or a tarball which contains all the required files. 

9.5. Root File System: Design and Building 124

We will also assume that our system is a typical resource-limited embedded system so we will especially look 

for solutions where the root file system can be stored on on-board flash memory or other flash memory based 

devices like CompactFlash or SD cards, MMC or USB memory sticks. 

A widespread approach to build a root file system is to use some Linux distribution (like the ELDK) and to 

remove things not needed. This approach may be pretty common, but it is almost always terribly wrong. You 

also don't build a family home by taking a skyscraper and removing parts. Like a house, a root file system 

should be built bottom up, starting from scratch and adding things you know you need. Never add anything 

where you don't exactly know what it's needed for. 

But our focus here is on the second item: the options we have for chosing a file system type and the 

consequences this has. 

In all cases we will base our experiments on the same content of the root filesystem; we use the images of the 

SELF (Simple Embedded Linux Framework) that come with the ELDK. In a first step we will transform the 

SELF images into a tarball to meet the requirements mentioned above: 

In a ELDK installation, the SELF images can be found in the /opt/eldk//images/ 

directory. There is already a compressed ramdisk image in this directory, which we will use 

(ramdisk_image.gz): 

1. Uncompress ramdisk image: 

bash$ gzip -d -c -v /opt/eldk/ppc_8xx/images/ramdisk_image.gz >/tmp/ramdisk_image 

/opt/eldk/ppc_8xx/images/ramdisk_image.gz: 61.4% 

Note: The following steps require root permissions! 

2. Mount ramdisk image: 

bash# mount -o loop /tmp/ramdisk_image /mnt/tmp 

3. Create tarball; to avoid the need for root permissions in the following steps we don't include the 

device files in our tarball: 

bash# cd /mnt/tmp 

bash# tar -zc --exclude='dev/*' -f /tmp/rootfs.tar.gz * 

4. Instead, we create a separate tarball which contains only the device entries so we can use them when 

necessary (with cramfs): 

bash# tar -zcf /tmp/devices.tar.gz dev/ 

bash# cd /tmp 

5. Unmount ramdisk image: 

bash# umount /mnt/tmp 

We will use the /tmp/rootfs.tar.gz tarball as master file in all following experiments. 

9.5.1. Root File System on a Ramdisk 

Ram disks are used very often to hold the root file system of embedded systems. They have several 

advantages: 

• well-known 

• well-supported by the Linux kernel 

• simple to build 

9.5.1. Root File System on a Ramdisk 125

• simple to use - you can even combine the ramdisk with the Linux kernel into a single image file 

• RAM based, thus pretty fast 

• writable file system 

• original state of file system after each reboot = easy recovery from accidental or malicious data 

corruption etc. 

On the other hand, there are several disadvantages, too: 

• big memory footprint: you always have to load the complete filesystem into RAM, even if only small 

parts of are actually used 

• slow boot time: you have to load (and uncompress) the whole image before the first application 

process can start 

• only the whole image can be replaced (not individual files) 

• additional storage needed for writable persistent data 

Actually there are only very few situations where a ramdisk image is the optimal solution. But because they 

are so easy to build and use we will discuss them here anyway. 

In almost all cases you will use an ext2 file system in your ramdisk image. The following steps are needed to 

create it: 

1. 

Create a directory tree with the content of the target root filesystem. We do this by unpacking our 

master tarball: 

$ mkdir rootfs 

$ cd rootfs 

$ tar zxf /tmp/rootfs.tar.gz 

2. We use the genext2fs tool to create the ramdisk image as this allows to use a simple text file to 

describe which devices shall be created in the generated file system image. That means that no root 

permissions are required at all. We use the following device table rootfs_devices.tab: 

# 

/dev d 755 0 0 - - - - - 

/dev/console c 640 0 0 5 1 - - - 

/dev/fb0 c 640 0 0 29 0 - - - 

/dev/full c 640 0 0 1 7 - - - 

/dev/hda b 640 0 0 3 0 - - - 

/dev/hda b 640 0 0 3 1 1 1 16 

/dev/kmem c 640 0 0 1 2 - - - 

/dev/mem c 640 0 0 1 1 - - - 

/dev/mtd c 640 0 0 90 0 0 2 16 

/dev/mtdblock b 640 0 0 31 0 0 1 16 

/dev/mtdr c 640 0 0 90 1 0 2 16 

/dev/nftla b 640 0 0 93 0 - - - 

/dev/nftla b 640 0 0 93 1 1 1 8 

/dev/nftlb b 640 0 0 93 16 - - - 

/dev/nftlb b 640 0 0 93 17 1 1 8 

/dev/null c 640 0 0 1 3 - - - 

/dev/ptyp c 640 0 0 2 0 0 1 10 

/dev/ptypa c 640 0 0 2 10 - - - 

/dev/ptypb c 640 0 0 2 11 - - - 

/dev/ptypc c 640 0 0 2 12 - - - 

/dev/ptypd c 640 0 0 2 13 - - - 

/dev/ptype c 640 0 0 2 14 - - - 

/dev/ptypf c 640 0 0 2 15 - - - 

/dev/ram b 640 0 0 1 0 0 1 2 

/dev/ram b 640 0 0 1 1 - - - 

/dev/rtc c 640 0 0 10 135 - - - 

/dev/tty c 640 0 0 4 0 0 1 4 

/dev/tty c 640 0 0 5 0 - - - 

/dev/ttyS c 640 0 0 4 64 0 1 8 

9.5.1. Root File System on a Ramdisk 126

3. 

4. 

/dev/ttyp c 640 0 0 3 0 0 1 10 

/dev/ttypa c 640 0 0 3 10 - - - 

/dev/ttypb c 640 0 0 3 11 - - - 

/dev/ttypc c 640 0 0 3 12 - - - 

/dev/ttypd c 640 0 0 3 13 - - - 

/dev/ttype c 640 0 0 3 14 - - - 

/dev/ttypf c 640 0 0 3 15 - - - 

/dev/zero c 640 0 0 1 5 - - - 

A description of the format of this table is part of the manual page for the genext2fs tool, 

genext2fs(8). 

We can now create an ext2 file system image using the genext2fs tool: 

$ ROOTFS_DIR=rootfs # directory with root file system content 

$ ROOTFS_SIZE=3700 # size of file system image 

$ ROOTFS_FREE=100 # free space wanted 

$ ROOTFS_INODES=380 # number of inodes 

$ ROOTFS_DEVICES=rootfs_devices.tab # device description file 

$ ROOTFS_IMAGE=ramdisk.img # generated file system image 

$ genext2fs -U \ 

-d ${ROOTFS_DIR} \ 

-D ${ROOTFS_DEVICES} \ 

-b ${ROOTFS_SIZE} \ 

-r ${ROOTFS_FREE} \ 

-i ${ROOTFS_INODES} \ 

${ROOTFS_IMAGE} 

Compress the file system image: 

$ gzip -v9 ramdisk.img 

rootfs.img: 55.6% -- replaced with ramdisk.img.gz 

5. Create an U-Boot image file from it: 

$ mkimage -T ramdisk -C gzip -n 'Test Ramdisk Image' \ 

> -d ramdisk.img.gz uRamdisk 

Image Name: Test Ramdisk Image 

Created: Sun Jun 12 16:58:06 2005 





We now have a root file system image uRamdisk that can be used with U-Boot. 

9.5.2. Root File System on a JFFS2 File System 

JFFS2 (Journalling Flash File System version 2) was specifically designed for use on flash memory devices in 

embedded systems. It is a log-structured file system which means that it is robust against loss of power, 

crashes or other unorderly shutdowns of the system ("robust" means that data that is just being written when 

the system goes down may be lost, but the file system itself does not get corrupted and the system can be 

rebootet without need for any kind of file system check). 

Some of the advantages of using JFFS2 as root file system in embedded systems are: 

• file system uses compression, thus making efficient use of flash memory 

• log-structured file system, thus robust against unorderly shutdown 

• flash sector wear-leveling 

• writable flash file system 

Disadvantages are: 

9.5.2. Root File System on a JFFS2 File System 127

• long mount times (especially older versions) 

• slow when reading: files to be read get uncompressed on the fly which eats CPU cycles and takes time 

• slow when writing: files to be written get compressed, which eats CPU cycles and takes time, but it 

may even take much longer until data gets actually stored in flash if the file system becomes full and 

blocks must be erased first or - even worse - if garbage collection becomes necessary 

• The garbage collector thread may run at any time, consuming CPU cycles and blocking accesses to 

the file system. 

Despite the aforementioned disadvantages, systems using a JFFS2 based root file system are easy to build, 

make efficient use of the available resources and can run pretty reliably. 

To create a JFFS2 based root file system please proceed as follows: 

1. 




$ cd rootfs 

$ tar zxf /tmp/rootfs.tar.gz 

2. We can now create a JFFS2 file system image using the mkfs.jffs2 tool: 

$ ROOTFS_DIR=rootfs # directory with root file system content 

$ ROOTFS_EBSIZE=0x20000 # erase block size of flash memory 

$ ROOTFS_ENDIAN=b # target system is big endian 

$ ROOTFS_DEVICES=rootfs_devices.tab # device description file 

$ ROOTFS_IMAGE=jffs2.img # generated file system image 

$ mkfs.jffs2 -U \ 

-d ${ROOTFS_DIR} \ 

-D ${ROOTFS_DEVICES} \ 

-${ROOTFS_ENDIAN} \ 

-e ${ROOTFS_EBSIZE} \ 

-o ${ROOTFS_IMAGE} 

mkfs.jffs2: skipping device_table entry '/dev': no parent directory! 

Note: When you intend to write the JFFS2 file system image to a NAND flash device, you should also 

add the "-n" (or "--no-cleanmarkers") option, as cleanmarkers are not needed then. 

When booting the Linux kernel prints the following messages showing the default partition map which is used 

for the flash memory on the TQM8xxL boards: 

TQM flash bank 0: Using static image partition definition 

Creating 7 MTD partitions on "TQM8xxL0": 

0x00000000-0x00040000 : "u-boot" 

0x00040000-0x00100000 : "kernel" 

0x00100000-0x00200000 : "user" 

0x00200000-0x00400000 : "initrd" 

0x00400000-0x00600000 : "cramfs" 

0x00600000-0x00800000 : "jffs" 

0x00400000-0x00800000 : "big_fs" 

We use U-Boot to load and store the JFFS2 image into the last partition and set up the Linux boot arguments 

to use this as root device: 

1. Erase flash: 

=> era 40400000 407FFFFF 

................. done 



2. Download JFFS2 image: 

=> tftp 100000 /tftpboot/TQM860L/jffs2.img 



Filename '/tftpboot/TQM860L/jffs2.img'. 


Loading: ################################################################# 

################################################################# 

################################################################# 

################################################################# 

################################################################# 

################################################################# 

######## 

done 

Bytes transferred = 2033888 (1f08e0 hex) 

3. Copy image to flash: 

=> cp.b 100000 40400000 ${filesize} 


4. set up boot arguments to use flash partition 6 as root device: 

=> setenv mtd_args setenv bootargs root=/dev/mtdblock6 rw rootfstype=jffs2 

=> printenv addip 

addip=setenv bootargs ${bootargs} ip=${ipaddr}:${serverip}:${gatewayip}:${netmask}:${hostna 

=> setenv flash_mtd 'run mtd_args addip;bootm ${kernel_addr}' 

=> run flash_mtd 



Filename '/tftpboot/TQM860L/uImage'. 


Loading: ################################################################# 

################################################################# 

########### 

done 

Bytes transferred = 719233 (af981 hex) 

## Booting image at 40040000 ... 


Created: 2005-06-12 16:32:24 UTC 







Linux version 2.4.25 (wd@xpert) (gcc version 3.3.3 (DENX ELDK 3.1.1 3.3.3-9)) #1 Sun Jun 12 

On node 0 totalpages: 4096 

zone(0): 4096 pages. 



Kernel command line: root=/dev/mtdblock6 rw rootfstype=jffs2 ip=192.168.3.80:192.168.3.1::2 

Decrementer Frequency = 187500000/60 

Calibrating delay loop... 49.86 BogoMIPS 

... 

NET4: Unix domain sockets 1.0/SMP for Linux NET4.0. 

VFS: Mounted root (jffs2 filesystem). 


BusyBox v0.60.5 (2005.03.07-06:54+0000) Built-in shell (msh) 

Enter 'help' for a list of built-in commands. 

# ### Application running ... 

# mount 

rootfs on / type rootfs (rw) 

/dev/mtdblock6 on / type jffs2 (rw) 



# df / 


rootfs 4096 2372 1724 58% / 

9.5.3. Root File System on a cramfs File System 

cramfs is a compressed, read-only file system. 

Advantages are: 

• file system uses compression, thus making efficient use of flash memory 

• Allows for quick boot times as only used files get loaded and uncompressed 

Disadvantages are: 

• only the whole image can be replaced (not individual files) 

• additional storage needed for writable persistent data 

• mkcramfs tool does not support device table, so we need root permissions to create the required 

device files 

To create a cramfs based root file system please proceed as follows: 

1. 




$ cd rootfs 

$ tar -zxf /tmp/rootfs.tar.gz 

2. Create the required device files. We do this here by unpacking a special tarball which holds only the 

device file entries. Note: this requires root permissions! 

# cd rootfs 

# tar -zxf /tmp/devices.tar.gz 

3. Many tools require some storage place in a filesystem, so we must provide at least one (small) 

writable filesystem. For all data which may be lost when the system goes down, a "tmpfs" 

filesystem is the optimal choice. To create such a writable tmpfs filesystem we add the following lines 

to the /etc/rc.sh script: 

# mount TMPFS because root-fs is readonly 

/bin/mount -t tmpfs -o size=2M tmpfs /tmpfs 

Some tools require write permissions on some device nodes (for example, to change ownership and 

permissions), or dynamically (re-) create such files (for example, /dev/log which is usually a Unix 

Domain socket). The files are placed in a writable filesystem; in the root filesystem symbolic links are 

used to point to their new locations: 

dev/ptyp0 → /tmpfs/dev/ptyp0 dev/ttyp0 → /tmpfs/dev/ttyp0 







9.5.3. Root File System on a cramfs File System 130

4. 




dev/ptypa → /tmpfs/dev/ptypa dev/ttypa → /tmpfs/dev/ttypa 

dev/ptypb → /tmpfs/dev/ptypb dev/ttypb → /tmpfs/dev/ttypb 

dev/ptypc → /tmpfs/dev/ptypc dev/ttypc → /tmpfs/dev/ttypc 

dev/ptypd → /tmpfs/dev/ptypd dev/ttypd → /tmpfs/dev/ttypd 

dev/ptype → /tmpfs/dev/ptype dev/ttype → /tmpfs/dev/ttype 

dev/ptypf → /tmpfs/dev/ptypf dev/ttypf → /tmpfs/dev/ttypf 

tmp → /tmpfs/tmp var → /tmpfs/var 

dev/log → /var/log/log 

In case you use dhclient also: 

etc/dhclient.conf → /tmpfs/var/lib/dhclient.conf etc/resolv.conf → /tmpfs/var/lib/resolv.conf 

To place the corresponding directories and device files in the tmpfs file system, the following code 

is added to the /etc/rc.sh script: 

mkdir -p /tmpfs/tmp /tmpfs/dev \ 

/tmpfs/var/lib/dhcp /tmpfs/var/lock /tmpfs/var/run 

while read name minor 

do 

mknod /tmpfs/dev/ptyp$name c 2 $minor 

mknod /tmpfs/dev/ttyp$name c 3 $minor 

done


CRC: c166be6d 

warning: gids truncated to 8 bits. (This may be a security concern.) 

5. We can use the same setup as before for the JFFS2 filesystem, just changing the bootargument to 

"rootfstype=cramfs" 

9.5.4. Root File System on a Read-Only ext2 File 

System 

When storing the root file system in on-board flash memory it seems only natural to look for special flash 

filesystems like JFFS2, or for other file system types that are designed for such environments like cramfs. It 

seems to be a bad idea to use a standard ext2 file system because it contains neither any type of wear 

leveling which is needed for writable file systems in flash memory, nor is it robust against unorderly 

shutdowns. 

The situation changes if we use an ext2 file system which we mount read-only. Such a configuration can be 

very useful in some situations. 

Advantages: 

• very fast 

• low RAM memory footprint 

Disadvantages: 

• high flash memory footprint because no compression 

To create an ext2 image that can be used as a read-only root file system the following steps are necessary: 

1. 




$ cd rootfs 

$ tar -zxf /tmp/rootfs.tar.gz 

2. Like with the cramfs root file system, we use "tmpfs" for cases where a writable file system is 

needed and add the following lines to the /etc/rc.sh script: 

# mount TMPFS because root-fs is readonly 

/bin/mount -t tmpfs -o size=2M tmpfs /tmpfs 

We also create the same symbolic links for device files that must be placed in a writable filesystem: 










9.5.4. Root File System on a Read-Only ext2 File System 132

3. 


dev/ptypa → /tmpfs/dev/ptypa dev/ttypa → /tmpfs/dev/ttypa 

dev/ptypb → /tmpfs/dev/ptypb dev/ttypb → /tmpfs/dev/ttypb 

dev/ptypc → /tmpfs/dev/ptypc dev/ttypc → /tmpfs/dev/ttypc 

dev/ptypd → /tmpfs/dev/ptypd dev/ttypd → /tmpfs/dev/ttypd 

dev/ptype → /tmpfs/dev/ptype dev/ttype → /tmpfs/dev/ttype 

dev/ptypf → /tmpfs/dev/ptypf dev/ttypf → /tmpfs/dev/ttypf 

tmp → /tmpfs/tmp var → /tmpfs/var 

dev/log → /var/log/log 

In case you use dhclient also: 

etc/dhclient.conf → /tmpfs/var/lib/dhclient.conf etc/resolv.conf → /tmpfs/var/lib/resolv.conf 

To place the corresponding directories and device files in the tmpfs file system, the following code 

is added to the /etc/rc.sh script: 

mkdir -p /tmpfs/tmp /tmpfs/dev \ 

/tmpfs/var/lib/dhcp /tmpfs/var/lock /tmpfs/var/run 

while read name minor 

do 

mknod /tmpfs/dev/ptyp$name c 2 $minor 

mknod /tmpfs/dev/ttyp$name c 3 $minor 

done

change the "rw" argument into "ro" to mount our root file system really read-only: 

... 






Kernel command line: root=/dev/mtdblock6 ro rootfstype=ext2 ip=192.168.3.80:192.168.3.1::25 



... 

9.5.5. Root File System on a Flash Card 

Using an ext2 file system on a flash memory card (like CompactFlash, SD, MMC or a USB memory stick) 

is standard technology. To avoid unnecessary flash wear it is a good idea to mount the root file system 

read-only, or at least using the "noatime" mount option. 

For our test we can use the "ext2.img" file from the previous step without changes: 

1. 

In this test we use a standard CompactFlash card which comes with a single partition on it. We use 

U-Boot to copy the ext2 file system image into this partition: 

=> tftp 100000 /tftpboot/TQM860L/ext2.img 



Filename '/tftpboot/TQM860L/ext2.img'. 


Loading: ################################################################# 

################################################################# 

################################################################# 

################################################################# 

################################################################# 

################################################################# 

################################################################# 

################################################################# 

################################################################# 

################################################################# 

################################################################# 

########################## 

done 

Bytes transferred = 3788800 (39d000 hex) 

=> ide part 

Partition Map for IDE device 0 -- 

Partition Type: DOS 

Partition Start Sector Num Sectors Type 

1 32 500704 6 

=> ide write 100000 20 1ce8 

IDE write: device 0 block # 32, count 7400 ... 7400 blocks written: OK 

Note that the "ide write" command takes parameters as hex numbers, and the write count is in 

terms of disk blocks of 512 bytes each. So we have to use 0x20 for the starts sector of the first 

partition, and 3788800 / 512 = 7400 = 0x1CE8 for the block count. 

2. We now prepare the Linux boot arguments to take this partition as read-only root device: 

=> setenv cf_args setenv bootargs root=/dev/hda1 ro 

=> setenv flash_cf 'run cf_args addip;bootm ${kernel_addr} - ${fdt_addr}' 

9.5.5. Root File System on a Flash Card 134

3. 

=> setenv bootcmd run flash_cf 

...and boot the system: 

... 






Kernel command line: root=/dev/hda1 ro ip=192.168.3.80:192.168.3.1::255.255.255.0:tqm860l:e 



... 

9.5.6. Root File System in a Read-Only File in a 

FAT File System 

This is a more complicated example that shows that - depending on project requirements - many other 

alternatives for chosing a root file system for your embedded system exist. 

The scenario is as follows: on your embedded device you use a cheap and popular storage medium like 

CompactFlash, MMC or SD cards or USB memory sticks to store both the Linux kernel and your root file 

system. You want to distribute software updates over the internet: your customers can download the file from 

your web site, or you sent the images by email. Your customers may use any flash card or memory stick they 

happen to find, so you have no information about brand or size of the storage device. 

Unfortunately most of your customers use Windows systems. And they don't want to be bothered with long 

instructions how to create special partitions on the storage device or how to write binary images or things like 

that. A simple "copy file" operation is nearly exhausting their capabilities. 

What to do Well, if copying a file is all your customers can do we should not ask for more. Storage devices 

like CompactFlash cards etc. typically come with a single partition on it, which holds a FAT or VFAT file 

system. This cannot be used as a Linux root file system directly, so we have to use some trickery. 

Here is one possible solution: Your software distribution consistes of two files: The first file is the Linux 

kernel with a minimal ramdisk image attached (using the multi-file image format for U-Boot); U-Boot can 

load and boot such files from a FAT or VFAT file system. The second file is your root file system. For 

convenience and speed we use again an image of an ext2 file system. When Linux boots, it will initially use 

the attached ramdisk as root file system. The programs in this ramdisk will mount the FAT or VFAT file 

system - read-only. Then we can use a loop device (see losetup(8)) to associate the root file system image with 

a block device which can be used as a mount point. And finally we use pivot_root(8) to change the root file 

system to our image on the CF card. 

This sounds not so complicated, and actually it is quite simple once you understand what needs to be done. 

Here is a more detailed description: 

1. The root file system image is easy: as mantioned before, we will use an ext2 file system image, and 

to avoid wearing the flash storage device we will use it in read-only mode - we did a read-only ext2 

root file system image before, and here we can just re-use the existing image file. 

2. The initial ramdisk image that performs the pivot_root step must be created from scratch, but we 

already know how to create ramdisk images, so we just have to figure out what to put in it. 

The most important tool here is nash, a script interpreter that was specifically designed for such 

purposes (see nash(8)). We don't need any additional tools, and if we use static linking, then the 

9.5.6. Root File System in a Read-Only File in a FAT File System 135

3. 

nash binary plus a small script to control it is all we need for our initial ramdisk. 

To be precise, we need a couple of (empty) directories (bin, dev, etc, lib, loopfs, mnt, proc, 

and sysroot), the bin/nash binary, the linuxrc script and a symbolic link sbin pointing to 

bin: 

drwxr-xr-x 2 wd users 4096 Apr 13 01:11 bin 

-rwxr-xr-x 1 wd users 469512 Apr 11 22:47 bin/nash 

drwxr-xr-x 2 wd users 4096 Apr 12 00:04 dev 

drwxr-xr-x 2 wd users 4096 Apr 12 00:04 etc 

drwxr-xr-x 2 wd users 4096 Apr 12 00:04 lib 

-rwxr-xr-x 1 wd users 511 Apr 13 01:28 linuxrc 

drwxr-xr-x 2 wd users 4096 Apr 12 00:04 loopfs 

drwxr-xr-x 2 wd users 4096 Apr 12 00:09 mnt 

drwxr-xr-x 2 wd users 4096 Apr 12 00:04 proc 

lrwxrwxrwx 1 wd users 3 Jun 12 18:54 sbin -> bin 

drwxr-xr-x 2 wd users 4096 Apr 12 00:04 sysroot 

We also need only a minimal device table for creating the initial ramdisk: 

# 

/dev d 755 0 0 - - - - - 

/dev/console c 640 0 0 5 1 - - - 

/dev/hda b 640 0 0 3 0 - - - 

/dev/hda b 640 0 0 3 1 1 1 8 

/dev/loop b 640 0 0 7 0 0 1 4 

/dev/null c 640 0 0 1 3 - - - 

/dev/ram b 640 0 0 1 0 0 1 2 

/dev/ram b 640 0 0 1 1 - - - 

/dev/tty c 640 0 0 4 0 0 1 4 

/dev/tty c 640 0 0 5 0 - - - 

/dev/ttyS c 640 0 0 4 64 0 1 4 

/dev/zero c 640 0 0 1 5 - - - 

4. To create the initial ramdisk we perform the usual steps: 

$ INITRD_DIR=initrd 

$ INITRD_SIZE=490 

$ INITRD_FREE=0 

$ INITRD_INODES=54 

$ INITRD_DEVICES=initrd_devices.tab 

$ INITRD_IMAGE=initrd.img 

$ genext2fs -U \ 

-d ${INITRD_DIR} \ 

-D ${INITRD_DEVICES} \ 

-b ${INITRD_SIZE} \ 

-r ${INITRD_FREE} \ 

-i ${INITRD_INODES} \ 

${INITRD_IMAGE} 

$ gzip -v9 ${INITRD_IMAGE} 

The result is a really small (233 kB) compressed ramdisk image. 

5. Assuming you already have your Linux kernel image, you can now use mkimage to build an U-Boot 

multi-file image that combines the Linux kernel and the initial ramdisk: 

$ LINUX_KERNEL=linuxppc_2_4_devel/arch/ppc/boot/images/vmlinux.gz 

$ mkimage -A ppc -O Linux -T multi -C gzip \ 

> -n 'Linux with Pivot Root Helper' \ 

> -d ${LINUX_KERNEL}:${INITRD_IMAGE}.gz linux.img 

Image Name: Linux with Pivot Root Helper 

Created: Mon Jun 13 01:48:11 2005 

Image Type: PowerPC Linux Multi-File Image (gzip compressed) 





Contents: 



The newly created file linux.img is the second image we have to copy to the CF card. 

We are done. 

But wait - one essential part was not mentioned yet: the linuxrc script in our initial ramdisk image which 

contains all the magic. This script is quite simple: 

#!/bin/nash 

echo Mounting /proc filesystem 

mount -t proc /proc /proc 

echo Creating block devices 

mkdevices /dev 

echo Creating root device 

mkrootdev /dev/root 

echo 0x0100 > /proc/sys/kernel/real-root-dev 

echo Mounting flash card 

mount -o noatime -t vfat /dev/hda1 /mnt 

echo losetup for filesystem image 

losetup /dev/loop0 /mnt/rootfs.img 

echo Mounting root filesystem image 

mount -o defaults --ro -t ext2 /dev/loop0 /sysroot 

echo Running pivot_root 

pivot_root /sysroot /sysroot/initrd 

umount /initrd/proc 

Let's go though it step by step: 

• The first line says that it's a script file for the /bin/nash interpreter. 

Note: even if this file looks like a shell script it is NOT interpreted by a shell, but by the nash 

interpreter. For a complete list of available nash commands and their syntax please refer to the 

manual page, nash(8). 

• The first action is to mount the /proc pseudo file system which is needed to find out some required 

information. 

• Then we create block device entries for all partitions listed in /proc/partitions (mkdevices 

command). 

• In the next step a block device for our new root file system is created (mkrootdev command). 

• Then we mount the CF card. We assume that there is only a single partition on it (/dev/hda1) 

which is of type VFAT (which also will work with FAT file systems). These assumptions work fine 

with basicly all memory devices used under Windows. 

• We further assume that the file name of the root file system image on the CF card is 

"rootfs.img" - this file now gets mounted using a loop device (losetup and mount 

commands). 

• Our file system image, is now mounted on the /sysroot directory. In the last step we use 

pivot_root to make this the new root file system. 

• As a final cleanup we unmount the /proc file system which is not needed any more. 

There is one tiny flaw in this method: since we mount the CF card on a directory in the ramdisk to be able to 

access to root file system image. This means that we cannot unmount the CF card, which in turn prevents us 


from freeing the space for the inital ramdisk. The consequence is that you permanently lose approx. 450 kB of 

RAM for the ramdisk. [We could of course re-use this ramdisk space for temporary data, but such 

optimization is beyond the scope of this document.] 

And how does this work on our target 

1. First we copy the two images to the CF card; we do this on the target under Linux: 

bash-2.05b# fdisk -l /dev/hda 

Disk /dev/hda: 256 MB, 256376832 bytes 

16 heads, 32 sectors/track, 978 cylinders 

Units = cylinders of 512 * 512 = 262144 bytes 


/dev/hda1 * 1 978 250352 6 FAT16 

bash-2.05b# mkfs.vfat /dev/hda1 

mkfs.vfat 2.8 (28 Feb 2001) 

bash-2.05b# mount -t vfat /dev/hda1 /mnt 

bash-2.05b# cp -v linux.img rootfs.img /mnt/ 

`linux.img' -> `/mnt/linux.img' 

`rootfs.img' -> `/mnt/rootfs.img' 

bash-2.05b# ls -l /mnt 

total 4700 

-rwxr--r-- 1 root root 1020729 Jun 14 05:36 linux.img 

-rwxr--r-- 1 root root 3788800 Jun 14 05:36 rootfs.img 

bash-2.05b# umount /mnt 

2. We now prepare U-Boot to load the "uMulti" file (combined Linux kernel and initial ramdisk) 

from the CF card and boot it: 

=> setenv fat_args setenv bootargs rw 

=> setenv fat_boot 'run fat_args addip;fatload ide 0:1 200000 linux.img;bootm' 

=> setenv bootcmd run fat_boot 

3. And finally we try it out: 

U-Boot 1.1.3 (Jun 13 2005 - 02:24:00) 

CPU: XPC86xxxZPnnD4 at 50 MHz: 4 kB I-Cache 4 kB D-Cache FEC present 

Board: TQM860LDB0A3-T50.202 

DRAM: 16 MB 

FLASH: 8 MB 

In: serial 

Out: serial 

Err: serial 

Net: SCC ETHERNET, FEC ETHERNET [PRIME] 

PCMCIA: 3.3V card found: Transcend 256M 

Fixed Disk Card 

IDE interface 

[silicon] [unique] [single] [sleep] [standby] [idle] [low power] 

Bus 0: OK 

Device 0: Model: Transcend 256M Firm: 1.1 Ser#: SSSC256M04Z27A25906T 

Type: Removable Hard Disk 

Capacity: 244.5 MB = 0.2 GB (500736 x 512) 

Type "run flash_nfs" to mount root filesystem over NFS 


reading linux.img 

1025657 bytes read 


Image Name: Linux with Pivot Root Helper 

Created: 2005-06-13 0:32:41 UTC 






Contents: 

Image 0: 787146 Bytes = 768.7 kB 

Image 1: 238433 Bytes = 232.8 kB 


Uncompressing Multi-File Image ... OK 

Loading Ramdisk to 00f3d000, end 00f77361 ... OK 

Linux version 2.4.25 (wd@xpert) (gcc version 3.3.3 (DENX ELDK 3.1.1 3.3.3-9)) #1 Mon Jun 13 





Kernel command line: rw ip=192.168.3.80:192.168.3.1::255.255.255.0:tqm860l:eth1:off panic=1 



... 

NET4: Unix domain sockets 1.0/SMP for Linux NET4.0. 

RAMDISK: Compressed image found at block 0 

Freeing initrd memory: 232k freed 

VFS: Mounted root (ext2 filesystem). 

Red Hat nash version 4.1.18 starting 

Mounting /proc filesystem 

Creating block devices 

Creating root device 

Mounting flash card 

hda: hda1 

hda: hda1 

losetup for filesystem image 

Mounting root filesystem image 

Running pivot_root 


BusyBox v0.60.5 (2005.03.07-06:54+0000) Built-in shell (msh) 

Enter 'help' for a list of built-in commands. 

# ### Application running ... 

Kernel with a Flattened Device Tree Blob 

When booting an arch/powerpc kernel that requires a flattened device tree blob, the above procedure must 

be slightly modified. Namely, the multi-image file has to include the blob as the thrid image. Here's an 

example of the mkimage command to create it: 

mkimage -A ppc -O Linux -T multi -C gzip -n 'Kernel + Pivot Root Helper initrd + FDT blob' -d vml 

Image Name: Kernel + Pivot Root Helper initrd + FDT blob 

Created: Fri Sep 14 18:24:29 2007 





Contents: 




The newly created file kernel+initrd+blob.img needs to be copied to the CF card. 

Kernel with a Flattened Device Tree Blob 139

9.6. Root File System Selection 

Now we know several options for file systems we can use, and know how to create the corresponding images. 

But how can we decide which one to chose 

For practical purposes in embedded systems the following criteria are often essential: 

• boot time (i. e. time needed from power on until application code is running) 

• flash memory footprint 

• RAM memory footprint 

• effects on software updates 

The following data was measured for the different configurations. All measurements were performed on the 

same TQM860L board (MPC860 CPU at 50 MHz, 16 MB RAM, 8 MB flash, 256 MB CompactFlash card): 

File System Type Boot Time Free Mem Updates while running 

ramdisk 16.3 sec 6.58 MB whole image yes 

JFFS2 21.4 sec 10.3 MB per file only non-active files 

cramfs 10.8 sec 10.3 MB whole image no 

ext2 (ro) 9.1 sec 10.8 MB whole image no 

ext2 on CF (ro) 9.3 sec 10.9 MB whole image no 

File on FAT fs 11.4 sec 7.8 MB whole image yes 

As you can see, the ramdisk solution is the worst of all in terms of RAM memory footprint; also it takes a 

pretty long time to boot. However, it is one of the few solutions that allow an in-situ update while the system 

is running. 

JFFS2 is easy to use as it's a writable file system but it takes a long time to boot. 

A read-only ext2 file system shines when boot time and RAM memory footprint are important; you pay for 

this with an increased flash memory footprint. 

External flash memory devices like CompactFlash cards or USB memory sticks can be cheap and efficient 

solutions especially when lots of data need to be stored or when easy update procedures are required. - 

9.7. Overlay File Systems 

Introduction 

Overlay File Systems provide an interesting approach to several frequent problems in Embedded Systems. For 

example, mini_fo is a virtual kernel file system that can make read-only file systems writable. This is done 

by redirecting modifying operations to a writeable location called "storage directory", and leaving the original 

data in the "base directory" untouched. When reading, the file system merges the modifed and original data so 

that only the newest versions will appear. This occurs transparently to the user, who can access the data like 

on any other read-write file system. 

9.7. Overlay File Systems 140

What it is good for 

In embedded systems the main use of mini_fo is to overlay the root file system. This means it is mounted 

on top of the regular root file system, thereby allowing applications or users to transparently make 

modifications to it but redirecting these to a different location. 

Some examples of why this is usefull are explained in the following sections. 

Making a read-only root filesystem writeable 

Root file systems stored in flash are often read only, such as cramfs or read only ext2. While this offers major 

advantages in terms of speed and flash memory footprint, it nevertheless is often desireable to be able to 

modify the root file system, for example to 

• apply (small) software updates without having to burn a whole new root file system image to flash 

• make modifications during developement when frequent changes to the root file system occur. 

This can be achieved by mounting mini_fo on top of the root file system and using a (probably small) 

writeable partition as the storage file system. This could be either a JFFS2 flash file system, or during 

development even an external hard disk. This has the following advantages: 

• read-only file systems (fast, small memory footprint) can be used like persistent writable file systems 

(in contrast to a ramdisk) 

• slow flash journalling file systems with large flash memory footprint can be avoided. 

Non persistant changes 

Ramdisks are often used when the root file system needs to be modified non-persistantly. This works well, but 

downsides are the large RAM memory footprint and the time costly operation of copying the ramdisk into 

RAM during startup. These can be avoided by overlaying the root file system as in the previous example but 

with the difference that the tmpfs file system is used as storage. Thus only modified files are stored in RAM, 

and can even be swapped out if neccessary. This saves boot time and RAM! 

Resetable changes 

Mini_fo can be easily used to implement a "reset to factory defaults" function by overlaying the default root 

file system. When configuration changes are made, these are automatically directed to the storage file system 

and take precedence over the original files. Now, to restore the system to factory defaults, all that needs to be 

done is delete the contents of the storage directory. This will remove all changes made to the root file system 

and return it to the original state. 

Note: Deleting the contents of the storage directory should only be done when the overlay file system is 

unmounted. 

Examples 

Generally, there are two different ways of overlaying the root file system, which both make sense in different 

scenarios. 

Starting a single application in a chrooted overlayed environment 

What it is good for 141

This is easy. Let's assume "/" is the read-only root file system and /dev/mtdblock5 contains a small JFFS2 

flash partition that shall be used to store modifications made by application "/usr/bin/autoPilot": 

# mount -t jffs2 /dev/mtdblock5 /tmp/sto 

# insmod mini_fo.o 

# mount -t mini_fo -o base=/,sto=/tmp/sto/ / /mnt/mini_fo/ 

# cd /mnt/mini_fo/ 

# chroot . /usr/bin/autoPilot 

The mini_fo file system is mounted with "/" as base directory, "/tmp/sto/" as storage directory to the mount 

point "/mnt/mini_fo". After that, chroot(1) is used to start the application with the new file system root 

"/mnt/mini_fo". All modifications made by the application will be stored to the JFFS2 file system in /tmp/sto. 

Starting the whole system system in chrooted overlayed environment 

This is more interesting, and a bit trickier, as mounting needs to be done during system startup after the root 

file system has been mounted, but before init is started. The best way to do this is to have a script that mounts 

the mini_fo file system on top of root and then starts init in the chrooted overlayed environment. For example 

assume the following script "overlay_init", stored in /sbin/: 

#!/bin/bash 

# 

# mount mini_fo overlay file system and execute init 

# 

# make sure these exist in the read-only file system 

STORAGE=/tmp/sto 

MOUNT_POINT=/mnt/mini_fo/ 

# mount tmpfs as storage file system with a maximum size of 32MB 

mount -t tmpfs -o rw,size=32M none $STORAGE 

/sbin/modprobe mini_fo 

mount -t mini_fo -o base=/,sto=$STORAGE / $MOUNT_POINT 

exec /usr/sbin/chroot $MOUNT_POINT /sbin/init 

echo "exec chroot failed, bad!" 

exec /bin/sh 

exit 1 

Now its easy to choose between a mini_fo overlayed and the regular non overlayed system just by setting 

the "init" kernel parameter in the boot loader to "init=/sbin/overlay_init". 

Tips 

• pivot_root(1) can be used with chroot if there is need to access the original non overlayed root 

file system from the chrooted overlayed environment. 

Performance overhead 

The mini_fo file system is inserted as an additional layer between the VFS and the native file system, and 

thus creates some overhead that varies strongly depending of the operation performed. 

1. modifying a regular file for the first time 

This results in a copy of the original file beeing created in the storage directory, that is then modified. 

Overhead depends on the size of the modified file. 

Starting a single application in a chrooted overlayed environment 142

2. Reading from files, creating new files, modifying already modified files 

These operations are passed directly through to the lower native layer, and only impose an overhead 

of 1-2%. 

Further information 

This section discusses how the mini_fo overlay file system can be used in embedded systems. More general 

information is available at the mini_fo project page: http://www.denx.de/wiki/Know/MiniFOHome. 

9.8. The Persistent RAM File system (PRAMFS) 

The pramfs file system supports persistent memory devices such as SRAM. Instead of having a block 

emulation layer over such a memory area and using a normal file system on top of that, pramfs seeks to 

induce minimal overhead in this situation. Most important in this respect is that the normal block layer 

caching of the Linux kernel is circumvented in pramfs. 

9.8.1. Mount Parameters 

The most important parameters for normal usage are 

• physaddr: The physical address of the static memory. 

• init: When given, it will initialize the file system to that size. 

9.8.2. Example 

We will show a sample usage of pramfs in this section using normal DRAM on a board with at least 256MB 

of memory. For pramfs we reserve the upper 32MB by appending mem=224M to the kernel command line. 

First off we generate some testdata on a persistent file system (/tmp) to demonstrate that pramfs survives a 

reboot (of course with power always applied to keep the DRAM refreshed): 

bash-3.00# dd if=/dev/urandom bs=1M count=8 of=/tmp/testdata 



bash-3.00# 

Next we mount the 32MB that we reserved and initialize it to be 32MB in size and copy the testfile. A final 

compare shows that the copy was indeed successful so we can reboot: 

bash-3.00# mount -t pramfs -o physaddr=0xe000000,init=0x2000000 none /mnt 

bash-3.00# cp /tmp/testdata /mnt 

bash-3.00# cmp /tmp/testdata /mnt/testdata 

bash-3.00# reboot 

Having rebooted (using mem=224M on the kernel command line again of course) we mount the file system 

but this time without the init parameter because it is preinitialized. We then check the contents again: 

bash-3.00# mount -t pramfs -o physaddr=0xe000000 none /mnt 

bash-3.00# ls /mnt 

testdata 

bash-3.00# cmp /tmp/testdata /mnt/testdata 

bash-3.00# 

9.8. The Persistent RAM File system (PRAMFS) 143

• 10. Debugging 

♦ 10.1. Debugging of U-Boot 

◊ 10.1.1. Debugging of U-Boot Before Relocation 

◊ 10.1.2. Debugging of U-Boot After Relocation 

♦ 10.2. Linux Kernel Debugging 

◊ 10.2.1. Linux Kernel and Statically Linked Device Drivers 

◊ 10.2.2. Dynamically Loaded Device Drivers (Modules) 

◊ 10.2.3. GDB Macros to Simplify Module Loading 

♦ 10.3. GDB Startup File and Utility Scripts 

♦ 10.4. Tips and Tricks 

♦ 10.5. Application Debugging 

◊ 10.5.1. Local Debugging 

◊ 10.5.2. Remote Debugging 

♦ 10.6. Debugging with Graphical User Interfaces 

10. Debugging 

The purpose of this document is not to provide an introduction into programming and debugging in general. 

We assume that you know how to use the GNU debugger gdb and probably it's graphical frontends like ddd. 

We also assume that you have access to adequate tools for your work, i. e. a BDI2000 BDM/JTAG debugger. 

The following discussion assumes that the host name of your BDI2000 is bdi. 

Please note that there are several limitations in earlier versions of GDB. The version of GDB as distributed 

with the ELDK contains several bug fixes and extensions. If you find that your GDB behaves differently, have 

a look at the GDB sources and patches that come with the ELDK source. 

10.1. Debugging of U-Boot 

When U-Boot starts it is running from ROM space. Running from flash would make it nearly impossible to 

read from flash while executing code from flash not to speak of updating the U-Boot image in flash itself. To 

be able to do just that, U-Boot relocates itself to RAM. We therefore have two phases with different program 

addresses. The following sections show how to debug U-Boot in both phases. 

10.1.1. Debugging of U-Boot Before Relocation 

Before relocation, the addresses in the ELF file can be used without any problems, so debugging U-Boot in 

this phase with the BDI2000 is quite easy: 

bash[0]$ ${CROSS_COMPILE}gdb u-boot 

GNU gdb 5.1.1 

Copyright 2002 Free Software Foundation, Inc. 

GDB is free software, covered by the GNU General Public License, and you are 

welcome to change it and/or distribute copies of it under certain conditions. 

Type "show copying" to see the conditions. 

There is absolutely no warranty for GDB. Type "show warranty" for details. 

This GDB was configured as "--host=i386-redhat-linux --target=ppc-linux"... 

(gdb) target remote bdi:2001 

Remote debugging using bdi:2001 

0xfffffffc in () 

(gdb) b cpu_init_f 

Breakpoint 1 at 0xfffd3310: file cpu_init.c, line 136. 

(gdb) c 

Continuing. 

Breakpoint 1, cpu_init_f () at cpu_init.c:136 

10.1. Debugging of U-Boot 144

136 asm volatile(" bl 0f" ::: "lr"); 

(gdb) s 

137 asm volatile("0: mflr 3" ::: "r3"); 

(gdb) 

138 asm volatile(" addi 4, 0, 14" ::: "r4"); 

(gdb) 

cpu_init_f is the first C function called from the code in start.C. 

10.1.2. Debugging of U-Boot After Relocation 

For debugging U-Boot after relocation we need to know the address to which U-Boot relocates itself to. When 

no exotic features like PRAM are used, this address usually is - CFG_MONITOR_LEN. In our 

example with 16MB RAM and CFG_MONITOR_LEN = 192KB this yields the address 0x1000000 - 

0x30000 = 0xFD0000. 

In other cases, check the source code, and apply some common sense. For example, on PowerPC we use "r2" 

to hold a pointer to the "global data" structure ("struct global_data"); this structure contains a field 

unsigned long reloc_off; /* Relocation Offset */ 

which is the offset between the image addresses in flash and in RAM. You can easily print this value in gdb 

like that: 

(gdb) print/x ((gd_t *)$r2)->reloc_off 

Then add this value to the value of TEXT_BASE as defined in your board's config.mk file, and you get the 

start address of the U-Boot image in RAM. 

With this knowledge, we can instruct gdb to forget the old symbol table and reload the symbols with our 

calculated offset: 

(gdb) symbol-file 

Discard symbol table from `/home/dzu/denx/cvs-trees/u-boot/u-boot' (y or n) y 

No symbol file now. 

(gdb) add-symbol-file u-boot 0xfd0000 

add symbol table from file "u-boot" at 

.text_addr = 0xfd0000 

(y or n) y 

Reading symbols from u-boot...done. 

(gdb) b board_init_r 

Breakpoint 2 at 0xfd99ac: file board.c, line 533. 

(gdb) c 

Continuing. 

Breakpoint 2, board_init_r (id=0xfbb1f0, dest_addr=16495088) at board.c:533 

533 { 

(gdb) 

board_init_r is the first C routine running in the newly relocated C friendly RAM environment. 

The simple example above relocates the symbols of only one section, .text. Other sections of the 

executable image (like .data, .bss, etc.) are not relocated and this prevents gdb from accessing static and 

global variables by name. See more sophisticated examples in section 10.3. GDB Startup File and Utility 

Scripts. 

10.1.1. Debugging of U-Boot Before Relocation 145

10.2. Linux Kernel Debugging 

10.2.1. Linux Kernel and Statically Linked Device Drivers 

10.2.2. Dynamically Loaded Device Drivers (Modules) 

First start GDB in the root directory of your Linux kernel, using the vmlinux kernel image as file to debug: 

bash$ cd 

bash$ ${CROSS_COMPILE}gdb vmlinux 

GNU gdb 5.1.1 






This GDB was configured as "--host=i386-redhat-linux --target=ppc-linux". 

(gdb) 

Now attach to the target and start execution with the commands: 

(gdb) target remote bdi:2001 

Remote debugging using bdi:2001 

0x00000100 in () 

(gdb) c 

Continuing. 

Now the target should boot Linux as usual. Next you need to load your kernel module on the target: 

bash# insmod -m ex_sw.o 

Sections: Size Address Align 

.this 00000060 cf030000 2**2 

.text 000002f4 cf030060 2**2 

.rodata 00000134 cf030354 2**2 

.data 00000000 cf030488 2**0 

.sdata 0000000c cf030488 2**2 

.kstrtab 00000085 cf030494 2**0 

.bss 00000000 cf030519 2**0 

.sbss 00000008 cf03051c 2**2 

... 

The option -m prints out the addresses of the various code and data segments ( .text, .data, .sdata, .bss, .sbss ) 

after relocation. GDB needs these addresses to know where all the symbols are located. We now interrupt 

GDB to load the symbol table of the module as follows: 

(gdb) ^C 

Program received signal SIGSTOP, Stopped (signal). 

... 

(gdb) add-symbol-file /ex_sw.o 0xcf030060\ 

-s .rodata 0xcf030354\ 

-s .data 0xcf030488\ 

-s .sdata 0xcf030488\ 

-s .bss 0xcf030519\ 

-s .sbss 0xcf03051c 

add symbol table from file "/ex_sw.o" at 

.text_addr = 0xcf030060 

.rodata_addr = 0xcf030354 

.data_addr = 0xcf030488 

.sdata_addr = 0xcf030488 

.bss_addr = 0xcf030519 

10.2. Linux Kernel Debugging 146

.sbss_addr = 0xcf03051c 

(y or n) y 

Reading symbols from /ex_sw.o...done. 

Now you can list the source code of the module, set break points or inspect variables as usual: 

(gdb) l fun 

61 static RT_TASK *thread; 

62 

63 static int cpu_used[NR_RT_CPUS]; 

64 

65 static void fun(int t) 

66 { 

67 unsigned int loops = LOOPS; 

68 while(loops--) { 

69 cpu_used[hard_cpu_id()]++; 

70 rt_leds_set_mask(1,t); 

(gdb) 

(gdb) b ex_sw.c:69 

Breakpoint 1 at 0xcf03007c: file ex_sw.c, line 69. 

(gdb) c 

Continuing. 

Breakpoint 1, fun (t=1) at ex_sw.c:69 


(gdb) p ntasks 

$1 = 16 

(gdb) p stack_size 

$2 = 3000 

The next section demonstrates a way to automate the symbol table loading procedure. 

10.2.3. GDB Macros to Simplify Module Loading 

The following GDB macros and scripts help you to load kernel modules into GDB in a half-automatic way. It 

assumes, that the module on the target has been installed with the command: 

bash# insmod -m my_module.o > my_module.o.map 

In your $HOME directory you need the scripts add-symbol-file.sh and the GDB startup file .gdbinit, which are 

listed in 10.3. GDB Startup File and Utility Scripts below. 

Now you can include the symbol definition into GDB with: 

bash$ ${CROSS_COMPILE}gdb vmlinux 

GNU gdb 5.1.1 






This GDB was configured as "--host=i386-redhat-linux --target=ppc-linux". 

0x00000100 in () 

c 

Continuing. 

^C 

Program received signal SIGSTOP, Stopped (signal). 

0xcf02a91c in () 

(gdb) add-module rtai4/examples/sw/ex_sw.o 

add symbol table from file "/HHL/8xx/target/home/wolf/rtai4/examples/sw/ex_sw.o" at 

.text_addr = 0xcf030060 

.rodata_addr = 0xcf030340 

.data_addr = 0xcf030464 

10.2.2. Dynamically Loaded Device Drivers (Modules) 147

.sdata_addr = 0xcf030464 

.bss_addr = 0xcf0304f5 

.sbss_addr = 0xcf0304f8 

(gdb) b ex_sw.c:69 

Breakpoint 1 at 0xcf03007c: file ex_sw.c, line 69. 

(gdb) c 

Continuing. 

Breakpoint 1, fun (t=0x1) at ex_sw.c:69 


(gdb) p/d loops 

$2 = 999986939 

(gdb) p t 

$3 = 0x1 

(gdb) d b 

Delete all breakpoints (y or n) y 

(gdb) c 

Continuing. 

10.3. GDB Startup File and Utility Scripts 

In addition to the add-module macro, the followin example GDB startup file contains a few other useful 

settings and macros, which you may want to adjust to your local environment: 

set output-radix 16 

target remote bdi:2001 

define reset 

detach 

target remote bdi:2001 

end 

define add-module 

shell ~/add-symbol-file.sh $arg0 

source ~/add-symbol-file.gdb 

end 

document add-module 

Usage: add-module 

end 

Do add-symbol-file for module automatically. 

Note: A map file with the extension ".map" must have 

been created with "insmod -m > .map" 

in advance. 

The following shell script ~/add-symbol-file.sh is used to run the GDB add-symbol-file command 

automatically: 

#!/bin/sh 

# 

# Constructs the GDB "add-symbol-file" command string 

# from the map file of the specified kernel module. 

add_sect() { 

ADDR=àwk '/^'$1' / {print $3}' $MAPFILE` 

if [ "$ADDR" != "" ]; then 

echo "-s $1 0xàwk '/^'$1' / {print $3}' $MAPFILE`" 

fi 

} 

[ $# == 1 ] && [ -r "$1" ] || { echo "Usage: $0 " >&2 ; exit 1 ; } 

10.3. GDB Startup File and Utility Scripts 148

MAPFILE=$1.map 

ARGS="0xàwk '/^.text / {print $3}' $MAPFILE`\ 

àdd_sect .rodata`\ 

àdd_sect .data`\ 

àdd_sect .sdata`\ 

àdd_sect .bss`\ 

àdd_sect .sbss`\ 

" 

echo "add-symbol-file $1 $ARGS" > ~/add-symbol-file.gdb 

10.4. Tips and Tricks 

• To prevent GDB from jumping around in the code when trying to single step, i. e. when it seems as if 

the code is not executing line by line, you can recompile your code with the following additional 

compiler options: 

-fno-schedule-insns -fno-schedule-insns2 

• On some systems (like the MPC8xx or MPC8260) you can only define one hardware breakpoint. 

Therefore you must delete an existing breakpoint before you can define a new one: 

(gdb) d b 

Delete all breakpoints (y or n) y 

(gdb) b ex_preempt.c:63 

Breakpoint 2 at 0xcf030080: file ex_preempt.c, line 63. 

10.5. Application Debugging 

10.5.1. Local Debugging 

In case there is a native GDB available for your target you can use it for application debugging as usual: 

bash$ gcc -Wall -g -o hello hello.c 

bash$ gdb hello 

... 

(gdb) l 

1 #include 

2 

3 int main(int argc, char* argv[]) 

4 { 

5 printf ("Hello world\n"); 

6 return 0; 

7 } 

(gdb) break 5 

Breakpoint 1 at 0x8048466: file hello.c, line 5. 

(gdb) run 

Starting program: /opt/eldk/ppc_8xx/tmp/hello 

Breakpoint 1, main (argc=0x1, argv=0xbffff9f4) at hello.c:5 


(gdb) c 

Continuing. 

Hello world 

Program exited normally. 

10.5. Application Debugging 149

10.5.2. Remote Debugging 

gdbserver allows you to connect your program with a remote GDB using the "target remote" command. 

On the target machine, you need to have a copy of the program you want to debug. gdbserver does not 

need your program's symbol table, so you can strip the program if necessary to save space. GDB on the host 

system does all the symbol handling. Here is an example: 

bash$ ${CROSS_COMPILE}gcc -Wall -g -o hello hello.c 

bash$ cp -p hello /hello-stripped 

bash$ ${CROSS_COMPILE}strip /hello-stripped 

To use the server, you must tell it how to communicate with GDB, the name of your program, and the 

arguments for your program. To start a debugging session via network type on the target: 

bash$ cd 

bash$ gdbserver 192.168.1.1:12345 hello-stripped 

Process hello-stripped created; pid = 353 

And then on the host: 

bash$ ${CROSS_COMPILE}gdb hello 

... 

(gdb) set solib-absolute-prefix /opt/eldk/$CROSS_COMPILE 

(gdb) dir /opt/eldk/$CROSS_COMPILE 

Source directories searched: 

/opt/eldk/$CROSS_COMPILE:$cdir:$cwd 

(gdb) target remote 192.168.1.99:12345 

Remote debugging using 192.168.1.99:12345 

0x30012748 in () 

... 

(gdb) l 

1 #include 

2 

3 int main(int argc, char* argv[]) 

4 { 


6 return 0; 

7 } 

(gdb) break 5 

Breakpoint 1 at 0x10000498: file hello.c, line 5. 

(gdb) continue 

Continuing. 

Breakpoint 1, main (argc=1, argv=0x7ffffbe4) at hello.c:5 


(gdb) p argc 

$1 = 1 

(gdb) continue 

Continuing. 

Program exited normally. 

If the target program you want to debug is linked against shared libraries, you must tell GDB where the 

proper target libraries are located. This is done using the set solib-absolute-prefix GDB 

command. If this command is omitted, then, apparently, GDB loads the host versions of the libraries and gets 

crazy because of that. 

10.6. Debugging with Graphical User Interfaces 

10.6. Debugging with Graphical User Interfaces 150

It is convenient to use DDD, a Graphical User Interface to GDB, for debugging as it allows to define and 

execute frequently used commands via buttons. You can start DDD with the command: 

bash$ ddd --debugger ${CROSS_COMPILE}gdb & 

If DDD is not already installed on your Linux system, have a look at your distribution media. 

11. Simple Embedded Linux Framework 

12. Books, Mailing Lists, Links, etc. 

This section provides references on where to find more information 

Contents: 

• 12. Books, Mailing Lists, Links, etc. 

♦ 12.1. Application Notes 

♦ 12.2. Further Reading 

◊ 12.2.1. Linux kernel 

◊ 12.2.2. General Linux / Unix programming 

◊ 12.2.3. Network Programming 

◊ 12.2.4. C++ programming 

◊ 12.2.5. Java programming 

◊ 12.2.6. PowerPC Programming 

◊ 12.2.7. Embedded Topics 

♦ 12.3. Mailing Lists 

♦ 12.4. Links 

♦ 12.5. Tools 

12.1. Application Notes 

A collection of Application Notes relevant for embedded computing can be found on the DENX web server. 

12.2. Further Reading 

12.2.1. Linux kernel 

Books 

• Karim Yaghmour, Jon Masters, Gilad Ben-Yossef, Philippe Gerum: "Building Embedded Linux 

Systems 2nd edition", 

Paperback: 462 pages, O'Reilly & Associates; (August 2008); ISBN 10: 0-596-52968-6; ISBN 13: 

9780596529680 ISBN 059600222X - IMHO the best book about Embedded Linux so far. An 

absolute must have. 

• Greg Kroah-Hartman: "Linux Kernel in a Nutshell", 

198 pages, O'Reilly ("In Nutshell" series), (December 2006), ISBN 10: 0-596-10079-5; ISBN 13: 

9780596100797 

- Tarball of PDF files (3 MB): 

12.2. Further Reading 151

http://www.kernel.org/pub/linux/kernel/people/gregkh/lkn/lkn_pdf.tar.bz2 

- Tarball of DocBook files (1 MB): 

http://www.kernel.org/pub/linux/kernel/people/gregkh/lkn/lkn_xml.tar.bz2 

• Craig Hollabaugh: "Embedded Linux: Hardware, Software, and Interfacing", 

Paperback: 432 pages; Addison Wesley Professional; (March 7, 2002); ISBN 0672322269 

• Christopher Hallinan: "Embedded Linux Primer: A Practical Real-World Approach", 

576 pages, Prentice Hall, September 2006, ISBN-10: 0-13-167984-8; ISBN-13: 978-0-13-167984-9 

• Jonathan Corbet, Alessandro Rubini, Greg Kroah-Hartman: "Linux Device Drivers", 3rd Edition 

; 

Paperback: 636 pages; O'Reilly & Associates; 3rd edition (February 2005); ISBN: 0-596-00590-31 - 

The reference book for writing Linux device drivers. An absolute must have. => Read online 

• Jürgen Quade, Eva-Katharina Kunst: "Linux-Treiber entwickeln"; Broschur: 436 pages; 

dpunkt.verlag, Juni 2004; ISBN 3898642380 

- focused on kernel 2.6, unfortunately German only 

- => Read online 

• Sreekrishnan Venkateswaran: "Essential Linux Device Drivers", 

744 pages, Prentice Hall, March 2008, ISBN-10: 0-13-239655-6; ISBN-13: 978-0-13-239655-4 

- => Read online 

Articles 

• The Linux Kernel - describing most aspects of the Linux Kernel. Probably, the first reference for 

beginners. Lots of illustrations explaining data structures use and relationships. In short: a must have. 

• Linux Kernel Module Programming Guide - Very nice 92 pages GPL book on the topic of modules 

programming. Lots of examples. 

• LWN: Porting device drivers to the 2.6 kernel - Series of articles (37) in Linux Weekly News: 

http://lwn.net/Articles/driver-porting/ 

• MIPS Linux Porting Guide: http://linux.junsun.net/porting-howto/porting-howto.html 

• Andries Brouwers remarks to the linux kernel: http://www.win.tue.nl/~aeb/linux/lk/lk.html 

12.2.2. General Linux / Unix programming 

Books 

• W. Richard Stevens: "Advanced Programming in the UNIX Environment", Addision Wesley, ISBN 

0-201-56317-7 

• Eric S. Raymond: "The Art of Unix Programming", Addision Wesley, ISBN 0131429019 => Read 

online 

• David R. Butenhof: "Programming with POSIX Threads", Addision Wesley, ISBN 0-201-63392-2. 

• Bradford Nichols, Dick Buttlar and Jacqueline Proulx Farrell: "Pthreads Programming", O'Reilly 

& Associates 

Articles 

• The GNU C Library: http://www.linuxselfhelp.com/gnu/glibc/html_chapter/libc_toc.html 

General Linux Programming: http://www.linuxselfhelp.com/cats/programming.html 

• Multi-Threaded Programming With POSIX Threads: 

http://users.actcom.co.il/~choo/lupg/tutorials/multi-thread/multi-thread.html 

• Ulrich Drepper : Position Independent Binaries: "Text Relocations" 

• Ulrich Drepper : "How to Write Shared Libraries" 

• Ulrich Drepper : "What Every Programmer Should Know About Memory" 

• David Goldberg : "What Every Computer Scientist Should Know About Floating-Point Arithmetic" 

Books 152

• More Ulrich Drepper stuff: http://people.redhat.com/drepper/ 

• How to optimize DSOs by identifying unused non-exported functions and data. 

• A quite complete history of the UNIX family can be found here: http://www.levenez.com/unix/ 

• Unix Manual, first edition, 3 November 1971 

• John Graham-Cumming: Debugging Makefiles 

Standards: 

• Linux Standard Base: http://refspecs.freestandards.org/lsb.shtml 

• Single UNIX Specification, Version 3 (needs registration even for online viewing) 

• Single UNIX Specification, Version 2 

• PCI Bus Bindings - Standard for Boot Firmware: 

http://playground.sun.com/1275/bindings/pci/pci2_1.pdf 

12.2.3. Network Programming 

Books 

• W. Richard Stevens: "TCP/IP Illustrated, Volume 1 - The Protocols", Addision Wesley, ISBN 

0-201-63346-9 

• Gary R. Wright, W. Richard Stevens: "TCP/IP Illustrated, Volume 2 - The Implementation", 

Addision Wesley, ISBN 0-201-63354-X 

• W. Richard Stevens: "TCP/IP Illustrated, Volume 3 - TCP for Transactions", Addision Wesley, 

ISBN 0-201-63495-3 

• W. Richard Stevens: "UNIX Network Programming, Volume 1 - Networking APIs: Sockets and 

XTI", 2nd ed., Prentice Hall, ISBN-0-13-490012-X 

• W. Richard Stevens: "UNIX Network Programming, Volume 2 - Interprocess Communication", 2nd 

ed., Prentice Hall, ISBN-0-13-081081-9 

Articles 

• Linux Networking topics (like NAPI, GSO, VLAN, IPsec etc.): 

http://linux-net.osdl.org/index.php/Main_Page 

12.2.4. C++ programming 

Books 

• Scott Meyers: "Effective C++: 55 Specific Ways to Improve Your Programs and Designs (3rd 

Edition)", Addison-Wesley, May 20, 2005, ISBN: 0321334876 

12.2.5. Java programming 

Books 

• Joshua Bloch: "Effective Java -- Programming Language Guide", 2001, Addison Wesley, ISBN 

0-201-31005-8, 250 pages 

Articles 153

12.2.6. PowerPC Programming 

Books 

• Programming Environments Manual for 32-Bit Implementations of the PowerPC architecture: 

http://www.freescale.com/files/product/doc/MPCFPE32B.pdf 

• IBM PDF file (600+ page book) on PowerPC assembly language: 

http://www-3.ibm.com/chips/techlib/techlib.nsf/techdocs/852569B20050FF778525699600719DF2 

• Power.org Standard for Embedded Power Architecture Platform Requirements (ePAPR): 

http://www.power.org/resources/downloads/Power_ePAPR_APPROVED_v1.0.pdf 

Articles 

• Introduction to Assembly on the PowerPC: 

http://www-106.ibm.com/developerworks/library/l-ppc/t=gr,lnxw09=PowPC 

• IBM PDF compiler writers guide on PPC asm tuning etc.: 

http://www-3.ibm.com/chips/techlib/techlib.nsf/techdocs/852569B20050FF7785256996007558C6 

• A developer's guide to the POWER architecture: 

http://www-128.ibm.com/developerworks/linux/library/l-powarch/index.html 

• PowerPC EABI Calling Sequence: 

ftp://sourceware.redhat.com/pub/binutils/ppc-docs/ppc-eabi-calling-sequence 

• PowerPC Embedded Application Binary Interface (32-Bit Implementation): 

ftp://sourceware.redhat.com/pub/binutils/ppc-docs/ppc-eabi-1995-01.pdf 

• Developing PowerPC Embedded Application Binary Interface (EABI) Compliant Programs 

http://www-306.ibm.com/chips/techlib/techlib.nsf/techdocs/852569B20050FF77852569970071B0D6 

• System V Application Binary Interface - PowerPC Processor Supplement: 

http://refspecs.freestandards.org/elf/elfspec_ppc.pdf 

• Linux for PowerPC Embedded Systems HOWTO (old): 

http://penguinppc.org/embedded/howto/PowerPC-Embedded-HOWTO.html 

• Linux for PowerPC Embedded Systems HOWTO (new): 

http://www.denx.de/twiki/bin/view/PPCEmbedded 

• Understanding MPC5200 Bestcomm Firmware: Posting on linuxppc-embedded@ozlabs.org mailing 

list (see also the mailing list archive entry), source code disasm.c for a disassember, and "SmartDMA 

Hand-Assembly Guides" document. 

12.2.7. Embedded Topics 

Articles 

• Things you always wanted to know about NAND flash but never dared to ask: Micron Application 

Note 

• The ultimate goal of Embedded C++ is to provide embedded systems programmers with a subset of 

C++ that is easy for the average C programmer to understand and use. 

• Our contribution to the Darwin year 2009: Hardware designs that will not replicate: Topic in DENX 

Wiki 

12.3. Mailing Lists 

These are some mailing lists of interest. If you are new to mailing lists then please take the time to read at 

least RFC 1855. 

12.3. Mailing Lists 154

• linux-arm-kernel - Communications among developers and users of Linux on arm boards 

• linuxppc-embedded - Communications among developers and users of Linux on embedded 

PowerPC boards 

This mailing list has been merged into the linuxppc-dev mailing list below and thus does not 

exist anymore. 

• linuxppc-dev - Communications among active developers of Linux on 32 bit PowerPC plattforms. 

Not intended for user support. 

• u-boot - Support for "U-Boot" Universal Bootloader 

• ELDK - Support for DENX Embedded Linux Development Kit 

12.4. Links 

Linux Kernel Resources: 

• The Linux Documentation Project : http://www.tldp.org/ 

• Generic ("official") Linux Kernel sources: 

git: http://git.kernel.org/p=linux/kernel/git/torvalds/linux-2.6.git;a=tree 

FTP: ftp://ftp.kernel.org/pub/linux/kernel/v2.6/ 

• Full git history of Linux: http://thread.gmane.org/gmane.linux.kernel/690811 

• Generic kernel sources for PowerPC systems: http://penguinppc.org/dev/kernel.shtml 

• DENX kernel sources: http://git.denx.de/p=linux-2.6-denx.git;a=summary 

• Cross-Referencing the Linx Kernel: http://lxr.linux.no/source/a=ppc 

• Starting point for Linux based asm (mostly x86): http://linuxassembly.org/ 

Realtime, Xenomai, RTAI: 

• Xenomai Home Page: http://www.xenomai.org/ 

• Hackbench, a commonly used system stress tool 

• Calibrator, determines cache 

• RTAI Home Page: http://www.rtai.org/ 

• DENX RTAI Patches: ftp://ftp.denx.de/pub/RTAI/ sizes at runtime, rendering it another useful system 

stress tool 

U-Boot: 

• U-Boot Project Page: http://www.denx.de/wiki/U-Boot/WebHome. 

Note that the old SourceForge page is not maintained anymore. 

• DENX U-Boot and Linux Guide: http://www.denx.de/twiki/bin/view/DULG 

Cross Development Tools: 

• DENX Embedded Linux Development Kit: http://www.denx.de/twiki/bin/view/DULG/ELDK 

Miscalleneous or unsorted material: 

• BDI2000 List of supported Flash Memories: This document not only lists the currently supported 

flash chips, but also the required settings in the BDI config file. 

• BDI2000 configuration files: ftp://78.31.64.234/bdigdb/config/ 

12.4. Links 155

12.5. Tools 

• http://lxr.linux.no/source/ - Cross-Referencing the Linux Kernel - using a versatile hypertext 

cross-referencing tool for the Linux Kernel source tree (the Linux Cross-Reference project) 

• ftp://ftp.denx.de/pub/tools/backtrace - Decode Stack Backtrace - Perl script to decode the Stack 

Backtrace printed by the Linux Kernel when it panics 

• ftp://ftp.denx.de/pub/tools/clone_tree - "Clone" a Source Tree - Perl script to create a working copy of 

a source tree (for example the Linux Kernel) which contains mainly symbolic links (and 

automagically omits "unwanted" files like CVS repository data, etc.) 

• 13. Appendix 

♦ 13.1. Flat Device Tree 

♦ 13.2. BDI2000 Configuration file 

13. Appendix 

13.1. Flat Device Tree 

/* 

* Device Tree Source for AMCC Canyonlands (460EX) 

* 

* Copyright 2008 DENX Software Engineering, Stefan Roese 

* 

* This file is licensed under the terms of the GNU General Public 

* License version 2. This program is licensed "as is" without 

* any warranty of any kind, whether express or implied. 

*/ 

/ { 






aliases { 

ethernet0 = &EMAC0; 

ethernet1 = &EMAC1; 

serial0 = &UART0; 

serial1 = &UART1; 

}; 

cpus { 



cpu@0 { 

device_type = "cpu"; 

model = "PowerPC,460EX"; 

reg = ; 

clock-frequency = ; /* Filled in by U-Boot */ 

timebase-frequency = ; /* Filled in by U-Boot */ 

i-cache-line-size = ; 

d-cache-line-size = ; 

i-cache-size = ; 

d-cache-size = ; 

dcr-controller; 

dcr-access-method = "native"; 

}; 

13. Appendix 156

}; 

memory { 

device_type = "memory"; 

reg = ; /* Filled in by U-Boot */ 

}; 

UIC0: interrupt-controller0 { 

compatible = "ibm,uic-460ex","ibm,uic"; 



dcr-reg = ; 




}; 





dcr-reg = ; 




interrupts = ; /* cascade */ 


}; 





dcr-reg = ; 






}; 





dcr-reg = ; 






}; 

SDR0: sdr { 

compatible = "ibm,sdr-460ex"; 

dcr-reg = ; 

}; 

CPR0: cpr { 

compatible = "ibm,cpr-460ex"; 

dcr-reg = ; 

}; 

plb { 

compatible = "ibm,plb-460ex", "ibm,plb4"; 



13.1. Flat Device Tree 157

anges; 


SDRAM0: sdram { 

compatible = "ibm,sdram-460ex", "ibm,sdram-405gp"; 

dcr-reg = ; 

}; 

MAL0: mcmal { 

compatible = "ibm,mcmal-460ex", "ibm,mcmal2"; 

dcr-reg = ; 

num-tx-chans = ; 

num-rx-chans = ; 




interrupts = < /*TXEOB*/ 6 4 

/*RXEOB*/ 7 4 

/*SERR*/ 3 4 

/*TXDE*/ 4 4 

/*RXDE*/ 5 4>; 

}; 

USB0: ehci@bffd0400 { 

compatible = "ibm,usb-ehci-460ex", "usb-ehci"; 



reg = ; 

}; 

USB1: usb@bffd0000 { 

compatible = "ohci-le"; 

reg = ; 



}; 

USBOTG0: usbotg@bff80000 { 

compatible = "amcc,usb-otg-460ex"; 

reg = ; 








}; 

POB0: opb { 

compatible = "ibm,opb-460ex", "ibm,opb"; 



ranges = ; 


EBC0: ebc { 

compatible = "ibm,ebc-460ex", "ibm,ebc"; 

dcr-reg = ; 




/* ranges property is supplied by U-Boot */ 




}; 

nor_flash@0,0 { 

compatible = "amd,s29gl512n", "cfi-flash"; 

bank-width = ; 

reg = ; 



partition@0 { 

label = "kernel"; 

reg = ; 

}; 

partition@1e0000 { 

label = "dtb"; 

reg = ; 

}; 


label = "root"; 

reg = ; 

}; 


label = "user"; 

reg = ; 

}; 

partition@3f60000 { 

label = "env"; 

reg = ; 

}; 

partition@3fa0000 { 

label = "u-boot"; 

reg = ; 

}; 

}; 

UART0: serial@ef600300 { 



reg = ; 



current-speed = ; /* Filled in by U-Boot */ 



}; 




reg = ; 






}; 




reg = ; 






}; 





reg = ; 






}; 

IIC0: i2c@ef600700 { 


reg = ; 



}; 

IIC1: i2c@ef600800 { 


reg = ; 



}; 

ZMII0: emac-zmii@ef600d00 { 

compatible = "ibm,zmii-460ex", "ibm,zmii"; 

reg = ; 

}; 

RGMII0: emac-rgmii@ef601500 { 

compatible = "ibm,rgmii-460ex", "ibm,rgmii"; 

reg = ; 

has-mdio; 

}; 

TAH0: emac-tah@ef601350 { 


reg = ; 

}; 

TAH1: emac-tah@ef601450 { 


reg = ; 

}; 

EMAC0: ethernet@ef600e00 { 









reg = ; 

local-mac-address = [000000000000]; /* Filled in by U-Boot */ 









phy-map = ; 


}; 

}; 







EMAC1: ethernet@ef600f00 { 









reg = ; 

local-mac-address = [000000000000]; /* Filled in by U-Boot */ 









phy-map = ; 







mdio-device = ; 

}; 

PCIX0: pci@c0ec00000 { 





compatible = "ibm,plb-pcix-460ex", "ibm,plb-pcix"; 

primary; 

large-inbound-windows; 

enable-msi-hole; 

reg = ; /* Internal messaging registers */ 

/* Outbound ranges, one memory and one IO, 

* later cannot be changed 

*/ 

ranges = ; 

/* Inbound 2GB range starting at 0 */ 

dma-ranges = ; 

/* This drives busses 0 to 0x3f */ 

bus-range = ; 

/* All PCI interrupts are routed to ext IRQ 2 -> UIC1-0 */ 


}; 


interrupt-map = < 0000 0 0 0 &UIC1 0 8 >; 

PCIE0: pciex@d00000000 { 





compatible = "ibm,plb-pciex-460ex", "ibm,plb-pciex"; 

primary; 

port = ; /* port number */ 

reg = ; /* Registers */ 

dcr-reg = ; 

sdr-base = ; 

}; 



*/ 

ranges = ; 



/* This drives busses 40 to 0x7f */ 

bus-range = ; 

/* Legacy interrupts (note the weird polarity, the bridge seems 

* to invert PCIe legacy interrupts). 

* We are de-swizzling here because the numbers are actually for 

* port of the root complex virtual P2P bridge. But I want 

* to avoid putting a node for it in the tree, so the numbers 

* below are basically de-swizzled numbers. 

* The real slot is on idsel 0, so the swizzling is 1:1 

*/ 


interrupt-map = < 

0000 0 0 1 &UIC3 c 4 /* swizzled int A */ 

0000 0 0 2 &UIC3 d 4 /* swizzled int B */ 

0000 0 0 3 &UIC3 e 4 /* swizzled int C */ 

0000 0 0 4 &UIC3 f 4 /* swizzled int D */>; 

PCIE1: pciex@d20000000 { 





compatible = "ibm,plb-pciex-460ex", "ibm,plb-pciex"; 

primary; 

port = ; /* port number */ 

reg = ; /* Registers */ 

dcr-reg = ; 

sdr-base = ; 



*/ 

ranges = ; 




}; 

}; 

}; 

/* This drives busses 80 to 0xbf */ 

bus-range = ; 

/* Legacy interrupts (note the weird polarity, the bridge seems 

* to invert PCIe legacy interrupts). 

* We are de-swizzling here because the numbers are actually for 

* port of the root complex virtual P2P bridge. But I want 

* to avoid putting a node for it in the tree, so the numbers 

* below are basically de-swizzled numbers. 

* The real slot is on idsel 0, so the swizzling is 1:1 

*/ 


interrupt-map = < 

0000 0 0 1 &UIC3 10 4 /* swizzled int A */ 

0000 0 0 2 &UIC3 11 4 /* swizzled int B */ 

0000 0 0 3 &UIC3 12 4 /* swizzled int C */ 

0000 0 0 4 &UIC3 13 4 /* swizzled int D */>; 

13.2. BDI2000 Configuration file 

; bdiGDB configuration file for AMCC 460EX Evaluation Kit "Canyonlands" 

; --------------------------------------------------------------------- 

; 

; 

[INIT] 

; Setup TLB 

WTLB 0xF0000095 0x4F00003F ;Boot Space 256MB 

WTLB 0x00000094 0x0000003F ;SDRAM 256MB @ 0x00000000 

WTLB 0x90000095 0x4000003F ;ISRAM/OCM 

; Setup Peripheral Bus 

;;;;;;;;;;;;;;;;;;;;;;;;;;;;; 

WDCR 0x12 0x00000010 ;Select EBC0_B0AP 

WDCR 0x13 0x10055e00 

WDCR 0x12 0x00000000 ;Select EBC0_B0CR 

WDCR 0x13 0xfc0da000 ; 64MByte 

; OCM 

;WDCR 0x20 0x40004580 ;16k 

[TARGET] 

JTAGCLOCK 1 ;use 8 MHz JTAG clock 

CPUTYPE 440 ;the used target CPU type 

WAKEUP 500 ;wakeup time after reset 

BREAKMODE HARD ;SOFT or HARD, HARD uses PPC hardware breakpoint 

STEPMODE HWBP ;JTAG or HWBP, HWBP uses one or two hardware breakpoints 

[HOST] 

IP 192.168.1.1 

FILE /tftpboot/canyonlands/u-boot.bin 

FORMAT BIN 

DUMP /tftpboot/canyonlands/dump.bin 

PROMPT 460EX> 

[FLASH] 

;WORKSPACE 0xe3040000 ;workspace in OCM 

;WORKSPACE 0x70000000 ;workspace in OCM 

;WORKSPACE 0x90040000 ;workspace in OCM 

CHIPTYPE MIRRORX16 ;Flash type 

CHIPSIZE 0x1000000 ;The size of one flash chip in bytes 

13.2. BDI2000 Configuration file 163

BUSWIDTH 16 ;The width of the flash memory bus in bits (8 | 16 | 32) 

FILE /tftpboot/canyonlands/u-boot.bin 

;FORMAT BIN 0xFFF80000 

FORMAT BIN 0xFFFA0000 

;ERASE 0xFFF80000 ;erase sector 4 

ERASE 0xFFFA0000 ;erase sector 4 

ERASE 0xFFFC0000 ;erase sector 4 

ERASE 0xFFFE0000 ;erase sector 6 

[REGS] 

FILE 

/tftpboot/BDI2000/reg460ex.def 

• 14. FAQ - Frequently Asked Questions 

♦ 14.1. ELDK 

◊ 14.1.1. ELDK Installation under FreeBSD 

◊ 14.1.2. ELDK Installation Hangs 

◊ 14.1.3. .gvfs: Permission Denied 

◊ 14.1.4. Installation on Local Harddisk 

◊ 14.1.5. ELDK Include Files Missing 

◊ 14.1.6. Using the ELDK on a 64 bit platform 

◊ 14.1.7. GDB Problems with BDI2000/BDI3000 on e500 Cores 

♦ 14.2. U-Boot 

◊ 14.2.1. Can U-Boot be configured such that it can be started in RAM 

◊ 14.2.2. Relocation cannot be done when using -mrelocatable 

◊ 14.2.3. U-Boot crashes after relocation to RAM 

◊ 14.2.4. Warning - bad CRC, using default environment 

◊ 14.2.5. Wrong debug symbols after relocation 

◊ 14.2.6. Decoding U-Boot Crash Dumps 

◊ 14.2.7. Porting Problem: cannot move location counter backwards 

◊ 14.2.8. U-Boot Doesn't Run after Upgrading my Compiler 

◊ 14.2.9. How Can I Reduce The Image Size 

◊ 14.2.10. Erasing Flash Fails 

◊ 14.2.11. Ethernet Does Not Work 

◊ 14.2.12. Where Can I Get a Valid MAC Address from 

◊ 14.2.13. Why do I get TFTP timeouts 

◊ 14.2.14. Why is my Ethernet operation not reliable 

◊ 14.2.15. How the Command Line Parsing Works 

⋅ 14.2.15.1. Old, simple command line parser 

⋅ 14.2.15.2. Hush shell 

⋅ 14.2.15.3. Hush shell scripts 

⋅ 14.2.15.4. General rules 

◊ 14.2.16. How can I load and uncompress a compressed image 

◊ 14.2.17. My standalone program does not work 

◊ 14.2.18. Linux hangs after uncompressing the kernel 

♦ 14.3. Linux 

◊ 14.3.1. Linux crashes randomly 

◊ 14.3.2. Linux crashes when uncompressing the kernel 

◊ 14.3.3. Linux Post Mortem Analysis 

◊ 14.3.4. Linux kernel register usage 

◊ 14.3.5. Linux Kernel Ignores my bootargs 

◊ 14.3.6. Cannot configure Root Filesystem over NFS 

◊ 14.3.7. Linux Kernel Panics because "init" process dies 

◊ 14.3.8. Unable to open an initial console 

13.2. BDI2000 Configuration file 164

◊ 14.3.9. Mounting a Filesystem over NFS hangs forever 

◊ 14.3.10. Ethernet does not work in Linux 

◊ 14.3.11. Loopback interface does not work 

◊ 14.3.12. Linux kernel messages are not printed on the console 

◊ 14.3.13. Linux ignores input when using the framebuffer driver 

◊ 14.3.14. How to switch off the screen saver and the blinking cursor 

◊ 14.3.15. BogoMIPS Value too low 

◊ 14.3.16. Linux Kernel crashes when using a ramdisk image 

◊ 14.3.17. Ramdisk Greater than 4 MB Causes Problems 

◊ 14.3.18. Combining a Kernel and a Ramdisk into a Multi-File Image 

◊ 14.3.19. Adding Files to Ramdisk is Non Persistent 

◊ 14.3.20. Kernel Configuration for PCMCIA 

◊ 14.3.21. Configure Linux for PCMCIA Cards using the Card Services package 

◊ 14.3.22. Configure Linux for PCMCIA Cards without the Card Services package 

⋅ 14.3.22.1. Using a MacOS Partition Table 

⋅ 14.3.22.2. Using a MS-DOS Partition Table 

◊ 14.3.23. Boot-Time Configuration of MTD Partitions 

◊ 14.3.24. Use NTP to synchronize system time against RTC 

◊ 14.3.25. Configure Linux for XIP (Execution In Place) 

⋅ 14.3.25.1. XIP Kernel 

⋅ 14.3.25.2. Cramfs Filesystem 

⋅ 14.3.25.3. Hints and Notes 

⋅ 14.3.25.4. Space requirements and RAM saving, an example 

◊ 14.3.26. Use SCC UART with Hardware Handshake 

◊ 14.3.27. How can I access U-Boot environment variables in Linux 

◊ 14.3.28. The =appWeb= server hangs *OR* /dev/random hangs 

◊ 14.3.29. Swapping over NFS 

♦ 14.4. Self 

◊ 14.4.1. How to Add Files to a SELF Ramdisk 

◊ 14.4.2. How to Increase the Size of the Ramdisk 

♦ 14.5. RTAI 

◊ 14.5.1. Conflicts with asm clobber list 

♦ 14.6. BDI2000 

◊ 14.6.1. Where can I find BDI2000 Configuration Files 

◊ 14.6.2. How to Debug Linux Exceptions 

◊ 14.6.3. How to single step through "RFI" instruction 

◊ 14.6.4. Setting a breakpoint doesn't work 

♦ 14.7. Motorola LITE5200 Board 

◊ 14.7.1. LITE5200 Installation Howto 

◊ 14.7.2. USB does not work on Lite5200 board 

14. FAQ - Frequently Asked Questions 

This is a collection of questions which came up repeatedly. Give me more feedback and I will add more stuff 

here. 

The items are categorized whether they concern U-Boot itself, the Linux kernel or the SELF framework. 

14.1. ELDK 

14.1. ELDK 165

14.1.1. ELDK Installation under FreeBSD 

Question: 

How can I install ELDK on a FreeBSD system 

Answer: 

[Thanks to Rafal Jaworowski for these detailed instructions.] This is a short tutorial how to host 

ELDK on FreeBSD 5.x and 6.x. The procedure described below was tested on 5.2.1, 5.3 and 6-current 

releases; we assume the reader is equipped with the ELDK 3.x CDROM or ISO image for installation, 

and is familiar with FreeBSD basic administration tasks like ports/packages installation. 

1. Prerequisites: 

1. Install linux_base 

2. 

The first step is to install the Linux compatibility layer from ports 

/usr/ports/emulators/linux_base/ or packages 

ftp://ftp.freebsd.org/pub/FreeBSD/ports/i386/packages/emulators 

Please make sure to install version 7.1_5 (linux_base-7.1_5.tbz) or later; 

in particular, version 6.1.5 which can also be found in the ports tree does not work 

properly! 

The compatibility layer is activated by 

# kldload linux 

2. Install bash 

Since ELDK and Linux build scripts are organised around bash while FreeBSD does 

not have it in base, this shell needs to be installed either from ports 

/usr/ports/shells/bash2/ or packages collection 

ftp://ftp.freebsd.org/pub/FreeBSD/ports/i386/packages/shells/ 

The installation puts the bash binary in /usr/local/bin. It is a good idea to 

create a symlink in /bin so that hash bang from scripts (#!/bin/bash) works 

without modifications: 

# cd /bin 

# ln -s /usr/local/bin/bash 

Prepare ELDK 

This step is only needed for ELDK release 3.1 and older versions. 

Copy the install files from the CDROM or ISO image to a writable location. Brand the ELDK 

installer as Linux ELF file: 

# cd 

# brandelf -t Linux ./install 

Note: The following workaround might be a good alternative for the tedious copying of 

the installation CDROM to a writable location and manual branding: you can set a fallback 

branding in FreeBSD - when the loader cannot recognise the ELF brand it will switch to the 

last resort defined. 

# sysctl -w kern.elf32.fallback_brand=3 

kern.elf32.fallback_brand: -1 -> 3 

14.1.1. ELDK Installation under FreeBSD 166

With this setting, the normal ELDK CDROM images should work. 

3. Install ELDK normally as described in 3.5.3. Initial Installation 

4. Set envrionment variables and PATH as needed for ELDK (in bash); for example: 

bash$ export CROSS_COMPILE=ppc_8xxbash$ 

export PATH=${PATH}:/opt/eldk/bin:/opt/eldk/usr/bin 

5. Hints for building U-Boot: 

FreeBSD normally uses BSD-style 'make' in base, but in order to compile U-Boot 

'gmake' (GNU make) has to be used; this is installed as part of the 'linux_base' 

package (see above). 

U-Boot should build according to standard ELDK instructions, for example: 

bash$ cd /opt/eldk/ppc_8xx/usr/src/u-boot-1.1.2 

bash$ gmake TQM823L_config 

bash$ gmake all 

6. Hints for building Linux: 

There are three issues with the Makefile in the Linux kernel source tree: 

⋅ GNU make has to be used. 

⋅ The 'expr' utility in FreeBSD base behaves differently from the version than is 

used in Linux so we need to modify the Makefile to explicitly use the Linux version 

(which is part of the Linux compatibility package). This is best achieved with 

defining "EXPR = /compat/linux/usr/bin/expr" somewhere at 

=Makefile='s beginning and replacing all references to 'expr' with the variable 

${EXPR). 

⋅ Some build steps (like when running 'scripts/mkdep' can generate very long 

arguments lists (especially is the Linux kernel tree is in a directory with long absolute 

filenames). A solution is to use xargs to split such long commands into several with 

shorter argument lists. 

The Linux kernel can then be built following the standard instructions, for example: 

bash$ cd /opt/eldk/ppc_8xx/usr/src/linux-2.4.25/ 

bash$ gmake mrproper 

bash$ gmake TQM823L_config 

bash$ gmake oldconfig 

bash$ gmake dep 

bash$ gmake -j6 uImage 

ELDK Installation Hangs 

Question: 

I try to install the ELDK on a Linux PC, and the installation hangs. It starts fine, but then it freezes 

like this: 

... 

Preparing... ########################################### [100%] 

1:db4-devel-ppc_4xx ########################################### [100%] 

Preparing... ########################################### [100%] 

1:db4-utils-ppc_4xx ########################################### [100%] 

Preparing... ########################################### [100%] 

1:glib2-ppc_4xx ########################################### [100%] 

Preparing... ########################################### [100%] 

1:glib2-devel-ppc_4xx ########################################### [100%] 

Preparing... ########################################### [100%] 

ELDK Installation Hangs 167

Answer: 

This is almost certainly a FUTEX problem. To verify this, please wait until the process grinds to a 

halt, then use ps to find the pid of the "rpm" process that was started by the "install" program 

(use "ps -axf" which gives you a nice hierarchy, look for the "install" process, then for 

"rpm") and then attach to it with "strace -p". Most probably you will see the something like 

this: 

# strace -p 21197 

Process 21197 attached - interrupt to quit 

futex(0x96fe17c, FUTEX_WAIT_PRIVATE, 1, NULL 

i. e. the process is hanging in a futex call. 

We have seen this more than once with differing Linux systems, but unfortunately we don't know a 

clean and reliable way to fix it yet. We suspect that it is a kernel/libc combination problem because it 

usually went away usually after changing the exact used kernel version. 

The only workaround we can recommend so far is to update your host system and install more recent 

versions of the Linux kernel and/or the glibc C library (assuming such are available for your Linux 

distribution; if not, falling back to a previous kernel version may help, too). 

Note: This is only needed for the installer, the problem does not happen with the regular use of the 

ELDK. 

14.1.3. .gvfs: Permission Denied 

Question: 

When trying to install the ELDK, I get error messages like this for each and every package that gets 

installed: 

Preparing... ################### 100% 

1: rpm... ################### 100% 

Error: Failed to stat /home/wd/.gvfs: Permission Denied 

This happens even though I run the installer as root. 

Answer: 

Even though flagged as an error, these messages are harmless warnings that can be safely ignored. 

Before the RPM tool starts to install a package, it checks if there is sufficient space for it in the file 

system. Unfortunately it is dumb and checks all mounted file systems for space, but the permissions 

of the ".gvfs" directory (the mount point for the Gnome Virtual File System) do not permit this. 

Note: 

Actually the messages are not printed despite the fact that you are running as root, but because you 

run as root. You have permissions to check the "$HOME/.gvfs" directory, while root gets an error: 

$ df -h /home/wd/.gvfs 

Filesystem 

Size Used Avail Use% Mounted on 

gvfs-fuse-daemon 0 0 0 - /home/wd/.gvfs 

$ sudo df -h /home/wd/.gvfs 

df: `/home/wd/.gvfs': Permission denied 

df: no file systems processed 

14.1.4. Installation on Local Harddisk 

Question: 

14.1.4. Installation on Local Harddisk 168

I have a local harddisk drive connected to my target board. Can I install the ELDK on it and run it like 

a standard Linux distribution 

Answer: 

Yes, this is possible. It requires only minor adjustments. The following example assumes you are 

using a SCSI disk drive, but the same can be done with standard SATA or PATA drives, too: 

1. Boot the target with root file system over NFS. 

2. Create the necessary partitions on your disk drive: you need at last a swap partition and a file 

system partition. 

bash-3.00# fdisk -l 

Disk /dev/sda: 36.9 GB, 36951490048 bytes 

64 heads, 32 sectors/track, 35239 cylinders 

Units = cylinders of 2048 * 512 = 1048576 bytes 


/dev/sda1 1 978 1001456 82 Linux swap / Solaris 

/dev/sda2 979 12423 11719680 83 Linux 



3. Format the partititons: 

bash-3.00# mkswap /dev/sda1 

bash-3.00# mke2fs -j -m1 /dev/sda2 

4. Mount the file system: 

bash-3.00# mount /dev/sda2 /mnt 

5. Copy the content of the (NFS) root file system into the mounted file system: 

bash-3.00# tar --one-file-system -c -f - / | ( cd /mnt ; tar xpf - ) 

6. Adjust /etc/fstab for the disk file system: 

bash-3.00# vi /mnt/etc/fstab 

bash-3.00# cat /mnt/etc/fstab 

/dev/sda2 / ext3 defaults 1 1 

/dev/sda1 swap swap defaults 0 0 

proc /proc proc defaults 0 0 

sysfs /sys sysfs defaults 0 0 

7. Adjust /etc/rc.sysinit for running from local disk; remove the following comments: 

8. 

bash-3.00# diff -u /mnt/etc/rc.sysinit.ORIG /mnt/etc/rc.sysinit 

--- /mnt/etc/rc.sysinit.ORIG 2007-01-21 04:37:00.000000000 +0100 

+++ /mnt/etc/rc.sysinit 2007-03-02 10:58:22.000000000 +0100 

@@ -460,9 +460,9 @@ 

# Remount the root filesystem read-write. 

update_boot_stage RCmountfs 

-#state=`LC_ALL=C awk '/ \/ / && ($3 !~ /rootfs/) { print $4 }' /proc/mounts` 

-#[ "$state" != "rw" -a "$READONLY" != "yes" ] && \ 

-# action $"Remounting root filesystem in read-write mode: " mount -n -o remount,rw 

+state=`LC_ALL=C awk '/ \/ / && ($3 !~ /rootfs/) { print $4 }' /proc/mounts` 

+[ "$state" != "rw" -a "$READONLY" != "yes" ] && \ 

+ action $"Remounting root filesystem in read-write mode: " mount -n -o remount,rw 

# Clean up SELinux labels 

if [ -n "$SELINUX" ]; then 

Unmount disk: 

bash-3.00# umount /mnt 

9. Reboot, and adjust boot arguments to use disk partition as root file system 

14.1.4. Installation on Local Harddisk 169

10. 

=> setenv diskargs setenv bootargs root=/dev/sda2 ro 

=> setenv net_disk 'tftp ${loadaddr} ${bootfile};run diskargs addip addcons;bootm' 

=> saveenv 

Boot with these settings 

=> run net_disk 

14.1.5. ELDK Include Files Missing 

Question: 

After configuring and compiling a Linux kernel in the kernel source tree that comes with the ELDK, I 

cannot compile user space programs any more - I get error messages because many #include file like 

etc. are missing. 

This is with ELDK 4.0 or 4.1. 

Answer: 

This problem is caused by the way how the ELDK is packaged. At the moment, the ELDK kernel 

headers are not packed into a separate "kernel-headers" RPM to avoid duplication, because the kernel 

source tree is always installed. Instead, the ELDK "kernel-headers" package is just a set of symlinks. 

This worked fine in the past, but fails with the new support for ARCH=powerpc systems. 

The next version of the ELDK will contain a real kernel-headers RPM, which will fix this problem. 

As a workaround on current systems, you can install the real kernel include files into the 

"include/asm", "include/linux" and "include/mtd" directories. 

To do this, the following commands can be used: 

bash$ /bin/rpm -e kernel-headers-ppc_ 

bash$ cd /ppc_ 

bash$ rm usr/include/asm 

bash$ tar -xvzf kernel-headers-powerpc.tar.gz 

The tarball mentioned above can be downloaded here. It contains the include files that get installed by 

running the "make ARCH=powerpc headers_install" command in the Linux kernel tree. 

This problem is fixed in ELDK 4.2 and later releases. 

14.1.6. Using the ELDK on a 64 bit platform 

As the ELDK is compiled for 32-bit host systems, a compatibility layer is required on 64-bit systems. This 

package is usually called ia32-libs. So on a Debian or Ubuntu system a 

sudo apt-get install ia32-libs 

should be enough to make the ELDK work. 

14.1.7. GDB Problems with BDI2000/BDI3000 on 

e500 Cores 

Question: 

I am using the cross-gdb from ELDK together with the BDI JTAG hardware debugger from Abatron 

to debug my e500 based system. When I try to attach to the BDI from within gdb, I get an error 

message like this: 

14.1.7. GDB Problems with BDI2000/BDI3000 on e500 Cores 170

$ ppc_85xxDP-gdb u-boot 

....... 

(gdb) target remote bdi14:2001 

Remote debugging using bdi14:2001 

Remote 'g' packet reply is too long: 

000000600fb7bd380fb7bf78e000450000000001000000000ffdd8c00ffd912400001c01000000000ffdd9fc000 

(gdb) 

Answer: 

If you are using at least BDI firmware v1.09 then most probably you forgot to include the following 

directive in the BDI config file: 

[TARGET] 

REGLIST E500 ;send registers in E500 sequence to GDB 

Also be sure that the gdb really thinks that it debugs an e500 core: 

(gdb) show architecture 

The target architecture is set automatically (currently powerpc:e500) 

(gdb) 

If this is not the case, then fix this problem first. It might just be that you are not using the right cross 

debugger in the first place. 

14.2. U-Boot 

14.2.1. Can U-Boot be configured such that it can 

be started in RAM 

Question: 

I don't want to erase my flash memory because I'm not sure if my new U-Boot image will work. Is it 

possible to configure U-Boot such that I can load it into RAM instead of flash, and start it from my 

old boot loader 

Answer: 

No. 

Question: 

But I've been told it is possible 

Answer: 

Well, yes. Of course this is possible. This is software, so everything is possible. But it is difficult, 

unsupported, and fraught with peril. You are on your own if you choose to do it. And it will not help 

you to solve your problem. 

Question: 

Why 

Answer: 

U-Boot expects to see a virgin CPU, i. e. the CPU state must match what you see if the processor 

starts executing the first instructions when it comes out of reset. If you want to start U-Boot from 

another boot loader, you must disable a lot of code, i. e. all initialization parts that already have been 

performed by this other boot loader, like setting up the memory controller, initializing the SDRAM, 

initializing the serial port, setting up a stack frame etc. Also you must disable the relocation to RAM 

14.2.1. Can U-Boot be configured such that it can be started in RAM 171

and adjust the link addresses etc. 

This requires a lot of experience with U-Boot, and the fact that you had to ask if this can be done 

means that you are not in a position to do this. 

The code you have to disable contains the most critical parts in U-Boot, i. e. these are the areas where 

99% or more of all errors are located when you port U-Boot to a new hardware. In the result, your 

RAM image may work, but in the end you will need a full image to program the flash memory with it, 

and then you will have to enable all this highly critical and completely untested code. 

You see You cannot use a RAM version of U-Boot to avoid testing a flash version, so you can save 

all this effort and just burn your image to flash. 

Question: 

So how can I test an U-Boot image and recover my system if it doesn't work 

Answer: 

Attach a BDI2000 to your board, burn the image to flash, and debug it in it's natural environment, i. e. 

U-Boot being the boot loader of the system and taking control over the CPU right as it comes out of 

reset. If something goes wrong, erase the flash and program a new image. This is a routine job using a 

BDI2000. 

14.2.2. Relocation cannot be done when using 

-mrelocatable 

Question: 

I use ELDK version 3.0. When I build U-Boot I get error messages like this: 

{standard input}: Assembler messages: 

{standard input}:4998: Error: Relocation cannot be done when using -mrelocatable 

... 

Answer: 

ELDK 3.0 uses GCC-3.2.2; your U-Boot sources are too old for this compiler. GCC-3.x requires a 

few adaptions which were added in later versions of U-Boot. Use for example the source tree (1.0.2) 

which is included with the ELDK, or download the latest version from CVS. 

14.2.3. U-Boot crashes after relocation to RAM 

Question: 

I have ported U-Boot to a custom board. It starts OK, but crashes or hangs after relocating itself to 

RAM. Why 

Answer: 

Your SDRAM initialization is bad, and the system crashes when it tries to fetch instructions from 

RAM. Note that simple read and write accesses may still work, it's the burst mode that is failing. This 

only shows up when caches are enabled because cache is the primary (or only) user of burst 

operations in U-Boot. In Linux, burst accesses may also result from DMA. For example, it is typical 

that a system may crash under heavy network load if the Ethernet controller uses DMA to memory. 

It is NOT sufficient to program the memory controller of your CPU; each SDRAM chip also 

requires a specific initialization sequence which you must adhere to to the letter - check with the chip 

14.2.3. U-Boot crashes after relocation to RAM 172

manufacturer's manual. 

It has been observed that some operating systems like pSOS+ or VxWorks do not stress the memory 

subsystem as much as Linux or other UNIX systems like LynxOS do, so just because your board 

appears to work running another OS does not mean it is 100% OK. 

Standard memory tests are not effective in identifying this type of problem because they do not cause 

stressful cache burst read/write operations. 

Argument: 

But my board ran fine with bootloader XYZ and/or operating system ABC. 

Answer: 

Double-check your configuration that you claim runs properly... 

1. Are you sure the SDRAM is initialized using the same init sequence and values 

2. Are you sure the memory controlling registers are set the same 

3. Are you sure your other configuration uses caches and/or DMA If it doesn't, it isn't a valid 

comparison. 

14.2.4. Warning - bad CRC, using default 

environment 

Question: 

I have ported U-Boot to a custom board. It seems to boot OK, but it prints: 


Why 

Answer: 

Most probably everything is OK. The message is printed because the flash sector or ERPROM 

containing the environment variables has never been initialized yet. The message will go away as 

soon as you save the envrionment variables using the saveenv command. 

14.2.5. Wrong debug symbols after relocation 

Question: 

I want to debug U-Boot after relocation to RAM, but it doesn't work since all the symbols are at 

wrong addresses now. 

Answer: 

To debug parts of U-Boot that are running from ROM/flash, i. e. before relocation, just use a 

command like "powerpc-linux-gdb uboot" as usual. 

For parts of U-Boot that run from RAM, i. e. after relocation, use "powerpc-linux-gdb" 

without arguments, and use the add-symbol-file command in GDB to load the symbol table at 

the relocation address in RAM. The only problem is that you need to know that address, which 

depends on RAM size, length reserved for U-Boot, size of "protected RAM" area, etc. If in doubt, 

enable DEBUG mode when building U-Boot so it prints the address to the console. 

14.2.5. Wrong debug symbols after relocation 173

Hint: I use definitions like these in my .gdbinit file: 

define rom 

symbol-file 

file u-boot 

end 

define ram 

symbol-file 

add-symbol-file u-boot 0x01fe0000 

end 

Note: when you want to switch modes during one debug session (i. e. without restarting GDB) you 

can "delete" the current symbol information by using the symbol-file command without 

arguments, and then either using "symbol-file u-boot" for code before relocation, or 

"add-symbol-file u-boot _offset_" for code after relocation. 

14.2.6. Decoding U-Boot Crash Dumps 

When you are porting U-Boot to new hardware, or implementing extensions, you might run into situations 

where U-Boot crashes and prints a register dump and a stack trace, for example like this: 

Bus Fault @ 0x00f8d70c, fixup 0x00000000 

Machine check in kernel mode. 

Caused by (from msr): regs 00f52cf8 Unknown values in msr 

NIP: 00F8D70C XER: 0000005F LR: 00F8D6F4 REGS: 00f52cf8 TRAP: 0200 DAR: F9F68C00 

MSR: 00009002 EE: 1 PR: 0 FP: 0 ME: 1 IR/DR: 00 

GPR00: 00016ACC 00F52DE8 00000000 F9F68C00 00FA38EC 00000001 F9F68BF8 0000000B 

GPR08: 00000002 00F55470 00000000 00F52D94 44004024 00000000 00FA2F00 C0F75000 

GPR16: 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 

GPR24: 00000000 00FA38EC 00F553C0 00F55480 00000000 00F52F80 00FA41C0 00000001 

Call backtrace: 

00000000 00F8F998 00F8FA88 00F8FAF8 00F90B5C 00F90CF8 00F8385C 

00F79E6C 00F773B0 

machine check 

To find out what happened, you can try to decode the stack backtrace (the list of addresses printed after the 

"Call backtrace:" line. The backtrace tool can be used for this purpose. However, there is a little 

problem: the addresses printed for the stack backtrace are after relocation of the U-Boot code to RAM; to use 

the backtrace tool you need to know U-Boot's address offset (the difference between the start address of 

U-Boot in flash and its relocation address in RAM). 

The easiest way to find out the relocation address is to enable debugging for the U-Boot source file 

lib_*/board.c - U-Boot will then print some debug messages 

... 

Now running in RAM - U-Boot at: 00f75000 

... 

Now you have to calculate the address offset between your link address (The value of the TEXT_BASE 

definition in your board//config.mk file). In our case this value is 0x40000000, so the address offset 

is 0x40000000 - 0x00f75000 = 0x3f08b000 

Now we use the backtrace script with the System.map file in the U-Boot source tree and this address 

offset: 

-> backtrace System.map 0x3f08b000 

14.2.6. Decoding U-Boot Crash Dumps 174

Reading symbols from System.map 

Using Address Offset 0x3f08b000 

0x3f08b000 -- unknown address 

0x4001a998 -- 0x4001a8d0 + 0x00c8 

0x4001aa88 -- 0x4001aa2c + 0x005c 

0x4001aaf8 -- 0x4001aad0 + 0x0028 

0x4001bb5c -- 0x4001ba68 + 0x00f4 

0x4001bcf8 -- 0x4001bcd8 + 0x0020 

0x4000e85c -- 0x4000e6f8 + 0x0164 

0x40004e6c -- 0x40004b9c + 0x02d0 

0x400023b0 -- 0x400023b0 + 0x0000 

free_pipe 

free_pipe_list 

run_list 

parse_stream_outer 

parse_file_outer 

main_loop 

board_init_r 

trap_init 

In this case the last "good" entry on the stack was in free_pipe... 

14.2.7. Porting Problem: cannot move location 

counter backwards 

Question: 

I'm trying to port U-Boot to a new board and the linker throws an error message like this: 

board//u-boot.lds:75 cannot move location counter backwards (from 00000000b0008 

Answer: 

Check your linker script board/your_board/u-boot.lds which controls how the object files 

are linked together to build the U-Boot image. 

It looks as if your board uses an "embedded" environment, i. e. the flash sector containing the 

environment variables is surrounded by code. The u-boot.lds tries to collect as many as possible 

code in the first part, making the gap between this first part and the environment sector as small as 

possible. Everything that does not fit is then placed in the second part, after the environment sector. 

Some your modifications caused the code that was put in this first part to grow, so that the linker finds 

that it would have to overwrite space that is already used. 

Try commenting out one (or more) line(s) before the line containing the 

"common/environment.o" statement. [ "lib_generic/zlib.o" is usually a good 

candidate for testing as it's big ]. Once you get U-Boot linked, you can check in the u-boot.map 

file how big the gap is, and which object files could be used to fill it up again. 

14.2.8. U-Boot Doesn't Run after Upgrading my 

Compiler 

Question: 

I encountered a big problem that U-Boot 1.1.4 compiled by ELDK 4.1 for MPC82xx crashed. 

But if I build it using gcc-3.4.6 based cross tools, U-Boot on my board boots correctly. 

The same U-Boot code built by ELDK 4.1 (gcc-4.0) failed, nothing occurs on the serial port. 

Answer: 

This is often a missing volatile attribute on shared variable references, particularly hardware 

registers. Newer compiler versions optimize more aggressively, making missing volatile 

14.2.8. U-Boot Doesn't Run after Upgrading my Compiler 175

attributes visible. 

If you use -O0 (no optimization) does it fix the problem 

If it does, it most likely is an optimization/volatile issue. The hard part is figuring out where. Device 

handling and board-specific code is the place to start. 

14.2.9. How Can I Reduce The Image Size 

Question: 

I am trying to reduce the size of the u-boot.bin file so that it fits into 256 KB. I disabled all the drivers 

that I didn't need but the binary size is still 512KB, it seems to be a hard number coded in somewhere. 

Where can the image size be altered from 

Answer: 

Some processors have a fixed reset vector address at 0xFFFFFFFC, so the U-Boot image has to 

include that address, i. e. it covers the full range from the start address to the end of the 32 bit address 

space. In such a case, the start address must be changed - check the setting of TEXT_BASE in your 

board//config.mk file. 

14.2.10. Erasing Flash Fails 

Question: 

I tried to erase the flash memory like 

erase 40050000 40050100 

It fails. What am I doing wrong 

Answer: 

Remember that flash memory cannot be erased in arbitrary areas, but only in so called "erase regions" 

or "sectors". If you have U-Boot running you can use the flinfo (Flash information, short fli) 

command to print information about the flash memory on your board, for instance: 

=> fli 

Bank # 1: AMD AM29LV160B (16 Mbit, bottom boot sect) 

Size: 4 MB in 35 Sectors 


40000000 (RO) 40008000 (RO) 4000C000 (RO) 40010000 (RO) 40020000 (RO) 

40040000 40060000 40080000 400A0000 400C0000 

400E0000 40100000 40120000 40140000 40160000 

40180000 401A0000 401C0000 401E0000 40200000 

40220000 40240000 40260000 40280000 402A0000 

402C0000 402E0000 40300000 40320000 40340000 

40360000 40380000 403A0000 403C0000 403E0000 

In the example above, the area 40050000 ... 40050100 lies right in the middle of a erase unit 

(40040000 ... 4005FFFF), so you cannot erase it without erasing the whole sector, i. e. you have to 

type 

=> erase 40040000 4005FFFF 

Also note that there are some sectors marked as read-only ((RO)); you cannot erase or overwrite 

14.2.10. Erasing Flash Fails 176

these sectors without un-protecting the sectors first (see the U-Boot protect command). 

14.2.11. Ethernet Does Not Work 

Question: 

Ethernet does not work on my board. 

Answer: 

Maybe you forgot to set a MAC address Check if the "ethaddr" environment variable is defined, 

and if it has a sane value. If there are more than one Ethernet interfaces on your board, you may also 

have to check the MAC addresses for these, i. e. check the "eth1addr", "eth2addr", etc. 

variables, too. 

Question: 

I have configured a MAC address of 01:02:03:04:05:06, and I can see that an ARP packet is sent by 

U-Boot, and that an ARP reply is sent by the server, but U-Boot never receives any packets. What's 

wrong 

Answer: 

You have chosen a MAC address which, according to the ANSI/IEEE 802-1990 standard, has the 

multicast bit set. Under normal conditions a network interface discards such packets, and this is what 

U-Boot is doing. This is not a bug, but correct behaviour. 

Please use only valid MAC addresses that were assigned to you. 

For bring-up testing in the lab you can also use so-called locally administered ethernet addresses. 

These are addresses that have the 2nd LSB in the most significant byte of MAC address set. The 

gen_eth_addr tool that comes with U-Boot (see "tools/gen_eth_addr" ) can be used to 

generate random addresses from this pool. 

14.2.12. Where Can I Get a Valid MAC Address 

from 

Question: 

Where can I get a valid MAC address from 

Answer: 

You have to buy a block of 4096 MAC addresses (IAB = Individual Address Block) or a block of 

16M MAC addresses (OUI = Organizationally Unique Identifier, also referred to as 'company id') 

from IEEE Registration Authority. The current cost of an IAB is $550.00, the cost of an OUI is 

$1,650.00. See http://standards.ieee.org/regauth/oui/index.shtml 

You can buy Eproms containing MAC addresses from: Maxim or Microchip. 

You can set the "locally administered" bit to make your own MAC address (no guarantee of 

uniqueness, but pretty good odds if you don't do something dumb). Ref: Wikipedia 

Universally administered and locally administered addresses are distinguished by 

setting the second least significant bit of the most significant byte of the address. If 

the bit is 0, the address is universally administered. If it is 1, the address is locally 

14.2.12. Where Can I Get a Valid MAC Address from 177

administered. The bit is 0 in all OUIs. For example, 02-00-00-00-00-01. The most 

significant byte is 02h. The binary is 00000010 and the second least significant bit is 

1. Therefore, it is a locally administered address. 

14.2.13. Why do I get TFTP timeouts 

Question 1:: When trying to download a file from the TFTP server I always get timeouts like these: 

... 

Loading: #######T ##################################T###################T ####T ##T # 

###T #T #########T ########T #############T ##T #############T ########T #############T 

#####T ###T ######T #######T #######T #############T ##T ##############T ########### 

########### 

done 

If the target is connected directly to the host PC (i. e. without a switch inbetween) the problem goes away or is 

at least less incisive. 

What's wrong 

Answer 1:: Most probably you have a full duplex/half duplex problem. Verify that U-Boot is setting the 

ethernet interface on your board to the proper duplex mode (full/half). I'm guessing your board is half duplex 

but your switch is full (typical of a switch ;-). 

The switch sends traffic to your board while your board is transmitting... that is a collision (late collision at 

that) to your board but is OK to the switch. This doesn't happen nearly as much with a direct link to your PC 

since then you have a dedicated link without much asynchronous traffic. 

The software (U-Boot/Linux) needs to poll the PHY chip for duplex mode and then (re)configure the MAC 

chip (separate or built into the CPU) to match. If the poll isn't happening or has a bug, you have problems like 

described above. 

Question 2:: When I use tftp, there are some problems. My terminal always displays "Loading: T T T T T T T 

T T T T T T T T T T T T T". The whole information as follows: 

U-Boot 1.1.4_XT (Jun 6 2006 - 17:36:18) 

U-Boot code: 0C300000 -> 0C31AD70 BSS: -> 0C31EF98 

RAM Configuration: 

Bank #0: 0c000000 8 MB 

Bank #1: 0c800000 8 MB 

Flash: 2 MB 


In: serial 

Out: serial 

Err: serial 


XT=> help tftp 

tftpboot [loadAddress] [bootfilename] 

XT=> tftpboot 0x0c700000 image.bin 


Filename 'image.bin'. 

Load address: 0xc700000 

Loading: T T T T T T T T T T T T T T T T T T T T 

Retry count exceeded; starting again 


Would someone give me some suggestions 

14.2.13. Why do I get TFTP timeouts 178

Answer 2:: (1) Verify your TFTP server is working. On a machine (not the TFTP server nor your 

development board) use tftp to read the target file. 

$ tftp 192.168.0.23 get image.bin 

If this doesn't work, fix your TFTP server configuration and make sure it is running. 

(2) If your TFTP server is working, run ethereal (or equivalent ethernet sniffing) to see what ethernet packets 

are being sent by your development board. It usually works best to run ethereal on your TFTP server (if you 

run it on a different machine and you use an ethernet switch, the third machine likely won't see the tftp 

packets). 

14.2.14. Why is my Ethernet operation not reliable 

Question: 

My ethernet connection is not working reliable. On one switch it works fine, but on another one it 

doesn't. 

or: 

Question: 

I always see transmit errors or timeouts for the first packet of a download, but then it works well. 

or: 

Question: 

I cannot mount the Linux root file system over NFS; especially not with recent Linux kernel versions 

(older kernel versions work better). Specifying "proto=tcp" as mount option greatly improves the 

situation. 

etc. 

Answer: 

There are many possible explanations for such problems. After eliminating the obvious sources (like 

broken cables etc.) you should check the configuration of your Ethernet PHY. One common cause of 

problems is if your PHY is hard configured in duplex mode (for example 100baseTX Full Duplex or 

10baseT Full Duplex). If such a setup is combined with a autonegotiating switch, then trouble is 

ahead. 

Jerry Van Baren explained this as follows: 

Ignoring the configuration where both ends are (presumably correctly) 

manually configured, you end up with five cases, two of them 

misconfigured and WRONG: 

1) Autonegotiation autonegotiation - reliable. 

2) 10bT half duplex autonegotiation - reliable. 

3) 100bT half duplex autonegotiation - reliable. 

4) 10bT *FULL* duplex autonegotiation - *UNreliable*. 

5) 100bT *FULL* duplex autonegotiation - *UNreliable*. 

The problem that I've observed is that the *humans* (the weak links) 

that do the manual configuration don't understand that "parallel 

detection" *must be* half duplex by definition in the spec (it is hard 

to define a reliable algorithm to detect full duplex capability so the 

spec writers punted). As a result, the human invariably picks "full 

duplex" because everybody knows full duplex is better... and end up as 

case (4) or (5). They inadvertently end up with a slower unreliable 

link (lots of "collisions" resulting in runt packets) rather than the 

14.2.14. Why is my Ethernet operation not reliable 179

faster better link they thought they were picking (d'oh!). The really 

bad thing is that the network works fine in testing on an isolated LAN 

with no traffic and absolutely craps its pants when it hits the real 

world. 

Rule: 

That is my reasoning behind my statement that we can generally ignore 

the autonegotiation fixed configuration case because the odds of it 

working properly are poor anyway. 

Always try to set up your PHY for autonegotiation. 

If you must use some fixed setting, then set it to half duplex mode. 

If you really must use a fixed full-duplex setting, then you absolutley must make sure that the link 

partner is configured exactly the same. 

14.2.15. How the Command Line Parsing Works 

There are two different command line parsers available with U-Boot: the old "simple" one, and the much 

more powerful "hush" shell: 

14.2.15.1. Old, simple command line parser 

• supports environment variables (through setenv / saveenv commands) 

• several commands on one line, separated by ';' 

• variable substitution using "... ${_variablename_} ..." syntax 

NOTE: Older versions of U-Boot used "$(...)" for variable substitution. Support for this 

syntax is still present in current versions, but will be removed soon. Please use "${...}" instead, 

which has the additional benefit that your environment definitions are compatible with the Hush shell, 

too. 

• special characters ('$', ';') can be escaped by prefixing with '\', for example: 

setenv bootcmd bootm \${address} 

• You can also escape text by enclosing in single apostrophes, for example: 

setenv addip 'setenv bootargs ${bootargs} ip=${ipaddr}:${serverip}:${gatewayip}:${n 

14.2.15.2. Hush shell 

• similar to Bourne shell, with control structures like if...then...else...fi, 

for...do...done, while...do...done, until...do...done, ... 

• supports environment ("global") variables (through setenv / saveenv commands) and local shell 

variables (through standard shell syntax name=value ); only environment variables can be used 

with the run command, especially as the variable to run (i. e. the first argument). 

• In the current implementation, the local variables space and global environment variables space are 

separated. Local variables are those you define by simply typing like name=value. To access a 

local variable later on, you have to write '$name' or '${name}'; to execute the contents of a 

variable directly you can type '$name' at the command prompt. Note that local variables can only 

be used for simple commands, not for compound commands etc. 

• Global environment variables are those you can set and print using setenv and printenv. To run 

a command stored in such a variable, you need to use the run command, and you must not use the '$' 

sign to access them. 

• To store commands and special characters in a variable, use single quotation marks surrounding the 

whole text of the variable, instead of the backslashes before semicolons and special symbols. 

• Be careful when using the hash ('#') character - like with a "real" Bourne shell it is the comment 

14.2.15. How the Command Line Parsing Works 180

Examples: 

character, so you have to escape it when you use it in the value of a variable. 

setenv bootcmd bootm \$address 

setenv addip 'setenv bootargs $bootargs ip=$ipaddr:$serverip:$gatewayip:$netmask:$hostnam 

14.2.15.3. Hush shell scripts 

Here are a few examples for the use of the advanced capabilities of the hush shell in U-Boot environment 

variables or scripts: 

Example: 

Example: 

=> setenv check 'if imi $addr; then echo Image OK; else echo Image corrupted!!; fi' 

=> print check 

check=if imi $addr; then echo Image OK; else echo Image corrupted!!; fi 

=> addr=0 ; run check 


Bad Magic Number 

Image corrupted!! 

=> addr=40000 ;run check 


Image Name: ARM Linux-2.4.18 

Created: 2003-06-02 14:10:54 UTC 

Image Type: ARM Linux Kernel Image (gzip compressed) 


Load Address: 0c008000 

Entry Point: 0c008000 


Image OK 

Instead of "echo Image OK" there could be a command (sequence) to boot or otherwise deal with 

the correct image; instead of the "echo Image corrupted!!" there could be a command 

(sequence) to (load and) boot an alternative image, etc. 

=> addr1=0 

=> addr2=10 

=> bootm $addr1 || bootm $addr2 || tftpboot $loadaddr $loadfile && bootm 






Filename '/tftpboot/TRAB/uImage'. 

Load address: 0xc400000 

Loading: ################################################################# 

################################################################# 

########################### 

done 

Bytes transferred = 801673 (c3b89 hex) 

## Booting image at 0c400000 ... 

Image Name: ARM Linux-2.4.18 

14.2.15.2. Hush shell 181

This will check if the image at (flash) address "addr1" is ok and boot it; if the image is not ok, the 

alternative image at address "addr2" will be checked and booted if it is found to be OK. If both 

images are missing or corrupted, a new image will be loaded over TFTP and booted. 

14.2.15.4. General rules 

1. If a command line (or an environment variable executed by a run command) contains several 

commands separated by semicolons, and one of these commands fails, the remaining commands will 

still be executed. 

2. If you execute several variables with one call to run (i. e. calling run with a list of variables as 

arguments), any failing command will cause run to terminate, i. e. the remaining variables are not 

executed. 

14.2.16. How can I load and uncompress a 

compressed image 

Question: 

Can I use U-Boot to load and uncompress a compressed image from flash into RAM And can I 

choose whether I want to automatically run it at that time, or wait until later 

Answer: 

Yes to both questions. First, you should generate your image as type "standalone" (using "mkimage 

... -T standalone ..."). When you use the bootm command for such an image, U-Boot 

will automatically uncompress the code while it is storing it at that image's load address in RAM 

(given by the -a option to the mkimage command). 

As to the second question, by default, unless you say differently, U-Boot will automatically start the 

image by jumping to its entry point (given by the -e option to mkimage) after loading it. If you want 

to prevent automatic execution, just set the environment variable "autostart" to "no" 

("setenv autostart no") before running bootm. 

14.2.17. My standalone program does not work 

Question: 

I tried adding some new code to the hellow_world.c demo program. This works well as soon as I 

only add code to the existing hello_world() function, but as soon as I add some functions of my own, 

things go all haywire: the code of the hello_world() function does not get executed correctly, and my 

new function gets called with unexpected arguments. What's wrong 

Answer: 

You probably failed to notice that any code you add to the example program may shift the entry point 

address. You should check this using the nm program: 

$ ${CROSS_COMPILE}nm -n examples/hello_world 

0000000000040004 T testfunc 

0000000000040058 T hello_world 

000000000004016c t dummy 

... 

As you can see, the entry point (function hello_world()) is no longer at 0x40004 as it was before and 

14.2.17. My standalone program does not work 182

as it's documented. Instead, it is now at 0x40058. So you have to start your standalone program at this 

address, and everything should work well. 

14.2.18. Linux hangs after uncompressing the 

kernel 

Question: 

I am using U-Boot with a Linux kernel version Y (Y < 2.4.5-pre5), but the last message I see is 


Then the system hangs. 

Answer: 

Most probably you pass bad parameters to the Linux kernel. 

There are several possible reasons: 

◊ Bad device tree; for example, check that the memory map set up by the boot loader (like 

mapping of IMMR, PCI addresses etc.) is consistent with what is encoded in your device tree 

specification. 

Here some possible reasons for older Linux kernel versions: 

Linux: 

arch/ppc: 

◊ arch/ppc: Bad definition of the bd_info structure 

You must make sure that your machine specific header file (for instance 

include/asm-ppc/tqm8xx.h) includes the same definition of the Board Information structure as 

we define in include/ppcboot.h, and make sure that your definition of IMAP_ADDR uses the 

same value as your U-Boot configuration in CFG_IMMR. 

◊ Bad clock information 

Before kernel version 2.4.5-pre5 (BitKeeper Patch 1.1.1.6, 22MAY2001) the kernel expected 

the clock information in MHz, but recent kernels expect it in Hz instead. U-Boot passes the 

clock information in Hz by default. To switch to the old behaviour, you can set the 

environment variable "clocks_in_mhz" in U-Boot: 

=> setenv clocks_in_mhz 1 

=> saveenv 

For recent kernel the "clocks_in_mhz" variable must not be set. If it is present in your environment, you 

can delete it as follows: 

=> setenv clocks_in_mhz 

=> saveenv 

A common error is to try "setenv clocks_in_mhz 0" or to some other value - this will not work, 

as the value of the variable is not important at all. It is the existence of the variable that will be checked. 

• 

♦ Inconsistent memory map 

Some boards may need corrct mappings for some special hardware devices like BCSR (Board 

Control and Status Registers) etc. Verify that the mappings expected by Linux match those 

created by U-Boot. 

14.2.18. Linux hangs after uncompressing the kernel 183

14.3. Linux 

14.3.1. Linux crashes randomly 

Question: 

On my board, Linux crashes randomly or has random exceptions (especially floating point exceptions 

if it is a PowerPC processor). Why 

Answer: 

Quite likely your SDRAM initialization is bad. See UBootCrashAfterRelocation for more 


On a PowerPC, the instructions beginning with 0xFF are floating point instructions. When your 

memory subsystem fails, the PowerPC is reading bad values (0xFF) and thus executing illegal 

floating point instructions. 

14.3.2. Linux crashes when uncompressing the 

kernel 

Question: 

When I try to boot Linux, it crashes during uncompressing the kernel image: 

=> bootm 100000 








Uncompressing Kernel Image ... Error: inflate() returned -3 

GUNZIP ERROR - must RESET board to recover 

Answer: 

Your kernel image is quite big - nearly 1 MB compressed; when it gets uncompressed it will need 2.5 

... 3 MB, starting at address 0x0000. But your compressed image was stored at 1 MB (0x100000), so 

the uncompressed code will overwrite the (remaining) compressed image. The solution is thus simple: 

just use a higher address to download the compressed image into RAM. For example, try: 

=> bootm 400000 

14.3.3. Linux Post Mortem Analysis 

You may find yourself in a situation where the Linux kernel crashes or hangs without any output on the 

console. The first attempt to get more information in such a situation is a Post Mortem dump of the log buffer 

- often the Linux kernel has already collected useful information in its console I/O buffer which just does not 

get printed because the kernel does not run until successful initialization of the console port. 

Proceed as follows: 

14.3.3. Linux Post Mortem Analysis 184

1. 

Find out the virtual address of the log buffer; For 2.4 Linux kernels search for "log_buf": 

2.4 Linux: 

bash$ grep log_buf System.map 

c0182f54 b log_buf 

Here the virtual address of the buffer is 0xC0182F54 

For 2.6 kernels "__log_buf" must be used: 

bash$ grep __log_buf System.map 

c02124c4 b __log_buf 

Here the virtual address of the buffer is 0xC02124C4 

2. Convert to physical address: on PowerPC systems, the kernel is usually configured for a virtual 

address of kernel base (CONFIG_KERNEL_START) of 0xC0000000. Just subtract this value from 

the address you found. In our case we get: 

physical address = 0xC0182F54 - 0xC0000000 = 0x00182F54 

3. Reset your board - do not power-cycle it! 

4. Use your boot loader (you're running U-Boot, right) to print a memory dump of that memory area: 

=> md 0x00182F54 

This whole operation is based on the assumption that your boot loader does not overwrite the RAM contents - 

U-Boot will take care not to destroy such valuable information. 

14.3.4. Linux kernel register usage 

For the PowerPC architecture, the Linux kernel uses the following registers: 

R1: 

stack pointer 

R2: 

pointer to task_struct for the current task 

R3-R4: 

parameter passing and return values 

R5-R10: 

parameter passing 

R13: 

small data area pointer 

R30: 

GOT pointer 

R31: 

frame pointer 

A function can use r0 and r3 - r12 without saving and restoring them. r13 - r31 have to be preserved so 

they must be saved and restored when you want to use them. Also, cr2 - cr4 must be preserved, while cr0, 

cr1, cr5 - cr7, lr, ctr and xer can be used without saving & restoring them. [ Posted Tue, 15 Jul 2003 

by Paul Mackerras to linuxppc-embedded@lists.linuxppc.org ]. 

See also the (E)ABI specifications for the PowerPC architecture, Developing PowerPC Embedded 

Application Binary Interface (EABI) Compliant Programs 

14.3.4. Linux kernel register usage 185

14.3.5. Linux Kernel Ignores my bootargs 

Question: 

Why doesn't the kernel use the command-line options I set in the "bootargs" environment variable in 

U-Boot when I boot my target system 

Answer: 

This problem is typical for ARM systems only. The following discussion is ARM-centric: 

First, check to ensure that you have configured your U-Boot build so that CONFIG_CMDLINE_TAG 

is enabled. (Other tags like CONFIG_SETUP_MEMORY_TAGS or CONFIG_INITRD_TAG may be 

needed, too.) This ensures that u-boot will boot the kernel with a command-line tag that incorporates 

the kernel options you set in the "bootargs" environment variable. 

If you have the CONFIG_CMDLINE_TAG option configured, the problem is almost certainly with 

your kernel build. You have to instruct the kernel to pick up the boot tags at a certain address. This is 

done in the machine descriptor macros, which are found in the processor start-up C code for your 

architecture. For the Intel DBPXA250 "Lubbock" development board, the machine descriptor 

macros are located at the bottom of the file arch/arm/mach-pxa/lubbock.c, and they look 

like this: 

MACHINE_START(LUBBOCK, "Intel DBPXA250 Development Platform") 

MAINTAINER("MontaVista Software Inc.") 

BOOT_MEM(0xa0000000, 0x40000000, io_p2v(0x40000000)) 

FIXUP(fixup_lubbock) 

MAPIO(lubbock_map_io) 

INITIRQ(lubbock_init_irq) 

MACHINE_END 

The machine descriptor macros for your machine will be located in a similar file in your kernel source 

tree. Having located your machine descriptor macros, the next step is to find out where U-Boot puts 

the kernel boot tags in memory for your architecture. On the Lubbock, this address turns out to be the 

start of physical RAM plus 0x100, or 0xa0000100. Add the "BOOT_PARAMS" macro with this 

address to your machine descriptor macros; the result should look something like this: 

MACHINE_START(LUBBOCK, "Intel DBPXA250 Development Platform") 

MAINTAINER("MontaVista Software Inc.") 

BOOT_PARAMS(0xa0000100) 

BOOT_MEM(0xa0000000, 0x40000000, io_p2v(0x40000000)) 

FIXUP(fixup_lubbock) 

MAPIO(lubbock_map_io) 

INITIRQ(lubbock_init_irq) 

MACHINE_END 

If there is already a BOOT_PARAMS macro in your machine descriptor macros, modify it so that it 

has the correct address. Then, rebuild your kernel and re-install it on your target. Now the kernel 

should be able to pick up the kernel options you have set in the "bootargs" environment variable. 

14.3.6. Cannot configure Root Filesystem over NFS 

Question: 

I want to configure my system with root filesystem over NFS, but I cannot find any such 

configuration option. 

Answer: 

14.3.6. Cannot configure Root Filesystem over NFS 186

What you are looking for is the CONFIG_ROOT_NFS configuration option, which depends on 

CONFIG_IP_PNP. 

To enable root filesystem over NFS you must enable the "IP: kernel level 

autoconfiguration" option in the "Networking options" menu first. 

14.3.7. Linux Kernel Panics because "init" process 

dies 

Question: 

I once had a running system but suddenly, without any changes, the Linux kernel started crashing 

because the "init" process was dying each time I tried to boot the system, for example like that: 

... 

VFS: Mounted root (nfs filesystem). 


init has generated signal 11 but has no handler for it 

Kernel panic - not syncing: Attempted to kill init! 

Answer: 

You probably run your system with the root file system mounted over NFS. Change into the root 

directory of your target file system, and remove the file "etc/ld.so.cache". That should fix this 

problem: 

# cd /opt/eldk/ppc_6xx/ 

# rm -f etc/ld.so.cache 

Explanation: 

Normally, the file "etc/ld.so.cache" contains a compiled list of system libraries. This file is 

used by the dynamic linker/loader ld.so to cache library information. If it does not exist, rebuilt 

automatically. For some reason, a corrupted or partial file was written to your root file system. This 

corrupt file then confused the dynamic linker so that it crashed when trying to start the init process. 

14.3.8. Unable to open an initial console 

Question: 

The Linux kernel boots, but then hangs after printing: "Warning: unable to open an initial console". 

Answer: 

Most probably you have one or missing entries in the /dev directory in your root filesystem. If you 

are using the ELDK's root filesystem over NFS, you probably forgot to run the ELDK_MAKEDEV and 

ELDK_FIXOWNER scripts as described in 3.7. Mounting Target Components via NFS. 

14.3.9. Mounting a Filesystem over NFS hangs 

forever 

Question: 

We use the SELF ramdisk image that comes with the ELDK. When we try to mount a filesystem over 

NFS from the server, for example: 

# mount -t nfs 192.168.1.1:/target/home /home 

14.3.9. Mounting a Filesystem over NFS hangs forever 187

the command waits nearly 5 minutes in uninterruptable sleep. Then the mount finally succeeds. 

What's wrong 

Answer: 

The default configuration of the SELF was not designed to mount additional filesystems with file 

locking over NFS, so no portmap deamon is running, which is causing your problems. There are two 

solutions for the problem: 

1. Add the portmap deamon (/sbin/portmap) to the target filesystem and start it as part of 

the init scripts. 

2. Tell the "mount" program and the kernel that you don't need file locking by passing the 

"nolock" option to the mount call, i. e. use 

# mount -o nolock -t nfs 192.168.1.1:/target/home /home 

Explanation: 

If you call the mount command like above (i. e. without the "nolock" option) an RPC call to the 

"portmap" deamon will be attempted which is required to start a lockd kernel thread which is 

necessary if you want to use file locking on the NFS filesystem. This call will fail only after a very 

long timeout. 

14.3.10. Ethernet does not work in Linux 

Question: 

Ethernet does not work on my board. But everything is fine when I use the ethernet interface in 

U-Boot (for example by performing a TFTP download). This is a bug in U-Boot, right 

Answer: 

No. It's a bug in the Linux ethernet driver. 

In some cases the Linux driver fails to set the MAC address. That's a buggy driver then - Linux 

ethernet drivers are supposed to read the MAC address at startup. On ->open, they are supposed to 

reprogram the MAC address back into the chip (but not the EEPROM, if any) whether or not the 

address has been changed. 

In general, a Linux driver shall not make any assumptions about any initialization being done (or not 

done) by a boot loader; instead, that driver is responsible for performing all of the necessary 

initialization itself. 

And U-Boot shall not touch any hardware it does not access itself. If you don't use the ethernet 

interface in U-Boot, it won't be initialized by U-Boot. 

A pretty extensive discussion of this issue can be found in the thread ATAG for MAC address on the 

ARM Linux mailing list. archive 1 archive 2 

Some current methods for handling the MAC address programming: 

• use custom ATAGs (ARM systems) 

• use a Flattened Device Tree (if your arch/port supports it) 

• parse the U-Boot environment directly 

• pass it via the command line 

If your device driver does not support one of these sources directly, then do it yourself: 

14.3.10. Ethernet does not work in Linux 188

• add an init board hook 

• program it from user space (ìfconfig hw ...`) 

• for people who need to do NFS root or similar, then use initramfs -- this is what it was designed for ! 

14.3.11. Loopback interface does not work 

Question: 

When I boot Linux I get a "socket: Address family not supported by protocol" 

error message when I try to configure the loopback interface. What's wrong 

Answer: 

This is most probably a problem with your kernel configuration. Make sure that the 

CONFIG_PACKET option is selected. 

14.3.12. Linux kernel messages are not printed on 

the console 

Question: 

I expect to see some Linux kernel messages on the console, but there aren't any. 

Answer: 

This is absolutely normal when using the ELDK with root filesystem over NFS. The ELDK startup 

routines will start the syslog daemon, which will collect all kernel messages and write them into a 

logfile ( /var/log/messages ). 

If you want to see the messages at the console, either run "tail -f /var/log/messages &" 

on the console window, or stop the syslog daemon by issuing a "/etc/rc.d/init.d/syslog 

stop" command. Another alternative is to increase the console_loglevel of the kernel (any 

message with log level less than console_loglevel will be printed to the console). With the 

following command the console_loglevel could be set at runtime: "echo 8 > 

/proc/sys/kernel/printk". Now all messages are displayed on the console. 

14.3.13. Linux ignores input when using the 

framebuffer driver 

Question: 

When using the framebuffer driver the console output goes to the LCD display, but I cannot input 

anything. What's wrong 

Answer: 

You can define "console devices" using the console= boot argument. Add something like this to your 

bootargs setting: 

... console=tty0 console=ttyS0,${baudrate} ... 

This will ensure that the boot messages are displayed on both the framebuffer (/dev/tty0) and the serial 

console (/dev/ttyS0); the last device named in a console= option will be the one that takes input, 

too, so with the settings above you can use the serial console to enter commands etc. For a more 

14.3.13. Linux ignores input when using the framebuffer driver 189

detailed description see 

http://www.tldp.org/HOWTO/Remote-Serial-Console-HOWTO/configure-kernel.html 

14.3.14. How to switch off the screen saver and the 

blinking cursor 

Question: 

I'm using a splash screen on my frame buffer display, but it is disturbed by a blinking cursor, and after 

a while the screen is blanked. How can I prevent this 

Answer: 

Screen saver and blinking cursor can be turned off (and on) using escape sequences. 

To turn off the screen saver, send the sequence "\E[9;0]" to the terminal ="/dev/tty1". For 

example, output the content of file "/etc/blank_off" in one of your init scripts: 

# cat /etc/blank_off 

To turn off the blinking cursor, send the sequence "\E[25l\E[1c" to the terminal. For 

example, copy the content of file "/etc/init_tty" to the terminal: 

# cat /etc/init_tty 

For details, please see "man 4 console_codes" . 

14.3.15. BogoMIPS Value too low 

Question: 

We are only seeing 263.78 bogomips on a MPC5200 running at 396 MHz. 

Doesn't this seem way to low With a 603e core I'd expect 1 bogomip per MHz or better. 

Answer: 

No, the values you see is correct. Please keep in mind that there is a good reason for the name 

BogoMIPS. 

On PowerPC, the bogomips calculation is measuring the speed of a dbnz instruction. On some 

processors like the MPC8xx it takes 2 clocks per dbnz instruction, and you get 1 BogoMIP/MHz. 

The MPC5200 takes 3 clocks per dbnz in this loop, so you get .67 BogoMIP/MHz. 

See also The frequently asked questions about BogoMips. 

14.3.16. Linux Kernel crashes when using a 

ramdisk image 

Question: 

I have a PowerPC board with 1 GiB of RAM (or more). It works fine with root file system over NFS, 

but it will crash when I try to use a ramdisk. 

Answer: 

14.3.16. Linux Kernel crashes when using a ramdisk image 190

Check where your ramdisk image gets loaded to. In the standard configuration, the Linux kernel can 

access only 768 MiB of RAM, so your ramdisk image must be loaded below this limit. Check your 

boot messages. You are hit by this problem when U-Boot reports something like this: 

Loading Ramdisk to 3fdab000, end 3ff2ff9d ... OK 

and then Linux shows a message like this: 

mem_pieces_remove: [3fdab000,3ff2ff9d) not in any region 

To fix, just tell U-Boot to load the ramdisk image below the 768 MB limit: 

=> setenv initrd_high 30000000 

14.3.17. Ramdisk Greater than 4 MB Causes 

Problems 

Question: 

I built a ramdisk image which is bigger than 4 MB. I run into problems when I try to boot Linux with 

this image, while other (smaller) ramdisk images work fine. 

Answer: 

The Linux kernel has a default maximum ramdisk size of 4096 kB. To boot with a bigger ramdisk 

image, you must raise this value. There are two methods: 

◊ Dynamical adjustment using boot arguments: 

You can pass a boot argument ramdisk_size= to the Linux kernel to 

overwrite the configured maximum. Note that this argument needs to be before any root 

argument. A flexible way to to this is using U-Boot environment variables. For instance, to 

boot with a ramdisk image of 6 MB (6144 kB), you can define: 

=> setenv rd_size 6144 

=> setenv bootargs ... ramdisk_size=\${rd_size} ... 

=> saveenv 

If you later find out that you need an even bigger ramdisk image, or that a smaller one is sufficient, all that 

needs changing is the value of the "rd_size" environment variable. 

• 

♦ Increasing the Linux kernel default value: 

When configuring your Linux kernel, adjust the value of the 

CONFIG_BLK_DEV_RAM_SIZE parameter so that it contains a number equal or larger than 

your ramdisk (in kB). (In the 2.4 kernel series, you'll find this setting under the "Block 

devices" menu choice while, in the 2.6 series, it will be under "Device drivers" -> "Block 

devices".) 

14.3.18. Combining a Kernel and a Ramdisk into a 

Multi-File Image 

Question: 

I used to build a zImage.initrd file which combined the Linux kernel with a ramdisk image. Can 

14.3.18. Combining a Kernel and a Ramdisk into a Multi-File Image 191

I do something similar with U-Boot 

Answer: 

Yes, you can create "Multi-File Images" which contain several images, typically an OS (Linux) kernel 

image and one or more data images like RAMDisks. This construct is useful for instance when you 

want to boot over the network using BOOTP etc., where the boot server provides just a single image 

file, but you want to get for instance an OS kernel and a RAMDisk image. 

The typical way to build such an image is: 

bash$ mkimage -A ppc -O Linux -T multi -C gzip \ 

-n 'Linux Multiboot-Image' -e 0 -a 0 \ 

-d vmlinux.gz:ramdisk_image.gz pMulti 

See also the usage message you get when you call "mkimage" without arguments. 

14.3.19. Adding Files to Ramdisk is Non Persistent 

Quetsion: 

I want to add some files to my ramdisk, but every time I reboot I lose all my changes. What can I do 

Answer: 

To add your files or modifications permanently, you have to rebuild the ramdisk image. You may 

check out the sources of our SELF package (Simple Embedded Linux Framework) to see how this can 

be done, see for example ftp://ftp.denx.de/pub/LinuxPPC/usr/src/SELF/ or check out the sources for 

ELDK (module eldk_build from our CVS server, see http://www.denx.de/re/linux.html. 

See also section 14.4.1. How to Add Files to a SELF Ramdisk for another way to change the ramdisk 

image. 

For further hints about the creation and use of initial ramdisk images see also the file 

Documentation/initrd.txt in your Linux kernel source directory. 

14.3.20. Kernel Configuration for PCMCIA 

Question: 

Which kernel configuration options are relevant to support PCMCIA cards under Linux 

Answer: 

The following kernel configuration options are required to support miscellaneous PCMCIA card types 

with Linux and the PCMCIA CS package: 

◊ PCMCIA IDE cards (CF and true-IDE) 

To support the IDE CardService client, the kernel has to be configured with general ATA IDE 

support. The MPC8xx IDE support (CONFIG_BLK_DEV_MPC8XX_IDE flag) must be 

turned off. 

◊ PCMCIA modem cards 

The kernel has to be configured with standard serial port support (CONFIG_SERIAL flag). 

After the kernel bootup the following preparation is needed: 

bash# mknod /dev/ttySp0 c 240 64 

This creates a new special device for the modem card; please note that /dev/ttyS0 ... S4 and 

TTY_MAJOR 4 are already used by the standard 8xx UART driver). /dev/ttySp0 becomes 

14.3.20. Kernel Configuration for PCMCIA 192

available for use as soon as the CardServices detect and initialize the PCMCIA modem card. 

◊ PCMCIA Wireless LAN cards 

Enable the "Network device support" --> "Wireless LAN (non-hamradio)" --> "Wireless 

LAN (non-hamradio)" option in the kernel configuration (CONFIG_NET_RADIO flag). 

14.3.21. Configure Linux for PCMCIA Cards using 

the Card Services package 

The following kernel configuration options are required to support miscellaneous PCMCIA card types with 

Linux and the PCMCIA CS package: 

1. PCMCIA IDE cards (CompactFlash and true-IDE) 

General setup -> Support for hot-pluggable devices (enable: Y) -> PCMCIA/CardBus support -> 

PCMCIA/CardBus support (enable: M) -> MPC8XX PCMCIA host bridge support (select) 

2. PCMCIA Modem Cards 

3. PCMCIA Network Cards 

4. PCMCIA WLAN Cards 

Build and install modules in target root filesystem, shared over NFS: 

bash$ make modules modules_install INSTALL_MOD_PATH=/opt/eldk/ppc_8xx 

Adjust PCMCIA configuration file (/opt/eldk/ppc_8xx/etc/sysconfig/pcmcia): 

PCMCIA=yes 

PCIC=m8xx_pcmcia 

PCIC_OPTS= 

CORE_OPTS= 

CARDMGR_OPTS= 

Start PCMCIA Card Services: 

bash-2.05# sh /etc/rc.d/init.d/pcmcia start 

14.3.22. Configure Linux for PCMCIA Cards without 

the Card Services package 

For "disk" type PC Cards (FlashDisks, CompactFlash, Hard Disk Adapters - basically anything that looks like 

an ordinary IDE drive), an alternative solution is available: direct support within the Linux kernel. This has 

the big advantage of minimal memory footprint, but of course it comes with a couple of disadvantages, too: 

• It works only with "disk" type PC Cards - no support for modems, network cards, etc; for these you 

still need the PCMCIA Card Services package. 

• There is no support for "hot plug", i. e. you cannot insert or remove the card while Linux is running. 

(Well, of course you can do this, but either you will not be able to access any card inserted, or when 

you remove a card you will most likely crash the system. Don't do it - you have been warned!) 

• The code relies on initialization of the PCMCIA controller by the firmware (of course U-Boot will do 

exactly what's required). 

On the other hand these are no real restrictions for use in an Embedded System. 

14.3.22. Configure Linux for PCMCIA Cards without the Card Services package 193

To enable the "direct IDE support" you have to select the following Linux kernel configuration options: 

CONFIG_IDE=y 

CONFIG_BLK_DEV_IDE=y 

CONFIG_BLK_DEV_IDEDISK=y 

CONFIG_IDEDISK_MULTI_MODE=y 

CONFIG_BLK_DEV_MPC8xx_IDE=y 

CONFIG_BLK_DEV_IDE_MODES=y 

and, depending on which partition types and languages you want to support: 

CONFIG_PARTITION_ADVANCED=y 

CONFIG_MAC_PARTITION=y 

CONFIG_MSDOS_PARTITION=y 

CONFIG_NLS=y 

CONFIG_NLS_DEFAULT="y" 

CONFIG_NLS_ISO8859_1=y 

CONFIG_NLS_ISO8859_15=y 

With these options you will see messages like the following when you boot the Linux kernel: 

... 

Uniform Multi-Platform E-IDE driver Revision: 6.31 

ide: Assuming 50MHz system bus speed for PIO modes; override with idebus=xx 

PCMCIA slot B: phys mem e0000000...ec000000 (size 0c000000) 

Card ID: CF 128MB CH 

Fixed Disk Card 

IDE interface 

[silicon] [unique] [single] [sleep] [standby] [idle] [low power] 

hda: probing with STATUS(0x50) instead of ALTSTATUS(0x41) 

hda: CF 128MB, ATA DISK drive 

ide0 at 0xc7000320-0xc7000327,0xc3000106 on irq 13 

hda: 250368 sectors (128 MB) w/16KiB Cache, CHS=978/8/32 

Partition check: 

hda: hda1 hda2 hda3 hda4 

... 

You can now access your PC Card "disk" like any normal IDE drive. If you start with a new drive, you have 

to start by creating a new partition table. For PowerPC systems, there are two commonly used options: 

14.3.22.1. Using a MacOS Partition Table 

A MacOS partition table is the "native" partition table format on PowerPC systems; most desktop PowerPC 

systems use it, so you may prefer it when you have PowerPC development systems around. 

To format your "disk" drive with a MacOS partition table you can use the pdisk command: 

We start printing the help menu, re-initializing the partition table and then printing the new, empty partition 

table so that we know the block numbers when we want to create new partitions: 

# pdisk /dev/hda 

Edit /dev/hda - 

Command ( for help): 

Notes: 

Base and length fields are blocks, which vary in size between media. 

The base field can be p; i.e. use the base of the nth partition. 

The length field can be a length followed by k, m, g or t to indicate 

kilo, mega, giga, or tera bytes; also the length can be p; i.e. use 

the length of the nth partition. 

The name of a partition is descriptive text. 

Commands are: 

14.3.22.1. Using a MacOS Partition Table 194

h help 

p print the partition table 

P (print ordered by base address) 

i initialize partition map 

s change size of partition map 

c create new partition (standard MkLinux type) 

C (create with type also specified) 

n (re)name a partition 

d delete a partition 

r reorder partition entry in map 

w write the partition table 

q quit editing (don't save changes) 

Command ( for help): i 

map already exists 

do you want to reinit [n/y]: y 

Command ( for help): p 

Partition map (with 512 byte blocks) on '/dev/hda' 

#: type name length base ( size ) 

1: Apple_partition_map Apple 63 @ 1 

2: Apple_Free Extra 1587536 @ 64 (775.2M) 

Device block size=512, Number of Blocks=1587600 (775.2M) 

DeviceType=0x0, DeviceId=0x0 

At first we create two small partitions that will be used to store a Linux boot image; a compressed Linux 

kernel is typically around 400 ... 500 kB, so chosing a partition size of 2 MB is more than generous. 2 MB 

coresponds to 4096 disk blocks of 512 bytes each, so we enter: 

Command ( for help): C 

First block: 64 

Length in blocks: 4096 

Name of partition: boot0 

Type of partition: PPCBoot 





2: PPCBoot boot0 4096 @ 64 ( 2.0M) 




To be able to select between two kernel images (for instance when we want to do a field upgrade of the Linux 

kernel) we create a second boot partition of exactly the same size: 




Name of partition: boot1 

Type of partition: PPCBoot 










Now we create a swap partition - 64 MB should be more than sufficient for our Embedded System; 64 MB 

means 64*1024*2 = 131072 disk blocks of 512 bytes: 





Name of partition: swap 

Type of partition: swap 







4: swap swap 131072 @ 8256 ( 64.0M) 




Finally, we dedicate all the remaining space to the root partition: 




Name of partition: root 

Type of partition: Linux 







4: swap swap 131072 @ 8256 ( 64.0M) 

5: Linux root 1448272 @ 139328 (707.2M) 



To make our changes permanent we must write the new partition table to the disk, before we quit the pdisk 

program: 

Command ( for help): w 

Writing the map destroys what was there before. Is that okay [n/y]: y 

hda: [mac] hda1 hda2 hda3 hda4 hda5 

hda: [mac] hda1 hda2 hda3 hda4 hda5 

Command ( for help): q 

Now we can initialize the swap space and the filesystem: 



# mke2fs /dev/hda5 

mke2fs 1.19, 13-Jul-2000 for EXT2 FS 0.5b, 95/08/09 

Filesystem label= 

OS type: Linux 

Block size=4096 (log=2) 

Fragment size=4096 (log=2) 

90624 inodes, 181034 blocks 

9051 blocks (5.00%) reserved for the super user 

First data block=0 

6 block groups 

32768 blocks per group, 32768 fragments per group 

15104 inodes per group 

Superblock backups stored on blocks: 

32768, 98304, 163840 

Writing inode tables: done 

Writing superblocks and filesystem accounting information: done 


14.3.22.2. Using a MS-DOS Partition Table 

The MS-DOS partition table is especially common on PC type computers, which these days means nearly 

everywhere. You will prefer this format if you want to exchange your "disk" media with any PC type host 

system. 

The fdisk command is used to create MS-DOS type partition tables; to create the same partitioning scheme as 

above you would use the following commands: 

# fdisk /dev/hda 

Device contains neither a valid DOS partition table, nor Sun, SGI or OSF disklabel 

Building a new DOS disklabel. Changes will remain in memory only, 

until you decide to write them. After that, of course, the previous 

content won't be recoverable. 

The number of cylinders for this disk is set to 1575. 

There is nothing wrong with that, but this is larger than 1024, 

and could in certain setups cause problems with: 

1) software that runs at boot time (e.g., old versions of LILO) 

2) booting and partitioning software from other OSs 

(e.g., DOS FDISK, OS/2 FDISK) 

Command (m for help): m 

Command action 

a toggle a bootable flag 

b edit bsd disklabel 

c toggle the dos compatibility flag 

d delete a partition 

l list known partition types 

m print this menu 

n add a new partition 

o create a new empty DOS partition table 

p print the partition table 

q quit without saving changes 

s create a new empty Sun disklabel 

t change a partition's system id 

u change display/entry units 

v verify the partition table 

w write table to disk and exit 

x extra functionality (experts only) 

Command (m for help): n 


e extended 

p primary partition (1-4) 

p 

Partition number (1-4): 1 

First cylinder (1-1575, default 1): 

Using default value 1 

Last cylinder or +size or +sizeM or +sizeK (1-1575, default 1575): +2M 

Command (m for help): p 







e extended 


p 






14.3.22.2. Using a MS-DOS Partition Table 197








e extended 


p 





Command (m for help): t 


Hex code (type L to list codes): 82 

Changed system type of partition 3 to 82 (Linux swap) 








Note that we had to use the t command to mark this partition as swap space. 



e extended 


p 




Last cylinder or +size or +sizeM or +sizeK (142-1575, default 1575): 










Command (m for help): w 

The partition table has been altered! 

Calling ioctl() to re-read partition table. 



WARNING: If you have created or modified any DOS 6.x 

partitions, please see the fdisk manual page for additional 


Syncing disks. 

Now we are ready to initialize the partitions: 



# mke2fs /dev/hda4 

mke2fs 1.19, 13-Jul-2000 for EXT2 FS 0.5b, 95/08/09 



14.3.22.2. Using a MS-DOS Partition Table 198










32768, 98304, 163840 



14.3.23. Boot-Time Configuration of MTD Partitions 

Instead of defining a static partition map as described in section Memory Technology Devices you can define 

the partitions for your flash memory at boot time using command line arguments. To do that you have to 

enable the CONFIG_MTD_CMDLINE_PARTS kernel configuration option. With this option enabled, the 

kernel will recognize a command line argument mtdparts and decode it as follows: 

mtdparts=[;

server 127.127.1.0 # local clock 

fudge 127.127.1.0 stratum 10 

by 

server 127.127.43.0 

# standard Linux RTC 

Then make sure to start the NTP daemon on your target by adding it to the corresponding init scripts and 

restart it if it is already running. 

The "address" of the RTC (127.127.43.0 in the example above) is not an IP address, but actually used 

as an index into an internal array of supported reference clocks in the NTP daemon code. You may need to 

check with your ntpd implementation if the example above does not work as expected. 

14.3.25. Configure Linux for XIP (Execution In 

Place) 

This document describes how to setup and use XIP in the kernel and the cramfs filesystem. (A patch to add 

XIP support to your kernel can be found at the bottom of this page.) 

14.3.25.1. XIP Kernel 

To select XIP you must enable the CONFIG_XIP option: 

$ cd 

$ make menuconfig 

... 

MPC8xx CPM Options ---> 

[*] Make a XIP (eXecute in Place) kernel 

(40100000) Physical XIP kernel address 

(c1100000) Virtual XIP kernel address 

(64) Image header size e.g. 64 bytes for PPCBoot 

The physical and virtual address of the flash memory used for XIP must be defined statically with the macros 

CONFIG_XIP_PHYS_ADDR and CONFIG_XIP_VIRT_ADDR. The virtual address usually points to the end 

of the kernel virtual address of the system memory. The physical and virtual address must be aligned relative 

to an 8 MB boundary: 

CONFIG_XIP_PHYS_ADDR = FLASH-base-address + offset-in-FLASH 

CONFIG_XIP_VIRT_ADDR = 0xc0000000 + DRAM-size + offset-in-FLASH 

The default configuration parameters shown above are for a system with 16MB of DRAM and the XIP kernel 

image located at the physical address 0x40100000 in flash memory. 

Note that the FLASH and MTD driver must be disabled. 

You can then build the "uImage", copy it to CONFIG_XIP_PHYS_ADDR in flash memory and boot it from 

CONFIG_XIP_PHYS_ADDR as usual. 

14.3.25.2. Cramfs Filesystem 

The cramfs filesystem enhancements: 

14.3.25. Configure Linux for XIP (Execution In Place) 200

• They allow cramfs optional direct access to a cramfs image in memory (ram, rom, flash). It eliminates 

the unnecessary step of passing data through an intermediate buffer, as compared to accessing the 

same image through a memory block device like mtdblock. 

• They allow optional cramfs linear root support. This eliminates the requirement of having to provide a 

block device to use a linear cramfs image as the root filesystem. 

• They provide optional XIP. It extends mkcramfs to store files marked "+t" uncompressed and 

page-aligned. Linux can then mmap those files and execute them in-place without copying them 

entirely to ram first. 

Note: the current implementation can only be used together with a XIP kernel, which provides the appropriate 

XIP memory (FLASH) mapping. 

To configure a root file system on linear cramfs with XIP select: 

$ cd 

$ make menuconfig 

... 

File systems --->" 

... 

Compressed ROM file system support 

[*] Use linear addressing for cramfs 

(40400000) Physical address of linear cramfs 

[*] Support XIP on linear cramfs 

[*] Root file system on linear cramfs 

This defines a cramfs filesystem located at the physical address 0x40400000 in FLASH memory. 

After building the kernel image "pImage" as usual, you will want to build a filesystem using the mkcramfs 

executable (it's located in /scripts/cramfs). If you do not already have a reasonable sized disk directory tree 

you will need to make one. The ramdisk directory of SELF (the Simple Embedded Linux Framework from 

DENX at ftp.denx.de) is a good starting point. Before you build your cramfs image you must mark the binary 

files to be executed in place later on with the "t" permission: 

$ mkcramfs -r ramdisk cramfs.img 

and copy it to the defined place in FLASH memory. 

You can then boot the XIP kernel with the cramfs root filesystem using the boot argument: 

$ setenv bootargs root=/dev/cramfs ... 

Be aware that cramfs is a read-only filesystem. 

14.3.25.3. Hints and Notes 

• XIP conserves RAM at the expense of flash. This might be useful if you have a big flash memory and 

little RAM. 

• Flash memory used for XIP must be readable all the time e.g. this excludes installation and usage the 

character device or MTD flash drivers, because they do device probing, sector erase etc. 

• The XIP extension is currently only available for PowerPC 8xx but can easily be extended to other 

architectures. 

• Currently only up to 8 MB of ROM/Flash are supported. 

• The original work was done for the amanda system. 

• Special thanks goes to David Petersen for collecting the availible XIP extension sources and 

highlighting how to put all the pieces together. 

14.3.25.2. Cramfs Filesystem 201

14.3.25.4. Space requirements and RAM saving, an example 

For ppc 8xx, all figures are in bytes: 

• Normal kernel + linear cramfs (patched): 

pImage: 538062 

cramfs: 1081344 

total: used: free: shared: buffers: cached: 

Mem: 14921728 3866624 11055104 2781184 0 2240512 

• XIP kernel + linear cramfs: 

pImage: 1395952 

cramfs: 1081344 


Mem: 16175104 3940352 12234752 2822144 0 2240512 

• XIP kernel + XIP cramfs (chmod +t: busybox, initd, libc): 

pImage: 1395952 

cramfs: 1871872 


Mem: 16175104 2367488 13807616 610304 0 671744 

The actual RAM saving is here approximately 1.1MB + 1.5M = 2.6 MB. 

Have fun with XIP. 

Wolfgang Grandegger (wg@denx.de) 

• linux-2.4.4-2002-03-21-xip.patch.gz: Linux patches for XIP on MPC8xx 

14.3.26. Use SCC UART with Hardware Handshake 

Question: 

I am using a SCC port of a MPC8xx / MPC82xx as UART; for the Linux UART driver I have 

configured support for hardware handshake. Then I used a null-modem cable to connect the port to 

the serial port of my PC. But this does not work. What am I doing wrong 

Answer: 

There is absolutely no way to connect a MPC8xx / MPC82xx SCC port to any DTE and use RS-232 

standard hardware flow control. 

Explanation: 

The serial interface of the SCC ports in MPC8xx / MPC82xx processors is designed as a DTE 

circuitry and the RS-232 standard hardware flow control can not be used in the DTE to DTE 

connection with the null-modem cable (with crossed RTS/CTS signals). 

The RS-232 standard specifies a DTE to DCE connection and its hardware handshaking is designed 

for this specific task. The hardware flow control signals in the PC (and similar equipment) are 

implemented as software readable/writable bits in a control register and therefore may be arbitrary 

14.3.26. Use SCC UART with Hardware Handshake 202

treated. Unlike that, in the 8xx/82xx the handshake protocol is handled by the CPM microcode. The 

meaning of the signals is fixed for the RS-232 standard with no way for user to change it. 

In widely spread DTE-to-DTE connections over the so called 'null-modem' cable with the hardware 

flow control lines the meaning of the handshake signals is changed with respect to the RS-232 

standard. Therefore this approach may not be used with the 8xx/82xx. 

Question: 

I succeeded in activating hardware handshake on the transmit side of the SCC using the CTS signal. 

However I have problems in the receive direction. 

Answer: 

This is caused by the semantics of the RTS signal as implemented on the SCC controllers: the CPM 

will assert this signal when it wants to send out data. This means you cannot use RTS to enable the 

transmitter on the other side, because it will be enabled only when the SCC is sending data itself. 

Conclusions: 

If you want to use 8xx/82xx based equipment in combination with RS-232 hardware control protocol, 

you must have a DCE device (modem, plotter, printer, etc) on the other end. 

Hardware flow control on a SCC works only in transmit direction; when receiving data the driver has 

to be fast enough to prevent data overrun conditions (normally this is no problem though). 

14.3.27. How can I access U-Boot environment 

variables in Linux 

Question: 

I would like to access U-Boot's environment variables from my Linux application. Is this possible 

Answer: 

Yes, you can. The environment variables must be stored in flash memory, and your Linux kernel must 

support flash access through the MTD layer. In the U-Boot source tree you can find the environment 

tools in the directory tools/env, which can be built with command: 

make env 

For building against older versions of the MTD headers (meaning before v2.6.8-rc1) it is required to pass the 

argument "MTD_VERSION=old" to make: 

make MTD_VERSION=old env 

The resulting binary is called fw_printenv, but actually includes support for setting environment variables 

too. To achieve this, the binary behaves according to the name it is invoked as, so you will have to create a 

link called fw_setenv to fw_printenv. 

These tools work exactly like the U-Boot commands printenv resp. setenv You can either build these 

tools with a fixed configuration selected at compile time, or you can configure the tools using the 

/etc/fw_env.config configuration file in your target root filesystem. Here is an example configuration 

file: 

# Configuration file for fw_(printenv/saveenv) utility. 

# Up to two entries are valid, in this case the redundand 

# environment sector is assumed present. 

14.3.27. How can I access U-Boot environment variables in Linux 203

######################################################################### 

# For TQM8xxL modules: 

######################################################################### 

# MTD device name Device offset Env. size Flash sector size 

/dev/mtd0 0x8000 0x4000 0x4000 

/dev/mtd0 0xC000 0x4000 0x4000 

######################################################################### 

# For NSCU: 

######################################################################### 


#/dev/mtd1 0x0000 0x8000 0x20000 

#/dev/mtd2 0x0000 0x8000 0x20000 

######################################################################### 

# For LWMON 

######################################################################### 


#/dev/mtd1 0x0000 0x2000 0x40000 

14.3.28. The appWeb server hangs OR /dev/random 

hangs 

Question: 

I try to run the appWeb server, but it hangs, because read accesses to /dev/random hang forever. 

What's wrong 

Answer: 

Your configuration of the Linux kernel does not contain drivers that feed enough entropy for 

/dev/random. Often mouse or keyboard drivers are used for this purpose, so on an embedded 

system without such devices /dev/random may not provide enough random numbers for your 

application. 

Workaround: 

As a quick workaround you can use /dev/urandom instead; i. e. try the following commands on 

your system: 

# cd /dev 

# rm -f random 

# ln -s urandom random 

Solution: 

The correct solution for the problem is of course to feed sufficient entropy into /dev/random. To 

do so you can modify one or more appropriate device drivers on your system; for example if you 

know that there is sufficient traffic on network or on a serial port than adding SA_SAMPLE_RANDOM 

to the 3rd argument when calling the request_irq() function in your ethernet and/or serial 

driver(s) will cause the inter-interrupt times to be used to build up entropy for /dev/random. 

14.3.29. Swapping over NFS 

In case that the available memory is not sufficient, i.e. for compiling the X.org server, and no hard-drive can 

be attached to the system it is possible to swap over NFS, although it is not quite straightforward. 

14.3.29. Swapping over NFS 204

Usually one would create a blank file, mkswap it and simply do a swapon swapfile. Doing this on a filesystem 

mounted over NFS, i.e. the ELDK root filesystem, fails however. 

With one level of indirection we can trick the kernel into doing it anyway. First we create a filesystem image 

(ext2 will do) on the NFS filesystem and mount it with the aid of the loopback device. Then we create a blank 

swapfile inside of this filesystem and turn on swapping: 

bash-2.05b# mount 

/dev/nfs on / type nfs (rw) 

none on /proc type proc (rw) 

bash-2.05b# cd /tmp 

bash-2.05b# dd if=/dev/zero of=ext2.img bs=1M count=66 



bash-2.05b# mkfs.ext2 ext2.img 

mke2fs 1.27 (8-Mar-2002) 

ext2.img is not a block special device. 

Proceed anyway (y,n) y 












8193, 24577, 40961, 57345 



This filesystem will be automatically checked every 26 mounts or 

180 days, whichever comes first. Use tune2fs -c or -i to override. 

bash-2.05b# for i in `seq 0 9` ; do mknod /dev/loop$i b 7 $i ; done 

bash-2.05b# mkdir /mnt2 

bash-2.05b# mount -o loop ext2.img /mnt2 

bash-2.05b# cd /mnt2 

bash-2.05b# dd if=/dev/zero of=swapfile bs=1M count=62 



bash-2.05b# mkswap swapfile 

Setting up swapspace version 1, size = 65007 kB 

bash-2.05b# free 


Mem: 14556 14260 296 0 772 9116 


Swap: 0 0 0 

bash-2.05b# swapon swapfile 

bash-2.05b# free 


Mem: 14556 14172 384 0 784 9020 


Swap: 63480 0 63480 

bash-2.05b# 

Because the ELDK right now has no device nodes for the loopback driver we create them along the way. It 

goes without saying that the loop driver has to be included in the kernel configuration. You can check this by 

looking for a driver for major number 7 (block devices) in /proc/devices. 

14.3.29. Swapping over NFS 205

14.4. Self 

14.4.1. How to Add Files to a SELF Ramdisk 

It is not always necessary to rebuild a SELF based ramdisk image if you want to modify or to extend it. 

Especially during development it is often eaiser to unpack it, modify it, and re-pack it again. To do so, you 

have to understand the internal structure of the uRamdisk (resp. pRamdisk) images files as used with the 

U-Boot (old: PPCBoot) boot loader: 

The uRamdisk image contains two parts: 

• a 64 byte U-Boot header 

• a (usually gzip compressed) ramdisk image 

To modify the contents you have to extract, uncompress and mount the ramdisk image. This can be done as 

follows: 

1. Extract compressed ramdisk image (ramdisk.gz) 

bash$ dd if=uRamdisk bs=64 skip=1 of=ramdisk.gz 



2. Uncompress ramdisk image (if it was a compressed one) 

bash$ gunzip -v ramdisk.gz 

ramdisk.gz: 66.6% -- replaced with ramdisk 

3. Mount ramdisk image 

bash# mount -o loop ramdisk /mnt/tmp 

Now you can add, remove, or modify files in the /mnt/tmp directory. If you are done, you can re-pack the 

ramdisk into a U-Boot image: 

1. Unmount ramdisk image: 


2. Compress ramdisk image 

bash$ gzip -v9 ramdisk 

ramdisk: 

66.6% -- replaced with ramdisk.gz 

3. Create new U-Boot image (new-uRamdisk) 

bash$ mkimage -T ramdisk -C gzip -n 'Simple Embedded Linux Framework' \ 

> -d ramdisk.gz new-uRamdisk 


Created: Sun May 4 13:23:48 2003 





Instead of re-packing into a U-boot ramdisk image you can of course also just extract the contents of the 

SELF image and re-use it as base of a (known to be working) root filesystem. 

14.4.1. How to Add Files to a SELF Ramdisk 206

• For example, you can create a JFFS2 filesystem using the mkfs.jffs2 command that comes with 

the MTD Tools: 

bash# mkfs.jffs2 -r /mnt/tmp -e 0x10000 -o image.jffs2 

• Or you can create a CramFS filesystem with mkcramfs: 

bash# mkcramfs -r /mnt/tmp image.cramfs 

Swapping filesystem endian-ness 

... 

Everything: 1656 kilobytes 


CRC: 7f34cae4 

14.4.2. How to Increase the Size of the Ramdisk 

1. Extract compressed ramdisk image (ramdisk.gz) from U-Boot image: 

bash$ dd if=uRamdisk bs=64 skip=1 of=ramdisk.gz 



2. Uncompress ramdisk image 

bash$ gunzip -v ramdisk.gz 

ramdisk.gz: 66.6% -- replaced with ramdisk 

3. Mount ramdisk image 

As root: 

bash# mkdir -p /mnt/tmp 

bash# mount -o loop ramdisk /mnt/tmp 

4. Create new ramdisk image, say 8 MB big: 

bash$ dd if=/dev/zero of=new_ramdisk bs=1024k count=8 

bash$ /sbin/mke2fs -F -m0 new_ramdisk 

bash$ /sbin/tune2fs -c 0 -i 0 new_ramdisk 

As root: 

bash# mkdir -p /mnt/new 

bash# mount -o loop new_ramdisk /mnt/new 

5. Copy files from old ramdisk to new ramdisk: 

As root: 

bash# cd /mnt/tmp 

bash# find . -depth -print | cpio -VBpdum /mnt/new 

Now you can add, remove, or modify files in the /mnt/new directory. If you are done, you can re-pack 

the ramdisk into a U-Boot image: 

6. Unmount ramdisk images: 

As root: 


bash# umount /mnt/new 

7. Compress new ramdisk image 

bash$ gzip -v9 new_ramdisk 

ramdisk: 

66.6% -- replaced with new_ramdisk.gz 

14.4.2. How to Increase the Size of the Ramdisk 207

8. Create new U-Boot image (new-uRamdisk) 

bash$ mkimage -T ramdisk -C gzip -n 'New Simple Embedded Linux Framework' \ 

> -d new_ramdisk.gz new_uRamdisk 


Created: Sun May 4 13:23:48 2003 





Remember that Linux by default supports only ramdisks up to a size of 4 MB. For bigger ramdisks, you 

have to either modify your LInux kernel configuration (parameter CONFIG_BLK_DEV_RAM_SIZE in the 

"Block devices" menue), or pass a "ramdisk_size=" boot argument to the Linux kernel. 

14.5. RTAI 

14.5.1. Conflicts with asm clobber list 

Question: 

When I try to compile my LInux kernel after applying the RTAI patch, I get a strange "asm-specifier 

for variable `__sc_3' conflicts with asm clobber list" error message. What does that mean 

Answer: 

You are using an old version of the Linux kernel / RTAI patch in combination with a more recent 

version of the cross compiler. Please use a recent kernel tree (and the corresponding RTAI patch), or 

apply the attached patch to fix this problem. 

See: http://www.denx.de/wiki/pub/DULG/ConflictsWithAsmClobberList/patch 

14.6. BDI2000 

14.6.1. Where can I find BDI2000 Configuration 

Files 

The configuration files provided by Abatrron can be found here: ftp://78.31.64.234/bdigdb/config/ 

A collection of configuration files for the BDI2000 BDM/JTAG debugger by Abatron can be found at 

ftp://ftp.denx.de/pub/BDI2000/ 

A list of FAQ (with answers) can be found at http://www.ultsol.com/faqs.htm 

A list of supported flash chips (and the needed matching entries for the config file) can be found at 

http://www.abatron.ch/fileadmin/user_upload/products/pdf/flashsupp.pdf 

14.6.1. Where can I find BDI2000 Configuration Files 208

14.6.2. How to Debug Linux Exceptions 

Question: 

I am trying to single step into a Linux exception handler. This does not seem to work. Setting a 

breakpoint does not work either. 

Answer: 

The problem is bit complex on a MPC8xx target. Debug mode entry is like an exception and therefore 

only safe at locations in the code where an exception does not lead to an unrecoverable state. Another 

exception can only be accepted if SRR0 and SRR1 are saved. The MSR[RI] should indicate if 

currently an exception is safe. MSR[RI] is cleared automatically at exception entry. 

The MPC8xx hardware breakpoints do only trigger if MSR[RI] is set in order to prevent 

non-recoverable state. 

The problem is that the Linux exception handler does not take all this into account. First priority has 

speed, therefore neither SRR0 nor SRR1 are saved immediately. Only after EXCEPTION_PROLOG 

this registers are saved. Also Linux does not handle the MSR[RI] bit. 

Hint: Use STEPMODE HWBP when debugging Linux. This allows the TLB Miss Exception 

handler to update the TLB while you are single stepping. 

Conclusion: 

You cannot debug Linux exception entry and exit code. Because of speed, DataStoreTLBMiss does 

not even make use of EXCEPTION_PROLOG, and SRR0/SRR1 are never saved. Therefore you 

cannot debug DataStoreTLBMiss unless you change it's code (save SRR0/SRR1, set MSR[RI]. 

14.6.3. How to single step through "RFI" 

instruction 

Question: 

I am trying to debug Linux on an IBM 405GP processor. Linux boots fine and I can step through the 

code until the "rfi" instruction in head_4xx.S; then I get the following: 

- TARGET: target has entered debug mode 

Target state : debug mode 

Debug entry cause : JTAG stop request 

Current PC : 0x00000700 

Current CR : 0x28004088 

Current MSR : 0x00000000 

Current LR : 0x000007a8 

# Step timeout detected 

Answer: 

Your single step problem most likely comes from the fact that GDB accesses some non-existent 

memory (at least some versions do/did in the past). This exception is stored in some way within the 

405 and when you step "rfi" it triggers. This is because some instructions like "rfi" are always 

stepped using a hardware breakpoint and not with the JTAG single step feature. 

Probably you can step over the "rfi" instruction when using the BDI2000's telnet command 

interface instead of GDB. 

14.6.3. How to single step through "RFI" instruction 209

Similar problems have also been reported when stepping through "mtmsr" or "mfmsr" during 

initial boot code. The problem comes also from the fact that GDB accesses non-existent memory 

(maybe it tries to read a non-existent stack frame). 

To debug the Linux kernel, I recommend that you run to a point where the MMU is on before you 

connect with GDB. 

To debug boot code where the MMU is off I recommend to use the MMAP feature of the BDI to 

prevent illegal memory accesses from GDB. 

14.6.4. Setting a breakpoint doesn't work 

Question: 

I am trying to set a breakpoint using the BDI2000 telnet interface. However, the code does not 

stop at the breakpoint. 

Answer: 

Make sure that the CPU has been stopped before setting the breakpoint. You can verify this by issuing 

the "info" command before setting the breakpoint. If the target state is "running" you must use 

the "halt" command to stop the CPU before you can successfully set the breakpoint. 

14.7. Motorola LITE5200 Board 

14.7.1. LITE5200 Installation Howto 

A nice "Application Note: Installing Embedded Linux on the Motorola MPC5200 Lite Evaluation Board" 

which covers the installation of U-Boot and Linux can be found at: 

http://emsys.denayer.wenk.be/emcam/Linux_on_MPC5200_(UK).pdf 

14.7.2. USB does not work on Lite5200 board 

Question: 

USB does not work on my Lite5200 board. Also, the green LED behind the USB connector remains 

always off. Why 

Answer: 

This is a hardware problem. The green LED must be on as soon as you power on the Lite5200 board. 

As a workaround you can short-circuit resistor R164 (bottom side of the board, close to the USB 

connector). Please note that you will probably lose all warranty and/or may ruin the board. You have 

been warned. 

15. Glossary 

15. Glossary 210

ABI 

- Application Binary Interface 

The convention for register usage and C linkage commonly used on desktop PowerPC machines. Similar, but 

not identical to the EABI. 

Includes binding specific ppc registers to certain fixed purposes, even though there may be no technical 

reason to enforce such binding, simplifying the process of linking together two separate sets of object code. 

e.g the ABI states that r1 shall be the stack pointer. 

BANK 

- also "memory bank" 

A bank of memory (flash or RAM) consists of all those memory chips on your system that are controlled by 

the same chip select signal. 

For example, a system might consist of one flash chip with a 8 bit bus interface, which is attached to the CS0 

chip select signal, 2 flash chips with a 16 bit bus interface, which are attached to the CS1 chip select signal, 

and 2 SDRAM chips with a 16 bit bus interface, which are attached to the CS2 chip select signal. 

This setup results in a system with 3 banks of memory: 

BDM 

• 1 bank of flash, 8 bit wide (CS0) 

• 1 bank of flash, 32 bit wide (CS1) 

• 1 bank of SDRAM, 32 bit wide (CS2) 

- Background Debug Mode 

An on-chip debug interface supported by a special hardware port on some processors. It allows to take full 

control over the CPU with minimal external hardware, in many cases eliminationg the need for expensive 

tools like In-Circuit-Emulators. 

BOOTP 

- Boot Protocol 

A network protocol which can be used to inquire a server about information for the intended system 

configuration (like IP address, host name, netmask, name server, routing, name of a boot image, address of 

NFS server, etc. 

CFI 

- Common Flash Interface 

CFI is a standard for flash chips that allows to create device independend drivers for such chips. 

ABI 211

CPM 

- Communications Processor Module 

The magic communications co-processor in Motorola PowerQUICC devices. It contains SCCs and SMCs, and 

performs SDMA and IDMA. 

CPU 

- Central Processor Unit 

Depending on the context, this may refer to the PowerPC core itself, or the physical processor device 

(including CPM, SIU, packaging etc) as a single unit. 

CramFs 

- Compressed ROM File System 

Cramfs is designed to be a simple, small, and compressed file system for ROM based embedded systems. 

CramFs is read-only, limited to 256MB file systems (with 16MB files), and doesn't support 16/32 bits uid/gid, 

hard links and timestamps. 

CVS 

- Concurrent Versions System 

CVS is a version control system; it can be used to record the history of files, so that it is for instance possible 

to retrieve specific versions of a source tree. 

DHCP 

- Dynamic Host Configuration Protocol 

A network protocol which can be used to inquire a server about information for the intended system 

configuration (like IP address, host name, netmask, name server, routing, name of a boot image, address of 

NFS server, etc.). Sucessor of BOOTP 

DMA 

- Direct Memory Access 

A form a data transfer directly between memory and a peripheral or between memory and memory, without 

normal program intervention. 

EABI 

- Embedded Application Binary Interface 

The convention for register usage and C linkage commonly used on embedded PowerPC machines, derived 

from the ABI. 

CPM 212

ELDK 

- Embedded Linux Development Kit 

A package which contains everything you need to get startet with an Embedded Linux project on your 

hardware: 

FEC 

• cross development tools (like compiler, assembler, linker etc.) that are running on a Host system 

while generating code for a Target system 

• native tools and libraries that can be use to build a system running on the target; they can also be 

exported on a NFS server and used as root filesystem for the target 

• source code and binary images for PPCBoot and Linux 

• Our SELF package as example configuration for an embedded system. 

- Fast Ethernet Controller 

The 100 Mbps (100Base) Ethernet controller, present on 'T' devices such as the 860T and 855T. 

FTP 

- File Transfer Protocol 

A protocol that can be used to transfer files over a network. 

GPL 

/ LGPL - GNU General Public License/Lesser General Public License 

The full license text can be found at http://www.gnu.org/copyleft/gpl.html. 

The licenses under which the Linux kernel and much of the utility and library code necessary to build a 

complete system may be copied, distributed and modified. Each portion of the software is copyright by its 

respected copyright holder, and you must comply with the terms of the license in order to legally copy (and 

hence use) it. One significant requirement is that you freely redistribute any modifications you make; if you 

can't cope with this, embedded Linux isn't for you. 

Host 

The computer system which is used for software development. For instance it is used to run the tools of the 

ELDK to build software packages. 

IDMA 

- Independent DMA 

ELDK 213

A general purpose DMA engine with relatively limited throughput provided by the microcoded CPM, for use 

with external peripherals or memory-to-memory transfers. 

JFFS 

- Journalling Flash File System 

JFFS (developed by Axis Communicartion AB, Sweden) is a log-based filesystem on top of the MTD layer; it 

promises to keep your filesystem and data in a consistent state even in cases of sudden power-down or system 

crashes. That's why it is especially useful for embedded devices where a regular shutdown procedure cannot 

always be guaranteed. 

JFFS2 

- Second version of the Journalling Flash File System 

Like JFFS this is a journalling flash filesystem that is based on the MTD layer; it fixes some design problems 

of JFFS and adds transparent compression. 

JTAG 

- Joint Test Action Group 

A standard (see "IEEE Standard 1149.1") that defines how to control the pins of JTAG compliant devices. 

Here: An on-chip debug interface supported by a special hardware port on some processors. It allows to take 

full control over the CPU with minimal external hardware, in many cases eliminationg the need for expensive 

tools like In-Circuit-Emulators. 

MII 

- Media Independent Interface 

The IEEE Ethernet standard control interface used to communicate between the Ethernet controller (MAC) 

and the external PHY. 

MMU 

- Memory Management Unit 

CPU component which maps kernel- and user-space virtual addresses to physical addresses, and is an integral 

part of Linux kernel operation. 

MTD 

- Memory Technology Devices 

The MTD functions in Linux support memory devices like flash or Disk-On-Chip in a device-independend 

way so that the higher software layers (like filesystem code) need no knowledge about the actual hardware 

properties. 

IDMA 214

PC 

Card 

PC Cards are self-contained extension cards especially for laptops and other types of portable computers. In 

just about the size of a credit card they provide functions like LAN cards (including wireless LAN), modems, 

ISDN cards, or hard disk drives - often "solid-state" disks based on flash chips. 

The PC Card technology has been has been developed and standardized by the Personal Computer Memory 

Card International Association (PCMCIA), see http://www.pcmcia.org/pccard.htm . 

PCMCIA 

- Personal Computer Memory Card International Association 

PCMCIA is an abbreviation that can stand for several things: the association which defines the standard, the 

specification itself, or the devices. The official term for the devices is PC-Card. 

PHY 

- Physical Interface 

The physical layer transceiver which implements the IEEE Ethernet standard interface between the ethernet 

wires (twisted pair, 50 ohm coax, etc.) and the ethernet controller (MAC). PHYs are often external 

transceivers but may be integrated in the MAC chip or in the CPU. 

The PHY is controlled more or less transparently to software via the MII. 

RTOS 

- Real-Time Operating System 

SCC 

- Serial Communications Controller 

The high performance module(s) within the CPM which implement the lowest layer of various serial 

protocols, such as Asynchronous serial (UART), 10 Mbps Ethernet, HDLC etc. 

SDMA 

- Serial DMA 

DMA used to transfer data to and from the SCCs. 

SELF 

- Simple Embedded Linux Framework 

A simple default configuration for Embedded Linux systems that is suitable as starting point for building your 

own systems. It is based on BusyBox to provide an init process, shell, and many common tools (from cat 

PC 215

and ls to vi), plus some other tools to provide network connectivity, allowing to access the system over the 

internet using telnet and FTP services. 

SIU 

- System Interface Unit 

Provides much of the external interfacing logic. It's the other major module on Motorola PowerQUICC 

devices alongside the CPU core and CPM. 

SMC 

- Serial Management Controller 

A lower performance version of the SCCs with more limited functionality, particularly useful for serial debug 

ports and low throughput serial protocols. 

SPI 

- Serial Peripheral Interface 

A relatively simple synchronous serial interface for connecting low speed external devices using minimal 

wires. 

S-Record 

- Motorola S-Record Format 

Motorola S-records are an industry-standard format for transmitting binary files to target systems and PROM 

programmers. 

See also: http://pmon.groupbsd.org/Info/srec.htm 

Target 

The computer system which will be used later in you application environment, for instance an Embedded 

System. In many cases it has a different architecture and much more limited resoucres than a typical Host 

system, so it is often not possible to develop the software directly (native) on this system. 

TFTP 

- Trivial File Transfer Protocol 

A simple network protocol for file transfer; used in combination with BOOTP or DHCP to load boot images 

etc. over the network. 

UART 

- Universal Asynchronous Receiver Transmitter 

SELF 216

Generically, this refers to any device capable of implementing a variety of asynchronous serial protocols, such 

as RS-232, HDLC and SDLC. In this context, it refers to the operating mode of the SCCs which provides this 

functionality. 

UPM 

- User Programmable Machine 

A highly flexible bus interfacing machine unit allowing external peripherals with an extremely wide variety of 

interfacing requirements to be connected directly to the CPU. 

YellowDog 

More information about the YellowDog GNU/Linux distribution for PowerPC systems can be found at 

http://www.yellowdoglinux.com. 

UART 217

The DENX U-Boot and Linux Guide (DULG) for canyonlands - Lysator

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