CM-T335: U-Boot: Building Images

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Overview

The CompuLab CM-T335 System-on-Module / Computer-on-Module firmware consists of two components: Secondary Program Loader (SPL) and U-Boot. Both components are based on U-Boot source code. SPL is the bootstrap utility invoked by the CPU internal boot ROM code of the AM335x SoC. SPL performs minimal hardware initialization and loads U-Boot from the same boot device. U-Boot initializes hardware modules necessary for system boot and loads the operating system.

Building Firmware images for CM-T335

Cross-Compiler

There are several options for cross-compilation toolchain setup. You can either compile your cross-compiler or use an already built cross-compiler. The cross-compiler should support the ARM embedded-application binary interface ("EABI")

  • Pre-built toolchain (recommended):
  • Tools for creating cross-compilers:
    • Crosstool-ng: Builds a cross-compiler from source. Non-distribution specific.
    • Crossdev: Gentoo's cross-compiler builder. Needs Gentoo.

Getting U-Boot sources

There are two ways to get U-Boot sources that can be used as a baseline for CM-T335 SPL and U-Boot. You can create a copy of "Das U-Boot" source tree or download a snapshot and extract it. We assume that you have created /home/development/cm-t335/u-boot directory for CM-T335 u-boot development.

Snapshot download

  • Download v2014.04 snapshot with your web browser.
  • Extract the downloaded archive u-boot-dda0dbfc69f3d560c87f5be85f127ed862ea6721.tar.bz2
cd /home/development/cm-t335/u-boot
tar xvf /path/to/downloaded/u-boot-dda0dbfc69f3d560c87f5be85f127ed862ea6721.tar.bz2
mv u-boot u-boot-cm-t335
This will create /home/development/cm-t335/u-boot/u-boot-cm-t335 directory containing U-Boot source code tree.
  • Apply the CM-T335 patch
cd /home/development/cm-t335/u-boot/u-boot-cm-t335
patch -p1 < /path/to/cm-t335-u-boot/u-boot/u-boot-v2014.04-cm-t335-2.4.patch

Git clone

  • Install git version control system.
  • Create a clone of U-Boot tree
cd /home/development/cm-t335/u-boot
git clone git://git.denx.de/u-boot.git u-boot-cm-t335
  • Create a branch for CM-T335 development. The CM-T335 patches are generated vs. v2014.04 tag (dda0dbfc69f3d560c87f5be85f127ed862ea6721 commit) in the U-Boot tree. It is recommended to use exactly the same baseline to avoid merge conflicts.
git checkout -b cm-t335-dev v2014.04
  • Apply the CM-T335 patch
cd /home/development/cm-t335/u-boot/u-boot-cm-t335
git apply /path/to/cm-t335-u-boot/u-boot/u-boot-v2014.04-cm-t335-2.4.patch

Building the firmware images

In this section we assume that any version of Sourcery CodeBench Lite toolchain is installed on a host machine and it's location is added to a PATH. 

export ARCH=arm
export CROSS_COMPILE=arm-none-linux-eabi-
make mrproper
make cm_t335_config && make

In the example above, CM-T335 firmware images for SPL (MLO) and U-Boot (u-boot.img) will be created in /home/development/cm-t335/u-boot/u-boot-cm-t335.

See also

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