CM-T335: U-Boot: Building Images

Overview

CM-T335 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):
  • Sourcery CodeBench Lite
• 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 v2014.01 snapshot with your web browser.
• Extract the downloaded archive u-boot-b44bd2c73c4cfb6e3b9e7f8cf987e8e39aa74a0b.tar.bz2

cd /home/development/cm-t335/u-boot
tar xvf /path/to/downloaded/u-boot-b44bd2c73c4cfb6e3b9e7f8cf987e8e39aa74a0b.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-v2014.01-cm-t335-2.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. v2014.01 tag (b44bd2c73c4cfb6e3b9e7f8cf987e8e39aa74a0b 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 v2014.01

• 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-v2014.01-cm-t335-2.patch

Building the firmware images

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

• U-Boot quick reference
• U-Boot images
• U-Boot documentation
• SD/MMC format for OMAP3 boot