Building the MitySOM-AM62 U-Boot¶

Table of contents
Building the MitySOM-AM62 U-Boot

Before you begin¶

There are multiple ways to customize and compile the U-Boot for your project. Please try to build U-Boot as-is with no changes before you add your customizations. This will ensure your environment and toolchain are setup correctly.

Docker Build - Build using a Docker image (as described in Docker Build Environment )
Linux Manual Install - You can use a previously compiled ARM toolchain provided by ARM by installing it on a Linux system.
Yocto Environment - If you are using the docker environment and Yocto for your filesystem, you can use its tools to customize and build U-Boot.

In most cases, you will use one of the first three options to build U-Boot for Critical Link development kit. Then, once you have everything working you can integrate your custom code into the U-Boot source.

Critical Link recommends using the mitysom-u-boot-2021.01 branch on our git server: https://support.criticallink.com/git/u-boot-ti.git.

Other MitySOM-AM62x U-Boot branches seen on the repository should not be considered stable, and are used for internal feature development.

U-Boot Build - Docker¶

See Docker build environment for details on how to setup and install the Docker build environment. Once that is installed, you can build U-Boot using the following commands:

$ git clone --single-branch --branch mitysom-u-boot-2021.01 https://support.criticallink.com/git/u-boot-ti.git
$ cd u-boot-ti
$ docker run --rm --volume "$PWD:/work" --workdir=/work mitysom_ubuntu:22.04 ./62x-build.sh -i

If the build is successful, subsequent use of the script can omit the -i option.

Please refer to the "Verifying Your U-Boot Build" section of this wiki page to verify your build and the next steps.

U-Boot Build - Linux Manual Install¶

Click here to view instructions...Click here to view instructions...

Configuring the Build Environment¶

Builds are done in a Linux environment

Download the ARM toolchain and setup the build environment using the following commands:

# mkdir -p /home/tools/mitysom-62x
# wget https://developer.arm.com/-/media/Files/downloads/gnu-a/9.2-2019.12/binrel/gcc-arm-9.2-2019.12-x86_64-aarch64-none-linux-gnu.tar.xz -O - | tar -Jxv -C /home/tools/mitysom-62x/ 
# wget https://developer.arm.com/-/media/Files/downloads/gnu-a/9.2-2019.12/binrel/gcc-arm-9.2-2019.12-x86_64-arm-none-linux-gnueabihf.tar.xz -O - | tar -Jxv -C /home/tools/mitysom-62x/ 
# cd /home/tools/mitysom-62x; tar xvf path/to/*aarch64-none*.tar.xz; tar xvf path/to/*arm-none*.tar.xz
# git clone --single-branch --branch mitysom-u-boot-2021.01 https://support.criticallink.com/git/u-boot-ti.git 
# cd u-boot-ti

Note that you will need to replace path/to with the correct path to the downloaded .tar.xz files.

You will also need the following packages installed on your Linux system to support this build method:

# sudo apt-get install bc bison build-essential \
#  device-tree-compiler dfu-util efitools flex gdisk liblz4-tool \
#  libguestfs-tools libncurses-dev libpython3-dev libsdl2-dev libssl-dev \
#  lzma-alone openssl python3 python3-coverage python3-pyelftools \
#  python3-pytest python3-sphinxcontrib.apidoc python3-sphinx-rtd-theme swig

This assumes you are running Ubuntu Linux. If you are not using Ubuntu, please consider using the Docker build option for your first build.

Choosing a configuration and compiling U-Boot¶

There is a build script (62x-build.sh) in the top-level directory of the git repository that you can use to build U-Boot. It is recommended you read through the script and understand the steps it takes to build the required artifacts as it is somewhat involved.

From the u-boot-ti directory, you can run the script using the --install-depends option for the initial build:

$ ./62x-build.sh --install-depends

Note that the build script assumes you installed the toolchains in the default locations and assumes you want to build U-Boot for the Critical Link AM62x Development Kit. If the build is successful, subsequent use of the script can omit the --install-depends option.

Please refer to the "Verifying Your U-Boot Build" section of this wiki page to verify your build and the next steps.

U-Boot Build - Yocto¶

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For this option, you should have an environment setup as described in Docker build environment and Building the Yocto Root Filesystem for MitySOM-AM62X.

With this option, the general Yocto setup configures your build environment. You can compile U-Boot by running bitbake commands from your build directory.

Customize your U-Boot¶

You can customize U-Boot by pointing the U-Boot recipe to your new branch location.

In your Yocto meta layer, create a u-boot bbappend file. File name is important to match existing u-boot recipe name, as of Mar 2023 the name is below
[meta-mitysom.git] / recipes-bsp / u-boot / u-boot-cl-ti_2021.01.bb

mkdir recipes-bsp/u-boot/
vim u-boot-cl-ti_2021.01.bb.bbappend

UBOOT_GIT_URI = "git://support.criticallink.com/git/u-boot-ti.git" 
UBOOT_GIT_PROTOCOL = "http" 

BRANCH = "mitysom-u-boot-2021.01" 
SRCREV = "${AUTOREV}"

Point UBOOT_GIT_URI to your repository
Update BRANCH to match your branch
SRCREV can be set to a specific git hash if you want to lock to a specific commit instead of letting it grab the latest in the branch.

Building U-Boot¶

Then, to build U-Boot (note that this is within the previously configured Docker environment):

user@8ec23474095b:~$ MACHINE=mitysom-am62x bitbake virtual/bootloader

If the build is successful, you will find your tiboot3.bin tispl.bin and u-boot.img file in ./arago-tmp-external-arm-glibc/deploy/images/mitysom-am62x/.

Verifying Your U-Boot Build and Next Steps¶

If successful, the build script lists the output binaries after completing the build:

lrwxrwxrwx 1 user mitysom 62 Mar 11 19:44 /work/build-mitysom_am62x_devkit/k3ig/tiboot3.bin -> /work/build-mitysom_am62x_devkit/k3ig/tiboot3-am62x-gp-evm.bin
-rw-r--r-- 1 user mitysom 934140 Mar 11 19:44 /work/build-mitysom_am62x_devkit/a53/tispl.bin
-rw-r--r-- 1 user mitysom 896728 Mar 11 19:44 /work/build-mitysom_am62x_devkit/a53/u-boot.img

You may copy those three files to your boot media to test your new build.

When U-Boot boots, it will display the build date and time. Please check this to make sure your new U-Boot files are being used.

For example, note the multiple dates, one for each stage of the boot process. If you are using the HS or HS-FS part, you will see additional messages relating to the secure boot process:

U-Boot SPL 2021.01-gf09de44c32 (Feb 21 2023 - 19:27:10 +0000)
SYSFW ABI: 3.1 (firmware rev 0x0008 '8.4.7--v08.04.07 (Jolly Jellyfi')
SPL initial stack usage: 13424 bytes
Trying to boot from MMC2

...

U-Boot SPL 2021.01 (Mar 03 2023 - 13:16:40 +0000)
SYSFW ABI: 3.1 (firmware rev 0x0008 '8.4.7--v08.04.07 (Jolly Jellyfi')
Trying to boot from MMC2

U-Boot 2021.01-00279-g3c10843487-dirty (Mar 06 2023 - 11:14:15 -0500)

Customizing U-Boot for your Application¶

Now that you can build U-Boot, you can customize the U-Boot source code for your specific application.

For most projects, you will want a custom defconfig and a custom pinmux. Example defconfigs can be found in the configs/ directory. It is recommended that you start with a similar board as a reference for your own configuration. You will need to update the build.sh script to use your custom defconfig files (search for defconfig to find the relevant strings).

An example pinmux for Critical Link's development board can be found in board/cl/mitysom-62x/mux_data.h.

Please contact Critical Link at info@criticallink.com if you need help with customizing your defconfig and pinmux for your application.

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