CL-SOM-iMX7: U-Boot: Building Images

Overview

CL-SOM-iMX7 firmware consists of single U-Boot binary image. It is based on U-Boot source code. U-Boot is invoked by the CPU internal boot ROM code of the i.MX7 SoC. U-Boot initializes hardware modules necessary for system boot and loads the operating system.

Building Firmware images for CL-SOM-iMX7

Getting U-Boot sources

There are two ways to get U-Boot sources that can be used as a baseline for CL-SOM-iMX7 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/cl-som-imx7/u-boot directory for CL-SOM-iMX7 u-boot development.

Snapshot download

• Download v2016.09 snapshot with your web browser.
• Extract the downloaded archive u-boot-8cbb389.tar.gz

cd /home/development/cl-som-imx7/u-boot
tar xvf /path/to/downloaded/u-boot-8cbb389.tar.gz
mv u-boot u-boot-cl-som-imx7

This will create /home/development/cl-som-imx7/u-boot/u-boot-cl-som-imx7 directory containing U-Boot source code tree.

• Apply the CL-SOM-iMX7 patch

cd /home/development/cl-som-imx7/u-boot/u-boot-cl-som-imx7
patch -p1 < /path/to/cl-som-imx7-u-boot-package/u-boot/u-boot-v2016.09-cl-som-imx7-*.patch

Git clone

• Install git version control system.
• Create a clone of U-Boot tree

cd /home/development/cl-som-imx7/u-boot
git clone git://git.denx.de/u-boot.git u-boot-cl-som-imx7
cd /home/development/cl-som-imx7/u-boot/u-boot-cl-som-imx7

• Create a branch for CL-SOM-iMX7 development. The CL-SOM-iMX7 patches are generated vs. v2016.09 tag (8cbb389bb3da80cbf8911f8386cbff92c6a78afe commit) in the U-Boot tree. It is recommended to use exactly the same baseline to avoid merge conflicts.

git checkout -b cl-som-imx7-dev v2016.09

• Apply CL-SOM-iMX7 patch

git am /path/to/cl-som-imx7-u-boot-package/u-boot/patches/*.patch

Building the firmware images

• First, compileU-Boot. The following commands create the u-boot.imx binary (along with other image types):

export ARCH=arm
export CROSS_COMPILE=arm-none-linux-eabi-
make mrproper
make cl_som_imax7_defconfig && make

• Rename the U-Boot binary image file:

cp u-boot.imx cl-som-imx7-firmware

• You can now install the cl-som-imx7-firmware file into an SD card or CL-SOM-iMX7 SPI flash.