STM32MP1 Buildroot external tree

This repository is a Buildroot BR2_EXTERNAL tree dedicated to supporting the STMicroelectronics STM32MP1 platforms. Using this project is not strictly necessary as Buildroot itself has support for STM32MP1, but this BR2_EXTERNAL tree provide example configurations demonstrating how to use the different features of the STM32MP1 platforms.

Available configurations

This BR2_EXTERNAL tree provides four example Buildroot configurations:

st_stm32mp157a_dk1_defconfig, which is a minimal configuration to support the STM32MP1 Discovery Kit 1 board. It builds the TF-A firmware, U-Boot bootloader, Linux kernel and a minimal user-space composed of just Busybox.
st_stm32mp157c_dk2_defconfig, which is a minimal configuration to support the STM32MP1 Discovery Kit 2 board. It builds the TF-A firmware, U-Boot bootloader, Linux kernel and a minimal user-space composed of just Busybox.
st_stm32mp157a_dk1_demo_defconfig, which is a more feature-ful configuration to support the STM32MP1 Discovery Kit 1 board. It has support for OpenGL and Qt5 for graphics, for OP-TEE as a Trusted Execution Environment. It also shows how Device Tree files generated by CubeMX can be integrated in a Buildroot configuration.
st_stm32mp157c_dk2_demo_defconfig, which is a more feature-ful configuration to support the STM32MP1 Discovery Kit 2 board. It has support for OpenGL and Qt5 for graphics, for OP-TEE as a Trusted Execution Environment. It also shows how Device Tree files generated by CubeMX can be integrated in a Buildroot configuration.

Feature	st_stm32mp157a_dk1	st_stm32mp157c_dk2	st_stm32mp157a_dk1_demo	st_stm32mp157c_dk2_demo
TF-A	v2.4-stm32mp-r1	v2.4-stm32mp-r1	v2.4-stm32mp-r1	v2.4-stm32mp-r1
U-Boot	v2020.10-stm32mp-r1.1	v2020.10-stm32mp-r1.1	v2020.10-stm32mp-r1.1	v2020.10-stm32mp-r1.1
Linux	v5.10-stm32mp-r1	v5.10-stm32mp-r1	v5.10-stm32mp-r1	v5.10-stm32mp-r1
OP-TEE	No	No	3.12.0-stm32mp-r1	3.12.0-stm32mp-r1
Qt5	No	No	Yes	Yes
OpenGL	No	No	Yes	Yes
WiFi	N/A	No	N/A	Yes
Bluetooth	N/A	No	N/A	Yes
Audio	No	No	Yes	Yes
CubeMX Device Tree	No	No	Yes	Yes
Cortex M4 Firmware examples	No	No	Yes	Yes

Note that upstream Buildroot also contains pre-defined configurations for STM32MP1 platforms, but they use the upstream versions of TF-A, U-Boot and Linux, while the configurations in this BR2_EXTERNAL tree use the versions provided and supported by ST.

Getting started

Pre-requisites

In order to use Buildroot, you need to have a Linux distribution installed on your workstation. Any reasonably recent Linux distribution (Ubuntu, Debian, Fedora, Redhat, OpenSuse, etc.) will work fine.

Then, you need to install a small set of packages, as described in the Buildroot manual System requirements section.

For Debian/Ubuntu distributions, the following command allows to install the necessary packages:

$ sudo apt install debianutils sed make binutils build-essential gcc g++ bash patch gzip bzip2 perl tar cpio unzip rsync file bc git

Getting the code

This BR2_EXTERNAL tree is designed to work with the latest LTS version of Buildroot, 2021.02.x. However, we needed a few changes on top of upstream Buildroot, so you need to use our own Buildroot fork together with this BR2_EXTERNAL tree, and more precisely its st/2021.02 branch.

$ git clone -b st/2021.02 https://github.com/bootlin/buildroot.git

See our documentation on internal details for more information about the changes we have compared to upstream Buildroot.

Now, clone the matching branch of the BR2_EXTERNAL tree:

$ git clone -b st/2021.02 https://github.com/bootlin/buildroot-external-st.git

You now have side-by-side a buildroot directory and a buildroot-external-st directory.

Configure and build

Go to the Buildroot directory:

$ cd buildroot/

And then, configure the system you want to build by using one of the 4 defconfigs provided in this BR2_EXTERNAL tree. For example:

buildroot/ $ make BR2_EXTERNAL=../buildroot-external-st st_stm32mp157c_dk2_defconfig

We are passing two informations to make:

The path to BR2_EXTERNAL tree, which we have cloned side-by-side to the Buildroot repository
The name of the Buildroot configuration we want to build.

If you want to further customize the Buildroot configuration, you can now run make menuconfig, but for your first build, we recommend you to keep the configuration unchanged so that you can verify that everything is working for you.

Start the build:

buildroot/ $ make

This will automaticaly download and build the entire Linux system for your STM32MP1 platform: cross-compilation toolchain, firmware, bootloader, Linux kernel, root filesystem. It might take between 30 and 60 minutes depending on the configuration you have chosen and how powerful your machine is.

Flashing and booting the system

The Buildroot configurations generate a ready-to-use SD card image, available at output/images/sdcard.img. Flash this image on a SD card:

buildroot/ $ dd if=output/images/sdcard.img of=/dev/sdX bs=1M

(Note: this assumes your SD card appears as /dev/sdX on your system.)

Then:

Insert the microSD card in connector CN15
Plug a micro-USB cable in connector CN11 and run your serial communication program on /dev/ttyACM0.
Configure the SW1 switch to boot on SD card
Plug a USB-C cable in CN6 to power-up the board.
The system will start, with the console on UART. You can log-in as root with no password (a password can of course be added by changing the Buildroot configuration)

Going further

Using the STM32 Cube Programmer
Using Device Tree files generated by STM32 CubeMX
Using the Firmware examples for the CM4
Testing display support
Using WiFi, only for the Discovery Kit 2
Using Bluetooth, only for the Discovery Kit 2
Using Audio
Using Qt5 demos
Using OP-TEE
Internal details on this BR2_EXTERNAL tree

References

Buildroot
Buildroot reference manual
Buildroot system development training course, with freely available training materials

Support

You can contact Bootlin at info@bootlin.com for commercial support on using Buildroot on STM32MP1 platforms.

jleni / buildroot-external-st