Modify, rebuild and reload the Linux® kernel

Applicable for

STM32MP13x lines, STM32MP15x lines, STM32MP25x lines

1. Overview[edit source]

This stage explains how modify, rebuild and reload the Linux^® kernel.
You will first be guided to install the Linux^® kernel source code in the Developer Package directory. Then you will execute step by step procedures to modify, rebuild and reload the Linux^® kernel.

2. Download OpenSTLinux BSP that includes the Linux^® kernel source code[edit source]

2.1. For STM32MP1 series[edit source]

The software package is provided AS IS, and by downloading it, you agree to be bound to the terms of the software license agreement (SLA0048). The detailed content licenses can be found here.

The OpenSTLinux BSP package is delivered through a tarball file named en.sources-stm32mp1-openstlinux-6.1-yocto-mickledore-mpu-v24.06.26.tar.gz for STM32MP157x-EV1 , STM32MP157x-DKx and STM32MP135x-DK boards.

Download and install the STM32MP1 OpenSTLinux BSP package.

STM32MP1 Developer Package - STM32MP1 ecosystem v5.1.0 release

Download

Go on st.com to download the STM32MP1 Developer Package, en.sources-stm32mp1-openstlinux-6.1-yocto-mickledore-mpu-v24.06.26.tar.gz file.

Installation

Go to the host PC directory where you extracted the package from the .jar file if you follow the proposition to organize the working directory, that is:

cd <working directory path>/Developer-Package

tar xvf en.sources-stm32mp1-openstlinux-6.1-yocto-mickledore-mpu-v24.06.26.tar.gz

Release note

Details about the content of the OpenSTLinux BSP package are available in the associated STM32 MPU OpenSTLinux release note.

For information on older releases, go to Archives.

2.2. For STM32MP2 series[edit source]

STM32MPU Developer Package - OpenSTLinux BSP

3. Prepare the Linux^® kernel source code[edit source]

 cd stm32mp1-openstlinux-6.1-yocto-mickledore-mpu-v24.06.26/sources/arm-ostl-linux-gnueabi/linux-stm32mp-6.1.82-stm32mp-r2-r0

Extract the Linux^® kernel source

 tar xvf linux-6.1.82.tar.xz

Apply ST patches

 cd linux-6.1.82
 for p in `ls -1 ../*.patch`; do patch -p1 < $p; done

3.1. For STM32MP1 series[edit source]

Apply fragments

 make ARCH=arm multi_v7_defconfig "fragment*.config"
 for f in `ls -1 ../fragment*.config`; do scripts/kconfig/merge_config.sh -m -r .config $f; done
 yes '' | make ARCH=arm oldconfig

3.2. For STM32MP2 series[edit source]

Apply fragments

 make defconfig fragment*.config
 for f in `ls -1 ../fragment*.config`; do scripts/kconfig/merge_config.sh -m -r .config $f; done
 (yes '' || true) | make oldconfig

Prepare external device tree source needed to build linux

 cd ../external-dt-v5.0-stm32mp-r1-c11-r0/
 tar xf external-dt-v5.0-stm32mp-r1-c11-r0.tar.xz

To enable use of external device tree source code for other component, you must set the EXTDT_DIR variable to your shell environment

  export EXTDT_DIR=$PWD/external-dt-v5.0-stm32mp-r1-c11

Return into linux directory

 cd $HOME/STM32MPU_workspace/STM32MPU-Ecosystem-v5.1.0/Developer-Package/stm32mp1-openstlinux-6.1-yocto-mickledore-mpu-v24.06.26/sources/arm-ostl-linux-gnueabi/linux-stm32mp-6.1.82-stm32mp-r2-r0/linux-6.1.82

4. Build the Linux^® kernel source code for the first time[edit source]

4.1. For STM32MP1 series[edit source]

Information

Building the kernel for the first time can take several minutes.

Build kernel images (uImage and vmlinux) and device tree (dtbs)

 make ARCH=arm uImage vmlinux dtbs LOADADDR=0xC2000040

Build kernel module

 make ARCH=arm modules

Generate output build artifacts

 mkdir -p $PWD/install_artifact/
 make ARCH=arm INSTALL_MOD_PATH="$PWD/install_artifact" modules_install

4.2. For STM32MP2 series[edit source]

Information

Building the kernel for the first time can take several minutes.

Build kernel images (uImage and vmlinux) and device tree (dtbs)

 make Image.gz vmlinux dtbs LOADADDR=0xC2000040 KBUILD_EXTDTS="${EXTDT_DIR}/linux"
 make modules

Generate output build artifacts

 make INSTALL_MOD_PATH="$PWD/install_artifact" modules_install
 mkdir -p $PWD/install_artifact/boot/
 cp $PWD/arch/$ARCH/boot/Image.gz $PWD/install_artifact/boot/
 cp $PWD/arch/$ARCH/boot/dts/st/st*.dtb $PWD/install_artifact/boot/

5. Deploy the Linux^® kernel on the board[edit source]

5.1. For STM32MP1 series[edit source]

5.1.1. Push the Linux^® kernel onto the board[edit source]

 scp arch/arm/boot/uImage root@<board ip address>:/boot

5.1.2. Push the devicetree into the board[edit source]

 scp arch/arm/boot/dts/stm32mp1xx*.dtb root@<board ip address>:/boot

5.1.3. Push the kernel modules onto the board[edit source]

Remove the link created inside the install_artifact/lib/modules/<kernel version> directory

 rm install_artifact/lib/modules/6.1.28/build install_artifact/lib/modules/6.1.28/source

Optionally, strip kernel modules (to reduce the size of each kernel modules)

 find install_artifact/ -name "*.ko" | xargs $STRIP --strip-debug --remove-section=.comment --remove-section=.note --preserve-dates

Copy kernel modules

 scp -r install_artifact/lib/modules/* root@<ip of board>:/lib/modules

Using the Linux^® console, regenerate the list of module dependencies (modules.dep) and the list of symbols provided by modules (modules.symbols)

 /sbin/depmod -a

Synchronize data on disk with memory

 sync

5.1.4. Reboot the board[edit source]

 reboot

5.2. For STM32MP2 series[edit source]

5.2.1. Push the Linux^® kernel + devicetree onto the board[edit source]

 cd install_artifact/
 scp -r boot/* root@<ip of board>:/boot/

5.2.2. Push the kernel modules onto the board[edit source]

Remove the link created inside the install_artifact/lib/modules/<kernel version> directory

 rm lib/modules/6.1.28/source lib/modules/6.1.28/build

Optionally, strip kernel modules (to reduce the size of each kernel modules)

 find . -name "*.ko" | xargs $STRIP --strip-debug --remove-section=.comment --remove-section=.note --preserve-dates

Copy kernel modules

 scp -r lib/modules/* root@<ip of board>:/lib/modules/

Generate a list of module dependencies (modules.dep) and a list of symbols provided by modules (modules.symbols):

 ssh root@<ip of board> /sbin/depmod -a

Synchronize data on disk with memory

 ssh root@<ip of board> sync

5.2.3. Reboot the board in order to take update into account[edit source]

 ssh root@<ip of board> reboot

6. Modify a built-in Linux^® kernel device driver[edit source]

This simple example adds unconditional log information when the display driver is probed.

Using the Linux^® console, check that there is no log information when the display driver is probed

 dmesg | grep -i stm_drm_platform_probe

Go to the Linux^® kernel source directory

 cd $HOME/STM32MPU_workspace/STM32MPU-Ecosystem-v5.1.0/Developer-Package/stm32mp1-openstlinux-6.1-yocto-mickledore-mpu-v24.06.26/sources/arm-ostl-linux-gnueabi/linux-stm32mp-6.1.82-stm32mp-r2-r0/linux-6.1.82

Edit the ./drivers/gpu/drm/stm/drv.c source file
Add a log information in the stm_drm_platform_probe function as follows

static int stm_drm_platform_probe(struct platform_device *pdev)
{
	struct device *dev = &pdev->dev;
	struct drm_device *ddev;
	int ret;
	[...]

	DRM_INFO("Simple example - %s\n", __func__);

	return 0;
	[...]
}

Save the file

6.1. For STM32MP1 series[edit source]

Rebuild the Linux^® kernel

 make uImage LOADADDR=0xC2000040

Update the Linux kernel image into board

 scp arch/arm/boot/uImage root@<board ip address>:/boot

Reboot the board

 reboot

Check that log information is now present when the display driver is probed

 dmesg | grep -i stm_drm_platform_probe
[    2.764080] [drm] Simple example - stm_drm_platform_probe

6.2. For STM32MP2 series[edit source]

Rebuild the Linux^® kernel

 make Image.gz vmlinux dtbs LOADADDR=0xC2000040 KBUILD_EXTDTS="${EXTDT_DIR}/linux"

Update the Linux kernel image into board

 scp arch/arm64/boot/Image.gz root@<ip of board>:/boot

Reboot the board

 ssh root@<ip of board> reboot

Check that log information is now present when the display driver is probed

 dmesg | grep -i stm_drm_platform_probe
[    2.764080] [drm] Simple example - stm_drm_platform_probe

7. STM32MP257F-EV1 Evaluation board with OSTL device tree[edit source]

For compilation of OSTL device tree in the external Git, linux/stm32mp257f-ev1-ca35tdcid-ostl.dts , you can add this git inside Linux^® kernel tree or outside Linux^® kernel tree.

7.1. External git inside Linux^® kernel tree[edit source]

  git submodule add https://github.com/STMicroelectronics/dt-stm32mp arch/arm64/boot/dts/st/external-dt
  make  dtbs
 or
  make  stm32mp257f-ev1-ca35tdcid-ostl.dtb

7.2. External git outside Linux^® kernel tree with KBUILD_EXTDTS[edit source]

  git clone https://github.com/STMicroelectronics/dt-stm32mp ../dt-stm32mp
  make dtbs KBUILD_EXTDTS=$PATH/dt-stm32mp
 or
  make stm32mp257f-ev1-ca35tdcid-ostl.dtb KBUILD_EXTDTS=$PATH/dt-stm32mp