Last edited 3 years ago

Modify, rebuild and reload the Linux® kernel

1. Overview↑

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 step by step you will execute procedures to modify, rebuild and reload the Linux® kernel.

2. Download the the Linux® kernel source code↑

2.1. For ecosystem release v1.1.0↑
  • Download the STM32MP15-Ecosystem-v1.1.0 Developer Package Sources to the following directory:
    $HOME/STM32MPU_workspace/STM32MP15-Ecosystem-v1.1.0/Developer-Package
  • Uncompress the tarball file to get the Linux® kernel tarball, the ST patches and the ST configuration fragments
 cd $HOME/STM32MPU_workspace/STM32MP15-Ecosystem-v1.1.0/Developer-Package
 tar xvf en.SOURCES-kernel-stm32mp1-openstlinux-4.19-thud-mp1-19-10-09.tar.xz
2.2. For ecosystem release v1.0.0↑

3. Prepare the Linux® kernel source code↑

  • Extract the Linux® kernel source
For ecosystem release  v1.1.0 
 cd stm32mp1-openstlinux-4.19-thud-mp1-19-10-09/sources/arm-openstlinux_weston-linux-gnueabi/linux-stm32mp-4.19-r0
 tar xvf linux-4.19.49.tar.xz

For ecosystem release  v1.0.0


  • Apply the ST patches
 cd linux-4.19.49/ /* For ecosystem release  v1.1.0  */

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


  • Apply fragments
 make 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 oldconfig

4. Build the Linux® kernel source code for the first time↑

Info white.png Information
The first time the kernel is build it could take several minutes.
  • Build kernel images (uImage and vmlinux) and device tree (dtbs)
 make uImage vmlinux dtbs LOADADDR=0xC2000040
  • Build kernel module
 make modules
  • Generate output build artifacts
 mkdir -p $PWD/install_artifact/
 make INSTALL_MOD_PATH="$PWD/install_artifact" modules_install

5. Deploy the Linux® kernel on the board↑

5.1. Push the Linux® kernel into the board↑

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

5.2. Push the devicetree into the board↑

 scp arch/arm/boot/dts/stm32mp157*.dtb root@<board ip address>:/boot

5.3. Push the kernel modules into the board↑

For ecosystem release v1.1.0 :

  • Remove the link created inside the install_artifact/lib/modules/4.19.49 directory
 rm install_artifact/lib/modules/4.19.49/build install_artifact/lib/modules/4.19.49/source

For ecosystem release v1.0.0 :


  • 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, re-generate 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

5.4. Reboot the board↑

 reboot

6. Modifying a built-in Linux kernel device driver↑

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
For ecosystem release  v1.1.0 :
 cd $HOME/STM32MPU_workspace/STM32MP15-Ecosystem-v1.1.0/Developer-Package/stm32mp1-openstlinux-4.19-thud-mp1-19-10-09/sources/arm-openstlinux_weston-linux-gnueabi/linux-stm32mp-4.19-r0/linux-4.19.49
For ecosystem release  v1.0.0 :

openstlinux-4.19-thud-mp1-19-02-20/sources/arm-openstlinux_weston-linux-gnueabi/linux-stm32mp-4.19- r0/linux-4.19.9
  • Edit the ./drivers/gpu/drm/stm/drv.c source file
  • Add a log information in the stm_drm_platform_probe function as follow
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
  • Rebuitd 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 there is now log information when the display driver is probed
 dmesg | grep -i stm_drm_platform_probe
[    2.764080] [drm] Simple example - stm_drm_platform_probe


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