1. Kernel Source Preparation

Begin by extracting the source package from the ST repository:

cd /linux/atk-mpl/stm32mp1-openstlinux-5.4-dunfell-mp1-20-06-24/sources/arm-ostl-linux-gnueabi/linux-stm32mp-5.4.31-r0/
tar -vxf linux-5.4.31.tar.xz

Apply Patches

Process all patch files in the parent directory:

cd linux-5.4.31/
find .. -name "*.patch" -exec patch -p1 < {} \;

Generate Configuration

Create initial configuration with fragment files:

make ARCH=arm stm32mp1_devkit_defconfig CONFIG_FRAGMENT="fragment*.config"
for f in ../fragment*.config; do scripts/kconfig/merge_config.sh -m -r .config $f; done
yes "" | make ARCH=arm oldconfig

Save the final configuration:

cp .config ./arch/arm/configs/stm32mp1_devkit_defconfig

2. Building the Kernel

Create build script stm32mp1_devkit.sh:

#!/bin/sh
make distclean
make stm32mp1_devkit_defconfig
make menuconfig
make uImage dtbs LOADADDR=0XC2000040 -j16

Execute the build:

chmod +x stm32mp1_devkit.sh
./stm32mp1_devkit.sh

Network Driver Integration

Copy driver files to kernel source:

cp motorcomm.c drivers/net/phy/
cp motorcomm_phy.h include/linux/

Update drivers/net/phy/Makefile:

obj-$(CONFIG_MOTORCOMM_PHY) += motorcomm.o

Add to drivers/net/phy/Kconfig:

config MOTORCOMM_PHY
    tristate "Motorcomm PHY Support"
    ---help---
    Enables support for YT8010, YT8510, YT8511, YT8512 PHY chips.

Enable in menuconfig:

Device Drivers → Network device support → PHY Device support → Motorcomm PHYs

3. Device Tree Customization

Create New Device Tree Files

cd arch/arm/boot/dts/
cp stm32mp15xx-edx.dtsi stm32mp157d-devkit.dtsi
cp stm32mp157d-ed1.dts stm32mp157d-devkit.dts

Modify Device Tree

Update stm32mp157d-devkit.dtsi with power management and hardware configuration:

/ {
    memory@c0000000 {
        reg = <0xC0000000 0x40000000>;
    };

    vddcore: buck1 {
        compatible = "regulator-fixed";
        regulator-min-microvolt = <1200000>;
        regulator-max-microvolt = <1350000>;
    };

    v3v3: regulator-3p3v {
        compatible = "regulator-fixed";
        regulator-min-microvolt = <3300000>;
    };
};

&cpu0 {
    cpu-supply = <&vddcore>;
};

ðernet0 {
    status = "okay";
    phy-mode = "rgmii-id";
    phy-handle = <&phy0>;
};

&sdmmc1 {
    vmmc-supply = <&v3v3>;
    status = "okay";
};

Update Build System

Add to arch/arm/boot/dts/Makefile:

dtb-$(CONFIG_ARCH_STM32MP1) += stm32mp157d-devkit.dtb

4. System Deployment

Image Packaging

Create boot filesystem:

dd if=/dev/zero of=bootfs.ext4 bs=1M count=10
mkfs.ext4 -L bootfs bootfs.ext4
mkdir -p /mnt/bootfs
mount bootfs.ext4 /mnt/bootfs
cp uImage stm32mp157d-devkit.dtb /mnt/bootfs/
umount /mnt/bootfs

EMMC Flashing

Transfer bootfs.ext4 to STM32CubeProgrammer and flash to EMMC. Configure U-Boot:

setenv bootcmd 'ext4load mmc 1:2 c2000000 uImage; ext4load mmc 1:2 c4000000 stm32mp157d-devkit.dtb; bootm c2000000 - c4000000'
saveenv
boot