STM32MP1-Old-Kits: Booting a Specific Kit Configuration

The STM32MP1-SOM BSP supports the following hardware platforms:

STM32MP1-SOM 800MHz in STM32MP1-BSB
STM32MP1-SOM 650MHz in STM32MP1-BSB
STM32MP1-SOM 800MHz in SLX-SOM-BSB
STM32MP1-SOM 650MHz in SLX-SOM-BSB

The installation image that is generated during Yocto build includes support for all the above-mentioned hardware platform in a single image.

Before Linux boot, it is possible to choose the Linux device tree for the specific platform in the extlinux boot menu in the board console:

Select the boot mode
1:      stm32mp157d-bsb
2:      stm32mp157a-som
3:      stm32mp157d-som
4:      stm32mp157a-bsb
Enter choice:

By default, the device tree for STM32MP1-SOM 800MHz in STM32MP1-BSB (the stm32mp157d-bsb menu item) is booted without any boot delay. If it is desirable to delay the boot in the menu and allow manual selection of the hardware platform, the extlinux configuration needs to be adjusted accordingly.

The extlinux configuration file is stored in /boot/mmc1_extlinux/stm32mp157d-bsb_extlinux.conf for EMMC boot and in /boot/mmc0_extlinux/stm32mp157d-bsb_extlinux.conf for the SD card boot.

The TIMEOUT option in the extlinux configuration file allows to set the delay which the system waits in the boot menu for the user input before proceeding to boot the default device tree if no user input provided. This value is set in 1/10 second.

The DEFAULT option in the extlinux configuration file sets the default boot platform. The following table provides the mapping between the hardware platform and boot items:

Hardware Platform	Boot menu item

Hardware Platform	Boot menu item
STM32MP1-SOM 800MHz in STM32MP1-BSB	`stm32mp157d-bsb`
STM32MP1-SOM 650MHz in STM32MP1-BSB	`stm32mp157a-bsb`
STM32MP1-SOM 800MHz in SLX-SOM-BSB	`stm32mp157d-som`
STM32MP1-SOM 650MHz in SLX-SOM-BSB	`stm32mp157a-som`

It is also possible to modify the default boot platform in Yocto build, so the generated stm32mp157d-bsb_extlinux.conf file includes the required boot menu item as default. For this, the UBOOT_EXTLINUX_DEFAULT_LABEL:stm32mp157d-bsb variable in layers/meta-st/meta-emcraft/conf/machine/stm32mp15-som.conf must be modified to point to one of the boot menu items from the table above.