4.26. STMicroelectronics STM32MP

Note

Support for the STM32MP architecure in barebox is still in progress. Bootstrapping an OS from mainline barebox is not yet supported.

The STM32MP is a line of 32-bit ARM SoCs. They reuse peripherals of the STM32 line of microcontrollers and can have a STM32 MCU embedded as co-processor as well.

The boot process of the STM32MP SoC is a two step process. The first stage boot loader (FSBL) is loaded by the ROM code into the built-in SYSRAM and executed. The FSBL sets up the SDRAM, install a secure monitor and then the second stage boot loader (SSBL) is loaded into DRAM.

When building barebox, the resulting barebox-${board}.img file has the STM32 header preprended, so it can be loaded directly as SSBL by the ARM TF-A (https://github.com/ARM-software/arm-trusted-firmware). Each entry point has a header-less image ending in *.pblb as well.

Use of barebox as FSBL is not supported.

4.26.1. Building barebox

With multi-image and device trees, it’s expected to have stm32mp_defconfig as sole defconfig for all STM32MP boards:

make ARCH=arm stm32mp_defconfig

The resulting images will be placed under images/:

barebox-stm32mp157c-dk2.img

4.26.2. Flashing barebox

An appropriate image for the boot media can be generated with following genimage(1) config:

image @STM32MP_BOARD@.img {
    hdimage {
        align = 1M
        gpt = "true"
    }
    partition fsbl1 {
        image = "tf-a-@STM32MP_BOARD@.stm32"
        size = 256K
    }
    partition fsbl2 {
        image = "tf-a-@STM32MP_BOARD@.stm32"
        size = 256K
    }
    partition ssbl {
        image = "barebox-@STM32MP_BOARD@.img"
        size = 1M
    }
}

Image can then be flashed on e.g. a SD-Card.

4.26.3. TODO

  • Extend barebox MMCI support to support the SDMMC2
  • Extend barebox DesignWare MAC support to support the stmmac