7.37.1. STM32 MPUs

STM32 MPUs are microprocessors designed by STMicroelectronics based on Arm Cortex-A. This page presents the common configuration of STM32 MPUs, more details and dedicated configuration can be found in each STM32 MPU page (STM32MP1 or STM32MP2)

7.37.1.1. Design

The STM32 MPU resets in the ROM code of the Cortex-A. The primary boot core (core 0) executes the boot sequence while secondary boot core (core 1) is kept in a holding pen loop. The ROM code boot sequence loads the TF-A binary image from boot device to embedded SRAM.

The TF-A image must be properly formatted with a STM32 header structure for ROM code is able to load this image. Tool stm32image can be used to prepend this header to the generated TF-A binary.

7.37.1.1.1. Boot

Only BL2 (with STM32 header) is loaded by ROM code. The other binaries are inside the FIP binary: BL31 (for Aarch64 platforms), BL32 (OP-TEE), U-Boot and their respective device tree blobs.

7.37.1.1.2. Boot sequence

ROM code -> BL2 (compiled with RESET_TO_BL2) -> OP-TEE -> BL33 (U-Boot)

7.37.1.2. Build Instructions

Boot media(s) supported by BL2 must be specified in the build command. Available storage medias are:

STM32MP_SDMMC
STM32MP_EMMC
STM32MP_RAW_NAND
STM32MP_SPI_NAND
STM32MP_SPI_NOR

Serial boot devices:

STM32MP_UART_PROGRAMMER
STM32MP_USB_PROGRAMMER

Other configuration flags:

DTB_FILE_NAME: to precise board device-tree blob to be used.

Default: stm32mp157c-ev1.dtb
DWL_BUFFER_BASE: the ‘serial boot’ load address of FIP,

default location (end of the first 128MB) is used when absent
STM32MP_EARLY_CONSOLE: to enable early traces before clock driver is setup.

Default: 0 (disabled)
STM32MP_RECONFIGURE_CONSOLE: to re-configure crash console (especially after BL2).

Default: 0 (disabled)
STM32MP_UART_BAUDRATE: to select UART baud rate.

Default: 115200

7.37.1.3. Populate SD-card

7.37.1.3.1. Boot with FIP

The SD-card has to be formatted with GPT. It should contain at least those partitions:

fsbl: to copy the tf-a-stm32mp157c-ev1.stm32 binary (BL2)
fip (GUID 19d5df83-11b0-457b-be2c-7559c13142a5): which contains the FIP binary

Usually, two copies of fsbl are used (fsbl1 and fsbl2) instead of one partition fsbl.