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 (:ref:`STM32MP1` or :ref:`STM32MP2`)

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.

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.

Boot sequence
~~~~~~~~~~~~~

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

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``

Only one storage or serial device should be selected in the build command line,
to save space and not overflow SYSRAM size, or else the platform won't build or boot.

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


Populate SD-card
----------------

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.

--------------

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