Using Only the M33 on the STM32MP2: Feasibility and Peripheral Support

[Haruki-Obuchi]

Hello everybody.

On STM32MP2, is it possible to operate only the M33 like a microcontroller, without booting the A35? Also, if only the M33 is operated, can major peripherals such as I2C and Ethernet be controlled from the M33? (I assume that PCIe would be difficult...)

[PatrickF · Accepted solution]

HI @Haruki-Obuchi 

Yes, on STM32MP25x, it would be possible to boot the Cortex-M33 first (this is listed as 'M33 cold boot' or 'Cortex-M33 TDCID'). This mean the Cortex-M33 will be the 'trusted domain' and so master of the system security and ressource management (e.g. clocks) and as well to load/start Linux.

https://wiki.st.com/stm32mpu/wiki/STM32_MPU_ROM_code_overview#Boot_device_selection_on_STM32MP2_series

The ecosystem able to do that is not yet published. Release is planned for mid-2025.

For the supported peripherals, I2C and Ethernet are already part of M33 HAL already delivered.
See  https://wiki.st.com/stm32mpu/wiki/STM32CubeMP2_Package#HAL_drivers.

Btw, why did you focus on STM32MP2 product if only M33 is under your consideration ?

Did you seek specific interfaces present only on STM32MP25 and not on any STM32 MCUs?

Regards.

[Haruki-Obuchi]

@PatrickF  Thank you!

> Btw, why did you focus on STM32MP2 product if only M33 is under your consideration ?
> Did you seek specific interfaces present only on STM32MP25 and not on any STM32 MCUs?

I started turning my attention to the STM32MP2 when I was considering developing a general-purpose SoM.

Basically, I plan to use Linux and the A35 as my main environment, but there are times when you don’t need a full-fledged OS like Linux and just want fast startup and direct low-level control, similar to a typical MCU.

It’s convenient to handle these requirements with a single SoM via a common interface, and from a hardware cost perspective, it’s advantageous if you don’t need to mass-produce.