How to use SYSRAM via MCU in production mode?

[Fheid.1]

Hi guys.

i can quickly and easily access SYSRAM in engineering mode.

i read in RM0436 Reference manual:backhand_index_pointing_down:

 SYSRAM is implicitly allocated to the MPU. So there is no enable bit for the MPU to allocate this memory. But when the MCU wants to access the SYSRAM, the memory must be enabled via RCC AXI Periph. Enable For MCU Set Register ...

I enabled the SYSRAM peripheral clocks, But nothing has changed yet:pensive_face: . i have no idea what to do...

thanks in advance for all your help🙏

[PatrickF]

Hello,

SYSRAM is set in secure mode by default, except in Engineering mode, this explain why you can access it.

SYSRAM cannot be assigned to Cortex-M4, this is a SW architecture choice.

During runtime, SYSRAM could only be split for secure (OP-TEE) and non-secure (Linux) usages, both for Cortex-A7.

see https://wiki.st.com/stm32mpu/wiki/STM32MP15_peripherals_overview

and https://wiki.st.com/stm32mpu/wiki/SYSRAM_internal_memory

Could you explain why you need to access SYSRAM from Cortex-M4 ?

For exchanging Cortex-M4 data with Linux, see https://wiki.st.com/stm32mpu/wiki/Linux_RPMsg_framework_overview and https://wiki.st.com/stm32mpu/wiki/Exchanging_buffers_with_the_coprocessor

Regards.