HSEM registers access has except on STM32MP257 in development mode

[Da_Vinci]

I have used HSEM on STM32H7 very well.

Recently，I test the HSEM of STM32MP257 in development mode， by JTAG/SWD，
I can lock the semaphore by reading the HSEM_RLRx register via CPU1~3,

but after power reset，when I write the HSEM_RLRx register to lock or unlock semaphore, it doesn't work!
the security /privilege / CID filtering of HSEM are all off after reset, and the cpu3 could  access the HSEM_RLRx register correctly，but after cpu1/2  write the HSEM_RLRx register or HSEM_CnIER，both lock and unlock operations have no effect.

pls give me some suggestions to check what I might have done wrong .thanks!

[Da_Vinci]

And why the newest STM32MP21 series has deleted the HSEM module ？

This module is quite useful in multi-core applications.

[PatrickF]

As far as I know, HSEM is inherited from STM32MP15 family but finally not used in STM32MP25 and STM32MP23 software as all our inter-processor communication uses IPCC (also in STM32MP15).

I confirm it has been removed in STM32MP21.

Regards.