DMA from SRAM to SRAM hanging in the M4 core

[ATringali]

Hi everybody,

I have generated an STM32 project via the STM32CubeIDE and modified the large example buffer (the firmware logic analyzer part), trying to substitute to the timer generated DMA transfer a second stream from SRAM to SRAM.

In the next future I would like to attach a memory to the FMC bus (M4 side) and use DMA to transfer from that memory into the SRAM, and from the SRAM into the DDR. In the meantime I would like to simulate that using an SRAM to SRAM transfer.

I try to run the attached code (main.c), but the first DMA transfer from SRAM to SRAM when I start the request in function StateMachine() through an 'S' command (HAL_DMA_Start_IT()) seems to hang. I see the "before" log at line 302, but not the "after" at line 315.

I cannot manage to attach to the M4 core when running using the integrated debugger, and the STM32CubeProgrammer says that reading registers is not supported yet for STM32MP1. I had some years ago experience with another STM32 microcontroller, so I guess I am doing something unconventional for this new (for me) architecture.

Could someone of you please point me to the right direction?

Thank you in advance,

Antonio

[ATringali]

I answer to myself.

From section 18.3.17 (Summary of the possible configurations) it would seem that DMA memory-to-memory transfers require a source AHB peripheral port and a destination AHB memory port. So it is not possible to transfer from SRAM to SRAM, just from an external memory.

The transfer immediately generated a bus fault, so it was stuck in the while(1) { } NMI handler, with MMFAR/BFAR registers assuming values equal to the end of FIFO values to transfer.