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Question about msgdma MM2MM mode utility


Hi, experts


I have built a NIOS II system to verify MSGDMA. The structure is shown as below:


The steps it works:

  1. NIOS write test pattern to some certain space in DDR3
  2. NIOS configure MSGDMA to mm2mm mode
  3. Write descriptors to MSGDMA and the Read Master read test pattern out and send to the 2-cycle delay module
  4. Write Master send the data back to DDR3, but at different memory space.
  5. NIOS read the data out and compare with the original test pattern.

When it begins to run, the system always hang on waiting for completion IRQ, but no IRQ generated. I checked the memory, some data were lost during transfer.

When I remove the delay module, and directly loopback the Avalon-S T port of Write Master and Read Master, everything goes well.

My question is , is it possible to add some processing module when MSGDMA in MM2MM mode ? if yes, How it handle it ?

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I come back to finish this , I solved this in a very simple way, that is , set the msgdma data fifo depth larger !