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omapl138 upp dma problem

Hi,

We are using UPP to send data from FPGA to DSP running on 40 MHz. It is 100K 4-byte data, thus we are storing this data at external DDR2.

In DSP, we DMA the data to external DDR2. And both ARM and DSP have access to the external DDR2.

We have found that when ARM is running some code (example like below) that is memory extensive, the UPP DMA to external DDR2 will fail with UOR (Underrun or Overflow) event, some data from FPGA is lost.

We guess this could be due to the bus contention between ARM and UPP DMA. Thus, to workaround this, we use DSP L2 RAM as the temporary destination for DMA, and then move the data from DSP L2 RAM to external DDR2 using memcpy.

I asking is there any better alternative than this workaround as we would like to increase the data size from 100K to 1M. And ideally we want to DMA the 1M data to the external DDR2 directly without having to go thorugh the L2 RAM first.

bool testMemCpy( void )

{

unit32 *src = new uint32[2600];

unit32 *dest = new uint32[2600];


memcpy( dest, src, 2600 );


delete [] src;

delete [] dest;

return true;

}

We

rgds,

kc Wong

  • Hi,
    Some of the customers also faced the same kind of problem and used internal RAM to avoid data loss as you have now.
    I don't see any other method to fix this bus contention problem, sorry.
  • Hi,

    As we are increasing the data size from 100K to 1M, moving the data from DSP L2 RAM to external DDR2 using memcpy may not be fast enough.

    Thus, we are thinking to use EDMA to move the data from DSP L2 RAM to external DDR2 instead of memcpy.

    Question is while UPP DMA to DSP L2 RAM, can EDMA move data from DSP L2 RAM to external DDR2 at the same time ?

    As both bus masters (UPP DMA and EDMA) are accessing the DSP L2 RAM at the same time, will it cause the bus contention problem also ?

    rgds,
    kc wong