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some PKTDMA issues

Bruce Chen
Prodigy 50 points

All,

    Hi,

    3 problems.

   1. Packet DMA polls multiple channels even only one channel is enabled.

      what does mutiple channel mean? all channel or a type channel?

     why not enabled channel still polls?

  2.Packet DMA transfers smaller burst (64 bytes at a time) than EDMA (up to 1024 bytes) .

    Packet DMA bus is 128 bit, how can PKTDMA transfer 64 byte at a time ?

 3. PKTDMA bandwidth performance is lower than EDMA, why not make pktdma bandwidth same as edma?

     Or just present pktdma bandwidth is enough, higher performance is not necessary.

Thanks!

Bruce

  • 0
    TI__Expert 5805 points

    Hi Bruce,

    I think your are misunderstanding the function of PKTDMA. I suggest you go over the Multicore Navigator User Guide first for more information on PKTDMA.

    http://www.ti.com/lit/ug/sprugr9e/sprugr9e.pdf

    PKTDMA is a packet based inter-IP communication module. Packets are defined as descriptors and these descriptors have a minimum size of 32 Bytes. But, PKTDMA as EDMA will transfer 128 bits per write/read request over the CPU/3 SCR. So each EDMA TC has a bandwidth of ~42GBPS as does the PKTDMA master port. PKTDMA is instantiated in NetCP, BCP, FFTC, SRIO, AIF and one for the Queue Manager itself ("Infrastructure DMA"). The throughput needed for each of this IP is different and thus actual performance will vary across IP. But, PKTDMA provides more than enough bandwidth for each of these IP's. The infrastructure PKTDMA mainly used for inter-core communication provides ~!6-19gbps with 32 channels active from DDR to L2 (depending the type of descriptor used).

    But the real benefit of PKTDMA is beyond the bandwitch it provides but the packet network based concept of communicaiton. It provides a centrilized buffer and queue management system minizming host side processing and allowing for non-blocking resource sharing. It also provides accumulator fimrwares as well as Quality of Service fimrwares. The concept behind PKTDMA is very differnt to EDMA and they both achieve a different purpose.  

    Regards,

    Javier