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KChan12's avatar
KChan12
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7 years ago

For PCIe DMA driver from altera multiple descriptors not working?

Hi , We are using AVMM PCIe DMA example design and modified as per our requirement. In place of onchip memory we are using FIFO. we are using PCIe DMA driver from altera. We can tap the data lines on FIFO side and check the data using signal tap. But data is proper when one single descriptor is used. As we go for multiple descriptors (like number of Dwords:/desc 256 and no of descriptors:2 total 2 kb of data). We can see only 1kb of data on bus ie for one descriptor. Please give inputs why its is not sending properly in case of multiple decriptors or the driver doesnt support multiple descriptor.

3 Replies

  • SengKok_L_Intel's avatar
    SengKok_L_Intel
    Icon for Regular Contributor rankRegular Contributor
    7 years ago

    ​Hi,

    The maximum transfer size for each descriptor is 1MB. If without modified the design, did you see the same behavior? What device that you are using? Are you saying, if only 1 descriptor with 2kb of data, you can also see it correctly in the FIFO?

    Regards -SK

  • KChan12's avatar
    KChan12
    Icon for New Contributor rankNew Contributor
    7 years ago

    Hi,

    Thanks for reply.

    For ex I am using 2 descriptor with 256 dwords ie 1 KB of data for each descriptor. I can see correct data for only one descriptor when seen through signal tap it is not working for second descriptor.

    ie while using multiple descriptor , it is sending data for only one descriptor.

    Thanks,

    Kamlendra

  • SengKok_L_Intel's avatar
    SengKok_L_Intel
    Icon for Regular Contributor rankRegular Contributor
    7 years ago

    ​Hi Sir,

    Are you seeing the same problem if using Onchip memory ( original design)? How about using 1 descriptor with 2KB of data?

    Regards -SK