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AM335x USB Host problems in DMA mode

Dave Hughes22
Prodigy 20 points

We are experiencing problems with our USB host driver in DMA mode.

The information available seems inconsistent. In the Linux SDk a bug is reported where the  Host fails if EP0 is used while a DMA transfer is ongoing - but this does not appear in the chip errata. Is this a real problem of the silicon? should DMA use be avoided if EP0 could be active during a transfer?

There is a second issue - that is the data toggle in DMA mode that is in the errata. But a workaround is recommended for this.

We need to make a design decision about the driver - and whether to revert to non-DMA mode. But really need to understand the real situation to do that.

Thanks

  • 0
    TI__Guru**** 393215 points

    Hi Dave,

    I will bring this to the attention of the factory team. Answer will be posted on this thread.

  • 0
    TI__Guru**** 168211 points

    Dave,

    Can you give more detail of the DMA issue you are facing? Do you use Linux? If so, what is the SDK version?

    The EP0 and data toggle you mentioned are the same issue. The workaround mentioned in the Errta is for AM335x rev 1.0. The issue is fixed in rev 2.1.

  • 0 in reply to Bin Liu
    Prodigy 20 points

    Thank you for the reply - we are not using Linux - we are investigating a problem with our drivers and mass storage devices - and because the Linux USB DMA errata is not tied to any silicon errata - we needed to know if this was another issue or not before we waste time trying to work out what our problem is.

    We are experiencing timeouts on the DMA transfers to the USB drive - and we do not know why this is happening at the moment.

    We will now work to find out what is wrong with our driver. Have you any experience of an issue like this?

    Thanks

    Dave