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    SubjectRe: [alsa-devel] USB transfer_buffer allocations on 64bit systems
    > > > Either the data isn't getting written to the buffer correctly or else
    > > > the buffer isn't getting sent to the device correctly. Can anybody
    > > > suggest a means of determining which is the case?
    > >
    > > I can't say anything about this log that including only DMA addresses.
    > > I'm not familiar with how the USB core does DMA stuff. And the USB
    > > stack design that the USB core does DMA stuff (allocating, mappings,
    > > etc) makes debugging DMA issues really difficult.
    > The DMA stuff is simple enough in this case. The urb->transfer_buffer
    > address is passed to dma_map_single(), and the DMA address it returns
    > is stored in urb->transfer_dma. Those are the two values printed out
    > by the debugging patch.

    Is that address (urb->transfer_dma) the same as 'virt_to_phys(urb->transfer_buffer)'
    (if not, then SWIOTLB is being utilized) and is the dma_sync_* done on the
    urb->transfer_dma (to properly sync the data from the SWIOTLB to the
    transfer_buffer) before you start using the urb->transfer_buffer?

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      Last update: 2010-05-12 10:15    [W:0.020 / U:19.008 seconds]
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