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    SubjectRe: [PATCH] sky2: Fix WARNING: at lib/dma-debug.c:902 check_sync
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    On Wed, 2010-01-20 at 10:03 -0800, Stephen Hemminger wrote:
    > On Wed, 20 Jan 2010 09:41:03 +0000
    > Jarek Poplawski <jarkao2@gmail.com> wrote:
    > > > Seems like an underlying bug in the DMA api. Maybe it just can't
    > > > handle operations on partial mapping.
    > > >
    > > > Other drivers with same problem:
    > > > bnx2, cassini, pcnet32, r8169, rrunner, skge, sungem, tg3,
    > >
    > > It seems using the same length (even without pci_unmap_len()) is
    > > crucial here, but I hope maintainers (added to CC) will take care.
    > >

    I'm still unsure how to do dma_sync properly in bnx2. In the current
    code, we always dma_sync_for_cpu a small portion of the SKB because the
    rx descriptor is at the beginning of the SKB. We get the packet length,
    for example, from the rx descriptor.

    If it's a big packet, we'll simply unmap the entire SKB buffer (with the
    beginning portion already dma_sync'ed). If the packet is smaller than
    what we dma_sync'ed, we'll just copy the data to a new SKB. We'll then
    dma_sync_for_device the portion of the original buffer and recycle the
    whole buffer back to the device for new packets.

    So, is it correct to just change the dma_sync length to the full length
    of the buffer? It doesn't sound right to me.

    Thanks.




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