Messages in this thread | | | Subject | Re: [PATCH] sky2: Fix WARNING: at lib/dma-debug.c:902 check_sync | From | "Michael Chan" <> | Date | Wed, 20 Jan 2010 12:11:52 -0800 |
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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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