Re: [PATCH] sky2: Fix WARNING: at lib/dma-debug.c:902 check_sync
From: Stephen Hemminger
Date: Wed Jan 20 2010 - 15:32:18 EST
On Wed, 20 Jan 2010 12:11:52 -0800
"Michael Chan" <mchan@xxxxxxxxxxxx> wrote:
> On Wed, 2010-01-20 at 10:03 -0800, Stephen Hemminger wrote:
> > On Wed, 20 Jan 2010 09:41:03 +0000
> > Jarek Poplawski <jarkao2@xxxxxxxxx> 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.
It looks like the size passed to sync_single has to match size of original
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/