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Subject: RE: [PATCH]iwlan dma mapping read and write changes
From: Johannes Berg <johannes@sipsolutions.net>
To: "Winkler, Tomas" <tomas.winkler@intel.com>
Cc: "Yu, Fenghua" <fenghua.yu@intel.com>,
       David Woodhouse <dwmw2@infradead.org>, Ingo Molnar <mingo@elte.hu>,
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Date: Wed, 11 Feb 2009 22:33:47 +0100
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On Wed, 2009-02-11 at 23:27 +0200, Winkler, Tomas wrote:

> >mapping with PCI_DMA_TODEVICE which is read only in mapping PTE. But iwl=
an
> >device
> >actually writes to the mapped page to update its contents. This issue is
> >not
> >exposed in swiotlb. But VT-d hardware can capture this fault and stop th=
e
> >fault
> >transaction.
> >
> >The following patch fixes the issue.
> >
> >Signed-off-by: Fenghua Yu <fenghua.yu@intel.com>
> Acked-by: Tomas Winkler <tomas.winkler@intel.com>
>=20
> Indeed the firmware/ucode write back to host memory to update retry
> counter for APMDU packets. I'm not sure if this is needed for legacy
> traffic, though.  =20

I don't think they can be seeing AMPDU packets since that is, well,
broken?

johannes

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