RE: [PATCH]iwlan dma mapping read and write changes

[Winkler, Tomas]

>-----Original Message-----
>From: Johannes Berg [mailto:johannes@xxxxxxxxxxxxxxxx]
>Sent: Wednesday, February 11, 2009 11:50 PM
>To: Winkler, Tomas
>Cc: Yu, Fenghua; David Woodhouse; Ingo Molnar; Stephen Rothwell; Grumbach,
>Emmanuel; Zhu, Yi; Chris Wright; LKML; iommu@xxxxxxxxxxxxxxxxxxxxxxxxxx
>Subject: RE: [PATCH]iwlan dma mapping read and write changes
>
>On Wed, 2009-02-11 at 22:47 +0100, Johannes Berg wrote:
>> > >> 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.
>> > >
>> > >I don't think they can be seeing AMPDU packets since that is, well,
>> > >broken?
>> >
>> > Currently I'm not aware of any other cases where memory is accessed
>> > back but I may have not complete info.  Will be back with the answer
>> > tomorrow.
>>
>> I don't think it really matters, since AMPDU packets will be fixed soon,
>> and for those you know it's necessary (and the report says that under
>> some other circumstances it's also necessary). Unless there'd be some
>> benefit from using BIDI only when we know it'll be needed, and using
>> TODEV in the other cases?
>
>Or if there's a firmware bug.

That's why it's better to clear the picture. 
Fenghua
What exact HW do you get this error?

Thanks
Tomas 

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