Re: [PATCH v2] PCI: Add ATS-disable quirk for AMD Stoney GPUs

[Joerg Roedel]

Hi Alexander,

On Tue, May 23, 2017 at 07:54:12PM +0000, Deucher, Alexander wrote:
> I finally got an answer from the hw team and we validated ATS on
> stoney as well so in theory this patch shouldnât actually be needed.
> I think we may actually be papering over some other issue.  The
> following patch seems to also fix this issue (and other issues):
> https://www.spinics.net/lists/stable/msg172631.html

Yeah, but it still looks to me like that the hardware got into some
weird state with the storm of ATS invalidations sent to it.

The Completion-Wait loop timeouts seen in the original bug report
indicate that the IOMMU is waiting for a response that never comes. And
this is probably the ATS flush completion response from the GPU, as
disabling ATS on the GPU makes the issue disappear.

Regards,

	Joerg