amd-iommu: can't boot with amdgpu, AMD-Vi: Completion-Wait loop timed out

[Tom St Denis]

On 21/03/17 12:25 PM, 'joro at 8bytes.org' wrote:
> On Tue, Mar 21, 2017 at 04:17:40PM +0000, Deucher, Alexander wrote:
>>> -----Original Message-----
>>> From: 'joro at 8bytes.org' [mailto:joro at 8bytes.org]
>>> Sent: Tuesday, March 21, 2017 12:11 PM
>>> To: Deucher, Alexander
>>> Cc: Alex Deucher; Daniel Drake; Chris Chiu; amd-gfx at lists.freedesktop.org;
>>> Nath, Arindam; iommu at lists.linux-foundation.org; Suthikulpanit, Suravee;
>>> Linux Upstreaming Team
>>> Subject: Re: amd-iommu: can't boot with amdgpu, AMD-Vi: Completion-Wait
>>> loop timed out
>>>
>>> On Tue, Mar 21, 2017 at 04:01:53PM +0000, Deucher, Alexander wrote:
>>>> It seems to only affect Stoney systems, but not others (Carrizo,
>>>> Bristol, etc.).  Maybe we could just disable it on Stoney until we
>>>> root cause it.
>>>
>>> Completion-wait loop timeouts indicate something is seriously wrong. How
>>> can I detect whether I am running on a 'Stoney' system?
>>
>> + John
>>
>> I'm not sure if the iommu ids are different on stoney systems compared to Carrizo/Bristol systems.  The pci ids of the GPUs are different.  Stoney parts have 0x98E4 as the pci id for the GPU.
>>
>>>
>>> Other question, a shot into the dark, does the GPU on these systems have
>>> ATS? Probably yes, as they are likely HSA compatible.
>>
>> Stoney is a small APU.  Kind of a mini Carrizo.  While it may claim to support ATS, I don't think it was ever validated on Stoney, only Carrizo/Bristol.
>
> Okay, so maybe ATS is broken in some way on these chips. When queue
> flushes happen it will also send the ATS-invalidates, and a queue flush
> can cause a storm of those. This may be the issue.
>
> I am preparing a debug-patch that disables ATS for these GPUs so someone
> with such a chip can test it.
>


I have a stoney I can test said patch on.

Thanks,
Tom