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

[Deucher, Alexander]

> -----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.

Alex