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

[Daniel Drake]

Hi,

On Mon, Mar 13, 2017 at 2:01 PM, Deucher, Alexander
<Alexander.Deucher at amd.com> wrote:
> > We are unable to boot Acer Aspire E5-553G (AMD FX-9800P RADEON R7) nor
> > Acer Aspire E5-523 with standard configurations because during boot
> > the screen is flooded with the following error message over and over:
> >
> >   AMD-Vi: Completion-Wait loop timed out
>
> We ran into similar issues and bisected it to commit b1516a14657acf81a587e9a6e733a881625eee53.  I'm not too familiar with the IOMMU hardware to know if this is an iommu or display driver issue yet.

We can confirm that reverting this commit solves the issue.

Given that that commit is an optimization, but it has introduced a
regression on multiple platforms, and has been like this for 8 months,
it would be common practice to now revert this patch upstream until
the regression is fixed. Could you please send a new patch to do this?

Also, we would be happy to test any real solutions to this issue while
we still have the affected units in hand.

Thanks
Daniel