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

[Alex Deucher]

On Fri, Mar 17, 2017 at 8:15 AM, Daniel Drake <drake at endlessm.com> wrote:
> 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.

No objections to a revert here.

Alex


>
> Thanks
> Daniel
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