[PATCH 1/2] drm/amdgpu: Enable scatter gather display support

[Christian König]

Am 07.03.2018 um 10:53 schrieb Michel Dänzer:
> On 2018-03-07 10:47 AM, Christian König wrote:
>> See when I tested this the DDX and Mesa where unmodified, so both still
>> assumed VRAM as placement for scanout BOs, but the kernel forced scanout
>> BOs into GTT for testing.
>>
>> So what happened was that on scanout we moved the VRAM BO to GTT and
>> after unpinning it on the first command submission which used the BO we
>> moved it back to VRAM again.
>>
>> So as long as we don't want a severe performance penalty when you
>> combine old userspace with new kernel using a kernel parameter to force
>> scanout from GTT is not possible.
> That means we either need to come up with a different workaround for
> hardware issues transitioning between scanout from VRAM and GTT, or we
> can't scan out from GTT in that case.

What exactly was the problem with the transition from VRAM to GTT?

I mean what we can rather easily do is check where the existing BO is 
pinned and then always pin into the same domain on page flip.

Christian.