[PATCH] drm/i915: Before pageflip, also wait for shared dmabuf fences.

[Christian König]

Am 21.09.2016 um 11:56 schrieb Michel Dänzer:
>
> Looks like there are different interpretations of the semantics of
> exclusive vs. shared fences. Where are these semantics documented?

Yeah, I think as well that this is the primary question here.

IIRC the fences were explicitly called exclusive/shared instead of 
writing/reading on purpose.

I absolutely don't mind switching to them to writing/reading semantics, 
but amdgpu really needs multiple writers at the same time.

So in this case the writing side of a reservation object needs to be a 
collection of fences as well.

> FWIW, we seem to have the same issue with radeon vs. amdgpu: radeon only
> seems to wait for exclusive fences, so e.g. running Xorg on amdgpu and
> using PRIME slave scanout on radeon leaves artifacts.

Yeah, I know. See radeon_display.c radeon_flip_work_func().

We pretty much need the same patch here I've done for amdgpu as well.

Regards,
Christian.