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

[Mario Kleiner]

On 10/28/2016 03:34 AM, Michel Dänzer wrote:
> On 27/10/16 10:33 PM, Mike Lothian wrote:
>>
>> Just another gentle ping to see where you are with this?
>
> I haven't got a chance to look into this any further.
>
>

Fwiw., as a proof of concept, the attached experimental patch does work 
as tested on Intel HD Haswell + AMD R9 380 Tonga under amdgpu and 
DRI3/Present when applied to drm-next (updated from a few days ago). 
With DRI_PRIME=1 tearing for page-flipped fullscreen windows is gone 
under all loads. The tearing with "windowed" windows now looks as 
expected for regular tearing not related to Prime.

ftrace confirms the i915 driver's pageflip function is waiting on the 
fence in reservation_object_wait_timeout_rcu() as it should.

That entry->tv.shared needs to be set false for such buffers in 
amdgpu_bo_list_set() makes sense to me, as that is part of the buffer 
validation for command stream submission. There are other places in the 
driver where tv.shared is set, which i didn't check so far.

I don't know which of these would need to be updated with a "exported 
bo" check as well, e.g., for video decoding or maybe gpu compute? Adding 
or removing the check to amdgpu_gem_va_update_vm(), e.g., made no 
difference. I assume that makes sense because that functions seems to 
deal with amdgpu internal vm page tables or page table entries for such 
a bo, not with something visible to external clients?

All i can say is it fixes 3D rendering under DRI3 + Prime + pageflipping 
without causing any obvious new problems.

-mario
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