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

[Michel Dänzer]

On 29/10/16 02:37 AM, Mario Kleiner wrote:
> 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.

[...]

> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_prime.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_prime.c
> index 7700dc2..bfbfeb9 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_prime.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_prime.c
> @@ -121,5 +121,8 @@ struct dma_buf *amdgpu_gem_prime_export(struct drm_device *dev,
>  	if (amdgpu_ttm_tt_get_usermm(bo->tbo.ttm))
>  		return ERR_PTR(-EPERM);
>  
> +	bo->prime_exported = true;
> +	DRM_DEBUG_PRIME("Exporting prime bo %p\n", bo);
> +
>  	return drm_gem_prime_export(dev, gobj, flags);
>  }
> 

This will take effect in non-PRIME cases as well, at least DRI3 and
GL<->[other API] interop off the top of my head. Is that okay?


-- 
Earthling Michel Dänzer               |               http://www.amd.com
Libre software enthusiast             |             Mesa and X developer