[PATCH 2/2] drm/amd/display: Prevent premature pageflip when comitting in vblank. (v3)

[Michel Dänzer]

On 25/04/17 01:54 AM, Mario Kleiner wrote:
> Make sure we do not program a hw pageflip inside vblank 'n' iff the
> atomic flip is comitted while inside the same vblank 'n'. We must
> defer such a flip by one refresh cycle to vblank 'n+1', unless this
> is a DRM_MODE_PAGE_FLIP_ASYNC async pageflip, which must always
> execute as soon as possible.
> 
> Without this, pageflips programmed via X11 GLX_OML_sync_control extensions
> glXSwapBuffersMscOML(..., target_msc, ...); call and/or via DRI3/Present
> PresentPixmap(..., target_msc, ...); request will complete one vblank
> too early whenever target_msc > current_msc + 1, ie. more than 1 vblank
> in the future. In such a case, the call of the pageflip ioctl() would be
> triggered by a queued drmWaitVblank() vblank event, which itself gets
> dispatched inside the vblank one frame before the target_msc vblank.
> 
> Testing with this patch does no longer show any problems with
> OML_sync_control swap scheduling or flip completion timestamps.
> Tested on R9 380 Tonga.
> 
> v2: Add acked/r-b by Harry and Michel.
> v3: Feedback from Andrey: Must not wait an extra frame for
>     DRM_MODE_PAGE_FLIP_ASYNC flips.
> 
> Signed-off-by: Mario Kleiner <mario.kleiner.de at gmail.com>
> Acked-by: Harry Wentland <harry.wentland at amd.com>
> Reviewed-by: Michel Dänzer <michel.daenzer at amd.com>

This patch and v2 of patch 1 pushed to the internal amd-staging-4.9
branch, thanks!


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