Commit 00d7930c authored by Mario Kleiner's avatar Mario Kleiner Committed by Alex Deucher
Browse files

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



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: default avatarMario Kleiner <mario.kleiner.de@gmail.com>
Acked-by: Harry Wentland <harry.wentland@amd.com> (v1)
Reviewed-by: default avatarMichel Dänzer <michel.daenzer@amd.com>
Reviewed-by: default avatarAndrey Grodzovsky <Andrey.Grodzovsky@amd.com>

Cc: Harry Wentland <Harry.Wentland@amd.com>
Cc: Alex Deucher <alexander.deucher@amd.com>
Cc: Michel Dänzer <michel.daenzer@amd.com>
Signed-off-by: default avatarAlex Deucher <alexander.deucher@amd.com>
parent 753c66c9

drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_types.c

+10 −10
Original line number Diff line number Diff line
@@ -2305,6 +2305,9 @@ static void amdgpu_dm_do_flip( 
	struct amdgpu_device *adev = crtc->dev->dev_private;

	bool async_flip = (acrtc->flip_flags & DRM_MODE_PAGE_FLIP_ASYNC) != 0;



	/* Prepare wait for target vblank early - before the fence-waits */

	target_vblank = target - drm_crtc_vblank_count(crtc) +

			amdgpu_get_vblank_counter_kms(crtc->dev, acrtc->crtc_id);



	/*TODO This might fail and hence better not used, wait

	 * explicitly on fences instead
@@ -2323,13 +2326,9 @@ static void amdgpu_dm_do_flip( 


	amdgpu_bo_unreserve(abo);



	/* Wait for target vblank */

	/* Wait until we're out of the vertical blank period before the one

	 * targeted by the flip

	 */

	target_vblank = target - drm_crtc_vblank_count(crtc) +

			amdgpu_get_vblank_counter_kms(crtc->dev, acrtc->crtc_id);



	while ((acrtc->enabled &&

		(amdgpu_get_crtc_scanoutpos(adev->ddev, acrtc->crtc_id, 0,

					&vpos, &hpos, NULL, NULL,
@@ -2605,14 +2604,15 @@ void amdgpu_dm_atomic_commit_tail( 
		pflip_needed = !state->allow_modeset;



		if (pflip_needed) {

			wait_for_vblank =

				acrtc->flip_flags & DRM_MODE_PAGE_FLIP_ASYNC ?

				false : true;



			amdgpu_dm_do_flip(

				crtc,

				fb,

					drm_crtc_vblank_count(crtc));

				drm_crtc_vblank_count(crtc) + wait_for_vblank);



			wait_for_vblank =

					acrtc->flip_flags & DRM_MODE_PAGE_FLIP_ASYNC ?

							false : true;

			/*clean up the flags for next usage*/

			acrtc->flip_flags = 0;

		}