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authorMario Kleiner <mario.kleiner.de@gmail.com>2016-09-17 15:25:39 +0300
committerAlex Deucher <alexander.deucher@amd.com>2016-10-04 18:15:58 +0300
commit363926dc9ef65a3813fa778e85f85dd756c8652f (patch)
treea4fe5829125a874cb1d8c5ce8d49ce53e5231888 /drivers/gpu/drm/radeon/radeon_display.c
parent73d4c23f5361928b12e7827e872612273cc1175a (diff)
downloadlinux-363926dc9ef65a3813fa778e85f85dd756c8652f.tar.xz
drm/radeon: Prevent races on pre DCE4 between flip submission and completion.
Pre DCE4 hw doesn't have reliable pageflip completion interrupts, so instead polling for flip completion is used from within the vblank irq handler to complete page flips. This causes a race if pageflip ioctl is called close to vblank: 1. pageflip ioctl queues execution of radeon_flip_work_func. 2. vblank irq fires, radeon_crtc_handle_vblank checks for flip_status == FLIP_SUBMITTED finds none, no-ops. 3. radeon_flip_work_func runs inside vblank, decides to set flip_status == FLIP_SUBMITTED and programs the flip into hw. 4. hw executes flip immediately (because in vblank), but as 2 already happened, the flip completion routine only emits the flip completion event one refresh later -> wrong vblank count/timestamp for completion and no performance gain, as instead of delaying the flip until next vblank, we now delay the next flip by 1 refresh while waiting for the delayed flip completion event. Given we often don't gain anything due to this race, but lose precision, prevent the programmed flip from executing in vblank on pre DCE4 asics to avoid this race. On pre-AVIVO hw we can't program the hw for edge-triggered flips, they always execute anywhere in vblank. Therefore delay the actual flip programming until after vblank on pre-AVIVO. Reviewed-by: Michel Dänzer <michel.daenzer@amd.com> Signed-off-by: Mario Kleiner <mario.kleiner.de@gmail.com> Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Diffstat (limited to 'drivers/gpu/drm/radeon/radeon_display.c')
-rw-r--r--drivers/gpu/drm/radeon/radeon_display.c17
1 files changed, 10 insertions, 7 deletions
diff --git a/drivers/gpu/drm/radeon/radeon_display.c b/drivers/gpu/drm/radeon/radeon_display.c
index 50706464d456..b8ab30a7dd6d 100644
--- a/drivers/gpu/drm/radeon/radeon_display.c
+++ b/drivers/gpu/drm/radeon/radeon_display.c
@@ -452,16 +452,19 @@ static void radeon_flip_work_func(struct work_struct *__work)
}
/* Wait until we're out of the vertical blank period before the one
- * targeted by the flip
+ * targeted by the flip. Always wait on pre DCE4 to avoid races with
+ * flip completion handling from vblank irq, as these old asics don't
+ * have reliable pageflip completion interrupts.
*/
while (radeon_crtc->enabled &&
- (radeon_get_crtc_scanoutpos(dev, work->crtc_id, 0,
- &vpos, &hpos, NULL, NULL,
- &crtc->hwmode)
+ (radeon_get_crtc_scanoutpos(dev, work->crtc_id, 0,
+ &vpos, &hpos, NULL, NULL,
+ &crtc->hwmode)
& (DRM_SCANOUTPOS_VALID | DRM_SCANOUTPOS_IN_VBLANK)) ==
- (DRM_SCANOUTPOS_VALID | DRM_SCANOUTPOS_IN_VBLANK) &&
- (int)(work->target_vblank -
- dev->driver->get_vblank_counter(dev, work->crtc_id)) > 0)
+ (DRM_SCANOUTPOS_VALID | DRM_SCANOUTPOS_IN_VBLANK) &&
+ (!ASIC_IS_AVIVO(rdev) ||
+ ((int) (work->target_vblank -
+ dev->driver->get_vblank_counter(dev, work->crtc_id)) > 0)))
usleep_range(1000, 2000);
/* We borrow the event spin lock for protecting flip_status */