Commit 1e1490a3 authored by Mario Kleiner's avatar Mario Kleiner Committed by Alex Deucher
Browse files

drm/radeon: Fix error handling in radeon_flip_work_func. 

This is a port of the patch "drm/amdgpu: Fix error handling in amdgpu_flip_work_func."
to fix the following problem for radeon as well which was
reported against amdgpu:

The patch e1d09dc0: "drm/amdgpu: Don't hang in
amdgpu_flip_work_func on disabled crtc." from Feb 19, 2016, leads to
the following static checker warning, as reported by Dan Carpenter in
https://lists.freedesktop.org/archives/dri-devel/2016-February/101987.html



drivers/gpu/drm/amd/amdgpu/amdgpu_display.c:127 amdgpu_flip_work_func()     warn: should this be 'repcnt == -1'
drivers/gpu/drm/amd/amdgpu/amdgpu_display.c:136 amdgpu_flip_work_func() error: double unlock 'spin_lock:&crtc->dev->event_lock'
drivers/gpu/drm/amd/amdgpu/amdgpu_display.c:136 amdgpu_flip_work_func() error: double unlock 'irqsave:flags'

This patch fixes both reported problems:

Change post-decrement of repcnt to pre-decrement, so
it can't underflow anymore, but still performs up to
three repetitions - three is the maximum one could
expect in practice.

Move the spin_unlock_irqrestore to where it actually
belongs.

Reviewed-by: default avatarMichel Dänzer <michel.daenzer@amd.com>
Reported-by: default avatarDan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: default avatarMario Kleiner <mario.kleiner.de@gmail.com>
Cc: <stable@vger.kernel.org> # 4.4+
Cc: Michel Dänzer <michel.daenzer@amd.com>
Cc: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: default avatarAlex Deucher <alexander.deucher@amd.com>
parent 90e94b16

drivers/gpu/drm/radeon/radeon_display.c

+2 −2
Original line number Diff line number Diff line
@@ -455,7 +455,7 @@ static void radeon_flip_work_func(struct work_struct *__work) 
	 * In practice this won't execute very often unless on very fast

	 * machines because the time window for this to happen is very small.

	 */

	while (radeon_crtc->enabled && repcnt--) {

	while (radeon_crtc->enabled && --repcnt) {

		/* GET_DISTANCE_TO_VBLANKSTART returns distance to real vblank

		 * start in hpos, and to the "fudged earlier" vblank start in

		 * vpos.
@@ -471,13 +471,13 @@ static void radeon_flip_work_func(struct work_struct *__work) 
			break;



		/* Sleep at least until estimated real start of hw vblank */

		spin_unlock_irqrestore(&crtc->dev->event_lock, flags);

		min_udelay = (-hpos + 1) * max(vblank->linedur_ns / 1000, 5);

		if (min_udelay > vblank->framedur_ns / 2000) {

			/* Don't wait ridiculously long - something is wrong */

			repcnt = 0;

			break;

		}

		spin_unlock_irqrestore(&crtc->dev->event_lock, flags);

		usleep_range(min_udelay, 2 * min_udelay);

		spin_lock_irqsave(&crtc->dev->event_lock, flags);

	};