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Commit bc215128 authored by Mario Kleiner's avatar Mario Kleiner Committed by Dave Airlie
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drm/vblank: Use memory barriers optimized for atomic_t instead of generics. 



Documentation/atomic_ops.txt tells us that there are memory
barriers optimized for atomic_inc and other atomic_t ops.

Use these instead of smp_wmb(), and also to make the required
memory barriers around vblank counter increments more explicit.

Signed-off-by: default avatarMario Kleiner <mario.kleiner@tuebingen.mpg.de>
Signed-off-by: default avatarDave Airlie <airlied@redhat.com>
parent c4cc3839

drivers/gpu/drm/drm_irq.c

+7 −3
Original line number Diff line number Diff line
@@ -164,8 +164,10 @@ static void vblank_disable_and_save(struct drm_device *dev, int crtc) 
	 * available. In that case we can't account for this and just

	 * hope for the best.

	 */

	if ((vblrc > 0) && (abs64(diff_ns) > 1000000))

	if ((vblrc > 0) && (abs64(diff_ns) > 1000000)) {

		atomic_inc(&dev->_vblank_count[crtc]);

		smp_mb__after_atomic_inc();

	}



	/* Invalidate all timestamps while vblank irq's are off. */

	clear_vblank_timestamps(dev, crtc);
@@ -858,10 +860,11 @@ static void drm_update_vblank_count(struct drm_device *dev, int crtc) 
	if (rc) {

		tslot = atomic_read(&dev->_vblank_count[crtc]) + diff;

		vblanktimestamp(dev, crtc, tslot) = t_vblank;

		smp_wmb();

	}



	smp_mb__before_atomic_inc();

	atomic_add(diff, &dev->_vblank_count[crtc]);

	smp_mb__after_atomic_inc();

}



/**
@@ -1296,12 +1299,13 @@ bool drm_handle_vblank(struct drm_device *dev, int crtc) 
	if (abs64(diff_ns) > DRM_REDUNDANT_VBLIRQ_THRESH_NS) {

		/* Store new timestamp in ringbuffer. */

		vblanktimestamp(dev, crtc, vblcount + 1) = tvblank;

		smp_wmb();



		/* Increment cooked vblank count. This also atomically commits

		 * the timestamp computed above.

		 */

		smp_mb__before_atomic_inc();

		atomic_inc(&dev->_vblank_count[crtc]);

		smp_mb__after_atomic_inc();

	} else {

		DRM_DEBUG("crtc %d: Redundant vblirq ignored. diff_ns = %d\n",

			  crtc, (int) diff_ns);