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: Mario Kleiner <mario.kleiner@tuebingen.mpg.de> Signed-off-by: Dave Airlie <airlied@redhat.com>
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@ -164,8 +164,10 @@ static void vblank_disable_and_save(struct drm_device *dev, int crtc)
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* available. In that case we can't account for this and just
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* hope for the best.
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*/
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if ((vblrc > 0) && (abs64(diff_ns) > 1000000))
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if ((vblrc > 0) && (abs64(diff_ns) > 1000000)) {
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atomic_inc(&dev->_vblank_count[crtc]);
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smp_mb__after_atomic_inc();
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}
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/* Invalidate all timestamps while vblank irq's are off. */
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clear_vblank_timestamps(dev, crtc);
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@ -858,10 +860,11 @@ static void drm_update_vblank_count(struct drm_device *dev, int crtc)
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if (rc) {
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tslot = atomic_read(&dev->_vblank_count[crtc]) + diff;
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vblanktimestamp(dev, crtc, tslot) = t_vblank;
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smp_wmb();
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}
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smp_mb__before_atomic_inc();
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atomic_add(diff, &dev->_vblank_count[crtc]);
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smp_mb__after_atomic_inc();
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}
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/**
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@ -1296,12 +1299,13 @@ bool drm_handle_vblank(struct drm_device *dev, int crtc)
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if (abs64(diff_ns) > DRM_REDUNDANT_VBLIRQ_THRESH_NS) {
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/* Store new timestamp in ringbuffer. */
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vblanktimestamp(dev, crtc, vblcount + 1) = tvblank;
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smp_wmb();
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/* Increment cooked vblank count. This also atomically commits
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* the timestamp computed above.
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*/
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smp_mb__before_atomic_inc();
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atomic_inc(&dev->_vblank_count[crtc]);
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smp_mb__after_atomic_inc();
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} else {
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DRM_DEBUG("crtc %d: Redundant vblirq ignored. diff_ns = %d\n",
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crtc, (int) diff_ns);
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