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| author | Daniel Vetter <daniel.vetter@ffwll.ch> | 2014-09-10 17:36:09 +0200 |
|---|---|---|
| committer | Daniel Vetter <daniel.vetter@ffwll.ch> | 2014-09-11 13:32:05 +0200 |
| commit | 855d30b402b91f09c90f65c34ec91debaae8cf3a (patch) | |
| tree | 49dc14e33919cf232cc37b49666cc21d317885db /drivers/gpu/drm/drm_irq.c | |
| parent | ab8905f1c6a74d695c6096791ec4b349bc985b8a (diff) | |
| download | linux-855d30b402b91f09c90f65c34ec91debaae8cf3a.tar.bz2 | |
drm: Only update final vblank count when precise ts is available
Drivers without a hardware vblank counter simply can't account for the
vblanks that happened while the vblank interrupt was off. To check
this grab a vblank timestamp and if the result is dubious follow the
normal save-and-disable logic.
Drivers should prevent this by setting vblank_disable_allowed = false,
but since running vblank interrupts constantly is not good for power
consumption most drivers lie. Testing for precise vblank timestamps is
the next best thing we can check for.
Suggested-by: Mario Kleiner <mario.kleiner.de@gmail.com>
Cc: Mario Kleiner <mario.kleiner.de@gmail.com>
Cc: Matt Roper <matthew.d.roper@intel.com>
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Mario Kleiner <mario.kleiner.de@gmail.com>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Diffstat (limited to 'drivers/gpu/drm/drm_irq.c')
| -rw-r--r-- | drivers/gpu/drm/drm_irq.c | 9 |
1 files changed, 8 insertions, 1 deletions
diff --git a/drivers/gpu/drm/drm_irq.c b/drivers/gpu/drm/drm_irq.c index 87d148cec877..ad699b729278 100644 --- a/drivers/gpu/drm/drm_irq.c +++ b/drivers/gpu/drm/drm_irq.c @@ -148,8 +148,15 @@ static void vblank_disable_and_save(struct drm_device *dev, int crtc) * has been ticking all along until this time. This makes the * count account for the entire time between drm_vblank_on() and * drm_vblank_off(). + * + * But only do this if precise vblank timestamps are available. + * Otherwise we might read a totally bogus timestamp since drivers + * lacking precise timestamp support rely upon sampling the system clock + * at vblank interrupt time. Which obviously won't work out well if the + * vblank interrupt is disabled. */ - if (!vblank->enabled) { + if (!vblank->enabled && + drm_get_last_vbltimestamp(dev, crtc, &tvblank, 0) > 0) { drm_update_vblank_count(dev, crtc); spin_unlock_irqrestore(&dev->vblank_time_lock, irqflags); return; |