Bypass all the spinlocks and return the last timestamp and counter from the last vblank if the driver delcares that it is accurate (and stable across on/off), and the vblank is currently enabled.
Signed-off-by: Chris Wilson chris@chris-wilson.co.uk Cc: Ville Syrjälä ville.syrjala@linux.intel.com Cc: Daniel Vetter daniel@ffwll.ch Cc: Michel Dänzer michel@daenzer.net Cc: Laurent Pinchart laurent.pinchart@ideasonboard.com Cc: Dave Airlie airlied@redhat.com, Cc: Mario Kleiner mario.kleiner.de@gmail.com --- drivers/gpu/drm/drm_irq.c | 26 ++++++++++++++++++++++++++ 1 file changed, 26 insertions(+)
diff --git a/drivers/gpu/drm/drm_irq.c b/drivers/gpu/drm/drm_irq.c index ba80b51b4b00..be9c210bb22e 100644 --- a/drivers/gpu/drm/drm_irq.c +++ b/drivers/gpu/drm/drm_irq.c @@ -1538,6 +1538,17 @@ err_put: return ret; }
+static bool drm_wait_vblank_is_query(union drm_wait_vblank *vblwait) +{ + if (vblwait->request.sequence) + return false; + + return _DRM_VBLANK_RELATIVE == + (vblwait->request.type & (_DRM_VBLANK_TYPES_MASK | + _DRM_VBLANK_EVENT | + _DRM_VBLANK_NEXTONMISS)); +} + /* * Wait for VBLANK. * @@ -1587,6 +1598,21 @@ int drm_wait_vblank(struct drm_device *dev, void *data,
vblank = &dev->vblank[crtc];
+ /* If the counter is currently enabled and accurate, short-circuit queries + * to return the cached timestamp of the last vblank. + */ + if (dev->vblank_disable_immediate && + drm_wait_vblank_is_query(vblwait) && + vblank->enabled) { + struct timeval now; + + vblwait->reply.sequence = + drm_vblank_count_and_time(dev, crtc, &now); + vblwait->reply.tval_sec = now.tv_sec; + vblwait->reply.tval_usec = now.tv_usec; + return 0; + } + ret = drm_vblank_get(dev, crtc); if (ret) { DRM_DEBUG("failed to acquire vblank counter, %d\n", ret);