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 at chris-wilson.co.uk>
Cc: Ville Syrjälä <ville.syrjala at linux.intel.com>
Cc: Daniel Vetter <daniel at ffwll.ch>
Cc: Michel Dänzer <michel at daenzer.net>
Cc: Laurent Pinchart <laurent.pinchart at ideasonboard.com>
Cc: Dave Airlie <airlied at redhat.com>,
Cc: Mario Kleiner <mario.kleiner.de at 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);
--
2.1.4
