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authorChris Wilson <chris@chris-wilson.co.uk>2017-03-17 20:20:30 +0000
committerVille Syrjälä <ville.syrjala@linux.intel.com>2017-03-29 14:02:22 +0300
commitb33b02707ba3eeccbf8e3687ab5c4124db6d3479 (patch)
tree37dcc14d876462e12ebc7e5f5d0d8576ef888d2a /drivers/gpu/drm/drm_irq.c
parent9a4d9babceeabb86669ff280e94c560193e66a72 (diff)
drm: Peek at the current counter/timestamp for vblank queries
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. This is dependent upon the both the hardware and driver to provide the proper barriers to facilitate reading our bookkeeping outside of the vblank interrupt and outside of the explicit vblank locks. 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> Link: http://patchwork.freedesktop.org/patch/msgid/20170317202030.24410-4-chris@chris-wilson.co.uk Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com> Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Diffstat (limited to 'drivers/gpu/drm/drm_irq.c')
-rw-r--r--drivers/gpu/drm/drm_irq.c26
1 files changed, 26 insertions, 0 deletions
diff --git a/drivers/gpu/drm/drm_irq.c b/drivers/gpu/drm/drm_irq.c
index 124402270568..aa23b9833588 100644
--- a/drivers/gpu/drm/drm_irq.c
+++ b/drivers/gpu/drm/drm_irq.c
@@ -1561,6 +1561,17 @@ 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.
*
@@ -1610,6 +1621,21 @@ int drm_wait_vblank(struct drm_device *dev, void *data,
vblank = &dev->vblank[pipe];
+ /* 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) &&
+ READ_ONCE(vblank->enabled)) {
+ struct timeval now;
+
+ vblwait->reply.sequence =
+ drm_vblank_count_and_time(dev, pipe, &now);
+ vblwait->reply.tval_sec = now.tv_sec;
+ vblwait->reply.tval_usec = now.tv_usec;
+ return 0;
+ }
+
ret = drm_vblank_get(dev, pipe);
if (ret) {
DRM_DEBUG("crtc %d failed to acquire vblank counter, %d\n", pipe, ret);