drm: Skip the waitqueue setup for vblank queries

Avoid adding to the waitqueue and reprobing the current vblank if the
caller is only querying the current vblank sequence and timestamp, where
we know that the wait would return immediately.

v2: Add CRTC identifier to debug messages

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>
Reviewed-by: Michel Dänzer <michel@daenzer.net>
Reviewed-and-tested-by: Mario Kleiner <mario.kleiner.de@gmail.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: http://patchwork.freedesktop.org/patch/msgid/20170315204027.20160-2-chris@chris-wilson.co.uk

diff --git a/drivers/gpu/drm/drm_irq.c b/drivers/gpu/drm/drm_irq.c
index e64b05ea95ea688f69f6e9fbf52870b00e9a6a37..53a526c7b24dcab0ad0a9e9f4302c9fc9803581f 100644 (file)
--- a/drivers/gpu/drm/drm_irq.c
+++ b/drivers/gpu/drm/drm_irq.c
@@ -1610,7 +1610,7 @@ int drm_wait_vblank(struct drm_device *dev, void *data,
 
        ret = drm_vblank_get(dev, pipe);
        if (ret) {
-               DRM_DEBUG("failed to acquire vblank counter, %d\n", ret);
+               DRM_DEBUG("crtc %d failed to acquire vblank counter, %d\n", pipe, ret);
                return ret;
        }
        seq = drm_vblank_count(dev, pipe);
@@ -1638,13 +1638,15 @@ int drm_wait_vblank(struct drm_device *dev, void *data,
                return drm_queue_vblank_event(dev, pipe, vblwait, file_priv);
        }
 
-       DRM_DEBUG("waiting on vblank count %u, crtc %u\n",
-                 vblwait->request.sequence, pipe);
-       DRM_WAIT_ON(ret, vblank->queue, 3 * HZ,
-                   (((drm_vblank_count(dev, pipe) -
-                      vblwait->request.sequence) <= (1 << 23)) ||
-                    !vblank->enabled ||
-                    !dev->irq_enabled));
+       if (vblwait->request.sequence != seq) {
+               DRM_DEBUG("waiting on vblank count %u, crtc %u\n",
+                         vblwait->request.sequence, pipe);
+               DRM_WAIT_ON(ret, vblank->queue, 3 * HZ,
+                           (((drm_vblank_count(dev, pipe) -
+                              vblwait->request.sequence) <= (1 << 23)) ||
+                            !vblank->enabled ||
+                            !dev->irq_enabled));
+       }
 
        if (ret != -EINTR) {
                struct timeval now;
@@ -1653,10 +1655,10 @@ int drm_wait_vblank(struct drm_device *dev, void *data,
                vblwait->reply.tval_sec = now.tv_sec;
                vblwait->reply.tval_usec = now.tv_usec;
 
-               DRM_DEBUG("returning %u to client\n",
-                         vblwait->reply.sequence);
+               DRM_DEBUG("crtc %d returning %u to client\n",
+                         pipe, vblwait->reply.sequence);
        } else {
-               DRM_DEBUG("vblank wait interrupted by signal\n");
+               DRM_DEBUG("crtc %d vblank wait interrupted by signal\n", pipe);
        }
 
 done: