Merge tag 'drm-vc4-next-2016-12-09' of https://github.com/anholt/linux into drm-next

This pull request brings in VEC (TV-out) support for vc4, along with a
pageflipping race fix.

* tag 'drm-vc4-next-2016-12-09' of https://github.com/anholt/linux:
  drm/vc4: Don't use drm_put_dev
  drm/vc4: Document VEC DT binding
  drm/vc4: Add support for the VEC (Video Encoder) IP
  drm: Add TV connector states to drm_connector_state
  drm: Turn DRM_MODE_SUBCONNECTOR_xx definitions into an enum
  drm/vc4: Fix ->clock_select setting for the VEC encoder
  drm/vc4: Fix race between page flip completion event and clean-up

1 files changed, 25 insertions, 8 deletions

diff --git a/drivers/gpu/drm/vc4/vc4_kms.c b/drivers/gpu/drm/vc4/vc4_kms.c
index f31f72af8551..be8dd8262f27 100644
--- a/drivers/gpu/drm/vc4/vc4_kms.c
+++ b/drivers/gpu/drm/vc4/vc4_kms.c
@@ -119,17 +119,34 @@ static int vc4_atomic_commit(struct drm_device *dev,
 
 	/* Make sure that any outstanding modesets have finished. */
 	if (nonblock) {
-		ret = down_trylock(&vc4->async_modeset);
-		if (ret) {
+		struct drm_crtc *crtc;
+		struct drm_crtc_state *crtc_state;
+		unsigned long flags;
+		bool busy = false;
+
+		/*
+		 * If there's an undispatched event to send then we're
+		 * obviously still busy.  If there isn't, then we can
+		 * unconditionally wait for the semaphore because it
+		 * shouldn't be contended (for long).
+		 *
+		 * This is to prevent a race where queuing a new flip
+		 * from userspace immediately on receipt of an event
+		 * beats our clean-up and returns EBUSY.
+		 */
+		spin_lock_irqsave(&dev->event_lock, flags);
+		for_each_crtc_in_state(state, crtc, crtc_state, i)
+			busy |= vc4_event_pending(crtc);
+		spin_unlock_irqrestore(&dev->event_lock, flags);
+		if (busy) {
 			kfree(c);
 			return -EBUSY;
 		}
-	} else {
-		ret = down_interruptible(&vc4->async_modeset);
-		if (ret) {
-			kfree(c);
-			return ret;
-		}
+	}
+	ret = down_interruptible(&vc4->async_modeset);
+	if (ret) {
+		kfree(c);
+		return ret;
 	}
 
 	ret = drm_atomic_helper_prepare_planes(dev, state);