drm/radeon: add error handling to fence_wait_empty_locked

Instead of returning the error handle it directly
and while at it fix the comments about the ring lock.
Signed-off-by: Christian König <deathsimple@vodafone.de>
Reviewed-by: Michel Dänzer <michel.daenzer@amd.com>
Reviewed-by: Jerome Glisse <jglisse@redhat.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/radeon/radeon.h

@@ -239,7 +239,7 @@ void radeon_fence_process(struct radeon_device *rdev, int ring);
 bool radeon_fence_signaled(struct radeon_fence *fence);
 int radeon_fence_wait(struct radeon_fence *fence, bool interruptible);
 int radeon_fence_wait_next_locked(struct radeon_device *rdev, int ring);
-int radeon_fence_wait_empty_locked(struct radeon_device *rdev, int ring);
+void radeon_fence_wait_empty_locked(struct radeon_device *rdev, int ring);
 int radeon_fence_wait_any(struct radeon_device *rdev,
 			  struct radeon_fence **fences,
 			  bool intr);

drivers/gpu/drm/radeon/radeon_fence.c

@@ -440,14 +440,11 @@ int radeon_fence_wait_any(struct radeon_device *rdev,
 	return 0;
 }
 
+/* caller must hold ring lock */
 int radeon_fence_wait_next_locked(struct radeon_device *rdev, int ring)
 {
 	uint64_t seq;
 
-	/* We are not protected by ring lock when reading current seq but
-	 * it's ok as worst case is we return to early while we could have
-	 * wait.
-	 */
 	seq = atomic64_read(&rdev->fence_drv[ring].last_seq) + 1ULL;
 	if (seq >= rdev->fence_drv[ring].sync_seq[ring]) {
 		/* nothing to wait for, last_seq is
@@ -457,15 +454,27 @@ int radeon_fence_wait_next_locked(struct radeon_device *rdev, int ring)
 	return radeon_fence_wait_seq(rdev, seq, ring, false, false);
 }
 
-int radeon_fence_wait_empty_locked(struct radeon_device *rdev, int ring)
+/* caller must hold ring lock */
+void radeon_fence_wait_empty_locked(struct radeon_device *rdev, int ring)
 {
-	/* We are not protected by ring lock when reading current seq
-	 * but it's ok as wait empty is call from place where no more
-	 * activity can be scheduled so there won't be concurrent access
-	 * to seq value.
-	 */
-	return radeon_fence_wait_seq(rdev, rdev->fence_drv[ring].sync_seq[ring],
-				     ring, false, false);
+	uint64_t seq = rdev->fence_drv[ring].sync_seq[ring];
+
+	while(1) {
+		int r;
+		r = radeon_fence_wait_seq(rdev, seq, ring, false, false);
+		if (r == -EDEADLK) {
+			mutex_unlock(&rdev->ring_lock);
+			r = radeon_gpu_reset(rdev);
+			mutex_lock(&rdev->ring_lock);
+			if (!r)
+				continue;
+		}
+		if (r) {
+			dev_err(rdev->dev, "error waiting for ring to become"
+				" idle (%d)\n", r);
+		}
+		return;
+	}
 }
 
 struct radeon_fence *radeon_fence_ref(struct radeon_fence *fence)