drm/radeon: fix UVD message buffer validation

When the message buffer is currently moving block until it is idle again.

Signed-off-by: Christian König <christian.koenig@amd.com>
Cc: stable@vger.kernel.org
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
diff --git a/drivers/gpu/drm/radeon/radeon_uvd.c b/drivers/gpu/drm/radeon/radeon_uvd.c
index f1c1575..b79f4f5 100644
--- a/drivers/gpu/drm/radeon/radeon_uvd.c
+++ b/drivers/gpu/drm/radeon/radeon_uvd.c
@@ -356,6 +356,14 @@
 		return -EINVAL;
 	}
 
+	if (bo->tbo.sync_obj) {
+		r = radeon_fence_wait(bo->tbo.sync_obj, false);
+		if (r) {
+			DRM_ERROR("Failed waiting for UVD message (%d)!\n", r);
+			return r;
+		}
+	}
+
 	r = radeon_bo_kmap(bo, &ptr);
 	if (r) {
 		DRM_ERROR("Failed mapping the UVD message (%d)!\n", r);