drm/radeon: check return value of radeon_ring_lock

Function radeon_ring_lock() returns an errno on failure, and its return
value should be validated. However, in functions r420_cp_errata_init()
and r420_cp_errata_fini(), its return value is not checked. This patch
adds the checks.
Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Pan Bian <bianpan2016@163.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/radeon/r420.c

@@ -203,6 +203,7 @@ static void r420_clock_resume(struct radeon_device *rdev)
 
 static void r420_cp_errata_init(struct radeon_device *rdev)
 {
+	int r;
 	struct radeon_ring *ring = &rdev->ring[RADEON_RING_TYPE_GFX_INDEX];
 
 	/* RV410 and R420 can lock up if CP DMA to host memory happens
@@ -212,7 +213,8 @@ static void r420_cp_errata_init(struct radeon_device *rdev)
 	 * of the CP init, apparently.
 	 */
 	radeon_scratch_get(rdev, &rdev->config.r300.resync_scratch);
-	radeon_ring_lock(rdev, ring, 8);
+	r = radeon_ring_lock(rdev, ring, 8);
+	WARN_ON(r);
 	radeon_ring_write(ring, PACKET0(R300_CP_RESYNC_ADDR, 1));
 	radeon_ring_write(ring, rdev->config.r300.resync_scratch);
 	radeon_ring_write(ring, 0xDEADBEEF);
@@ -221,12 +223,14 @@ static void r420_cp_errata_init(struct radeon_device *rdev)
 
 static void r420_cp_errata_fini(struct radeon_device *rdev)
 {
+	int r;
 	struct radeon_ring *ring = &rdev->ring[RADEON_RING_TYPE_GFX_INDEX];
 
 	/* Catch the RESYNC we dispatched all the way back,
 	 * at the very beginning of the CP init.
 	 */
-	radeon_ring_lock(rdev, ring, 8);
+	r = radeon_ring_lock(rdev, ring, 8);
+	WARN_ON(r);
 	radeon_ring_write(ring, PACKET0(R300_RB3D_DSTCACHE_CTLSTAT, 0));
 	radeon_ring_write(ring, R300_RB3D_DC_FINISH);
 	radeon_ring_unlock_commit(rdev, ring, false);