1 files changed, 7 insertions, 0 deletions

diff --git a/drivers/char/drm/radeon_cp.c b/drivers/char/drm/radeon_cp.c
index 5ad43ba7b5a..3956628b257 100644
--- a/drivers/char/drm/radeon_cp.c
+++ b/drivers/char/drm/radeon_cp.c
@@ -1258,6 +1258,13 @@ static void radeon_test_writeback(drm_radeon_private_t * dev_priv)
                 dev_priv->writeback_works = 0;
                 DRM_INFO("writeback forced off\n");
         }
+
+        if (!dev_priv->writeback_works) {
+                /* Disable writeback to avoid unnecessary bus master transfer */
+                RADEON_WRITE(RADEON_CP_RB_CNTL, RADEON_READ(RADEON_CP_RB_CNTL) |
+                             RADEON_RB_NO_UPDATE);
+                RADEON_WRITE(RADEON_SCRATCH_UMSK, 0);
+        }
 }
 
 /* Enable or disable PCI-E GART on the chip */