drm/radeon: add some additional 6xx/7xx/EG register init

- SMX_SAR_CTL0 needs to be programmed correctly to prevent
problems with memory exports in certain cases.
- VC_ENHANCE needs to be initialized on 6xx/7xx.

Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Cc: stable@vger.kernel.org
Signed-off-by: Dave Airlie <airlied@redhat.com>
diff --git a/drivers/gpu/drm/radeon/evergreen.c b/drivers/gpu/drm/radeon/evergreen.c
index 01550d0..7fb3d2e 100644
--- a/drivers/gpu/drm/radeon/evergreen.c
+++ b/drivers/gpu/drm/radeon/evergreen.c
@@ -1932,6 +1932,9 @@
 	smx_dc_ctl0 |= NUMBER_OF_SETS(rdev->config.evergreen.sx_num_of_sets);
 	WREG32(SMX_DC_CTL0, smx_dc_ctl0);
 
+	if (rdev->family <= CHIP_SUMO2)
+		WREG32(SMX_SAR_CTL0, 0x00010000);
+
 	WREG32(SX_EXPORT_BUFFER_SIZES, (COLOR_BUFFER_SIZE((rdev->config.evergreen.sx_max_export_size / 4) - 1) |
 					POSITION_BUFFER_SIZE((rdev->config.evergreen.sx_max_export_pos_size / 4) - 1) |
 					SMX_BUFFER_SIZE((rdev->config.evergreen.sx_max_export_smx_size / 4) - 1)));