drm/radeon/kms: disable writeback on pre-R300 asics

We often end up missing fences on older asics with
writeback enabled which leads to delays in the userspace
accel code, so just disable it by default on those asics.

Reported-by: Helge Deller <deller@gmx.de>
Reported-by: Dave Airlie <airlied@redhat.com>
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/radeon_device.c b/drivers/gpu/drm/radeon/radeon_device.c
index 846eeb852e5990e2616eb3d86c7239260c4d9472..79b08b487298c9fe131caa4c048be79b24814339 100644 (file)
--- a/drivers/gpu/drm/radeon/radeon_device.c
+++ b/drivers/gpu/drm/radeon/radeon_device.c
@@ -224,8 +224,11 @@ int radeon_wb_init(struct radeon_device *rdev)
        if (radeon_no_wb == 1)
                rdev->wb.enabled = false;
        else {
-               /* often unreliable on AGP */
                if (rdev->flags & RADEON_IS_AGP) {
+                       /* often unreliable on AGP */
+                       rdev->wb.enabled = false;
+               } else if (rdev->family < CHIP_R300) {
+                       /* often unreliable on pre-r300 */
                        rdev->wb.enabled = false;
                } else {
                        rdev->wb.enabled = true;