From 28eebb703e28bc455ba704adb1026f76649b768c Mon Sep 17 00:00:00 2001
From: Alex Deucher <alexander.deucher@amd.com>
Date: Tue, 3 Jan 2012 09:48:38 -0500
Subject: 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 846eeb8..79b08b4 100644
--- 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;
-- 
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