From: Jesse Barnes <jbarnes@virtuousgeek.org>

When scheduled swaps occur, we need to blit between front & back buffers. 
If the buffers are tiled, we need to set the appropriate XY_SRC_COPY tile
bit, but only on 965 chips, since it will cause corruption on pre-965
(e.g.  945).

Bug reported by and fix tested by Tomas Janousek.

Reported-by: Tomas Janousek <tomi@nomi.cz>
Tested-by: Tomas Janousek <tomi@nomi.cz>
Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>
Cc: Dave Airlie <airlied@linux.ie>
Cc: Keith Packard <keithp@keithp.com>
Cc: "Rafael J. Wysocki" <rjw@sisk.pl>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 drivers/char/drm/i915_irq.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff -puN drivers/char/drm/i915_irq.c~drm-i915-only-use-tiled-blits-on-965 drivers/char/drm/i915_irq.c
--- a/drivers/char/drm/i915_irq.c~drm-i915-only-use-tiled-blits-on-965
+++ a/drivers/char/drm/i915_irq.c
@@ -62,11 +62,11 @@ static void i915_vblank_tasklet(struct d
 	u32 ropcpp = (0xcc << 16) | ((cpp - 1) << 24);
 	RING_LOCALS;
 
-	if (sarea_priv->front_tiled) {
+	if (IS_I965G(dev) && sarea_priv->front_tiled) {
 		cmd |= XY_SRC_COPY_BLT_DST_TILED;
 		dst_pitch >>= 2;
 	}
-	if (sarea_priv->back_tiled) {
+	if (IS_I965G(dev) && sarea_priv->back_tiled) {
 		cmd |= XY_SRC_COPY_BLT_SRC_TILED;
 		src_pitch >>= 2;
 	}
_