DRM/i915: only use tiled blits on 965+

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 <tomi@nomi.cz>.
Signed-off-by: NJesse Barnes <jbarnes@virtuousgeek.org>
Acked-by: NDave Airlie <airlied@linux.ie>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

drivers/char/drm/i915_irq.c

@@ -62,11 +62,11 @@ static void i915_vblank_tasklet(struct drm_device *dev)
 	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;
 	}