sna: Avoid using TILING_Y for large objects on gen2/3

References: https://bugs.freedesktop.org/show_bug.cgi?id=48636
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>

src/sna/sna_accel.c

@@ -458,6 +458,16 @@ static inline uint32_t default_tiling(PixmapPtr pixmap)
 		     __FUNCTION__));
 		sna_damage_destroy(&priv->gpu_damage);
 		priv->undamaged = false;
+
+		/* Only on later generations was the render pipeline
+		 * more flexible than the BLT. So on gen2/3, prefer to
+		 * keep large objects accessible through the BLT.
+		 */
+		if (sna->kgem.gen < 40 &&
+		    (pixmap->drawable.width > sna->render.max_3d_size ||
+		     pixmap->drawable.height > sna->render.max_3d_size))
+			return I915_TILING_X;
+
 		return I915_TILING_Y;
 	}