agp/intel: Fix cache control for Sandybridge

Sandybridge GTT has new cache control bits in PTE, which controls
graphics page cache in LLC or LLC/MLC, so we need to extend the mask
function to respect the new bits.

And set cache control to always LLC only by default on Gen6.

Signed-off-by: Zhenyu Wang <zhenyuw@linux.intel.com>
Cc: stable@kernel.org
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>

include/linux/intel-gtt.h

@@ -0,0 +1,20 @@
+/*
+ * Common Intel AGPGART and GTT definitions.
+ */
+#ifndef _INTEL_GTT_H
+#define _INTEL_GTT_H
+
+#include <linux/agp_backend.h>
+
+/* This is for Intel only GTT controls.
+ *
+ * Sandybridge: AGP_USER_CACHED_MEMORY default to LLC only
+ */
+
+#define AGP_USER_CACHED_MEMORY_LLC_MLC (AGP_USER_TYPES + 2)
+#define AGP_USER_UNCACHED_MEMORY (AGP_USER_TYPES + 4)
+
+/* flag for GFDT type */
+#define AGP_USER_CACHED_MEMORY_GFDT (1 << 3)
+
+#endif