i965: Force X-tiling for 128 bpp formats on Sandybridge.

128 bpp formats are not allowed to be Y-tiled on any architectures
except Gen7.

+11 Piglits on Sandybridge (mostly regression fixes since the
switch to Y-tiling).

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=63867
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=64261
Signed-off-by: Kenneth Graunke <kenneth@whitecape.org>
Reviewed-by: Chad Versace <chad.versace@linux.intel.com>
Reviewed-by: Ian Romanick <ian.d.romanick@intel.com>
Cc: "9.2" <mesa-stable@lists.freedesktop.org>

src/mesa/drivers/dri/i965/intel_mipmap_tree.c

@@ -468,6 +468,15 @@ intel_miptree_choose_tiling(struct brw_context *brw,
    if (brw->gen < 6)
       return I915_TILING_X;
 
+   /* From the Sandybridge PRM, Volume 1, Part 2, page 32:
+    * "NOTE: 128BPE Format Color Buffer ( render target ) MUST be either TileX
+    *  or Linear."
+    * 128 bits per pixel translates to 16 bytes per pixel.  This is necessary
+    * all the way back to 965, but is explicitly permitted on Gen7.
+    */
+   if (brw->gen != 7 && mt->cpp >= 16)
+      return I915_TILING_X;
+
    return I915_TILING_Y | I915_TILING_X;
 }