sna: Mark the stencil as untiled

In reality, Mesa will be treating it as W-tiling, only we have no way of
communicating that requirement to the kernel (as not only does the
kernel not understand W-tiling, but also the GTT is incapable of fencing
a W-tiled region.).

Ported from Chad Versace's 3e55f3e88.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>

1 files changed, 13 insertions, 3 deletions

diff --git a/src/sna/sna_dri.c b/src/sna/sna_dri.c
index ec656426..9b0ce200 100644
--- a/src/sna/sna_dri.c
+++ b/src/sna/sna_dri.c
@@ -246,12 +246,22 @@ sna_dri_create_buffer(DrawablePtr drawable,
 		 *
 		 * If we neglect to double the pitch, then
 		 * drm_intel_gem_bo_map_gtt() maps the memory incorrectly.
+		 *
+		 * The alignment for W-tiling is quite different to the
+		 * nominal no-tiling case, so we have to account for
+		 * the tiled access pattern explicitly.
+		 *
+		 * The stencil buffer is W tiled. However, we request from
+		 * the kernel a non-tiled buffer because the kernel does
+		 * not understand W tiling and the GTT is incapable of
+		 * W fencing.
 		 */
 		bpp = format ? format : drawable->bitsPerPixel;
 		bo = kgem_create_2d(&sna->kgem,
-				    drawable->width,
-				    drawable->height/2, 2*bpp,
-				    I915_TILING_Y,
+				    ALIGN(drawable->width, 64),
+				    ALIGN((drawable->height + 1) / 2, 64),
+				    2*bpp,
+				    I915_TILING_NONE,
 				    CREATE_EXACT);
 		break;