[Mesa-dev] [PATCH 1/2] i965/gen7: Prefer vertical alignment of 4 when possible.

[Paul Berry]

Gen6+ allows for color buffers to use a vertical alignment of either 4
or 2.  Previously we defaulted to 2.  This may have caused problems on
Gen7 because Y-tiled render targets are not allowed to use a vertical
alignment of 2.

This patch changes the vertical alignment to 4 on Gen7, except for the
few formats where a vertical alignment of 2 is required.
---
 src/mesa/drivers/dri/i965/brw_tex_layout.c | 25 ++++++++++++++++++++++---
 1 file changed, 22 insertions(+), 3 deletions(-)

diff --git a/src/mesa/drivers/dri/i965/brw_tex_layout.c b/src/mesa/drivers/dri/i965/brw_tex_layout.c
index d05dbeb..2c81eed 100644
--- a/src/mesa/drivers/dri/i965/brw_tex_layout.c
+++ b/src/mesa/drivers/dri/i965/brw_tex_layout.c
@@ -105,11 +105,11 @@ intel_vertical_texture_alignment_unit(struct brw_context *brw,
     * | Depth Buffer                           |  2  |  2  |  2  |  4  |  4  |
     * | Separate Stencil Buffer                | N/A | N/A | N/A |  4  |  8  |
     * | Multisampled (4x or 8x) render target  | N/A | N/A | N/A |  4  |  4  |
-    * | All Others                             |  2  |  2  |  2  |  2  |  2  |
+    * | All Others                             |  2  |  2  |  2  |  *  |  *  |
     * +----------------------------------------------------------------------+
     *
-    * On SNB+, non-special cases can be overridden by setting the SURFACE_STATE
-    * "Surface Vertical Alignment" field to VALIGN_2 or VALIGN_4.
+    * Where "*" means either VALIGN_2 or VALIGN_4 depending on the setting of
+    * the SURFACE_STATE "Surface Vertical Alignment" field.
     */
    if (_mesa_is_format_compressed(format))
       return 4;
@@ -128,6 +128,25 @@ intel_vertical_texture_alignment_unit(struct brw_context *brw,
       return 4;
    }
 
+   if (brw->gen == 7) {
+      /* On Gen7, we prefer a vertical alignment of 4 when possible, because
+       * that allows Y tiled render targets.
+       *
+       * From the Ivy Bridge PRM, Vol4 Part1 2.12.2.1 (SURFACE_STATE for most
+       * messages), on p64, under the heading "Surface Vertical Alignment":
+       *
+       *     Value of 1 [VALIGN_4] is not supported for format YCRCB_NORMAL
+       *     (0x182), YCRCB_SWAPUVY (0x183), YCRCB_SWAPUV (0x18f), YCRCB_SWAPY
+       *     (0x190)
+       *
+       *     VALIGN_4 is not supported for surface format R32G32B32_FLOAT.
+       */
+      if (base_format == GL_YCBCR_MESA || format == MESA_FORMAT_RGB_FLOAT32)
+         return 2;
+
+      return 4;
+   }
+
    return 2;
 }
 
-- 
1.8.4.2