intel/isl: Refactor gen7_choose_image_alignment_el

The Ivy Bridge PRM provides a nice table that handles most of the
alignment cases in one place.  For standard color buffers we have a
little freedom of choice but for most depth, stencil and compressed it's
hard-coded.  Chad's original functions split halign and valign apart and
implemented them almost entirely based on restrictions and not the
table.  This makes things way more confusing than they need to be.  This
commit gets rid of the split and makes us implement the exact table
up-front.  If our surface isn't one of the ones in the table then we
have to make real choices.

Reviewed-by: Topi Pohjolainen <[email protected]>
Reviewed-by: Chad Versace <[email protected]>

1 files changed, 74 insertions, 83 deletions

diff --git a/src/intel/isl/isl_gen7.c b/src/intel/isl/isl_gen7.c
index 8e6b441b9b6..4c5edb4b93c 100644
--- a/src/intel/isl/isl_gen7.c
+++ b/src/intel/isl/isl_gen7.c
@@ -289,105 +289,96 @@ isl_gen6_filter_tiling(const struct isl_device *dev,
       *flags &= ~ISL_TILING_Y0_BIT;
 }
 
-/**
- * Choose horizontal subimage alignment, in units of surface elements.
- */
-static uint32_t
-gen7_choose_halign_el(const struct isl_device *dev,
-                      const struct isl_surf_init_info *restrict info)
+void
+isl_gen7_choose_image_alignment_el(const struct isl_device *dev,
+                                   const struct isl_surf_init_info *restrict info,
+                                   enum isl_tiling tiling,
+                                   enum isl_dim_layout dim_layout,
+                                   enum isl_msaa_layout msaa_layout,
+                                   struct isl_extent3d *image_align_el)
 {
-   if (isl_format_is_compressed(info->format))
-      return 1;
+   assert(ISL_DEV_GEN(dev) == 7);
 
-   /* From the Ivybridge PRM (2012-05-31), Volume 4, Part 1, Section 2.12.1,
-    * RENDER_SURFACE_STATE Surface Hoizontal Alignment:
+   /* Handled by isl_choose_image_alignment_el */
+   assert(info->format != ISL_FORMAT_HIZ);
+
+   /* IVB+ does not support combined depthstencil. */
+   assert(!isl_surf_usage_is_depth_and_stencil(info->usage));
+
+   /* From the Ivy Bridge PRM, Vol. 2, Part 2, Section 6.18.4.4,
+    * "Alignment unit size", the alignment parameters are summarized in the
+    * following table:
     *
-    *    - This field is intended to be set to HALIGN_8 only if the surface
-    *      was rendered as a depth buffer with Z16 format or a stencil buffer,
-    *      since these surfaces support only alignment of 8. Use of HALIGN_8
-    *      for other surfaces is supported, but uses more memory.
+    *     Surface Defined By | Surface Format  | Align Width | Align Height
+    *    --------------------+-----------------+-------------+--------------
+    *       DEPTH_BUFFER     |   D16_UNORM     |      8      |      4
+    *                        |     other       |      4      |      4
+    *    --------------------+-----------------+-------------+--------------
+    *       STENCIL_BUFFER   |      N/A        |      8      |      8
+    *    --------------------+-----------------+-------------+--------------
+    *       SURFACE_STATE    | BC*, ETC*, EAC* |      4      |      4
+    *                        |      FXT1       |      8      |      4
+    *                        |   all others    |   HALIGN    |   VALIGN
+    *    -------------------------------------------------------------------
     */
-   if (isl_surf_info_is_z16(info) ||
-       isl_surf_usage_is_stencil(info->usage))
-      return 8;
-
-   return 4;
-}
+   if (isl_surf_usage_is_depth(info->usage)) {
+      *image_align_el = info->format == ISL_FORMAT_R16_UNORM ?
+                        isl_extent3d(8, 4, 1) : isl_extent3d(4, 4, 1);
+      return;
+   } else if (isl_surf_usage_is_stencil(info->usage)) {
+      *image_align_el = isl_extent3d(8, 8, 1);
+      return;
+   } else if (isl_format_is_compressed(info->format)) {
+      /* Compressed formats all have alignment equal to block size. */
+      *image_align_el = isl_extent3d(1, 1, 1);
+      return;
+   }
 
-/**
- * Choose vertical subimage alignment, in units of surface elements.
- */
-static uint32_t
-gen7_choose_valign_el(const struct isl_device *dev,
-                      const struct isl_surf_init_info *restrict info,
-                      enum isl_tiling tiling)
-{
-   MAYBE_UNUSED bool require_valign2 = false;
-   bool require_valign4 = false;
+   /* Everything after this point is in the "set by Surface Horizontal or
+    * Vertical Alignment" case.  Now it's just a matter of applying
+    * restrictions.
+    */
 
-   if (isl_format_is_compressed(info->format))
-      return 1;
+   /* There are no restrictions on halign beyond what's given in the table
+    * above.  We set it to the minimum value of 4 because that uses the least
+    * memory.
+    */
+   const uint32_t halign = 4;
 
-   if (gen7_format_needs_valign2(dev, info->format))
-      require_valign2 = true;
+   bool require_valign4 = false;
 
    /* From the Ivybridge PRM, Volume 4, Part 1, Section 2.12.1:
     * RENDER_SURFACE_STATE Surface Vertical Alignment:
     *
-    *    - This field is intended to be set to VALIGN_4 if the surface was
-    *      rendered as a depth buffer, for a multisampled (4x) render target,
-    *      or for a multisampled (8x) render target, since these surfaces
-    *      support only alignment of 4.  Use of VALIGN_4 for other surfaces is
-    *      supported, but uses more memory.  This field must be set to
-    *      VALIGN_4 for all tiled Y Render Target surfaces.
+    *    * This field is intended to be set to VALIGN_4 if the surface was
+    *      rendered as a depth buffer,
     *
+    *    * for a multisampled (4x) render target, or for a multisampled (8x)
+    *      render target, since these surfaces support only alignment of 4.
+    *
+    *    * This field must be set to VALIGN_4 for all tiled Y Render Target
+    *      surfaces
+    *
+    *    * Value of 1 is not supported for format YCRCB_NORMAL (0x182),
+    *      YCRCB_SWAPUVY (0x183), YCRCB_SWAPUV (0x18f), YCRCB_SWAPY (0x190)
+    *
+    *    * If Number of Multisamples is not MULTISAMPLECOUNT_1, this field
+    *      must be set to VALIGN_4."
+    *
+    * The first restriction is already handled by the table above and the
+    * second restriction is redundant with the fifth.
     */
-   if (isl_surf_usage_is_depth(info->usage) ||
-       info->samples > 1 ||
-       ((info->usage & ISL_SURF_USAGE_RENDER_TARGET_BIT) &&
-        tiling == ISL_TILING_Y0)) {
+   if (info->samples > 1)
       require_valign4 = true;
-   }
-
-   if (isl_surf_usage_is_stencil(info->usage)) {
-      /* The Ivybridge PRM states that the stencil buffer's vertical alignment
-       * is 8 [Ivybridge PRM, Volume 1, Part 1, Section 6.18.4.4 Alignment
-       * Unit Size]. valign=8 is outside the set of valid values of
-       * RENDER_SURFACE_STATE.SurfaceVerticalAlignment, but that's ok because
-       * a stencil buffer will never be used directly for texturing or
-       * rendering on gen7.
-       */
-      return 8;
-   }
-
-   assert(!require_valign2 || !require_valign4);
-
-   if (require_valign4)
-      return 4;
 
-   /* Prefer VALIGN_2 because it conserves memory. */
-   return 2;
-}
-
-void
-isl_gen7_choose_image_alignment_el(const struct isl_device *dev,
-                                   const struct isl_surf_init_info *restrict info,
-                                   enum isl_tiling tiling,
-                                   enum isl_dim_layout dim_layout,
-                                   enum isl_msaa_layout msaa_layout,
-                                   struct isl_extent3d *image_align_el)
-{
-   assert(ISL_DEV_GEN(dev) == 7);
+   if (tiling == ISL_TILING_Y0 &&
+       (info->usage & ISL_SURF_USAGE_RENDER_TARGET_BIT))
+      require_valign4 = true;
 
-   /* Handled by isl_choose_image_alignment_el */
-   assert(info->format != ISL_FORMAT_HIZ);
+   assert(!(require_valign4 && gen7_format_needs_valign2(dev, info->format)));
 
-   /* IVB+ does not support combined depthstencil. */
-   assert(!isl_surf_usage_is_depth_and_stencil(info->usage));
+   /* We default to VALIGN_2 because it uses the least memory. */
+   const uint32_t valign = require_valign4 ? 4 : 2;
 
-   *image_align_el = (struct isl_extent3d) {
-      .w = gen7_choose_halign_el(dev, info),
-      .h = gen7_choose_valign_el(dev, info, tiling),
-      .d = 1,
-   };
+   *image_align_el = isl_extent3d(halign, valign, 1);
 }