[Mesa-dev] [PATCH 3/3] intel/blorp: Work around HiZ clear bugs on Sky Lake

[Jason Ekstrand]

---
 src/intel/blorp/blorp_clear.c | 49 +++++++++++++++++++++++++++++++++++
 1 file changed, 49 insertions(+)

diff --git a/src/intel/blorp/blorp_clear.c b/src/intel/blorp/blorp_clear.c
index 7f0d3b70993..82672dd2282 100644
--- a/src/intel/blorp/blorp_clear.c
+++ b/src/intel/blorp/blorp_clear.c
@@ -708,6 +708,55 @@ blorp_can_hiz_clear_depth(const struct gen_device_info *devinfo,
           x1 % align_px_w || y1 % align_px_h)
          return false;
    }
+
+   if (devinfo->gen >= 9) {
+      /* We can always do full-surface clears */
+      if (is_full_surface_clear(surf, level, x0, y0, x1, y1))
+         return true;
+
+      /* The Bspec says the following about fast depth clears on Sky Lake:
+       *
+       *    "The minimum granularity of clear is one pixel, but all samples of
+       *    the pixel must be cleared. Clearing partial samples of a pixel is
+       *    not supported. If a newly allocated depth buffer is not padded to
+       *    an integer multiple of 8x4 pixels, and if the first operation on
+       *    the depth buffer does not clear the entire width and height of the
+       *    surface, then first a HiZ ambiguate must be done on the portions
+       *    of the depth buffer that are not cleared. If the depth buffer
+       *    clear operation does clear the entire width and height of the
+       *    surface, then the “full surface clear” bit in 3DSTATE_WM_OP must
+       *    be set to 1."
+       *
+       * This seems to imply that HiZ clears should "just work" on Sky Lake.
+       * Unfortunately, that is not true in all cases.  It works for the most
+       * part but if the clear encounters a block in the pass-through state
+       * (i.e. one that has been touched by an ambiguate/hiz resolve) it falls
+       * over and just does nothing.
+       *
+       * The following table of alignments was determined experimentally using
+       * the crucible test group func.renderpass.depth-partial-clear.*
+       *
+       * TODO: Test on future hardware
+       */
+      unsigned x_align_px, y_align_px;
+      if (surf->format == ISL_FORMAT_R16_UNORM && surf->samples == 1) {
+         x_align_px = 8;
+         y_align_px = 4;
+      } else if (surf->samples <= 2) {
+         x_align_px = 4;
+         y_align_px = 4;
+      } else if (surf->format == ISL_FORMAT_R16_UNORM && surf->samples == 4) {
+         x_align_px = 4;
+         y_align_px = 2;
+      } else {
+         x_align_px = 2;
+         y_align_px = 2;
+      }
+      if (x0 % x_align_px || y0 % y_align_px ||
+          x1 % x_align_px || y1 % y_align_px)
+         return false;
+   }
+
    return true;
 }
 
-- 
2.19.1