intel/isl: Allow multisampling with ISL_FORMAT_HiZ

HiZ buffers can be multisampled and, on Broadwell and earlier, simply using
interleaved multisampling with a compression block size of 8x4 samples
yields the correct HiZ surface size calculations.  Unfortunately,
choose_msaa_layout was rejecting multisampled HiZ buffers because of format
checks.  Now that we have a simple helper for determining if a format
supports multisampling, that's an easy enough issue to fix.

Signed-off-by: Jason Ekstrand <[email protected]>
Reviewed-by: Chad Versace <[email protected]>
Reviewed-by: Nanley Chery <[email protected]>

1 files changed, 9 insertions, 2 deletions

diff --git a/src/intel/isl/isl_format.c b/src/intel/isl/isl_format.c
index 81c01e0b8ca..daf2d813436 100644
--- a/src/intel/isl/isl_format.c
+++ b/src/intel/isl/isl_format.c
@@ -444,9 +444,16 @@ isl_format_supports_multisampling(const struct gen_device_info *devinfo,
     *       - any compressed texture format (BC*)
     *       - any YCRCB* format
     *
-    * The restriction on the format's size is removed on Broadwell.
+    * The restriction on the format's size is removed on Broadwell.  Also,
+    * there is an exception for HiZ which we treat as a compressed format and
+    * is allowed to be multisampled on Broadwell and earlier.
     */
-   if (devinfo->gen < 8 && isl_format_get_layout(format)->bpb > 64) {
+   if (format == ISL_FORMAT_HIZ) {
+      /* On SKL+, HiZ is always single-sampled even when the primary surface
+       * is multisampled.  See also isl_surf_get_hiz_surf().
+       */
+      return devinfo->gen <= 8;
+   } else if (devinfo->gen < 8 && isl_format_get_layout(format)->bpb > 64) {
       return false;
    } else if (isl_format_is_compressed(format)) {
       return false;