[Mesa-dev] [PATCH 2/2] intel/isl: Divide QPitch by 2 for 3-D stencil textures on SKL+

[Jason Ekstrand]

---
 src/intel/isl/isl_surface_state.c | 15 ++++++++++++++-
 1 file changed, 14 insertions(+), 1 deletion(-)

diff --git a/src/intel/isl/isl_surface_state.c b/src/intel/isl/isl_surface_state.c
index f8ea122..22fef3d 100644
--- a/src/intel/isl/isl_surface_state.c
+++ b/src/intel/isl/isl_surface_state.c
@@ -173,7 +173,20 @@ get_qpitch(const struct isl_surf *surf)
       unreachable("Bad isl_surf_dim");
    case ISL_DIM_LAYOUT_GEN4_2D:
       if (GEN_GEN >= 9) {
-         return isl_surf_get_array_pitch_el_rows(surf);
+         if (surf->dim == ISL_SURF_DIM_3D && surf->tiling == ISL_TILING_W) {
+            /* This is rather annoying and completely undocumented.  It
+             * appears that the hardware has a bug (or undocumented feature)
+             * regarding stencil buffers most likely related to the way
+             * W-tiling is handled as modified Y-tiling.  If you bind a 3-D or
+             * 2-D array stencil buffer normally, and use texelFetch on it,
+             * the z or array index will get implicitly multiplied by 2 for no
+             * obvious reason.  The fix appears to be to divide qpitch by 2
+             * for W-tiled surfaces.
+             */
+            return isl_surf_get_array_pitch_el_rows(surf) / 2;
+         } else {
+            return isl_surf_get_array_pitch_el_rows(surf);
+         }
       } else {
          /* From the Broadwell PRM for RENDER_SURFACE_STATE.QPitch
           *
-- 
2.5.0.400.gff86faf