[Mesa-dev] [PATCH 2/3] isl: add MCS width constraint 16 samples

[Jason Ekstrand]

From: Lionel Landwerlin <lionel.g.landwerlin at intel.com>

v3 (Jason Ekstrand): Add a comment explaining why

Signed-off-by: Lionel Landwerlin <lionel.g.landwerlin at intel.com>
Reviewed-by: Jason Ekstrand <jason at jlekstrand.net>
---
 src/intel/isl/isl.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/src/intel/isl/isl.c b/src/intel/isl/isl.c
index 1a47da5..6979063 100644
--- a/src/intel/isl/isl.c
+++ b/src/intel/isl/isl.c
@@ -1417,6 +1417,16 @@ isl_surf_get_mcs_surf(const struct isl_device *dev,
    assert(surf->levels == 1);
    assert(surf->logical_level0_px.depth == 1);
 
+   /* The "Auxiliary Surface Pitch" field in RENDER_SURFACE_STATE is only 9
+    * bits which means the maximum pitch of a compression surface is 512
+    * tiles or 64KB (since MCS is always Y-tiled).  Since a 16x MCS buffer is
+    * 64bpp, this gives us a maximum width of 8192 pixels.  We can create
+    * larger multisampled surfaces, we just can't compress them.   For 2x, 4x,
+    * and 8x, we have enough room for the full 16k supported by the hardware.
+    */
+   if (surf->samples == 16 && surf->width > 8192)
+      return false;
+
    enum isl_format mcs_format;
    switch (surf->samples) {
    case 2:  mcs_format = ISL_FORMAT_MCS_2X;  break;
-- 
2.5.0.400.gff86faf