[Mesa-dev] [PATCH 03/17] i965/gen6: Adjust render height in errata case for MSAA

[Jordan Justen]

In the gen6 PRM Volume 1 Part 1: Graphics Core, Section
7.18.3.7.1 (Surface Arrays For all surfaces other than separate
stencil buffer):

 "[DevSNB] Errata: Sampler MSAA Qpitch will be 4 greater than the
  value calculated in the equation above , for every other odd Surface
  Height starting from 1 i.e. 1,5,9,13"

Since this Qpitch errata only impacts the sampler, we have to adjust
the input for the rendering surface to achieve the same qpitch. For
the affected heights, we increment the height by 1 for the rendering
surface.

Signed-off-by: Jordan Justen <jordan.l.justen at intel.com>
---
 src/mesa/drivers/dri/i965/gen6_surface_state.c | 18 +++++++++++++++++-
 1 file changed, 17 insertions(+), 1 deletion(-)

diff --git a/src/mesa/drivers/dri/i965/gen6_surface_state.c b/src/mesa/drivers/dri/i965/gen6_surface_state.c
index 6fc8bdf..29a4800 100644
--- a/src/mesa/drivers/dri/i965/gen6_surface_state.c
+++ b/src/mesa/drivers/dri/i965/gen6_surface_state.c
@@ -96,8 +96,24 @@ gen6_update_renderbuffer_surface(struct brw_context *brw,
    /* reloc */
    surf[1] = mt->bo->offset64;
 
+   /* In the gen6 PRM Volume 1 Part 1: Graphics Core, Section 7.18.3.7.1
+    * (Surface Arrays For all surfaces other than separate stencil buffer):
+    *
+    * "[DevSNB] Errata: Sampler MSAA Qpitch will be 4 greater than the value
+    *  calculated in the equation above , for every other odd Surface Height
+    *  starting from 1 i.e. 1,5,9,13"
+    *
+    * Since this Qpitch errata only impacts the sampler, we have to adjust the
+    * input for the rendering surface to achieve the same qpitch. For the
+    * affected heights, we increment the height by 1 for the rendering
+    * surface.
+    */
+   int height0 = irb->mt->logical_height0;
+   if (brw->gen == 6 && irb->mt->num_samples > 1 && (height0 % 4) == 1)
+      height0++;
+
    surf[2] = SET_FIELD(mt->logical_width0 - 1, BRW_SURFACE_WIDTH) |
-             SET_FIELD(mt->logical_height0 - 1, BRW_SURFACE_HEIGHT) |
+             SET_FIELD(height0 - 1, BRW_SURFACE_HEIGHT) |
              SET_FIELD(irb->mt_level - irb->mt->first_level, BRW_SURFACE_LOD);
 
    surf[3] = brw_get_surface_tiling_bits(mt->tiling) |
-- 
2.0.1