[Mesa-dev] [PATCH] i965/blorp: Fix clear rectangle alignment in fast color clear

[Anuj Phogat]

For HSW GT3 clear rectangle must be aligned to two times the number of
pixels in the table shown in Ivy Bridge PRM, Vol2 Part1 11.7.
It should be safe to do this for all gen7 systems unless we see any
performance regressions. I observed no piglit, gles3conform regressions
with this patch.

It fixes: https://bugs.freedesktop.org/show_bug.cgi?id=65744

Signed-off-by: Anuj Phogat <anuj.phogat at gmail.com>
---
Thanks Paul for your great help in figuring out the fix.

 src/mesa/drivers/dri/i965/brw_blorp_clear.cpp | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/src/mesa/drivers/dri/i965/brw_blorp_clear.cpp b/src/mesa/drivers/dri/i965/brw_blorp_clear.cpp
index bf11135..2bebe8e 100644
--- a/src/mesa/drivers/dri/i965/brw_blorp_clear.cpp
+++ b/src/mesa/drivers/dri/i965/brw_blorp_clear.cpp
@@ -261,10 +261,14 @@ brw_blorp_clear_params::brw_blorp_clear_params(struct brw_context *brw,
       intel_get_non_msrt_mcs_alignment(intel, irb->mt, &x_align, &y_align);
       x_align *= 16;
       y_align *= 32;
-      x0 = ROUND_DOWN_TO(x0, x_align);
-      y0 = ROUND_DOWN_TO(y0, y_align);
-      x1 = ALIGN(x1, x_align);
-      y1 = ALIGN(y1, y_align);
+      /* For HSW GT3 clear rectangle must be aligned to two times the number
+       * of pixels in the table.
+       */
+
+      x0 = ROUND_DOWN_TO(x0, (intel->gen > 6 ? 2 * x_align : x_align));
+      y0 = ROUND_DOWN_TO(y0, (intel->gen > 6 ? 2 * y_align : y_align));
+      x1 = ALIGN(x1, (intel->gen > 6 ? 2 * x_align : x_align));
+      y1 = ALIGN(y1, (intel->gen > 6 ? 2 * y_align : y_align));
 
       /* From the Ivy Bridge PRM, Vol2 Part1 11.7 "MCS Buffer for Render
        * Target(s)", beneath the "Fast Color Clear" bullet (p327):
-- 
1.8.1.4