[Mesa-dev] [PATCH] intel/i965: Disable SampleAlphaToOne if dual source blending enabled

[Anuj Phogat]

>From SandyBridge PRM, volume 2 Part 1, section 12.2.3, BLEND_STATE:
DWord 1, Bit 30 (AlphaToOne Enable):
"If Dual Source Blending is enabled, this bit must be disabled"

Signed-off-by: Anuj Phogat <anuj.phogat at gmail.com>
---
 src/mesa/drivers/dri/i965/gen6_cc.c |   13 +++++++++++--
 1 files changed, 11 insertions(+), 2 deletions(-)

diff --git a/src/mesa/drivers/dri/i965/gen6_cc.c b/src/mesa/drivers/dri/i965/gen6_cc.c
index 6aeaaa2..e9c7f50 100644
--- a/src/mesa/drivers/dri/i965/gen6_cc.c
+++ b/src/mesa/drivers/dri/i965/gen6_cc.c
@@ -174,8 +174,17 @@ gen6_upload_blend_state(struct brw_context *brw)
          /* _NEW_MULTISAMPLE */
          blend[b].blend1.alpha_to_coverage =
             ctx->Multisample._Enabled && ctx->Multisample.SampleAlphaToCoverage;
-         blend[b].blend1.alpha_to_one =
-            ctx->Multisample._Enabled && ctx->Multisample.SampleAlphaToOne;
+
+	/* From SandyBridge PRM, volume 2 Part 1, section 8.2.3, BLEND_STATE:
+	 * DWord 1, Bit 30 (AlphaToOne Enable):
+	 * "If Dual Source Blending is enabled, this bit must be disabled"
+	 */
+	 if (ctx->Color.Blend[b]._UsesDualSrc)
+            blend[b].blend1.alpha_to_one = false;
+	 else
+	    blend[b].blend1.alpha_to_one =
+	       ctx->Multisample._Enabled && ctx->Multisample.SampleAlphaToOne;
+
          blend[b].blend1.alpha_to_coverage_dither = (brw->intel.gen >= 7);
       }
       else {
-- 
1.7.7.6