No change in piglit results on gen6.
---
src/mesa/drivers/dri/i965/gen6_cc.c | 20 ++++++++++++++++++++
1 files changed, 20 insertions(+), 0 deletions(-)
diff --git a/src/mesa/drivers/dri/i965/gen6_cc.c
b/src/mesa/drivers/dri/i965/gen6_cc.c
index b8047d5..1e6c4cf 100644
--- a/src/mesa/drivers/dri/i965/gen6_cc.c
+++ b/src/mesa/drivers/dri/i965/gen6_cc.c
@@ -99,6 +99,26 @@ prepare_blend_state(struct brw_context *brw)
eqA != eqRGB);
}
+ /* See section 8.1.6 "Pre-Blend Color Clamping" of the
+ * SandyBridge PRM Volume 2 Part 1 for HW requirements.
+ *
+ * We do our ARB_color_buffer_float CLAMP_FRAGMENT_COLOR
+ * clamping in the fragment shader. For its clamping of
+ * blending, the spec says:
+ *
+ * "RESOLVED: For fixed-point color buffers, the inputs and
+ * the result of the blending equation are clamped. For
+ * floating-point color buffers, no clamping occurs."
+ *
+ * So, generally, we want clamping to the render target's range.
+ * And, good news, the hardware tables for both pre- and
+ * post-blend color clamping are either ignored, or any are
+ * allowed, or clamping is required but RT range clamping is a
+ * valid option.
+ */
+ blend[b].blend1.pre_blend_clamp_enable = 1;
+ blend[b].blend1.post_blend_clamp_enable = 1;
+ blend[b].blend1.clamp_range = BRW_RENDERTARGET_CLAMPRANGE_FORMAT;
/* _NEW_COLOR */
if (ctx->Color.AlphaEnabled) {
--
1.7.5.4
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