3 files changed, 22 insertions, 8 deletions
diff --git a/src/mesa/drivers/dri/i965/brw_cc.c b/src/mesa/drivers/dri/i965/brw_cc.c
index 78809da804b..f5affcfedc5 100644
--- a/src/mesa/drivers/dri/i965/brw_cc.c
+++ b/src/mesa/drivers/dri/i965/brw_cc.c
@@ -75,8 +75,8 @@ const struct brw_tracked_state brw_cc_vp = {
  * replace it with a function that hard-wires destination alpha to 1.0.  This
  * is used when rendering to xRGB targets.
  */
-static GLenum
-fix_xRGB_alpha(GLenum function)
+GLenum
+brw_fix_xRGB_alpha(GLenum function)
 {
    switch (function) {
    case GL_DST_ALPHA:
@@ -159,10 +159,10 @@ static void upload_cc_unit(struct brw_context *brw)
        * with GL_ONE and GL_ONE_MINUS_DST_ALPHA with GL_ZERO.
        */
       if (ctx->DrawBuffer->Visual.alphaBits == 0) {
-	 srcRGB = fix_xRGB_alpha(srcRGB);
-	 srcA   = fix_xRGB_alpha(srcA);
-	 dstRGB = fix_xRGB_alpha(dstRGB);
-	 dstA   = fix_xRGB_alpha(dstA);
+	 srcRGB = brw_fix_xRGB_alpha(srcRGB);
+	 srcA   = brw_fix_xRGB_alpha(srcA);
+	 dstRGB = brw_fix_xRGB_alpha(dstRGB);
+	 dstA   = brw_fix_xRGB_alpha(dstA);
       }
 
       if (eqRGB == GL_MIN || eqRGB == GL_MAX) {
diff --git a/src/mesa/drivers/dri/i965/brw_util.h b/src/mesa/drivers/dri/i965/brw_util.h
index c0fc1330e4b..5cba99a9306 100644
--- a/src/mesa/drivers/dri/i965/brw_util.h
+++ b/src/mesa/drivers/dri/i965/brw_util.h
@@ -39,7 +39,6 @@
 extern GLuint brw_parameter_list_state_flags(struct gl_program_parameter_list *paramList);
 extern GLuint brw_translate_blend_factor( GLenum factor );
 extern GLuint brw_translate_blend_equation( GLenum mode );
-
-
+extern GLenum brw_fix_xRGB_alpha(GLenum function);
 
 #endif
diff --git a/src/mesa/drivers/dri/i965/gen6_cc.c b/src/mesa/drivers/dri/i965/gen6_cc.c
index b61a816cd87..fcd1794b8f5 100644
--- a/src/mesa/drivers/dri/i965/gen6_cc.c
+++ b/src/mesa/drivers/dri/i965/gen6_cc.c
@@ -118,6 +118,21 @@ gen6_upload_blend_state(struct brw_context *brw)
 	    srcA = dstA = GL_ONE;
 	 }
 
+         /* Due to hardware limitations, the destination may have information
+          * in an alpha channel even when the format specifies no alpha
+          * channel. In order to avoid getting any incorrect blending due to
+          * that alpha channel, coerce the blend factors to values that will
+          * not read the alpha channel, but will instead use the correct
+          * implicit value for alpha.
+          */
+         if (_mesa_get_format_bits(rb->Format, GL_ALPHA_BITS) == 0)
+         {
+            srcRGB = brw_fix_xRGB_alpha(srcRGB);
+            srcA = brw_fix_xRGB_alpha(srcA);
+            dstRGB = brw_fix_xRGB_alpha(dstRGB);
+            dstA = brw_fix_xRGB_alpha(dstA);
+         }
+
 	 blend[b].blend0.dest_blend_factor = brw_translate_blend_factor(dstRGB);
 	 blend[b].blend0.source_blend_factor = brw_translate_blend_factor(srcRGB);
 	 blend[b].blend0.blend_func = brw_translate_blend_equation(eqRGB);