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-rw-r--r--src/gallium/drivers/r300/r300_state.c9
1 files changed, 7 insertions, 2 deletions
diff --git a/src/gallium/drivers/r300/r300_state.c b/src/gallium/drivers/r300/r300_state.c
index 534c1b5935f..1dbf0bbd8cc 100644
--- a/src/gallium/drivers/r300/r300_state.c
+++ b/src/gallium/drivers/r300/r300_state.c
@@ -66,7 +66,11 @@ static void* r300_create_blend_state(struct pipe_context* pipe,
( r300_translate_blend_factor(srcRGB) << R300_SRC_BLEND_SHIFT) |
( r300_translate_blend_factor(dstRGB) << R300_DST_BLEND_SHIFT);
- /* optimization: some operations do not require the destination color */
+ /* Optimization: some operations do not require the destination color.
+ *
+ * When SRC_ALPHA_SATURATE is used, colorbuffer reads must be enabled,
+ * otherwise blending gives incorrect results. It seems to be
+ * a hardware bug. */
if (eqRGB == PIPE_BLEND_MIN || eqA == PIPE_BLEND_MIN ||
eqRGB == PIPE_BLEND_MAX || eqA == PIPE_BLEND_MAX ||
dstRGB != PIPE_BLENDFACTOR_ZERO ||
@@ -78,7 +82,8 @@ static void* r300_create_blend_state(struct pipe_context* pipe,
srcA == PIPE_BLENDFACTOR_DST_COLOR ||
srcA == PIPE_BLENDFACTOR_DST_ALPHA ||
srcA == PIPE_BLENDFACTOR_INV_DST_COLOR ||
- srcA == PIPE_BLENDFACTOR_INV_DST_ALPHA)
+ srcA == PIPE_BLENDFACTOR_INV_DST_ALPHA ||
+ srcRGB == PIPE_BLENDFACTOR_SRC_ALPHA_SATURATE)
blend->blend_control |= R300_READ_ENABLE;
/* XXX implement the optimization with DISCARD_SRC_PIXELS*/