freedreno/a3xx: fix alpha-blending on RGBX formats

Expert debugging assistance provided by Chris Forbes.

Signed-off-by: Ilia Mirkin <[email protected]>
Reviewed-by: Rob Clark <[email protected]>

5 files changed, 55 insertions, 8 deletions

diff --git a/src/gallium/auxiliary/Makefile.sources b/src/gallium/auxiliary/Makefile.sources
index 862626461b1..ab794e16441 100644
--- a/src/gallium/auxiliary/Makefile.sources
+++ b/src/gallium/auxiliary/Makefile.sources
@@ -168,6 +168,7 @@ C_SOURCES := \
 	util/u_atomic.h \
 	util/u_bitmask.c \
 	util/u_bitmask.h \
+	util/u_blend.h \
 	util/u_blit.c \
 	util/u_blit.h \
 	util/u_blitter.c \
diff --git a/src/gallium/auxiliary/util/u_blend.h b/src/gallium/auxiliary/util/u_blend.h
new file mode 100644
index 00000000000..2485c34d418
--- /dev/null
+++ b/src/gallium/auxiliary/util/u_blend.h
@@ -0,0 +1,25 @@
+#ifndef U_BLEND_H
+#define U_BLEND_H
+
+#include "pipe/p_state.h"
+
+/**
+ * When faking RGBX render target formats with RGBA ones, the blender is still
+ * supposed to treat the destination's alpha channel as 1 instead of the
+ * garbage that's there. Return a blend factor that will take that into
+ * account.
+ */
+static INLINE int
+util_blend_dst_alpha_to_one(int factor)
+{
+   switch (factor) {
+   case PIPE_BLENDFACTOR_DST_ALPHA:
+      return PIPE_BLENDFACTOR_ONE;
+   case PIPE_BLENDFACTOR_INV_DST_ALPHA:
+      return PIPE_BLENDFACTOR_ZERO;
+   default:
+      return factor;
+   }
+}
+
+#endif /* U_BLEND_H */
diff --git a/src/gallium/drivers/freedreno/a3xx/fd3_blend.c b/src/gallium/drivers/freedreno/a3xx/fd3_blend.c
index 329d304694c..92295566147 100644
--- a/src/gallium/drivers/freedreno/a3xx/fd3_blend.c
+++ b/src/gallium/drivers/freedreno/a3xx/fd3_blend.c
@@ -27,6 +27,7 @@
  */
 
 #include "pipe/p_state.h"
+#include "util/u_blend.h"
 #include "util/u_string.h"
 #include "util/u_memory.h"
 
@@ -99,14 +100,21 @@ fd3_blend_state_create(struct pipe_context *pctx,
 	for (i = 0; i < ARRAY_SIZE(so->rb_mrt); i++) {
 		const struct pipe_rt_blend_state *rt = &cso->rt[i];
 
-		so->rb_mrt[i].blend_control =
+		so->rb_mrt[i].blend_control_rgb =
 				A3XX_RB_MRT_BLEND_CONTROL_RGB_SRC_FACTOR(fd_blend_factor(rt->rgb_src_factor)) |
 				A3XX_RB_MRT_BLEND_CONTROL_RGB_BLEND_OPCODE(blend_func(rt->rgb_func)) |
-				A3XX_RB_MRT_BLEND_CONTROL_RGB_DEST_FACTOR(fd_blend_factor(rt->rgb_dst_factor)) |
+				A3XX_RB_MRT_BLEND_CONTROL_RGB_DEST_FACTOR(fd_blend_factor(rt->rgb_dst_factor));
+
+		so->rb_mrt[i].blend_control_alpha =
 				A3XX_RB_MRT_BLEND_CONTROL_ALPHA_SRC_FACTOR(fd_blend_factor(rt->alpha_src_factor)) |
 				A3XX_RB_MRT_BLEND_CONTROL_ALPHA_BLEND_OPCODE(blend_func(rt->alpha_func)) |
 				A3XX_RB_MRT_BLEND_CONTROL_ALPHA_DEST_FACTOR(fd_blend_factor(rt->alpha_dst_factor));
 
+		so->rb_mrt[i].blend_control_no_alpha_rgb =
+				A3XX_RB_MRT_BLEND_CONTROL_RGB_SRC_FACTOR(fd_blend_factor(util_blend_dst_alpha_to_one(rt->rgb_src_factor))) |
+				A3XX_RB_MRT_BLEND_CONTROL_RGB_BLEND_OPCODE(blend_func(rt->rgb_func)) |
+				A3XX_RB_MRT_BLEND_CONTROL_RGB_DEST_FACTOR(fd_blend_factor(util_blend_dst_alpha_to_one(rt->rgb_dst_factor)));
+
 		so->rb_mrt[i].control =
 				A3XX_RB_MRT_CONTROL_ROP_CODE(rop) |
 				A3XX_RB_MRT_CONTROL_COMPONENT_ENABLE(rt->colormask);
diff --git a/src/gallium/drivers/freedreno/a3xx/fd3_blend.h b/src/gallium/drivers/freedreno/a3xx/fd3_blend.h
index d269d74dd74..4f6eeb74481 100644
--- a/src/gallium/drivers/freedreno/a3xx/fd3_blend.h
+++ b/src/gallium/drivers/freedreno/a3xx/fd3_blend.h
@@ -35,7 +35,12 @@
 struct fd3_blend_stateobj {
 	struct pipe_blend_state base;
 	struct {
-		uint32_t blend_control;
+		/* Blend control bits for color if there is an alpha channel */
+		uint32_t blend_control_rgb;
+		/* Blend control bits for color if there is no alpha channel */
+		uint32_t blend_control_no_alpha_rgb;
+		/* Blend control bits for alpha channel */
+		uint32_t blend_control_alpha;
 		uint32_t control;
 	} rb_mrt[4];
 };
diff --git a/src/gallium/drivers/freedreno/a3xx/fd3_emit.c b/src/gallium/drivers/freedreno/a3xx/fd3_emit.c
index 44f8ac4bb40..f721303cefe 100644
--- a/src/gallium/drivers/freedreno/a3xx/fd3_emit.c
+++ b/src/gallium/drivers/freedreno/a3xx/fd3_emit.c
@@ -571,11 +571,12 @@ fd3_emit_state(struct fd_context *ctx, struct fd_ringbuffer *ring,
 		uint32_t i;
 
 		for (i = 0; i < ARRAY_SIZE(blend->rb_mrt); i++) {
-			bool is_float = util_format_is_float(
-					pipe_surface_format(ctx->framebuffer.cbufs[i]));
-			bool is_int = util_format_is_pure_integer(
-					pipe_surface_format(ctx->framebuffer.cbufs[i]));
+			enum pipe_format format = pipe_surface_format(ctx->framebuffer.cbufs[i]);
+			bool is_float = util_format_is_float(format);
+			bool is_int = util_format_is_pure_integer(format);
+			bool has_alpha = util_format_has_alpha(format);
 			uint32_t control = blend->rb_mrt[i].control;
+			uint32_t blend_control = blend->rb_mrt[i].blend_control_alpha;
 
 			if (is_int) {
 				control &= (A3XX_RB_MRT_CONTROL_COMPONENT_ENABLE__MASK |
@@ -583,11 +584,18 @@ fd3_emit_state(struct fd_context *ctx, struct fd_ringbuffer *ring,
 				control |= A3XX_RB_MRT_CONTROL_ROP_CODE(ROP_COPY);
 			}
 
+			if (has_alpha) {
+				blend_control |= blend->rb_mrt[i].blend_control_rgb;
+			} else {
+				blend_control |= blend->rb_mrt[i].blend_control_no_alpha_rgb;
+				control &= ~A3XX_RB_MRT_CONTROL_BLEND2;
+			}
+
 			OUT_PKT0(ring, REG_A3XX_RB_MRT_CONTROL(i), 1);
 			OUT_RING(ring, control);
 
 			OUT_PKT0(ring, REG_A3XX_RB_MRT_BLEND_CONTROL(i), 1);
-			OUT_RING(ring, blend->rb_mrt[i].blend_control |
+			OUT_RING(ring, blend_control |
 					COND(!is_float, A3XX_RB_MRT_BLEND_CONTROL_CLAMP_ENABLE));
 		}
 	}