[Mesa-dev] [PATCH 1/4] radeonsi: only set dual source blending for MRT0

[Marek Olšák]

From: Marek Olšák <marek.olsak at amd.com>

This is the proper fix for Overlord and Witcher 2 hangs.

The hang condition is that 1 app must write to MRT0 and MRT1 from a pixel
shader while MRT1 is disabled in CB_TARGET_MASK (does this generate
unflushable pixel quads? I don't know), and another app (e.g. Glamor)
must enable dual source blending in both MRT0 and MRT1. The hw gets
confused, which leads to corruption and hangs.

Cc: 12.0 11.2 <mesa-stable at lists.freedesktop.org>
---
 src/gallium/drivers/radeonsi/si_state.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/src/gallium/drivers/radeonsi/si_state.c b/src/gallium/drivers/radeonsi/si_state.c
index 47fc7a0..f5b2330 100644
--- a/src/gallium/drivers/radeonsi/si_state.c
+++ b/src/gallium/drivers/radeonsi/si_state.c
@@ -453,20 +453,24 @@ static void *si_create_blend_state_mode(struct pipe_context *ctx,
 		unsigned srcA = state->rt[j].alpha_src_factor;
 		unsigned dstA = state->rt[j].alpha_dst_factor;
 
 		unsigned srcRGB_opt, dstRGB_opt, srcA_opt, dstA_opt;
 		unsigned blend_cntl = 0;
 
 		sx_mrt_blend_opt[i] =
 			S_028760_COLOR_COMB_FCN(V_028760_OPT_COMB_BLEND_DISABLED) |
 			S_028760_ALPHA_COMB_FCN(V_028760_OPT_COMB_BLEND_DISABLED);
 
+		/* Only set dual source blending for MRT0 to avoid a hang. */
+		if (i >= 1 && blend->dual_src_blend)
+			continue;
+
 		if (!state->rt[j].colormask)
 			continue;
 
 		/* cb_render_state will disable unused ones */
 		blend->cb_target_mask |= (unsigned)state->rt[j].colormask << (4 * i);
 
 		if (!state->rt[j].blend_enable) {
 			si_pm4_set_reg(pm4, R_028780_CB_BLEND0_CONTROL + i * 4, blend_cntl);
 			continue;
 		}
-- 
2.7.4