Mesa (master): radeonsi: only set dual source blending for MRT0

[Marek Olšák]

Module: Mesa
Branch: master
Commit: 947e0614d091c260651e4f3d6209bd6bcc2cfa0d
URL:    http://cgit.freedesktop.org/mesa/mesa/commit/?id=947e0614d091c260651e4f3d6209bd6bcc2cfa0d

Author: Marek Olšák <marek.olsak at amd.com>
Date:   Tue Aug  9 12:43:13 2016 +0200

radeonsi: only set dual source blending for MRT0

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>
Reviewed-by: Michel Dänzer <michel.daenzer at amd.com>
Reviewed-by: Edward O'Callaghan <funfunctor at folklore1984.net>

---

 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
@@ -460,6 +460,10 @@ static void *si_create_blend_state_mode(struct pipe_context *ctx,
 			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;