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@lists.freedesktop.org>
Reviewed-by: Michel Dänzer <michel.daenzer@amd.com>
Reviewed-by: Edward O'Callaghan <funfunctor@folklore1984.net>
(cherry picked from commit 947e0614d091c260651e4f3d6209bd6bcc2cfa0d)

diff --git a/src/gallium/drivers/radeonsi/si_state.c b/src/gallium/drivers/radeonsi/si_state.c
index 366f56b..ba22655 100644 (file)
--- 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;