From: Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com>
Date: Thu, 26 Mar 2020 14:06:49 +0000 (-0400)
Subject: pan/bi: Fix overzealous write barriers
X-Git-Url: https://git.libre-soc.org/?a=commitdiff_plain;h=f3726a08743a100c7e163489800fd0560da015b9;p=mesa.git

pan/bi: Fix overzealous write barriers

It's possible this triggers an INSTR_INVALID_ENC.

Signed-off-by: Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/4382>
---

diff --git a/src/panfrost/bifrost/bi_schedule.c b/src/panfrost/bifrost/bi_schedule.c
index 4adab3bc60e..589c84897ac 100644
--- a/src/panfrost/bifrost/bi_schedule.c
+++ b/src/panfrost/bifrost/bi_schedule.c
@@ -110,7 +110,10 @@ bi_schedule(bi_context *ctx)
                         ids = ids & 1;
                         last_id = u->scoreboard_id;
                         u->back_to_back = true;
-                        u->data_register_write_barrier = true;
+
+                        /* Rule: first instructions cannot have write barriers */
+                        if (!is_first)
+                                u->data_register_write_barrier = true;
 
                         u->constant_count = 1;
                         u->constants[0] = ins->constant.u64;