From be32288992092b061dec9a2170f1e0e862749822 Mon Sep 17 00:00:00 2001
From: Jimmy Kizito <Jimmy.Kizito@amd.com>
Date: Wed, 15 Sep 2021 15:24:45 -0400
Subject: drm/amd/display: Fix MST link encoder availability check.
Git-commit: 43dc2ad561c94dbb4a16477d99033279e2ae378a
Patch-mainline: v5.16-rc1
References: jsc#PED-1166 jsc#PED-1168 jsc#PED-1170 jsc#PED-1218 jsc#PED-1220 jsc#PED-1222 jsc#PED-1223 jsc#PED-1225

[Why]
MST streams share the same link and should share the same encoder.
The current availability check may erroneously determine that an
encoder is unavailable for MST streams.

[How]
When checking for link encoder availability, check if an encoder
in use shares a link with the stream for which the availability
check is being conducted. If the link is shared, then the link
encoder should be shared too and will be deemed available.

Reviewed-by: Jun Lei <Jun.Lei@amd.com>
Acked-by: Anson Jacob <Anson.Jacob@amd.com>
Signed-off-by: Jimmy Kizito <Jimmy.Kizito@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Acked-by: Patrik Jakobsson <pjakobsson@suse.de>
---
 .../drm/amd/display/dc/core/dc_link_enc_cfg.c | 23 +++++++++++++++----
 1 file changed, 18 insertions(+), 5 deletions(-)

diff --git a/drivers/gpu/drm/amd/display/dc/core/dc_link_enc_cfg.c b/drivers/gpu/drm/amd/display/dc/core/dc_link_enc_cfg.c
index 4dce25c39b75..1cab4bf06abe 100644
--- a/drivers/gpu/drm/amd/display/dc/core/dc_link_enc_cfg.c
+++ b/drivers/gpu/drm/amd/display/dc/core/dc_link_enc_cfg.c
@@ -1,5 +1,4 @@
-/*
- * Copyright 2021 Advanced Micro Devices, Inc.
+/* Copyright 2021 Advanced Micro Devices, Inc. All rights reserved.
  *
  * Permission is hereby granted, free of charge, to any person obtaining a
  * copy of this software and associated documentation files (the "Software"),
@@ -177,13 +176,27 @@ static enum engine_id find_first_avail_link_enc(
 	return eng_id;
 }
 
-static bool is_avail_link_enc(struct dc_state *state, enum engine_id eng_id)
+/* Check for availability of link encoder eng_id. */
+static bool is_avail_link_enc(struct dc_state *state, enum engine_id eng_id, struct dc_stream_state *stream)
 {
 	bool is_avail = false;
 	int eng_idx = eng_id - ENGINE_ID_DIGA;
 
-	if (eng_id != ENGINE_ID_UNKNOWN && state->res_ctx.link_enc_cfg_ctx.link_enc_avail[eng_idx] != ENGINE_ID_UNKNOWN)
+	/* An encoder is available if it is still in the availability pool. */
+	if (eng_id != ENGINE_ID_UNKNOWN && state->res_ctx.link_enc_cfg_ctx.link_enc_avail[eng_idx] != ENGINE_ID_UNKNOWN) {
 		is_avail = true;
+	} else {
+		struct dc_stream_state *stream_assigned = NULL;
+
+		/* MST streams share the same link and should share the same encoder.
+		 * If a stream that has already been assigned a link encoder uses as the
+		 * same link as the stream checking for availability, it is an MST stream
+		 * and should use the same link encoder.
+		 */
+		stream_assigned = get_stream_using_link_enc(state, eng_id);
+		if (stream_assigned && stream != stream_assigned && stream->link == stream_assigned->link)
+			is_avail = true;
+	}
 
 	return is_avail;
 }
@@ -296,7 +309,7 @@ void link_enc_cfg_link_encs_assign(
 				if (stream == prev_stream && stream->link == prev_stream->link &&
 						prev_state->res_ctx.link_enc_cfg_ctx.link_enc_assignments[j].valid) {
 					eng_id = prev_state->res_ctx.link_enc_cfg_ctx.link_enc_assignments[j].eng_id;
-					if (is_avail_link_enc(state, eng_id))
+					if (is_avail_link_enc(state, eng_id, stream))
 						add_link_enc_assignment(state, stream, eng_id);
 				}
 			}
-- 
2.38.1