[PATCH 17/26] drm/amd/display: Link train only when link is DP and backend is enabled

[Bhawanpreet Lakha]

From: Samson Tam <Samson.Tam at amd.com>

[Why]
In certain cases we do link training when we don't have a backend.

[How]
In dc_link_set_preferred_link_settings(), store preferred link settings
first and then verify that the link is DP and the link stream's backend is
enabled.  If either is false, then we will not do any link retraining.

Change-Id: I0af4250f00b5fb229d336294581d914584dbacbb
Signed-off-by: Samson Tam <Samson.Tam at amd.com>
Reviewed-by: Aric Cyr <Aric.Cyr at amd.com>
Acked-by: Anthony Koo <Anthony.Koo at amd.com>
Acked-by: Bhawanpreet Lakha <Bhawanpreet.Lakha at amd.com>
---
 drivers/gpu/drm/amd/display/dc/core/dc.c | 13 ++++++++++++-
 1 file changed, 12 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/amd/display/dc/core/dc.c b/drivers/gpu/drm/amd/display/dc/core/dc.c
index cc1087933f4d..cebd083df07a 100644
--- a/drivers/gpu/drm/amd/display/dc/core/dc.c
+++ b/drivers/gpu/drm/amd/display/dc/core/dc.c
@@ -530,6 +530,14 @@ void dc_link_set_preferred_link_settings(struct dc *dc,
 	struct dc_stream_state *link_stream;
 	struct dc_link_settings store_settings = *link_setting;
 
+	link->preferred_link_setting = store_settings;
+
+	/* Retrain with preferred link settings only relevant for
+	 * DP signal type
+	 */
+	if (!dc_is_dp_signal(link->connector_signal))
+		return;
+
 	for (i = 0; i < MAX_PIPES; i++) {
 		pipe = &dc->current_state->res_ctx.pipe_ctx[i];
 		if (pipe->stream && pipe->stream->link) {
@@ -544,7 +552,10 @@ void dc_link_set_preferred_link_settings(struct dc *dc,
 
 	link_stream = link->dc->current_state->res_ctx.pipe_ctx[i].stream;
 
-	link->preferred_link_setting = store_settings;
+	/* Cannot retrain link if backend is off */
+	if (link_stream->dpms_off)
+		return;
+
 	if (link_stream)
 		decide_link_settings(link_stream, &store_settings);
 
-- 
2.17.1