[PATCH 5.15 471/913] drm/msm/dp: always add fail-safe mode into connector mode list

[Greg Kroah-Hartman]

From: Kuogee Hsieh <quic_khsieh@xxxxxxxxxxx>

[ Upstream commit d4aca422539c441a7f3fec749287b36de37d9b6b ]

Some of DP link compliant test expects to return fail-safe mode
if prefer detailed timing mode can not be supported by mainlink's
lane and rate after link training. Therefore add fail-safe mode
into connector mode list as backup mode. This patch fixes test
case 4.2.2.1.

Changes in v2:
-- add Fixes text string

Fixes: 4b85d405cfe9 ( "drm/msm/dp: reduce link rate if failed at link training 1")
Signed-off-by: Kuogee Hsieh <quic_khsieh@xxxxxxxxxxx>
Reviewed-by: Stephen Boyd <swboyd@xxxxxxxxxxxx>
Link: https://lore.kernel.org/r/1643066274-25814-1-git-send-email-quic_khsieh@xxxxxxxxxxx
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 drivers/gpu/drm/msm/dp/dp_panel.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/drivers/gpu/drm/msm/dp/dp_panel.c b/drivers/gpu/drm/msm/dp/dp_panel.c
index 2181b60e1d1d..5f23e6f09199 100644
--- a/drivers/gpu/drm/msm/dp/dp_panel.c
+++ b/drivers/gpu/drm/msm/dp/dp_panel.c
@@ -212,6 +212,11 @@ int dp_panel_read_sink_caps(struct dp_panel *dp_panel,
 		if (drm_add_modes_noedid(connector, 640, 480))
 			drm_set_preferred_mode(connector, 640, 480);
 		mutex_unlock(&connector->dev->mode_config.mutex);
+	} else {
+		/* always add fail-safe mode as backup mode */
+		mutex_lock(&connector->dev->mode_config.mutex);
+		drm_add_modes_noedid(connector, 640, 480);
+		mutex_unlock(&connector->dev->mode_config.mutex);
 	}
 
 	if (panel->aux_cfg_update_done) {
-- 
2.34.1