[PATCH v2] drm/msm/dp: check hpd_state before push idle pattern at dp_bridge_disable()

[Kuogee Hsieh]

dp_bridge_disable() is the first step toward tearing down main link.
Its major function is to start transmitting idle pattern to replace
video stream. This patch will check hpd_state to make sure main link
is enabled before commit changes of main link's configuration to
push idle pattern out to avoid system crashing due to main link clock
is disabled while access main link registers.

Changes in v2:
-- changes Fixes patch
-- fix eported-by
-- add Closes tag

Fixes: 375a126090b9 ("drm/msm/dp: tear down main link at unplug handle immediately")
Reported-by: leonard at lausen.nl
Closes: https://gitlab.freedesktop.org/drm/msm/-/issues/17
Signed-off-by: Kuogee Hsieh <quic_khsieh at quicinc.com>
---
 drivers/gpu/drm/msm/dp/dp_display.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/drivers/gpu/drm/msm/dp/dp_display.c b/drivers/gpu/drm/msm/dp/dp_display.c
index b36f8b6..678289a 100644
--- a/drivers/gpu/drm/msm/dp/dp_display.c
+++ b/drivers/gpu/drm/msm/dp/dp_display.c
@@ -1729,10 +1729,20 @@ void dp_bridge_disable(struct drm_bridge *drm_bridge)
 	struct msm_dp_bridge *dp_bridge = to_dp_bridge(drm_bridge);
 	struct msm_dp *dp = dp_bridge->dp_display;
 	struct dp_display_private *dp_display;
+	u32 state;
 
 	dp_display = container_of(dp, struct dp_display_private, dp_display);
 
+	mutex_lock(&dp_display->event_mutex);
+
+	state = dp_display->hpd_state;
+	if (state != ST_DISCONNECT_PENDING && state != ST_CONNECTED) {
+		mutex_unlock(&dp_display->event_mutex);
+		return;
+	}
+
 	dp_ctrl_push_idle(dp_display->ctrl);
+	mutex_unlock(&dp_display->event_mutex);
 }
 
 void dp_bridge_post_disable(struct drm_bridge *drm_bridge)
-- 
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