drm/msm/dp: update is_connected status base on sink count at dp_pm_resume()

Currently at dp_pm_resume() is_connected state is decided base on hpd connection
status only. This will put is_connected in wrongly "true" state at the scenario
that dongle attached to DUT but without hmdi cable connecting to it. Fix this
problem by adding read sink count from dongle and decided is_connected state base
on both sink count and hpd connection status.

Changes in v2:
-- remove dp_get_sink_count() cand call drm_dp_read_sink_count()

Changes in v3:
-- delete status local variable from dp_pm_resume()

Changes in v4:
-- delete un necessary comment at dp_pm_resume()

Fixes: d9aa657 ("drm/msm/dp: check sink_count before update is_connected status")
Signed-off-by: Kuogee Hsieh <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Tested-by: Stephen Boyd <[email protected]>
Reviewed-by: Stephen Boyd <[email protected]>
Signed-off-by: Dmitry Baryshkov <[email protected]>
Signed-off-by: Rob Clark <[email protected]>

Author: Kuogee Hsieh

drivers/gpu/drm/msm/dp/dp_display.c

@@ -1278,7 +1278,7 @@ static int dp_pm_resume(struct device *dev)
 	struct platform_device *pdev = to_platform_device(dev);
 	struct msm_dp *dp_display = platform_get_drvdata(pdev);
 	struct dp_display_private *dp;
-	u32 status;
+	int sink_count = 0;
 
 	dp = container_of(dp_display, struct dp_display_private, dp_display);
 
@@ -1292,14 +1292,25 @@ static int dp_pm_resume(struct device *dev)
 
 	dp_catalog_ctrl_hpd_config(dp->catalog);
 
-	status = dp_catalog_link_is_connected(dp->catalog);
+	/*
+	 * set sink to normal operation mode -- D0
+	 * before dpcd read
+	 */
+	dp_link_psm_config(dp->link, &dp->panel->link_info, false);
+
+	if (dp_catalog_link_is_connected(dp->catalog)) {
+		sink_count = drm_dp_read_sink_count(dp->aux);
+		if (sink_count < 0)
+			sink_count = 0;
+	}
 
+	dp->link->sink_count = sink_count;
 	/*
 	 * can not declared display is connected unless
 	 * HDMI cable is plugged in and sink_count of
 	 * dongle become 1
 	 */
-	if (status && dp->link->sink_count)
+	if (dp->link->sink_count)
 		dp->dp_display.is_connected = true;
 	else
 		dp->dp_display.is_connected = false;