[PATCH v2 3/3] drm/msm/dp: continue link training downgrade when cable is still plugged

[naidu nama <naidu.nama@oss.qualcomm.com>]

From: Saurabh Anand <saurabh.anand@oss.qualcomm.com>

During a Type-C reconnect the AUX channel may report link-disconnected
transiently while the physical cable is still present. The link training
retry loop in msm_dp_ctrl_on_link() was aborting immediately on any
msm_dp_aux_is_link_connected() failure, preventing the rate/lane downgrade
path from running.

When the display is known to be plugged (msm_dp_ctrl->plugged), an AUX
link-disconnected status is likely a transient glitch rather than a true
unplug. Allow the downgrade loop to continue in that case by requiring both
conditions before breaking out of the retry loop: AUX reports disconnected
and the display is not plugged.

Signed-off-by: Saurabh Anand <saurabh.anand@oss.qualcomm.com>
---
 drivers/gpu/drm/msm/dp/dp_ctrl.c    | 15 ++++++++-------
 drivers/gpu/drm/msm/dp/dp_ctrl.h    |  4 ++--
 drivers/gpu/drm/msm/dp/dp_display.c |  7 +++----
 3 files changed, 13 insertions(+), 13 deletions(-)

diff --git a/drivers/gpu/drm/msm/dp/dp_ctrl.c b/drivers/gpu/drm/msm/dp/dp_ctrl.c
index 6b9d9a76ba05..f8a6bd7b0d10 100644
--- a/drivers/gpu/drm/msm/dp/dp_ctrl.c
+++ b/drivers/gpu/drm/msm/dp/dp_ctrl.c
@@ -2274,7 +2274,8 @@ void msm_dp_ctrl_off_pixel_clk(struct msm_dp_ctrl *msm_dp_ctrl, enum msm_dp_stre
 }
 
 static int msm_dp_ctrl_process_phy_test_request(struct msm_dp_ctrl_private *ctrl,
-						struct msm_dp_panel *panel)
+						struct msm_dp_panel *panel,
+						bool plugged)
 {
 	int ret;
 	unsigned long pixel_rate;
@@ -2293,7 +2294,7 @@ static int msm_dp_ctrl_process_phy_test_request(struct msm_dp_ctrl_private *ctrl
 	msm_dp_ctrl_off_pixel_clk(&ctrl->msm_dp_ctrl, panel->stream_id);
 	msm_dp_ctrl_off_link(&ctrl->msm_dp_ctrl, panel);
 
-	ret = msm_dp_ctrl_on_link(&ctrl->msm_dp_ctrl, panel);
+	ret = msm_dp_ctrl_on_link(&ctrl->msm_dp_ctrl, panel, plugged);
 	if (ret) {
 		DRM_ERROR("failed to enable DP link controller\n");
 		return ret;
@@ -2310,7 +2311,7 @@ static int msm_dp_ctrl_process_phy_test_request(struct msm_dp_ctrl_private *ctrl
 }
 
 void msm_dp_ctrl_handle_sink_request(struct msm_dp_ctrl *msm_dp_ctrl,
-				     struct msm_dp_panel *panel)
+				     struct msm_dp_panel *panel, bool plugged)
 {
 	struct msm_dp_ctrl_private *ctrl;
 	u32 sink_request = 0x0;
@@ -2325,7 +2326,7 @@ void msm_dp_ctrl_handle_sink_request(struct msm_dp_ctrl *msm_dp_ctrl,
 
 	if (sink_request & DP_TEST_LINK_PHY_TEST_PATTERN) {
 		drm_dbg_dp(ctrl->drm_dev, "PHY_TEST_PATTERN request\n");
-		if (msm_dp_ctrl_process_phy_test_request(ctrl, panel)) {
+		if (msm_dp_ctrl_process_phy_test_request(ctrl, panel, plugged)) {
 			DRM_ERROR("process phy_test_req failed\n");
 			return;
 		}
@@ -2377,7 +2378,7 @@ static bool msm_dp_ctrl_channel_eq_ok(struct msm_dp_ctrl_private *ctrl)
 }
 
 int msm_dp_ctrl_on_link(struct msm_dp_ctrl *msm_dp_ctrl,
-			struct msm_dp_panel *panel)
+			struct msm_dp_panel *panel, bool plugged)
 {
 	int rc = 0;
 	struct msm_dp_ctrl_private *ctrl;
@@ -2427,7 +2428,7 @@ int msm_dp_ctrl_on_link(struct msm_dp_ctrl *msm_dp_ctrl,
 			break;
 		} else if (training_step == DP_TRAINING_1) {
 			/* link train_1 failed */
-			if (!msm_dp_aux_is_link_connected(ctrl->aux))
+			if (!msm_dp_aux_is_link_connected(ctrl->aux) && !plugged)
 				break;
 
 			drm_dp_dpcd_read_link_status(ctrl->aux, link_status);
@@ -2452,7 +2453,7 @@ int msm_dp_ctrl_on_link(struct msm_dp_ctrl *msm_dp_ctrl,
 			}
 		} else if (training_step == DP_TRAINING_2) {
 			/* link train_2 failed */
-			if (!msm_dp_aux_is_link_connected(ctrl->aux))
+			if (!msm_dp_aux_is_link_connected(ctrl->aux) && !plugged)
 				break;
 
 			drm_dp_dpcd_read_link_status(ctrl->aux, link_status);
diff --git a/drivers/gpu/drm/msm/dp/dp_ctrl.h b/drivers/gpu/drm/msm/dp/dp_ctrl.h
index fc884038182f..3edf954cc805 100644
--- a/drivers/gpu/drm/msm/dp/dp_ctrl.h
+++ b/drivers/gpu/drm/msm/dp/dp_ctrl.h
@@ -17,7 +17,7 @@ struct msm_dp_ctrl {
 struct phy;
 
 int msm_dp_ctrl_on_link(struct msm_dp_ctrl *msm_dp_ctrl,
-			struct msm_dp_panel *panel);
+			struct msm_dp_panel *panel, bool plugged);
 int msm_dp_ctrl_on_stream(struct msm_dp_ctrl *msm_dp_ctrl, struct msm_dp_panel *panel);
 int msm_dp_ctrl_prepare_stream_on(struct msm_dp_ctrl *msm_dp_ctrl,
 				  struct msm_dp_panel *panel);
@@ -28,7 +28,7 @@ void msm_dp_ctrl_push_idle(struct msm_dp_ctrl *msm_dp_ctrl);
 irqreturn_t msm_dp_ctrl_isr(struct msm_dp_ctrl *msm_dp_ctrl,
 			    struct msm_dp_panel *panel);
 void msm_dp_ctrl_handle_sink_request(struct msm_dp_ctrl *msm_dp_ctrl,
-				     struct msm_dp_panel *panel);
+				     struct msm_dp_panel *panel, bool plugged);
 struct msm_dp_ctrl *msm_dp_ctrl_get(struct device *dev,
 				    struct msm_dp_link *link,
 				    struct drm_dp_aux *aux,
diff --git a/drivers/gpu/drm/msm/dp/dp_display.c b/drivers/gpu/drm/msm/dp/dp_display.c
index 169938ba515e..551d2c63ef8e 100644
--- a/drivers/gpu/drm/msm/dp/dp_display.c
+++ b/drivers/gpu/drm/msm/dp/dp_display.c
@@ -399,7 +399,7 @@ static int msm_dp_display_handle_irq_hpd(struct msm_dp_display_private *dp)
 
 	drm_dbg_dp(dp->drm_dev, "%d\n", sink_request);
 
-	msm_dp_ctrl_handle_sink_request(dp->ctrl, dp->panel);
+	msm_dp_ctrl_handle_sink_request(dp->ctrl, dp->panel, dp->plugged);
 
 	if (sink_request & DP_TEST_LINK_VIDEO_PATTERN)
 		msm_dp_display_handle_video_request(dp);
@@ -648,11 +648,10 @@ static int msm_dp_display_prepare_link(struct msm_dp_display_private *dp)
 	if (dp->link->sink_count == 0)
 		return -ENOTCONN;
 
-	if (!msm_dp_display->power_on) {
+	if (!msm_dp_display->power_on)
 		msm_dp_display_host_phy_init(dp);
-	}
 
-	rc = msm_dp_ctrl_on_link(dp->ctrl, dp->panel);
+	rc = msm_dp_ctrl_on_link(dp->ctrl, dp->panel, dp->plugged);
 	if (rc) {
 		DRM_ERROR("Failed link training (rc=%d)\n", rc);
 		// TODO: schedule drm_connector_set_link_status_property()
-- 
2.43.0