disp: msm: dp: abort aux before going to dp suspend

During resume, DP uses AUX to perform various functionalities
like DPCD/EDID read or link training etc. This involves other
hardware modules as well like USB and Charger. In a situation
like continuous suspend/resume, while DP is processing resume,
suspend can trigger resulting in dependent hardware modules
to go to sleep. As AUX communication is hardware interrupt
based, this can result in unstable system.

Abort all functionalities before going to suspend to
avoid unnecessary AUX and other functionality failures.

Change-Id: Id52d408270232adf7258a7eb064ee969eba4be71
Signed-off-by: Sankeerth Billakanti <sbillaka@codeaurora.org>
Signed-off-by: Tatenda Chipeperekwa <tatendac@codeaurora.org>

msm/dp/dp_display.c

@@ -1155,8 +1155,8 @@ static int dp_display_handle_disconnect(struct dp_display_private *dp)
 	rc = dp_display_process_hpd_low(dp);
 	if (rc) {
 		/* cancel any pending request */
-		dp->ctrl->abort(dp->ctrl);
-		dp->aux->abort(dp->aux);
+		dp->ctrl->abort(dp->ctrl, true);
+		dp->aux->abort(dp->aux, true);
 	}
 
 	mutex_lock(&dp->session_lock);
@@ -1177,8 +1177,8 @@ static void dp_display_disconnect_sync(struct dp_display_private *dp)
 	/* cancel any pending request */
 	dp_display_state_add(DP_STATE_ABORTED);
 
-	dp->ctrl->abort(dp->ctrl);
-	dp->aux->abort(dp->aux);
+	dp->ctrl->abort(dp->ctrl, true);
+	dp->aux->abort(dp->aux, true);
 
 	/* wait for idle state */
 	cancel_work_sync(&dp->connect_work);
@@ -3104,9 +3104,25 @@ static int dp_pm_prepare(struct device *dev)
 	struct dp_display_private *dp = container_of(g_dp_display,
 			struct dp_display_private, dp_display);
 
+	mutex_lock(&dp->session_lock);
 	dp_display_set_mst_state(g_dp_display, PM_SUSPEND);
 
+	/*
+	 * There are a few instances where the DP is hotplugged when the device
+	 * is in PM suspend state. After hotplug, it is observed the device
+	 * enters and exits the PM suspend multiple times while aux transactions
+	 * are taking place. This may sometimes cause an unclocked register
+	 * access error. So, abort aux transactions when such a situation
+	 * arises i.e. when DP is connected but display not enabled yet.
+	 */
+	if (dp_display_state_is(DP_STATE_CONNECTED) &&
+			!dp_display_state_is(DP_STATE_ENABLED)) {
+		dp->aux->abort(dp->aux, true);
+		dp->ctrl->abort(dp->ctrl, true);
+	}
+
 	dp_display_state_add(DP_STATE_SUSPENDED);
+	mutex_unlock(&dp->session_lock);
 
 	return 0;
 }
@@ -3116,9 +3132,25 @@ static void dp_pm_complete(struct device *dev)
 	struct dp_display_private *dp = container_of(g_dp_display,
 			struct dp_display_private, dp_display);
 
+	mutex_lock(&dp->session_lock);
 	dp_display_set_mst_state(g_dp_display, PM_DEFAULT);
 
+	/*
+	 * There are multiple PM suspend entry and exits observed before
+	 * the connect uevent is issued to userspace. The aux transactions are
+	 * aborted during PM suspend entry in dp_pm_prepare to prevent unclocked
+	 * register access. On PM suspend exit, there will be no host_init call
+	 * to reset the abort flags for ctrl and aux incase DP is connected
+	 * but display not enabled. So, resetting abort flags for aux and ctrl.
+	 */
+	if (dp_display_state_is(DP_STATE_CONNECTED) &&
+			!dp_display_state_is(DP_STATE_ENABLED)) {
+		dp->aux->abort(dp->aux, false);
+		dp->ctrl->abort(dp->ctrl, false);
+	}
+
 	dp_display_state_remove(DP_STATE_SUSPENDED);
+	mutex_unlock(&dp->session_lock);
 }
 
 static const struct dev_pm_ops dp_pm_ops = {