disp: msm: dp: do not abort DP display init if link is aborted

It is possible that by the time DP display is initialized by the
user mode in response to a hotplug connect event, the DP display has
already been disconnected. In such cases, the link aborted flag is
set by the driver prior to sending the HPD disconnect event. Current
implementation will abort the connection callback when this aborted
flag is set. As a result, the DP stream clocks would not be enabled
and the DP interface will not be able to generate any vsyncs. This can
cause a lot of instability. Allow the connection callbacks from the
usermode to complete successfully to avoid these issues. This will also
help in subsequent disconnect and connect notifications to be handled
gracefully.

Change-Id: I9a0d44492a3590e1b6026bc545ee81f7414925cd
Signed-off-by: Aravind Venkateswaran <[email protected]>
Signed-off-by: Tatenda Chipeperekwa <[email protected]>

msm/dp/dp_display.c

@@ -1778,8 +1778,22 @@ static int dp_display_prepare(struct dp_display *dp_display, void *panel)
 	SDE_EVT32_EXTERNAL(SDE_EVTLOG_FUNC_ENTRY, dp->state);
 	mutex_lock(&dp->session_lock);
 
-	if (dp_display_state_is(DP_STATE_ABORTED | DP_STATE_ENABLED)) {
-		dp_display_state_show("[not initialized]");
+	/*
+	 * If the physical connection to the sink is already lost by the time
+	 * we try to set up the connection, we can just skip all the steps
+	 * here safely.
+	 */
+	if (dp_display_state_is(DP_STATE_ABORTED)) {
+		dp_display_state_log("[aborted]");
+		goto end;
+	}
+
+	/*
+	 * If DP_STATE_ENABLED, there is nothing left to do.
+	 * However, this should not happen ideally. So, log this.
+	 */
+	if (dp_display_state_is(DP_STATE_ENABLED)) {
+		dp_display_state_show("[already enabled]");
 		goto end;
 	}
 
@@ -1900,15 +1914,25 @@ static int dp_display_enable(struct dp_display *dp_display, void *panel)
 	SDE_EVT32_EXTERNAL(SDE_EVTLOG_FUNC_ENTRY, dp->state);
 	mutex_lock(&dp->session_lock);
 
+	/*
+	 * If DP_STATE_READY is not set, we should not do any HW
+	 * programming.
+	 */
 	if (!dp_display_state_is(DP_STATE_READY)) {
 		dp_display_state_show("[host not ready]");
 		goto end;
 	}
 
-	if (dp_display_state_is(DP_STATE_ABORTED)) {
-		dp_display_state_show("[aborted]");
-		goto end;
-	}
+	/*
+	 * It is possible that by the time we get call back to establish
+	 * the DP pipeline e2e, the physical DP connection to the sink is
+	 * already lost. In such cases, the DP_STATE_ABORTED would be set.
+	 * However, it is necessary to NOT abort the display setup here so as
+	 * to ensure that the rest of the system is in a stable state prior to
+	 * handling the disconnect notification.
+	 */
+	if (dp_display_state_is(DP_STATE_ABORTED))
+		dp_display_state_log("[aborted, but continue on]");
 
 	rc = dp_display_stream_enable(dp, panel);
 	if (rc)
@@ -1945,13 +1969,22 @@ static int dp_display_post_enable(struct dp_display *dp_display, void *panel)
 	SDE_EVT32_EXTERNAL(SDE_EVTLOG_FUNC_ENTRY, dp->state);
 	mutex_lock(&dp->session_lock);
 
+	/*
+	 * If DP_STATE_READY is not set, we should not do any HW
+	 * programming.
+	 */
 	if (!dp_display_state_is(DP_STATE_ENABLED)) {
 		dp_display_state_show("[not enabled]");
 		goto end;
 	}
 
+	/*
+	 * If the physical connection to the sink is already lost by the time
+	 * we try to set up the connection, we can just skip all the steps
+	 * here safely.
+	 */
 	if (dp_display_state_is(DP_STATE_ABORTED)) {
-		dp_display_state_show("[aborted]");
+		dp_display_state_log("[aborted]");
 		goto end;
 	}