disp: msm: dp: skip HPD connect notification if IRQ HPD is pending

Upon completing the link setup, check to see if any IRQ HPD
notification is pending prior to sending the connect notification
to the user mode. If an IRQ HPD is pending, address the IRQ first
prior to sending the notification. This will ensure that the link
setup is stable first before the connection setup is started. This
will also help in adhering to the CTS timing requirements for
responding to IRQ HPD notifications. The current patchset limits
this logic only for SST connections.

Change-Id: I3f5e8e9290f915b98ec5e9e6cf9ff14aa9929d96
Signed-off-by: Aravind Venkateswaran <[email protected]>
Signed-off-by: Tatenda Chipeperekwa <[email protected]>

msm/dp/dp_display.c

@@ -733,6 +733,24 @@ static int dp_display_send_hpd_notification(struct dp_display_private *dp)
 	bool hpd = !!dp_display_state_is(DP_STATE_CONNECTED);
 
 	SDE_EVT32_EXTERNAL(SDE_EVTLOG_FUNC_ENTRY, dp->state, hpd);
+
+	/*
+	 * Send the notification only if there is any change. This check is
+	 * necessary since it is possible that the connect_work may or may not
+	 * skip sending the notification in order to respond to a pending
+	 * attention message. Attention work thread will always attempt to
+	 * send the notification after successfully handling the attention
+	 * message. This check here will avoid any unintended duplicate
+	 * notifications.
+	 */
+	if (dp_display_state_is(DP_STATE_CONNECT_NOTIFIED) && hpd) {
+		DP_DEBUG("connection notified already, skip notification\n");
+		goto skip_wait;
+	} else if (dp_display_state_is(DP_STATE_DISCONNECT_NOTIFIED) && !hpd) {
+		DP_DEBUG("disonnect notified already, skip notification\n");
+		goto skip_wait;
+	}
+
 	dp->aux->state |= DP_STATE_NOTIFICATION_SENT;
 
 	if (!dp->mst.mst_active)
@@ -990,9 +1008,30 @@ static int dp_display_process_hpd_high(struct dp_display_private *dp)
 end:
 	mutex_unlock(&dp->session_lock);
 
+	/*
+	 * If an IRQ HPD is pending, then do not send a connect notification.
+	 * Once this work returns, the IRQ HPD would be processed and any
+	 * required actions (such as link maintenance) would be done which
+	 * will subsequently send the HPD notification. To keep things simple,
+	 * do this only for SST use-cases. MST use cases require additional
+	 * care in order to handle the side-band communications as well.
+	 *
+	 * One of the main motivations for this is DP LL 1.4 CTS use case
+	 * where it is possible that we could get a test request right after
+	 * a connection, and the strict timing requriements of the test can
+	 * only be met if we do not wait for the e2e connection to be set up.
+	 */
+	if (!dp->mst.mst_active &&
+		(work_busy(&dp->attention_work) == WORK_BUSY_PENDING)) {
+		SDE_EVT32_EXTERNAL(dp->state, 99);
+		DP_DEBUG("Attention pending, skip HPD notification\n");
+		goto skip_notify;
+	}
+
 	if (!rc && !dp_display_state_is(DP_STATE_ABORTED))
 		dp_display_send_hpd_notification(dp);
 
+skip_notify:
 	SDE_EVT32_EXTERNAL(SDE_EVTLOG_FUNC_EXIT, dp->state, rc);
 	return rc;
 }
@@ -1311,6 +1350,10 @@ static void dp_display_attention_work(struct work_struct *work)
 		if (dp_display_is_sink_count_zero(dp)) {
 			dp_display_handle_disconnect(dp);
 		} else {
+			/*
+			 * connect work should take care of sending
+			 * the HPD notification.
+			 */
 			if (!dp->mst.mst_active)
 				queue_work(dp->wq, &dp->connect_work);
 		}
@@ -1323,6 +1366,10 @@ static void dp_display_attention_work(struct work_struct *work)
 		dp_display_handle_disconnect(dp);
 
 		dp->panel->video_test = true;
+		/*
+		 * connect work should take care of sending
+		 * the HPD notification.
+		 */
 		queue_work(dp->wq, &dp->connect_work);
 
 		goto mst_attention;
@@ -1355,8 +1402,18 @@ static void dp_display_attention_work(struct work_struct *work)
 		mutex_unlock(&dp->session_lock);
 
 		if (dp->link->sink_request & (DP_TEST_LINK_PHY_TEST_PATTERN |
-			DP_TEST_LINK_TRAINING))
+			DP_TEST_LINK_TRAINING)) {
 			goto mst_attention;
+		} else {
+			/*
+			 * It is possible that the connect_work skipped sending
+			 * the HPD notification if the attention message was
+			 * already pending. Send the notification here to
+			 * account for that. This is not needed if this
+			 * attention work was handling a test request
+			 */
+			dp_display_send_hpd_notification(dp);
+		}
 	}
 
 cp_irq: