drm: apple: Use delayed work for debounced oob HPD

When connecting too quickly the USB Type-C controller signals HPD
disconnect resulting in a time consuming connect/disconnect/connect
sequence. Instead defer the connect for 2 seconds. Usually a second HPD
arrives on which we can start the connect on DCP level immediately
(currently the timer is reduced to 100ms, which is probably not needed).

Signed-off-by: Janne Grunau <j@jannau.net>

Author: jannau

drivers/gpu/drm/apple/dcp-internal.h

@@ -112,6 +112,12 @@ struct apple_dcp_hw_data {
 	u32 num_dptx_ports;
 };
 
+enum dcp_hdp_state {
+	DCP_HPD_UNKNOWN,
+	DCP_HPD_OOB_CONNECTED,
+	DCP_HPD_OOB_DISCONNECTED,
+};
+
 /* TODO: move IOMFB members to its own struct */
 struct apple_dcp {
 	struct device *dev;
@@ -257,6 +263,12 @@ struct apple_dcp {
 	struct gpio_desc *dp2hdmi_pwren;
 
 	struct mutex hpd_mutex;
+	struct mutex hpd_deferred_mutex;
+	struct delayed_work hpd_wq;
+	struct {
+		enum dcp_hdp_state state;
+		u32 port;
+	} hpd;
 
 	u32 dptx_phy;
 	u32 dptx_die;

drivers/gpu/drm/apple/dcp.c

@@ -370,7 +370,7 @@ int dcp_get_connector_type(struct platform_device *pdev)
 }
 EXPORT_SYMBOL_GPL(dcp_get_connector_type);
 
-#define DPTX_CONNECT_TIMEOUT msecs_to_jiffies(1000)
+#define DPTX_CONNECT_TIMEOUT msecs_to_jiffies(2000)
 
 static int dcp_dptx_connect(struct apple_dcp *dcp, u32 port)
 {
@@ -410,24 +410,16 @@ static int dcp_dptx_connect(struct apple_dcp *dcp, u32 port)
 
 	usleep_range(5, 10);
 
+	if (dcp->connector_type == DRM_MODE_CONNECTOR_DisplayPort)
+		dptxport_set_hpd(dcp->dptxport[port].service, true);
+
 	return 0;
 
 out_unlock:
 	mutex_unlock(&dcp->hpd_mutex);
 	return ret;
 }
 
-int dcp_dptx_connect_oob(struct platform_device *pdev, u32 port)
-{
-	struct apple_dcp *dcp = platform_get_drvdata(pdev);
-	int err = dcp_dptx_connect(dcp, port);
-	if (err < 0)
-		return err;
-	dptxport_set_hpd(dcp->dptxport[port].service, true);
-	return 0;
-}
-EXPORT_SYMBOL_GPL(dcp_dptx_connect_oob);
-
 static int dcp_dptx_disconnect(struct apple_dcp *dcp, u32 port)
 {
 	dev_info(dcp->dev, "%s(port=%d)\n", __func__, port);
@@ -442,11 +434,69 @@ static int dcp_dptx_disconnect(struct apple_dcp *dcp, u32 port)
 	return 0;
 }
 
+static void dcp_deferred_hpd_work(struct work_struct *work)
+{
+	struct apple_dcp *dcp = container_of(to_delayed_work(work), struct apple_dcp, hpd_wq);
+	int err;
+
+	guard(mutex)(&dcp->hpd_deferred_mutex);
+	dev_info(dcp->dev, "%s\n", __func__);
+
+	switch (dcp->hpd.state) {
+	case DCP_HPD_OOB_CONNECTED:
+		err = dcp_dptx_connect(dcp, dcp->hpd.port);
+		if (err < 0)
+			dev_warn(dcp->dev, "OOB HPD connect failed:%d\n", err);
+		break;
+	case DCP_HPD_OOB_DISCONNECTED:
+		dptxport_set_hpd(dcp->dptxport[dcp->hpd.port].service, false);
+		err = dcp_dptx_disconnect(dcp, dcp->hpd.port);
+		if (err < 0)
+			dev_warn(dcp->dev, "OOB HPD disconnect failed:%d\n", err);
+		break;
+	default:
+		return;
+	}
+}
+
+static int dcp_dptx_schedule_hdp_work(struct apple_dcp *dcp,
+				      enum dcp_hdp_state state, u32 port)
+{
+	guard(mutex)(&dcp->hpd_deferred_mutex);
+	dcp->hpd.port = port;
+	dcp->hpd.state = state;
+
+	if (state == DCP_HPD_OOB_CONNECTED)
+	{
+		guard(mutex)(&dcp->hpd_mutex);
+		if (dcp->dptxport[port].connected)
+			return 0;
+
+		if (delayed_work_pending(&dcp->hpd_wq))
+			timer_reduce(&dcp->hpd_wq.timer, msecs_to_jiffies(100));
+		else
+			schedule_delayed_work(&dcp->hpd_wq, msecs_to_jiffies(2000));
+	} else {
+		if (!delayed_work_pending(&dcp->hpd_wq))
+			schedule_delayed_work(&dcp->hpd_wq, msecs_to_jiffies(25));
+	}
+
+	return 0;
+}
+
+int dcp_dptx_connect_oob(struct platform_device *pdev, u32 port)
+{
+	struct apple_dcp *dcp = platform_get_drvdata(pdev);
+
+	return dcp_dptx_schedule_hdp_work(dcp, DCP_HPD_OOB_CONNECTED, port);
+}
+EXPORT_SYMBOL_GPL(dcp_dptx_connect_oob);
+
 int dcp_dptx_disconnect_oob(struct platform_device *pdev, u32 port)
 {
 	struct apple_dcp *dcp = platform_get_drvdata(pdev);
-	dptxport_set_hpd(dcp->dptxport[port].service, false);
-	return dcp_dptx_disconnect(dcp, port);
+
+	return dcp_dptx_schedule_hdp_work(dcp, DCP_HPD_OOB_DISCONNECTED, port);
 }
 EXPORT_SYMBOL_GPL(dcp_dptx_disconnect_oob);
 
@@ -971,6 +1021,8 @@ static int dcp_comp_bind(struct device *dev, struct device *main, void *data)
 		dev_info(dev, "DCP index:%u dptx target phy: %u dptx die: %u\n",
 			 dcp->index, dcp->dptx_phy, dcp->dptx_die);
 	mutex_init(&dcp->hpd_mutex);
+	mutex_init(&dcp->hpd_deferred_mutex);
+	INIT_DELAYED_WORK(&dcp->hpd_wq, dcp_deferred_hpd_work);
 
 	if (!show_notch)
 		ret = of_property_read_u32(dev->of_node, "apple,notch-height",
@@ -1114,6 +1166,7 @@ static void dcp_comp_unbind(struct device *dev, struct device *main, void *data)
 		cancel_work_sync(&dcp->bl_update_wq);
 	}
 	cancel_work_sync(&dcp->vblank_wq);
+	cancel_delayed_work_sync(&dcp->hpd_wq);
 
 	devm_clk_put(dev, dcp->clk);
 	dcp->clk = NULL;