drm/bridge: ti-tfp410: Fall back to HPD polling if HPD irq is not available

In case either the HPD gpio is not specified or when the HPD gpio can not
be used as interrupt we should tell the core that the HPD needs to be
polled for detecting hotplug.
Signed-off-by: Peter Ujfalusi <peter.ujfalusi@ti.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Andrzej Hajda <a.hajda@samsung.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190401123342.15767-1-peter.ujfalusi@ti.com

drivers/gpu/drm/bridge/ti-tfp410.c

@@ -31,6 +31,7 @@ struct tfp410 {
 
 	struct i2c_adapter	*ddc;
 	struct gpio_desc	*hpd;
+	int			hpd_irq;
 	struct delayed_work	hpd_work;
 	struct gpio_desc	*powerdown;
 
@@ -124,8 +125,10 @@ static int tfp410_attach(struct drm_bridge *bridge)
 		return -ENODEV;
 	}
 
-	if (dvi->hpd)
+	if (dvi->hpd_irq >= 0)
 		dvi->connector.polled = DRM_CONNECTOR_POLL_HPD;
+	else
+		dvi->connector.polled = DRM_CONNECTOR_POLL_CONNECT | DRM_CONNECTOR_POLL_DISCONNECT;
 
 	drm_connector_helper_add(&dvi->connector,
 				 &tfp410_con_helper_funcs);
@@ -324,10 +327,15 @@ static int tfp410_init(struct device *dev, bool i2c)
 		return PTR_ERR(dvi->powerdown);
 	}
 
-	if (dvi->hpd) {
+	if (dvi->hpd)
+		dvi->hpd_irq = gpiod_to_irq(dvi->hpd);
+	else
+		dvi->hpd_irq = -ENXIO;
+
+	if (dvi->hpd_irq >= 0) {
 		INIT_DELAYED_WORK(&dvi->hpd_work, tfp410_hpd_work_func);
 
-		ret = devm_request_threaded_irq(dev, gpiod_to_irq(dvi->hpd),
+		ret = devm_request_threaded_irq(dev, dvi->hpd_irq,
 			NULL, tfp410_hpd_irq_thread, IRQF_TRIGGER_RISING |
 			IRQF_TRIGGER_FALLING | IRQF_ONESHOT,
 			"hdmi-hpd", dvi);