drm/vc4: hdmi: Rely on interrupts to handle hotplug

DRM currently polls for the HDMI connector status every 10s, which can
be an issue when we connect/disconnect a display quickly or the device
on the other end only issues a hotplug pulse (for example on EDID
change).

Switch the driver to rely on the internal controller logic for the
BCM2711/RPi4.
Signed-off-by: Maxime Ripard <maxime@cerno.tech>
Reviewed-by: Dave Stevenson <dave.stevenson@raspberrypi.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20210524132018.264396-1-maxime@cerno.tech

drivers/gpu/drm/vc4/vc4_hdmi.c

@@ -1621,6 +1621,47 @@ static int vc4_hdmi_audio_init(struct vc4_hdmi *vc4_hdmi)
 
 }
 
+static irqreturn_t vc4_hdmi_hpd_irq_thread(int irq, void *priv)
+{
+	struct vc4_hdmi *vc4_hdmi = priv;
+	struct drm_device *dev = vc4_hdmi->connector.dev;
+
+	if (dev)
+		drm_kms_helper_hotplug_event(dev);
+
+	return IRQ_HANDLED;
+}
+
+static int vc4_hdmi_hotplug_init(struct vc4_hdmi *vc4_hdmi)
+{
+	struct drm_connector *connector = &vc4_hdmi->connector;
+	struct platform_device *pdev = vc4_hdmi->pdev;
+	struct device *dev = &pdev->dev;
+	int ret;
+
+	if (vc4_hdmi->variant->external_irq_controller) {
+		ret = devm_request_threaded_irq(dev,
+						platform_get_irq_byname(pdev, "hpd-connected"),
+						NULL,
+						vc4_hdmi_hpd_irq_thread, IRQF_ONESHOT,
+						"vc4 hdmi hpd connected", vc4_hdmi);
+		if (ret)
+			return ret;
+
+		ret = devm_request_threaded_irq(dev,
+						platform_get_irq_byname(pdev, "hpd-removed"),
+						NULL,
+						vc4_hdmi_hpd_irq_thread, IRQF_ONESHOT,
+						"vc4 hdmi hpd disconnected", vc4_hdmi);
+		if (ret)
+			return ret;
+
+		connector->polled = DRM_CONNECTOR_POLL_HPD;
+	}
+
+	return 0;
+}
+
 #ifdef CONFIG_DRM_VC4_HDMI_CEC
 static irqreturn_t vc4_cec_irq_handler_rx_thread(int irq, void *priv)
 {
@@ -2179,6 +2220,10 @@ static int vc4_hdmi_bind(struct device *dev, struct device *master, void *data)
 	if (ret)
 		goto err_destroy_encoder;
 
+	ret = vc4_hdmi_hotplug_init(vc4_hdmi);
+	if (ret)
+		goto err_destroy_conn;
+
 	ret = vc4_hdmi_cec_init(vc4_hdmi);
 	if (ret)
 		goto err_destroy_conn;