drm/probe-helper: enable and disable HPD on connectors

Introduce two drm_connector_helper_funcs: enable_hpd() and disable_hpd().
They are called by drm_kms_helper_poll_enable() and
drm_kms_helper_poll_disable() (and thus drm_kms_helper_poll_init() and
drm_kms_helper_poll_fini()) respectively.

This allows DRM drivers to rely on drm_kms_helper_poll for enabling and
disabling HPD detection rather than doing that manually.
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Reviewed-by: Tomi Valkeinen <tomi.valkeinen@ideasonboard.com>
Signed-off-by: Neil Armstrong <neil.armstrong@linaro.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20221102180705.459294-3-dmitry.baryshkov@linaro.org

drivers/gpu/drm/drm_probe_helper.c

@@ -250,6 +250,12 @@ void drm_kms_helper_poll_enable(struct drm_device *dev)
 
 	drm_connector_list_iter_begin(dev, &conn_iter);
 	drm_for_each_connector_iter(connector, &conn_iter) {
+		const struct drm_connector_helper_funcs *funcs =
+			connector->helper_private;
+
+		if (funcs && funcs->enable_hpd)
+			funcs->enable_hpd(connector);
+
 		if (connector->polled & (DRM_CONNECTOR_POLL_CONNECT |
 					 DRM_CONNECTOR_POLL_DISCONNECT))
 			poll = true;
@@ -804,12 +810,25 @@ EXPORT_SYMBOL(drm_kms_helper_is_poll_worker);
 
 static void drm_kms_helper_poll_disable_fini(struct drm_device *dev, bool fini)
 {
+	struct drm_connector *connector;
+	struct drm_connector_list_iter conn_iter;
+
 	if (!dev->mode_config.poll_enabled)
 		return;
 
 	if (fini)
 		dev->mode_config.poll_enabled = false;
 
+	drm_connector_list_iter_begin(dev, &conn_iter);
+	drm_for_each_connector_iter(connector, &conn_iter) {
+		const struct drm_connector_helper_funcs *funcs =
+			connector->helper_private;
+
+		if (funcs && funcs->disable_hpd)
+			funcs->disable_hpd(connector);
+	}
+	drm_connector_list_iter_end(&conn_iter);
+
 	cancel_delayed_work_sync(&dev->mode_config.output_poll_work);
 }
 

include/drm/drm_modeset_helper_vtables.h

@@ -1143,6 +1143,28 @@ struct drm_connector_helper_funcs {
 	 */
 	void (*cleanup_writeback_job)(struct drm_writeback_connector *connector,
 				      struct drm_writeback_job *job);
+
+	/**
+	 * @enable_hpd:
+	 *
+	 * Enable hot-plug detection for the connector.
+	 *
+	 * This operation is optional.
+	 *
+	 * This callback is used by the drm_kms_helper_poll_enable() helpers.
+	 */
+	void (*enable_hpd)(struct drm_connector *connector);
+
+	/**
+	 * @disable_hpd:
+	 *
+	 * Disable hot-plug detection for the connector.
+	 *
+	 * This operation is optional.
+	 *
+	 * This callback is used by the drm_kms_helper_poll_disable() helpers.
+	 */
+	void (*disable_hpd)(struct drm_connector *connector);
 };
 
 /**