Revert "drm/probe-helpers: Drop locking from poll_enable"

This reverts commit 3846fd9b.

There were some precursor commits missing for this around connector
locking, we should probably merge Lyude's nouveau avoid the problem patch.

drivers/gpu/drm/drm_probe_helper.c

@@ -115,27 +115,24 @@ static int drm_helper_probe_add_cmdline_mode(struct drm_connector *connector)
 
 #define DRM_OUTPUT_POLL_PERIOD (10*HZ)
 /**
- * drm_kms_helper_poll_enable - re-enable output polling.
+ * drm_kms_helper_poll_enable_locked - re-enable output polling.
  * @dev: drm_device
  *
- * This function re-enables the output polling work, after it has been
- * temporarily disabled using drm_kms_helper_poll_disable(), for example over
- * suspend/resume.
+ * This function re-enables the output polling work without
+ * locking the mode_config mutex.
  *
- * Drivers can call this helper from their device resume implementation. It is
- * an error to call this when the output polling support has not yet been set
- * up.
- *
- * Note that calls to enable and disable polling must be strictly ordered, which
- * is automatically the case when they're only call from suspend/resume
- * callbacks.
+ * This is like drm_kms_helper_poll_enable() however it is to be
+ * called from a context where the mode_config mutex is locked
+ * already.
  */
-void drm_kms_helper_poll_enable(struct drm_device *dev)
+void drm_kms_helper_poll_enable_locked(struct drm_device *dev)
 {
 	bool poll = false;
 	struct drm_connector *connector;
 	unsigned long delay = DRM_OUTPUT_POLL_PERIOD;
 
+	WARN_ON(!mutex_is_locked(&dev->mode_config.mutex));
+
 	if (!dev->mode_config.poll_enabled || !drm_kms_helper_poll)
 		return;
 
@@ -163,7 +160,7 @@ void drm_kms_helper_poll_enable(struct drm_device *dev)
 	if (poll)
 		schedule_delayed_work(&dev->mode_config.output_poll_work, delay);
 }
-EXPORT_SYMBOL(drm_kms_helper_poll_enable);
+EXPORT_SYMBOL(drm_kms_helper_poll_enable_locked);
 
 static enum drm_connector_status
 drm_connector_detect(struct drm_connector *connector, bool force)
@@ -290,7 +287,7 @@ int drm_helper_probe_single_connector_modes(struct drm_connector *connector,
 
 	/* Re-enable polling in case the global poll config changed. */
 	if (drm_kms_helper_poll != dev->mode_config.poll_running)
-		drm_kms_helper_poll_enable(dev);
+		drm_kms_helper_poll_enable_locked(dev);
 
 	dev->mode_config.poll_running = drm_kms_helper_poll;
 
@@ -482,12 +479,8 @@ static void output_poll_execute(struct work_struct *work)
  * This function disables the output polling work.
  *
  * Drivers can call this helper from their device suspend implementation. It is
- * not an error to call this even when output polling isn't enabled or already
- * disabled. Polling is re-enabled by calling drm_kms_helper_poll_enable().
- *
- * Note that calls to enable and disable polling must be strictly ordered, which
- * is automatically the case when they're only call from suspend/resume
- * callbacks.
+ * not an error to call this even when output polling isn't enabled or arlready
+ * disabled.
  */
 void drm_kms_helper_poll_disable(struct drm_device *dev)
 {
@@ -497,6 +490,24 @@ void drm_kms_helper_poll_disable(struct drm_device *dev)
 }
 EXPORT_SYMBOL(drm_kms_helper_poll_disable);
 
+/**
+ * drm_kms_helper_poll_enable - re-enable output polling.
+ * @dev: drm_device
+ *
+ * This function re-enables the output polling work.
+ *
+ * Drivers can call this helper from their device resume implementation. It is
+ * an error to call this when the output polling support has not yet been set
+ * up.
+ */
+void drm_kms_helper_poll_enable(struct drm_device *dev)
+{
+	mutex_lock(&dev->mode_config.mutex);
+	drm_kms_helper_poll_enable_locked(dev);
+	mutex_unlock(&dev->mode_config.mutex);
+}
+EXPORT_SYMBOL(drm_kms_helper_poll_enable);
+
 /**
  * drm_kms_helper_poll_init - initialize and enable output polling
  * @dev: drm_device

drivers/gpu/drm/i915/intel_hotplug.c

@@ -180,7 +180,7 @@ static void intel_hpd_irq_storm_disable(struct drm_i915_private *dev_priv)
 
 	/* Enable polling and queue hotplug re-enabling. */
 	if (hpd_disabled) {
-		drm_kms_helper_poll_enable(dev);
+		drm_kms_helper_poll_enable_locked(dev);
 		mod_delayed_work(system_wq, &dev_priv->hotplug.reenable_work,
 				 msecs_to_jiffies(HPD_STORM_REENABLE_DELAY));
 	}
@@ -511,7 +511,7 @@ static void i915_hpd_poll_init_work(struct work_struct *work)
 	}
 
 	if (enabled)
-		drm_kms_helper_poll_enable(dev);
+		drm_kms_helper_poll_enable_locked(dev);
 
 	mutex_unlock(&dev->mode_config.mutex);
 

include/drm/drm_crtc_helper.h

@@ -73,5 +73,6 @@ extern void drm_kms_helper_hotplug_event(struct drm_device *dev);
 
 extern void drm_kms_helper_poll_disable(struct drm_device *dev);
 extern void drm_kms_helper_poll_enable(struct drm_device *dev);
+extern void drm_kms_helper_poll_enable_locked(struct drm_device *dev);
 
 #endif