[Intel-gfx] [PATCH] drm/probe-helpers: Drop locking from poll_enable

[Daniel Vetter]

It was only needed to protect the connector_list walking, see

commit 8c4ccc4ab6f64e859d4ff8d7c02c2ed2e956e07f
Author: Daniel Vetter <daniel.vetter at ffwll.ch>
Date:   Thu Jul 9 23:44:26 2015 +0200

    drm/probe-helper: Grab mode_config.mutex in poll_init/enable

Unfortunately the commit message of that patch fails to mention that
the new locking check was for the connector_list.

But that requirement disappeared in

commit c36a3254f7857f1ad9badbe3578ccc92be541a8e
Author: Daniel Vetter <daniel.vetter at ffwll.ch>
Date:   Thu Dec 15 16:58:43 2016 +0100

    drm: Convert all helpers to drm_connector_list_iter

and so we can drop this again.

This fixes a locking inversion on nouveau, where the rpm code needs to
re-enable. But in other places the rpm_get() calls are nested within
the big modeset locks.

While at it, also improve the kerneldoc for these two functions a
notch.

Cc: Dave Airlie <airlied at gmail.com>
Signed-off-by: Daniel Vetter <daniel.vetter at intel.com>
---
 drivers/gpu/drm/drm_probe_helper.c   | 41 ++++++++++--------------------------
 drivers/gpu/drm/i915/intel_hotplug.c |  4 ++--
 include/drm/drm_crtc_helper.h        |  1 -
 3 files changed, 13 insertions(+), 33 deletions(-)

diff --git a/drivers/gpu/drm/drm_probe_helper.c b/drivers/gpu/drm/drm_probe_helper.c
index 060211ac74a1..7c70f2a52250 100644
--- a/drivers/gpu/drm/drm_probe_helper.c
+++ b/drivers/gpu/drm/drm_probe_helper.c
@@ -115,25 +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_locked - re-enable output polling.
+ * drm_kms_helper_poll_enable - re-enable output polling.
  * @dev: drm_device
  *
- * This function re-enables the output polling work without
- * locking the mode_config mutex.
+ * 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 is like drm_kms_helper_poll_enable() however it is to be
- * called from a context where the mode_config mutex is locked
- * already.
+ * 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_locked(struct drm_device *dev)
+void drm_kms_helper_poll_enable(struct drm_device *dev)
 {
 	bool poll = false;
 	struct drm_connector *connector;
 	struct drm_connector_list_iter conn_iter;
 	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;
 
@@ -153,7 +152,7 @@ void drm_kms_helper_poll_enable_locked(struct drm_device *dev)
 	if (poll)
 		schedule_delayed_work(&dev->mode_config.output_poll_work, delay);
 }
-EXPORT_SYMBOL(drm_kms_helper_poll_enable_locked);
+EXPORT_SYMBOL(drm_kms_helper_poll_enable);
 
 static enum drm_connector_status
 drm_connector_detect(struct drm_connector *connector, bool force)
@@ -280,7 +279,7 @@ 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_locked(dev);
+		drm_kms_helper_poll_enable(dev);
 
 	dev->mode_config.poll_running = drm_kms_helper_poll;
 
@@ -475,7 +474,7 @@ static void output_poll_execute(struct work_struct *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 arlready
- * disabled.
+ * disabled. Polling is re-enabled by calling drm_kms_helper_poll_enable().
  */
 void drm_kms_helper_poll_disable(struct drm_device *dev)
 {
@@ -486,24 +485,6 @@ 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
  *
diff --git a/drivers/gpu/drm/i915/intel_hotplug.c b/drivers/gpu/drm/i915/intel_hotplug.c
index 2ddc9e5842ec..5122d4bfb70e 100644
--- a/drivers/gpu/drm/i915/intel_hotplug.c
+++ b/drivers/gpu/drm/i915/intel_hotplug.c
@@ -182,7 +182,7 @@ 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_locked(dev);
+		drm_kms_helper_poll_enable(dev);
 		mod_delayed_work(system_wq, &dev_priv->hotplug.reenable_work,
 				 msecs_to_jiffies(HPD_STORM_REENABLE_DELAY));
 	}
@@ -519,7 +519,7 @@ static void i915_hpd_poll_init_work(struct work_struct *work)
 	drm_connector_list_iter_put(&conn_iter);
 
 	if (enabled)
-		drm_kms_helper_poll_enable_locked(dev);
+		drm_kms_helper_poll_enable(dev);
 
 	mutex_unlock(&dev->mode_config.mutex);
 
diff --git a/include/drm/drm_crtc_helper.h b/include/drm/drm_crtc_helper.h
index 982c299e435a..d026f5017c33 100644
--- a/include/drm/drm_crtc_helper.h
+++ b/include/drm/drm_crtc_helper.h
@@ -73,6 +73,5 @@ 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
-- 
2.11.0