[PATCH 4/4] PM / devfreq: Handle monitor start/stop in the devfreq core

[Matthias Kaehlcke]

devfreq expects governors to call devfreq_monitor_start/stop()
in response to DEVFREQ_GOV_START/STOP events. Since the devfreq
core itself generates these events and invokes the governor's event
handler the start/stop of the load monitor can be done in the common
code.

Call devfreq_monitor_start/stop() when the governor reports a
successful handling of DEVFREQ_GOV_START/STOP and remove these
calls from the simpleondemand and tegra governors. Make
devfreq_monitor_start/stop() static since these functions are now
only used by the devfreq core. For better integration with the
callers the functions must now be called with devfreq->lock held.

Also stop manipulating the monitor workqueue directly, use
devfreq_monitor_start/stop() instead.

Signed-off-by: Matthias Kaehlcke <mka@xxxxxxxxxxxx>
---
 drivers/devfreq/devfreq.c                 | 45 +++++++++++------------
 drivers/devfreq/governor.h                |  2 -
 drivers/devfreq/governor_simpleondemand.c |  8 ----
 drivers/devfreq/tegra-devfreq.c           |  2 -
 4 files changed, 22 insertions(+), 35 deletions(-)

diff --git a/drivers/devfreq/devfreq.c b/drivers/devfreq/devfreq.c
index eb86461648d74..ac553c00f6790 100644
--- a/drivers/devfreq/devfreq.c
+++ b/drivers/devfreq/devfreq.c
@@ -404,14 +404,14 @@ static void devfreq_monitor(struct work_struct *work)
  * devfreq_monitor_start() - Start load monitoring of devfreq instance
  * @devfreq:	the devfreq instance.
  *
- * Helper function for starting devfreq device load monitoing. By
- * default delayed work based monitoring is supported. Function
- * to be called from governor in response to DEVFREQ_GOV_START
- * event when device is added to devfreq framework.
+ * Helper function for starting devfreq device load monitoring. By
+ * default delayed work based monitoring is supported. Must be called
+ * with devfreq->lock held.
  */
-void devfreq_monitor_start(struct devfreq *devfreq)
+static void devfreq_monitor_start(struct devfreq *devfreq)
 {
-	mutex_lock(&devfreq->lock);
+	WARN(!mutex_is_locked(&devfreq->lock),
+	     "devfreq->lock must be held by the caller.\n");
 
 	if (devfreq->profile->polling_ms) {
 		INIT_DEFERRABLE_WORK(&devfreq->work, devfreq_monitor);
@@ -420,28 +420,28 @@ void devfreq_monitor_start(struct devfreq *devfreq)
 
 		devfreq->monitor_state = DEVFREQ_MONITOR_RUNNING;
 	}
-
-	mutex_unlock(&devfreq->lock);
 }
-EXPORT_SYMBOL(devfreq_monitor_start);
 
 /**
  * devfreq_monitor_stop() - Stop load monitoring of a devfreq instance
  * @devfreq:	the devfreq instance.
  *
- * Helper function to stop devfreq device load monitoing. Function
- * to be called from governor in response to DEVFREQ_GOV_STOP
- * event when device is removed from devfreq framework.
+ * Helper function to stop devfreq device load monitoring. Must be
+ * called with devfreq->lock held.
  */
-void devfreq_monitor_stop(struct devfreq *devfreq)
+static void devfreq_monitor_stop(struct devfreq *devfreq)
 {
+	/* mutex must be held for symmetry with _start() */
+	WARN(!mutex_is_locked(&devfreq->lock),
+	     "devfreq->lock must be held by the caller.\n");
+
+	mutex_unlock(&devfreq->lock);
 	cancel_delayed_work_sync(&devfreq->work);
 
 	mutex_lock(&devfreq->lock);
 	devfreq->monitor_state = DEVFREQ_MONITOR_STOPPED;
 	mutex_unlock(&devfreq->lock);
 }
-EXPORT_SYMBOL(devfreq_monitor_stop);
 
 /**
  * devfreq_monitor_suspend() - Suspend load monitoring of a devfreq instance
@@ -518,27 +518,22 @@ void devfreq_interval_update(struct devfreq *devfreq, unsigned int *delay)
 
 	/* if new delay is zero, stop polling */
 	if (!new_delay) {
+		devfreq_monitor_stop(devfreq);
 		mutex_unlock(&devfreq->lock);
-		cancel_delayed_work_sync(&devfreq->work);
-		devfreq->monitor_state == DEVFREQ_MONITOR_STOPPED;
 		return;
 	}
 
 	/* if current delay is zero, start polling with new delay */
 	if (!cur_delay) {
-		queue_delayed_work(devfreq_wq, &devfreq->work,
-			msecs_to_jiffies(devfreq->profile->polling_ms));
+		devfreq_monitor_start(devfreq);
 		goto out;
 	}
 
 	/* if current delay is greater than new delay, restart polling */
 	if (cur_delay > new_delay) {
-		mutex_unlock(&devfreq->lock);
-		cancel_delayed_work_sync(&devfreq->work);
-		mutex_lock(&devfreq->lock);
+		devfreq_monitor_stop(devfreq);
 		if (devfreq->monitor_state != DEVFREQ_MONITOR_SUSPENDED)
-			queue_delayed_work(devfreq_wq, &devfreq->work,
-			      msecs_to_jiffies(devfreq->profile->polling_ms));
+			devfreq_monitor_start(devfreq);
 	}
 out:
 	mutex_unlock(&devfreq->lock);
@@ -601,6 +596,8 @@ static int devfreq_governor_start(struct devfreq *devfreq)
 		return err;
 	}
 
+	devfreq_monitor_start(devfreq);
+
 	return 0;
 }
 
@@ -624,6 +621,8 @@ static int devfreq_governor_stop(struct devfreq *devfreq)
 		return err;
 	}
 
+	devfreq_monitor_stop(devfreq);
+
 	return 0;
 }
 
diff --git a/drivers/devfreq/governor.h b/drivers/devfreq/governor.h
index d136792c0cc91..47efe747b6f79 100644
--- a/drivers/devfreq/governor.h
+++ b/drivers/devfreq/governor.h
@@ -57,8 +57,6 @@ struct devfreq_governor {
 				unsigned int event, void *data);
 };
 
-extern void devfreq_monitor_start(struct devfreq *devfreq);
-extern void devfreq_monitor_stop(struct devfreq *devfreq);
 extern void devfreq_interval_update(struct devfreq *devfreq,
 					unsigned int *delay);
 
diff --git a/drivers/devfreq/governor_simpleondemand.c b/drivers/devfreq/governor_simpleondemand.c
index 52eb0c734b312..e0f0944a9c7aa 100644
--- a/drivers/devfreq/governor_simpleondemand.c
+++ b/drivers/devfreq/governor_simpleondemand.c
@@ -91,14 +91,6 @@ static int devfreq_simple_ondemand_handler(struct devfreq *devfreq,
 				unsigned int event, void *data)
 {
 	switch (event) {
-	case DEVFREQ_GOV_START:
-		devfreq_monitor_start(devfreq);
-		break;
-
-	case DEVFREQ_GOV_STOP:
-		devfreq_monitor_stop(devfreq);
-		break;
-
 	case DEVFREQ_GOV_INTERVAL:
 		devfreq_interval_update(devfreq, (unsigned int *)data);
 		break;
diff --git a/drivers/devfreq/tegra-devfreq.c b/drivers/devfreq/tegra-devfreq.c
index 79efa1e51bd06..515fb852dbad6 100644
--- a/drivers/devfreq/tegra-devfreq.c
+++ b/drivers/devfreq/tegra-devfreq.c
@@ -580,13 +580,11 @@ static int tegra_governor_event_handler(struct devfreq *devfreq,
 
 	switch (event) {
 	case DEVFREQ_GOV_START:
-		devfreq_monitor_start(devfreq);
 		tegra_actmon_enable_interrupts(tegra);
 		break;
 
 	case DEVFREQ_GOV_STOP:
 		tegra_actmon_disable_interrupts(tegra);
-		devfreq_monitor_stop(devfreq);
 		break;
 
 	case DEVFREQ_GOV_SUSPEND:
-- 
2.20.1.791.gb4d0f1c61a-goog