[PATCH] drivers: devfreq: change devfreq workqueue mechanism

[Lukasz Luba]

This patch removes devfreq's custom workqueue and uses system one.
It switches from queue_delayed_work() to schedule_delayed_work().
It also changes deferred work to delayed work, which is now not missed
when timer is put on CPU that entered idle state.
The devfreq framework governor was not called, thus changing the frequency
of the device did not happen.
Benchmarks for stressing Dynamic Memory Controller show x2
performance boost with this patch when 'simpleondemand_governor' is
responsible for monitoring the device load and frequency changes.
With this patch, the scheduled delayed work is done no mater CPUs' idle.
It also does not wake up the system when it enters suspend (this
functionality stays the same).
All of the drivers in devfreq which rely on periodic, guaranteed wakeup
intervals should benefit from it.

Signed-off-by: Lukasz Luba <l.luba@xxxxxxxxxxxxxxxxxxx>
---
 drivers/devfreq/devfreq.c | 27 +++++++--------------------
 1 file changed, 7 insertions(+), 20 deletions(-)

diff --git a/drivers/devfreq/devfreq.c b/drivers/devfreq/devfreq.c
index 0ae3de7..c200b3c 100644
--- a/drivers/devfreq/devfreq.c
+++ b/drivers/devfreq/devfreq.c
@@ -31,13 +31,6 @@
 
 static struct class *devfreq_class;
 
-/*
- * devfreq core provides delayed work based load monitoring helper
- * functions. Governors can use these or can implement their own
- * monitoring mechanism.
- */
-static struct workqueue_struct *devfreq_wq;
-
 /* The list of all device-devfreq governors */
 static LIST_HEAD(devfreq_governor_list);
 /* The list of all device-devfreq */
@@ -391,8 +384,8 @@ static void devfreq_monitor(struct work_struct *work)
 	if (err)
 		dev_err(&devfreq->dev, "dvfs failed with (%d) error\n", err);
 
-	queue_delayed_work(devfreq_wq, &devfreq->work,
-				msecs_to_jiffies(devfreq->profile->polling_ms));
+	schedule_delayed_work(&devfreq->work,
+			      msecs_to_jiffies(devfreq->profile->polling_ms));
 	mutex_unlock(&devfreq->lock);
 }
 
@@ -407,9 +400,9 @@ static void devfreq_monitor(struct work_struct *work)
  */
 void devfreq_monitor_start(struct devfreq *devfreq)
 {
-	INIT_DEFERRABLE_WORK(&devfreq->work, devfreq_monitor);
+	INIT_DELAYED_WORK(&devfreq->work, devfreq_monitor);
 	if (devfreq->profile->polling_ms)
-		queue_delayed_work(devfreq_wq, &devfreq->work,
+		schedule_delayed_work(&devfreq->work,
 			msecs_to_jiffies(devfreq->profile->polling_ms));
 }
 EXPORT_SYMBOL(devfreq_monitor_start);
@@ -473,7 +466,7 @@ void devfreq_monitor_resume(struct devfreq *devfreq)
 
 	if (!delayed_work_pending(&devfreq->work) &&
 			devfreq->profile->polling_ms)
-		queue_delayed_work(devfreq_wq, &devfreq->work,
+		schedule_delayed_work(&devfreq->work,
 			msecs_to_jiffies(devfreq->profile->polling_ms));
 
 	devfreq->last_stat_updated = jiffies;
@@ -516,7 +509,7 @@ void devfreq_interval_update(struct devfreq *devfreq, unsigned int *delay)
 
 	/* if current delay is zero, start polling with new delay */
 	if (!cur_delay) {
-		queue_delayed_work(devfreq_wq, &devfreq->work,
+		schedule_delayed_work(&devfreq->work,
 			msecs_to_jiffies(devfreq->profile->polling_ms));
 		goto out;
 	}
@@ -527,7 +520,7 @@ void devfreq_interval_update(struct devfreq *devfreq, unsigned int *delay)
 		cancel_delayed_work_sync(&devfreq->work);
 		mutex_lock(&devfreq->lock);
 		if (!devfreq->stop_polling)
-			queue_delayed_work(devfreq_wq, &devfreq->work,
+			schedule_delayed_work(&devfreq->work,
 			      msecs_to_jiffies(devfreq->profile->polling_ms));
 	}
 out:
@@ -1430,12 +1423,6 @@ static int __init devfreq_init(void)
 		return PTR_ERR(devfreq_class);
 	}
 
-	devfreq_wq = create_freezable_workqueue("devfreq_wq");
-	if (!devfreq_wq) {
-		class_destroy(devfreq_class);
-		pr_err("%s: couldn't create workqueue\n", __FILE__);
-		return -ENOMEM;
-	}
 	devfreq_class->dev_groups = devfreq_groups;
 
 	return 0;
-- 
2.7.4