The devfreq monitor depends on the device to provide load information
by .get_dev_status() to calculate the next target freq.

And this will cause changing governor to simple ondemand fail
if device can't support.

Signed-off-by: Dong Aisheng <aisheng.dong@nxp.com>
---
  drivers/devfreq/devfreq.c                 | 10 +++++++---
  drivers/devfreq/governor.h                |  2 +-
  drivers/devfreq/governor_simpleondemand.c |  3 +--
  3 files changed, 9 insertions(+), 6 deletions(-)

diff --git a/drivers/devfreq/devfreq.c b/drivers/devfreq/devfreq.c
index 7231fe6862a2..d1787b6c7d7c 100644
--- a/drivers/devfreq/devfreq.c
+++ b/drivers/devfreq/devfreq.c

@@ -482,10 +482,13 @@ static void devfreq_monitor(struct work_struct *work)
   * to be called from governor in response to DEVFREQ_GOV_START
   * event when device is added to devfreq framework.
   */
-void devfreq_monitor_start(struct devfreq *devfreq)
+int devfreq_monitor_start(struct devfreq *devfreq)
  {
  	if (IS_SUPPORTED_FLAG(devfreq->governor->flags, IRQ_DRIVEN))
-		return;
+		return 0;
+
+	if (!devfreq->profile->get_dev_status)
+		return -EINVAL;
  
  	switch (devfreq->profile->timer) {
  	case DEVFREQ_TIMER_DEFERRABLE:

@@ -495,12 +498,13 @@ void devfreq_monitor_start(struct devfreq *devfreq)
  		INIT_DELAYED_WORK(&devfreq->work, devfreq_monitor);
  		break;
  	default:
-		return;
+		return -EINVAL;
  	}
  
  	if (devfreq->profile->polling_ms)
  		queue_delayed_work(devfreq_wq, &devfreq->work,
  			msecs_to_jiffies(devfreq->profile->polling_ms));
+	return 0;
  }
  EXPORT_SYMBOL(devfreq_monitor_start);
  

diff --git a/drivers/devfreq/governor.h b/drivers/devfreq/governor.h
index 5cee3f64fe2b..31af6d072a10 100644
--- a/drivers/devfreq/governor.h
+++ b/drivers/devfreq/governor.h

@@ -75,7 +75,7 @@ struct devfreq_governor {
  				unsigned int event, void *data);
  };
  
-void devfreq_monitor_start(struct devfreq *devfreq);
+int devfreq_monitor_start(struct devfreq *devfreq);
  void devfreq_monitor_stop(struct devfreq *devfreq);
  void devfreq_monitor_suspend(struct devfreq *devfreq);
  void devfreq_monitor_resume(struct devfreq *devfreq);

diff --git a/drivers/devfreq/governor_simpleondemand.c b/drivers/devfreq/governor_simpleondemand.c
index d57b82a2b570..ea287b57cbf3 100644
--- a/drivers/devfreq/governor_simpleondemand.c
+++ b/drivers/devfreq/governor_simpleondemand.c

@@ -89,8 +89,7 @@ static int devfreq_simple_ondemand_handler(struct devfreq *devfreq,
  {
  	switch (event) {
  	case DEVFREQ_GOV_START:
-		devfreq_monitor_start(devfreq);
-		break;
+		return devfreq_monitor_start(devfreq);
  
  	case DEVFREQ_GOV_STOP:
  		devfreq_monitor_stop(devfreq);