[PATCH] PM / devfreq: Add missing function description and rename static functions

[PATCH] PM / devfreq: Add missing function description and rename static functions

[Chanwoo Choi]

Rename internal function name used by devfreq core without 'devfreq_'
prefix in order to separate them from the exported functions.
And add missing function description for improving the readability.

Lastly, add the comments of devfreq_add_device to increase
the understanding of behavior of devfreq_add_device.

Signed-off-by: Chanwoo Choi <cw00.choi@samsung.com>
---
 drivers/devfreq/devfreq.c | 81 +++++++++++++++++++++++++++++++--------
 1 file changed, 64 insertions(+), 17 deletions(-)

diff --git a/drivers/devfreq/devfreq.c b/drivers/devfreq/devfreq.c
index acd21345a070..254f11b31824 100644
--- a/drivers/devfreq/devfreq.c
+++ b/drivers/devfreq/devfreq.c
@@ -48,7 +48,7 @@ static LIST_HEAD(devfreq_list);
 static DEFINE_MUTEX(devfreq_list_lock);
 
 /**
- * find_device_devfreq() - find devfreq struct using device pointer
+ * find_device_devfreq() - Find devfreq struct using device pointer
  * @dev:	device pointer used to lookup device devfreq.
  *
  * Search the list of device devfreqs and return the matched device's
@@ -73,6 +73,13 @@ static struct devfreq *find_device_devfreq(struct device *dev)
 	return ERR_PTR(-ENODEV);
 }
 
+/**
+ * find_available_min_freq() - Find available min frequency via OPP interface
+ * @devfreq:	the devfreq instance
+ *
+ * Find available minimum frequency among the active OPP entries
+ * because could either enable or disable the frequency by using OPP interface.
+ */
 static unsigned long find_available_min_freq(struct devfreq *devfreq)
 {
 	struct dev_pm_opp *opp;
@@ -87,6 +94,13 @@ static unsigned long find_available_min_freq(struct devfreq *devfreq)
 	return min_freq;
 }
 
+/**
+ * find_available_max_freq() - Find available max frequency via OPP interface
+ * @devfreq:	the devfreq instance
+ *
+ * Find available maximum frequency among the active OPP entries
+ * because could either enable or disable the frequency by using OPP interface.
+ */
 static unsigned long find_available_max_freq(struct devfreq *devfreq)
 {
 	struct dev_pm_opp *opp;
@@ -150,11 +164,11 @@ static void get_freq_range(struct devfreq *devfreq,
 }
 
 /**
- * devfreq_get_freq_level() - Lookup freq_table for the frequency
+ * get_freq_level() - Lookup freq_table for the frequency
  * @devfreq:	the devfreq instance
  * @freq:	the target frequency
  */
-static int devfreq_get_freq_level(struct devfreq *devfreq, unsigned long freq)
+static int get_freq_level(struct devfreq *devfreq, unsigned long freq)
 {
 	int lev;
 
@@ -165,6 +179,13 @@ static int devfreq_get_freq_level(struct devfreq *devfreq, unsigned long freq)
 	return -EINVAL;
 }
 
+/**
+ * set_freq_table() - Fill out the freq_table of devfreq instance
+ * @devfreq:	the devfreq instance
+ *
+ * If freq_table array is NULL, fill out the freq_table array
+ * by using OPP interface because OPP is mandatory.
+ */
 static int set_freq_table(struct devfreq *devfreq)
 {
 	struct devfreq_dev_profile *profile = devfreq->profile;
@@ -218,7 +239,7 @@ int devfreq_update_status(struct devfreq *devfreq, unsigned long freq)
 	if (!devfreq->previous_freq)
 		goto out;
 
-	prev_lev = devfreq_get_freq_level(devfreq, devfreq->previous_freq);
+	prev_lev = get_freq_level(devfreq, devfreq->previous_freq);
 	if (prev_lev < 0) {
 		ret = prev_lev;
 		goto out;
@@ -227,7 +248,7 @@ int devfreq_update_status(struct devfreq *devfreq, unsigned long freq)
 	devfreq->stats.time_in_state[prev_lev] +=
 			cur_time - devfreq->stats.last_update;
 
-	lev = devfreq_get_freq_level(devfreq, freq);
+	lev = get_freq_level(devfreq, freq);
 	if (lev < 0) {
 		ret = lev;
 		goto out;
@@ -246,7 +267,7 @@ int devfreq_update_status(struct devfreq *devfreq, unsigned long freq)
 EXPORT_SYMBOL(devfreq_update_status);
 
 /**
- * find_devfreq_governor() - find devfreq governor from name
+ * find_devfreq_governor() - Find devfreq governor from name
  * @name:	name of the governor
  *
  * Search the list of devfreq governors and return the matched
@@ -314,8 +335,17 @@ static struct devfreq_governor *try_then_request_governor(const char *name)
 	return governor;
 }
 
-static int devfreq_notify_transition(struct devfreq *devfreq,
-		struct devfreq_freqs *freqs, unsigned int state)
+/**
+ * notify_transition() - Send the transition notification
+ * @name:	name of the governor
+ * @freqs:	the data containing the both old and new frequency
+ * @state:	the kind of notification
+ *
+ * Send the transition notification to the registered receivers
+ * in order to inform the frequency change.
+ */
+static int notify_transition(struct devfreq *devfreq,
+			struct devfreq_freqs *freqs, unsigned int state)
 {
 	if (!devfreq)
 		return -EINVAL;
@@ -337,8 +367,17 @@ static int devfreq_notify_transition(struct devfreq *devfreq,
 	return 0;
 }
 
-static int devfreq_set_target(struct devfreq *devfreq, unsigned long new_freq,
-			      u32 flags)
+/**
+ * set_target() - Set target frequency of devfreq instance
+ * @devfreq:	the devfreq instance
+ * @new_freq:	the target frequency
+ * @flags:	flags handed from devfreq framework
+ *
+ * Set the target frequency of which is decided by governor
+ * and then is adjusted with constraints.
+ */
+static int set_target(struct devfreq *devfreq,
+			unsigned long new_freq, u32 flags)
 {
 	struct devfreq_freqs freqs;
 	unsigned long cur_freq;
@@ -351,17 +390,17 @@ static int devfreq_set_target(struct devfreq *devfreq, unsigned long new_freq,
 
 	freqs.old = cur_freq;
 	freqs.new = new_freq;
-	devfreq_notify_transition(devfreq, &freqs, DEVFREQ_PRECHANGE);
+	notify_transition(devfreq, &freqs, DEVFREQ_PRECHANGE);
 
 	err = devfreq->profile->target(devfreq->dev.parent, &new_freq, flags);
 	if (err) {
 		freqs.new = cur_freq;
-		devfreq_notify_transition(devfreq, &freqs, DEVFREQ_POSTCHANGE);
+		notify_transition(devfreq, &freqs, DEVFREQ_POSTCHANGE);
 		return err;
 	}
 
 	freqs.new = new_freq;
-	devfreq_notify_transition(devfreq, &freqs, DEVFREQ_POSTCHANGE);
+	notify_transition(devfreq, &freqs, DEVFREQ_POSTCHANGE);
 
 	if (devfreq_update_status(devfreq, new_freq))
 		dev_err(&devfreq->dev,
@@ -413,7 +452,7 @@ int update_devfreq(struct devfreq *devfreq)
 		flags |= DEVFREQ_FLAG_LEAST_UPPER_BOUND; /* Use LUB */
 	}
 
-	return devfreq_set_target(devfreq, freq, flags);
+	return set_target(devfreq, freq, flags);
 
 }
 EXPORT_SYMBOL(update_devfreq);
@@ -421,7 +460,6 @@ EXPORT_SYMBOL(update_devfreq);
 /**
  * devfreq_monitor() - Periodically poll devfreq objects.
  * @work:	the work struct used to run devfreq_monitor periodically.
- *
  */
 static void devfreq_monitor(struct work_struct *work)
 {
@@ -739,11 +777,13 @@ struct devfreq *devfreq_add_device(struct device *dev,
 	static atomic_t devfreq_no = ATOMIC_INIT(-1);
 	int err = 0;
 
+	/* Check the parameter is valid */
 	if (!dev || !profile || !governor_name) {
 		dev_err(dev, "%s: Invalid parameters.\n", __func__);
 		return ERR_PTR(-EINVAL);
 	}
 
+	/* Check the device is already added or not */
 	mutex_lock(&devfreq_list_lock);
 	devfreq = find_device_devfreq(dev);
 	mutex_unlock(&devfreq_list_lock);
@@ -754,6 +794,7 @@ struct devfreq *devfreq_add_device(struct device *dev,
 		goto err_out;
 	}
 
+	/* Initialize the devfreq instance */
 	devfreq = kzalloc(sizeof(struct devfreq), GFP_KERNEL);
 	if (!devfreq) {
 		err = -ENOMEM;
@@ -798,6 +839,7 @@ struct devfreq *devfreq_add_device(struct device *dev,
 	devfreq->suspend_freq = dev_pm_opp_get_suspend_opp_freq(dev);
 	atomic_set(&devfreq->suspend_count, 0);
 
+	/* Register a device for devfreq instance */
 	dev_set_name(&devfreq->dev, "devfreq%d",
 				atomic_inc_return(&devfreq_no));
 	err = device_register(&devfreq->dev);
@@ -807,6 +849,7 @@ struct devfreq *devfreq_add_device(struct device *dev,
 		goto err_out;
 	}
 
+	/* Initialize the statistics of devfreq device behavior */
 	devfreq->stats.trans_table = devm_kzalloc(&devfreq->dev,
 			array3_size(sizeof(unsigned int),
 				    devfreq->profile->max_state,
@@ -831,10 +874,12 @@ struct devfreq *devfreq_add_device(struct device *dev,
 	devfreq->stats.total_trans = 0;
 	devfreq->stats.last_update = get_jiffies_64();
 
+	/* Initialize notifiers for informing the transition of devfreq */
 	srcu_init_notifier_head(&devfreq->transition_notifier_list);
 
 	mutex_unlock(&devfreq->lock);
 
+	/* Initialize PM QoS for applying the constraints */
 	err = dev_pm_qos_add_request(dev, &devfreq->user_min_freq_req,
 				     DEV_PM_QOS_MIN_FREQUENCY, 0);
 	if (err < 0)
@@ -859,6 +904,7 @@ struct devfreq *devfreq_add_device(struct device *dev,
 
 	mutex_lock(&devfreq_list_lock);
 
+	/* Find the devfreq governor and start */
 	governor = try_then_request_governor(devfreq->governor_name);
 	if (IS_ERR(governor)) {
 		dev_err(dev, "%s: Unable to find governor for the device\n",
@@ -876,6 +922,7 @@ struct devfreq *devfreq_add_device(struct device *dev,
 		goto err_init;
 	}
 
+	/* Add the devfreq instance to global devfreq list finally */
 	list_add(&devfreq->node, &devfreq_list);
 
 	mutex_unlock(&devfreq_list_lock);
@@ -1076,7 +1123,7 @@ int devfreq_suspend_device(struct devfreq *devfreq)
 
 	if (devfreq->suspend_freq) {
 		mutex_lock(&devfreq->lock);
-		ret = devfreq_set_target(devfreq, devfreq->suspend_freq, 0);
+		ret = set_target(devfreq, devfreq->suspend_freq, 0);
 		mutex_unlock(&devfreq->lock);
 		if (ret)
 			return ret;
@@ -1106,7 +1153,7 @@ int devfreq_resume_device(struct devfreq *devfreq)
 
 	if (devfreq->resume_freq) {
 		mutex_lock(&devfreq->lock);
-		ret = devfreq_set_target(devfreq, devfreq->resume_freq, 0);
+		ret = set_target(devfreq, devfreq->resume_freq, 0);
 		mutex_unlock(&devfreq->lock);
 		if (ret)
 			return ret;
-- 
2.17.1

Re: [PATCH] PM / devfreq: Add missing function description and rename static functions

[Chanwoo Choi]

On 1/7/20 10:35 AM, Chanwoo Choi wrote:
> Rename internal function name used by devfreq core without 'devfreq_'
> prefix in order to separate them from the exported functions.
> And add missing function description for improving the readability.
> 
> Lastly, add the comments of devfreq_add_device to increase
> the understanding of behavior of devfreq_add_device.
> 
> Signed-off-by: Chanwoo Choi <cw00.choi@samsung.com>
> ---
>  drivers/devfreq/devfreq.c | 81 +++++++++++++++++++++++++++++++--------
>  1 file changed, 64 insertions(+), 17 deletions(-)
> 
> diff --git a/drivers/devfreq/devfreq.c b/drivers/devfreq/devfreq.c
> index acd21345a070..254f11b31824 100644
> --- a/drivers/devfreq/devfreq.c
> +++ b/drivers/devfreq/devfreq.c
> @@ -48,7 +48,7 @@ static LIST_HEAD(devfreq_list);
>  static DEFINE_MUTEX(devfreq_list_lock);
>  
>  /**
> - * find_device_devfreq() - find devfreq struct using device pointer
> + * find_device_devfreq() - Find devfreq struct using device pointer
>   * @dev:	device pointer used to lookup device devfreq.
>   *
>   * Search the list of device devfreqs and return the matched device's
> @@ -73,6 +73,13 @@ static struct devfreq *find_device_devfreq(struct device *dev)
>  	return ERR_PTR(-ENODEV);
>  }
>  
> +/**
> + * find_available_min_freq() - Find available min frequency via OPP interface
> + * @devfreq:	the devfreq instance
> + *
> + * Find available minimum frequency among the active OPP entries
> + * because could either enable or disable the frequency by using OPP interface.
> + */
>  static unsigned long find_available_min_freq(struct devfreq *devfreq)
>  {
>  	struct dev_pm_opp *opp;
> @@ -87,6 +94,13 @@ static unsigned long find_available_min_freq(struct devfreq *devfreq)
>  	return min_freq;
>  }
>  
> +/**
> + * find_available_max_freq() - Find available max frequency via OPP interface
> + * @devfreq:	the devfreq instance
> + *
> + * Find available maximum frequency among the active OPP entries
> + * because could either enable or disable the frequency by using OPP interface.
> + */
>  static unsigned long find_available_max_freq(struct devfreq *devfreq)
>  {
>  	struct dev_pm_opp *opp;
> @@ -150,11 +164,11 @@ static void get_freq_range(struct devfreq *devfreq,
>  }
>  
>  /**
> - * devfreq_get_freq_level() - Lookup freq_table for the frequency
> + * get_freq_level() - Lookup freq_table for the frequency
>   * @devfreq:	the devfreq instance
>   * @freq:	the target frequency
>   */
> -static int devfreq_get_freq_level(struct devfreq *devfreq, unsigned long freq)
> +static int get_freq_level(struct devfreq *devfreq, unsigned long freq)
>  {
>  	int lev;
>  
> @@ -165,6 +179,13 @@ static int devfreq_get_freq_level(struct devfreq *devfreq, unsigned long freq)
>  	return -EINVAL;
>  }
>  
> +/**
> + * set_freq_table() - Fill out the freq_table of devfreq instance
> + * @devfreq:	the devfreq instance
> + *
> + * If freq_table array is NULL, fill out the freq_table array
> + * by using OPP interface because OPP is mandatory.
> + */
>  static int set_freq_table(struct devfreq *devfreq)
>  {
>  	struct devfreq_dev_profile *profile = devfreq->profile;
> @@ -218,7 +239,7 @@ int devfreq_update_status(struct devfreq *devfreq, unsigned long freq)
>  	if (!devfreq->previous_freq)
>  		goto out;
>  
> -	prev_lev = devfreq_get_freq_level(devfreq, devfreq->previous_freq);
> +	prev_lev = get_freq_level(devfreq, devfreq->previous_freq);
>  	if (prev_lev < 0) {
>  		ret = prev_lev;
>  		goto out;
> @@ -227,7 +248,7 @@ int devfreq_update_status(struct devfreq *devfreq, unsigned long freq)
>  	devfreq->stats.time_in_state[prev_lev] +=
>  			cur_time - devfreq->stats.last_update;
>  
> -	lev = devfreq_get_freq_level(devfreq, freq);
> +	lev = get_freq_level(devfreq, freq);
>  	if (lev < 0) {
>  		ret = lev;
>  		goto out;
> @@ -246,7 +267,7 @@ int devfreq_update_status(struct devfreq *devfreq, unsigned long freq)
>  EXPORT_SYMBOL(devfreq_update_status);
>  
>  /**
> - * find_devfreq_governor() - find devfreq governor from name
> + * find_devfreq_governor() - Find devfreq governor from name
>   * @name:	name of the governor
>   *
>   * Search the list of devfreq governors and return the matched
> @@ -314,8 +335,17 @@ static struct devfreq_governor *try_then_request_governor(const char *name)
>  	return governor;
>  }
>  
> -static int devfreq_notify_transition(struct devfreq *devfreq,
> -		struct devfreq_freqs *freqs, unsigned int state)
> +/**
> + * notify_transition() - Send the transition notification
> + * @name:	name of the governor
> + * @freqs:	the data containing the both old and new frequency
> + * @state:	the kind of notification
> + *
> + * Send the transition notification to the registered receivers
> + * in order to inform the frequency change.
> + */
> +static int notify_transition(struct devfreq *devfreq,
> +			struct devfreq_freqs *freqs, unsigned int state)
>  {
>  	if (!devfreq)
>  		return -EINVAL;
> @@ -337,8 +367,17 @@ static int devfreq_notify_transition(struct devfreq *devfreq,
>  	return 0;
>  }
>  
> -static int devfreq_set_target(struct devfreq *devfreq, unsigned long new_freq,
> -			      u32 flags)
> +/**
> + * set_target() - Set target frequency of devfreq instance
> + * @devfreq:	the devfreq instance
> + * @new_freq:	the target frequency
> + * @flags:	flags handed from devfreq framework
> + *
> + * Set the target frequency of which is decided by governor
> + * and then is adjusted with constraints.
> + */
> +static int set_target(struct devfreq *devfreq,
> +			unsigned long new_freq, u32 flags)
>  {
>  	struct devfreq_freqs freqs;
>  	unsigned long cur_freq;
> @@ -351,17 +390,17 @@ static int devfreq_set_target(struct devfreq *devfreq, unsigned long new_freq,
>  
>  	freqs.old = cur_freq;
>  	freqs.new = new_freq;
> -	devfreq_notify_transition(devfreq, &freqs, DEVFREQ_PRECHANGE);
> +	notify_transition(devfreq, &freqs, DEVFREQ_PRECHANGE);
>  
>  	err = devfreq->profile->target(devfreq->dev.parent, &new_freq, flags);
>  	if (err) {
>  		freqs.new = cur_freq;
> -		devfreq_notify_transition(devfreq, &freqs, DEVFREQ_POSTCHANGE);
> +		notify_transition(devfreq, &freqs, DEVFREQ_POSTCHANGE);
>  		return err;
>  	}
>  
>  	freqs.new = new_freq;
> -	devfreq_notify_transition(devfreq, &freqs, DEVFREQ_POSTCHANGE);
> +	notify_transition(devfreq, &freqs, DEVFREQ_POSTCHANGE);
>  
>  	if (devfreq_update_status(devfreq, new_freq))
>  		dev_err(&devfreq->dev,
> @@ -413,7 +452,7 @@ int update_devfreq(struct devfreq *devfreq)
>  		flags |= DEVFREQ_FLAG_LEAST_UPPER_BOUND; /* Use LUB */
>  	}
>  
> -	return devfreq_set_target(devfreq, freq, flags);
> +	return set_target(devfreq, freq, flags);
>  
>  }
>  EXPORT_SYMBOL(update_devfreq);
> @@ -421,7 +460,6 @@ EXPORT_SYMBOL(update_devfreq);
>  /**
>   * devfreq_monitor() - Periodically poll devfreq objects.
>   * @work:	the work struct used to run devfreq_monitor periodically.
> - *
>   */
>  static void devfreq_monitor(struct work_struct *work)
>  {
> @@ -739,11 +777,13 @@ struct devfreq *devfreq_add_device(struct device *dev,
>  	static atomic_t devfreq_no = ATOMIC_INIT(-1);
>  	int err = 0;
>  
> +	/* Check the parameter is valid */
>  	if (!dev || !profile || !governor_name) {
>  		dev_err(dev, "%s: Invalid parameters.\n", __func__);
>  		return ERR_PTR(-EINVAL);
>  	}
>  
> +	/* Check the device is already added or not */
>  	mutex_lock(&devfreq_list_lock);
>  	devfreq = find_device_devfreq(dev);
>  	mutex_unlock(&devfreq_list_lock);
> @@ -754,6 +794,7 @@ struct devfreq *devfreq_add_device(struct device *dev,
>  		goto err_out;
>  	}
>  
> +	/* Initialize the devfreq instance */
>  	devfreq = kzalloc(sizeof(struct devfreq), GFP_KERNEL);
>  	if (!devfreq) {
>  		err = -ENOMEM;
> @@ -798,6 +839,7 @@ struct devfreq *devfreq_add_device(struct device *dev,
>  	devfreq->suspend_freq = dev_pm_opp_get_suspend_opp_freq(dev);
>  	atomic_set(&devfreq->suspend_count, 0);
>  
> +	/* Register a device for devfreq instance */
>  	dev_set_name(&devfreq->dev, "devfreq%d",
>  				atomic_inc_return(&devfreq_no));
>  	err = device_register(&devfreq->dev);
> @@ -807,6 +849,7 @@ struct devfreq *devfreq_add_device(struct device *dev,
>  		goto err_out;
>  	}
>  
> +	/* Initialize the statistics of devfreq device behavior */
>  	devfreq->stats.trans_table = devm_kzalloc(&devfreq->dev,
>  			array3_size(sizeof(unsigned int),
>  				    devfreq->profile->max_state,
> @@ -831,10 +874,12 @@ struct devfreq *devfreq_add_device(struct device *dev,
>  	devfreq->stats.total_trans = 0;
>  	devfreq->stats.last_update = get_jiffies_64();
>  
> +	/* Initialize notifiers for informing the transition of devfreq */
>  	srcu_init_notifier_head(&devfreq->transition_notifier_list);
>  
>  	mutex_unlock(&devfreq->lock);
>  
> +	/* Initialize PM QoS for applying the constraints */
>  	err = dev_pm_qos_add_request(dev, &devfreq->user_min_freq_req,
>  				     DEV_PM_QOS_MIN_FREQUENCY, 0);
>  	if (err < 0)
> @@ -859,6 +904,7 @@ struct devfreq *devfreq_add_device(struct device *dev,
>  
>  	mutex_lock(&devfreq_list_lock);
>  
> +	/* Find the devfreq governor and start */
>  	governor = try_then_request_governor(devfreq->governor_name);
>  	if (IS_ERR(governor)) {
>  		dev_err(dev, "%s: Unable to find governor for the device\n",
> @@ -876,6 +922,7 @@ struct devfreq *devfreq_add_device(struct device *dev,
>  		goto err_init;
>  	}
>  
> +	/* Add the devfreq instance to global devfreq list finally */
>  	list_add(&devfreq->node, &devfreq_list);
>  
>  	mutex_unlock(&devfreq_list_lock);
> @@ -1076,7 +1123,7 @@ int devfreq_suspend_device(struct devfreq *devfreq)
>  
>  	if (devfreq->suspend_freq) {
>  		mutex_lock(&devfreq->lock);
> -		ret = devfreq_set_target(devfreq, devfreq->suspend_freq, 0);
> +		ret = set_target(devfreq, devfreq->suspend_freq, 0);
>  		mutex_unlock(&devfreq->lock);
>  		if (ret)
>  			return ret;
> @@ -1106,7 +1153,7 @@ int devfreq_resume_device(struct devfreq *devfreq)
>  
>  	if (devfreq->resume_freq) {
>  		mutex_lock(&devfreq->lock);
> -		ret = devfreq_set_target(devfreq, devfreq->resume_freq, 0);
> +		ret = set_target(devfreq, devfreq->resume_freq, 0);
>  		mutex_unlock(&devfreq->lock);
>  		if (ret)
>  			return ret;
> 

Applied it.

-- 
Best Regards,
Chanwoo Choi
Samsung Electronics

Re: [PATCH] PM / devfreq: Add missing function description and rename static functions

[Chanwoo Choi]

On 1/8/20 2:03 PM, Chanwoo Choi wrote:
> On 1/7/20 10:35 AM, Chanwoo Choi wrote:
>> Rename internal function name used by devfreq core without 'devfreq_'
>> prefix in order to separate them from the exported functions.
>> And add missing function description for improving the readability.
>>
>> Lastly, add the comments of devfreq_add_device to increase
>> the understanding of behavior of devfreq_add_device.
>>
>> Signed-off-by: Chanwoo Choi <cw00.choi@samsung.com>
>> ---
>>  drivers/devfreq/devfreq.c | 81 +++++++++++++++++++++++++++++++--------
>>  1 file changed, 64 insertions(+), 17 deletions(-)
>>
>> diff --git a/drivers/devfreq/devfreq.c b/drivers/devfreq/devfreq.c
>> index acd21345a070..254f11b31824 100644
>> --- a/drivers/devfreq/devfreq.c
>> +++ b/drivers/devfreq/devfreq.c
>> @@ -48,7 +48,7 @@ static LIST_HEAD(devfreq_list);
>>  static DEFINE_MUTEX(devfreq_list_lock);
>>  
>>  /**
>> - * find_device_devfreq() - find devfreq struct using device pointer
>> + * find_device_devfreq() - Find devfreq struct using device pointer
>>   * @dev:	device pointer used to lookup device devfreq.
>>   *
>>   * Search the list of device devfreqs and return the matched device's
>> @@ -73,6 +73,13 @@ static struct devfreq *find_device_devfreq(struct device *dev)
>>  	return ERR_PTR(-ENODEV);
>>  }
>>  
>> +/**
>> + * find_available_min_freq() - Find available min frequency via OPP interface
>> + * @devfreq:	the devfreq instance
>> + *
>> + * Find available minimum frequency among the active OPP entries
>> + * because could either enable or disable the frequency by using OPP interface.
>> + */
>>  static unsigned long find_available_min_freq(struct devfreq *devfreq)
>>  {
>>  	struct dev_pm_opp *opp;
>> @@ -87,6 +94,13 @@ static unsigned long find_available_min_freq(struct devfreq *devfreq)
>>  	return min_freq;
>>  }
>>  
>> +/**
>> + * find_available_max_freq() - Find available max frequency via OPP interface
>> + * @devfreq:	the devfreq instance
>> + *
>> + * Find available maximum frequency among the active OPP entries
>> + * because could either enable or disable the frequency by using OPP interface.
>> + */
>>  static unsigned long find_available_max_freq(struct devfreq *devfreq)
>>  {
>>  	struct dev_pm_opp *opp;
>> @@ -150,11 +164,11 @@ static void get_freq_range(struct devfreq *devfreq,
>>  }
>>  
>>  /**
>> - * devfreq_get_freq_level() - Lookup freq_table for the frequency
>> + * get_freq_level() - Lookup freq_table for the frequency
>>   * @devfreq:	the devfreq instance
>>   * @freq:	the target frequency
>>   */
>> -static int devfreq_get_freq_level(struct devfreq *devfreq, unsigned long freq)
>> +static int get_freq_level(struct devfreq *devfreq, unsigned long freq)
>>  {
>>  	int lev;
>>  
>> @@ -165,6 +179,13 @@ static int devfreq_get_freq_level(struct devfreq *devfreq, unsigned long freq)
>>  	return -EINVAL;
>>  }
>>  
>> +/**
>> + * set_freq_table() - Fill out the freq_table of devfreq instance
>> + * @devfreq:	the devfreq instance
>> + *
>> + * If freq_table array is NULL, fill out the freq_table array
>> + * by using OPP interface because OPP is mandatory.
>> + */
>>  static int set_freq_table(struct devfreq *devfreq)
>>  {
>>  	struct devfreq_dev_profile *profile = devfreq->profile;
>> @@ -218,7 +239,7 @@ int devfreq_update_status(struct devfreq *devfreq, unsigned long freq)
>>  	if (!devfreq->previous_freq)
>>  		goto out;
>>  
>> -	prev_lev = devfreq_get_freq_level(devfreq, devfreq->previous_freq);
>> +	prev_lev = get_freq_level(devfreq, devfreq->previous_freq);
>>  	if (prev_lev < 0) {
>>  		ret = prev_lev;
>>  		goto out;
>> @@ -227,7 +248,7 @@ int devfreq_update_status(struct devfreq *devfreq, unsigned long freq)
>>  	devfreq->stats.time_in_state[prev_lev] +=
>>  			cur_time - devfreq->stats.last_update;
>>  
>> -	lev = devfreq_get_freq_level(devfreq, freq);
>> +	lev = get_freq_level(devfreq, freq);
>>  	if (lev < 0) {
>>  		ret = lev;
>>  		goto out;
>> @@ -246,7 +267,7 @@ int devfreq_update_status(struct devfreq *devfreq, unsigned long freq)
>>  EXPORT_SYMBOL(devfreq_update_status);
>>  
>>  /**
>> - * find_devfreq_governor() - find devfreq governor from name
>> + * find_devfreq_governor() - Find devfreq governor from name
>>   * @name:	name of the governor
>>   *
>>   * Search the list of devfreq governors and return the matched
>> @@ -314,8 +335,17 @@ static struct devfreq_governor *try_then_request_governor(const char *name)
>>  	return governor;
>>  }
>>  
>> -static int devfreq_notify_transition(struct devfreq *devfreq,
>> -		struct devfreq_freqs *freqs, unsigned int state)
>> +/**
>> + * notify_transition() - Send the transition notification
>> + * @name:	name of the governor
>> + * @freqs:	the data containing the both old and new frequency
>> + * @state:	the kind of notification
>> + *
>> + * Send the transition notification to the registered receivers
>> + * in order to inform the frequency change.
>> + */
>> +static int notify_transition(struct devfreq *devfreq,
>> +			struct devfreq_freqs *freqs, unsigned int state)
>>  {
>>  	if (!devfreq)
>>  		return -EINVAL;
>> @@ -337,8 +367,17 @@ static int devfreq_notify_transition(struct devfreq *devfreq,
>>  	return 0;
>>  }
>>  
>> -static int devfreq_set_target(struct devfreq *devfreq, unsigned long new_freq,
>> -			      u32 flags)
>> +/**
>> + * set_target() - Set target frequency of devfreq instance
>> + * @devfreq:	the devfreq instance
>> + * @new_freq:	the target frequency
>> + * @flags:	flags handed from devfreq framework
>> + *
>> + * Set the target frequency of which is decided by governor
>> + * and then is adjusted with constraints.
>> + */
>> +static int set_target(struct devfreq *devfreq,
>> +			unsigned long new_freq, u32 flags)
>>  {
>>  	struct devfreq_freqs freqs;
>>  	unsigned long cur_freq;
>> @@ -351,17 +390,17 @@ static int devfreq_set_target(struct devfreq *devfreq, unsigned long new_freq,
>>  
>>  	freqs.old = cur_freq;
>>  	freqs.new = new_freq;
>> -	devfreq_notify_transition(devfreq, &freqs, DEVFREQ_PRECHANGE);
>> +	notify_transition(devfreq, &freqs, DEVFREQ_PRECHANGE);
>>  
>>  	err = devfreq->profile->target(devfreq->dev.parent, &new_freq, flags);
>>  	if (err) {
>>  		freqs.new = cur_freq;
>> -		devfreq_notify_transition(devfreq, &freqs, DEVFREQ_POSTCHANGE);
>> +		notify_transition(devfreq, &freqs, DEVFREQ_POSTCHANGE);
>>  		return err;
>>  	}
>>  
>>  	freqs.new = new_freq;
>> -	devfreq_notify_transition(devfreq, &freqs, DEVFREQ_POSTCHANGE);
>> +	notify_transition(devfreq, &freqs, DEVFREQ_POSTCHANGE);
>>  
>>  	if (devfreq_update_status(devfreq, new_freq))
>>  		dev_err(&devfreq->dev,
>> @@ -413,7 +452,7 @@ int update_devfreq(struct devfreq *devfreq)
>>  		flags |= DEVFREQ_FLAG_LEAST_UPPER_BOUND; /* Use LUB */
>>  	}
>>  
>> -	return devfreq_set_target(devfreq, freq, flags);
>> +	return set_target(devfreq, freq, flags);
>>  
>>  }
>>  EXPORT_SYMBOL(update_devfreq);
>> @@ -421,7 +460,6 @@ EXPORT_SYMBOL(update_devfreq);
>>  /**
>>   * devfreq_monitor() - Periodically poll devfreq objects.
>>   * @work:	the work struct used to run devfreq_monitor periodically.
>> - *
>>   */
>>  static void devfreq_monitor(struct work_struct *work)
>>  {
>> @@ -739,11 +777,13 @@ struct devfreq *devfreq_add_device(struct device *dev,
>>  	static atomic_t devfreq_no = ATOMIC_INIT(-1);
>>  	int err = 0;
>>  
>> +	/* Check the parameter is valid */
>>  	if (!dev || !profile || !governor_name) {
>>  		dev_err(dev, "%s: Invalid parameters.\n", __func__);
>>  		return ERR_PTR(-EINVAL);
>>  	}
>>  
>> +	/* Check the device is already added or not */
>>  	mutex_lock(&devfreq_list_lock);
>>  	devfreq = find_device_devfreq(dev);
>>  	mutex_unlock(&devfreq_list_lock);
>> @@ -754,6 +794,7 @@ struct devfreq *devfreq_add_device(struct device *dev,
>>  		goto err_out;
>>  	}
>>  
>> +	/* Initialize the devfreq instance */
>>  	devfreq = kzalloc(sizeof(struct devfreq), GFP_KERNEL);
>>  	if (!devfreq) {
>>  		err = -ENOMEM;
>> @@ -798,6 +839,7 @@ struct devfreq *devfreq_add_device(struct device *dev,
>>  	devfreq->suspend_freq = dev_pm_opp_get_suspend_opp_freq(dev);
>>  	atomic_set(&devfreq->suspend_count, 0);
>>  
>> +	/* Register a device for devfreq instance */
>>  	dev_set_name(&devfreq->dev, "devfreq%d",
>>  				atomic_inc_return(&devfreq_no));
>>  	err = device_register(&devfreq->dev);
>> @@ -807,6 +849,7 @@ struct devfreq *devfreq_add_device(struct device *dev,
>>  		goto err_out;
>>  	}
>>  
>> +	/* Initialize the statistics of devfreq device behavior */
>>  	devfreq->stats.trans_table = devm_kzalloc(&devfreq->dev,
>>  			array3_size(sizeof(unsigned int),
>>  				    devfreq->profile->max_state,
>> @@ -831,10 +874,12 @@ struct devfreq *devfreq_add_device(struct device *dev,
>>  	devfreq->stats.total_trans = 0;
>>  	devfreq->stats.last_update = get_jiffies_64();
>>  
>> +	/* Initialize notifiers for informing the transition of devfreq */
>>  	srcu_init_notifier_head(&devfreq->transition_notifier_list);
>>  
>>  	mutex_unlock(&devfreq->lock);
>>  
>> +	/* Initialize PM QoS for applying the constraints */
>>  	err = dev_pm_qos_add_request(dev, &devfreq->user_min_freq_req,
>>  				     DEV_PM_QOS_MIN_FREQUENCY, 0);
>>  	if (err < 0)
>> @@ -859,6 +904,7 @@ struct devfreq *devfreq_add_device(struct device *dev,
>>  
>>  	mutex_lock(&devfreq_list_lock);
>>  
>> +	/* Find the devfreq governor and start */
>>  	governor = try_then_request_governor(devfreq->governor_name);
>>  	if (IS_ERR(governor)) {
>>  		dev_err(dev, "%s: Unable to find governor for the device\n",
>> @@ -876,6 +922,7 @@ struct devfreq *devfreq_add_device(struct device *dev,
>>  		goto err_init;
>>  	}
>>  
>> +	/* Add the devfreq instance to global devfreq list finally */
>>  	list_add(&devfreq->node, &devfreq_list);
>>  
>>  	mutex_unlock(&devfreq_list_lock);
>> @@ -1076,7 +1123,7 @@ int devfreq_suspend_device(struct devfreq *devfreq)
>>  
>>  	if (devfreq->suspend_freq) {
>>  		mutex_lock(&devfreq->lock);
>> -		ret = devfreq_set_target(devfreq, devfreq->suspend_freq, 0);
>> +		ret = set_target(devfreq, devfreq->suspend_freq, 0);
>>  		mutex_unlock(&devfreq->lock);
>>  		if (ret)
>>  			return ret;
>> @@ -1106,7 +1153,7 @@ int devfreq_resume_device(struct devfreq *devfreq)
>>  
>>  	if (devfreq->resume_freq) {
>>  		mutex_lock(&devfreq->lock);
>> -		ret = devfreq_set_target(devfreq, devfreq->resume_freq, 0);
>> +		ret = set_target(devfreq, devfreq->resume_freq, 0);
>>  		mutex_unlock(&devfreq->lock);
>>  		if (ret)
>>  			return ret;
>>
> 
> Applied it.
> 

I'm sorry. Drop this patch because it is not enough to add
the missing description for functions. I'll add the more description
and then resend it.

-- 
Best Regards,
Chanwoo Choi
Samsung Electronics