Re: [PATCH 7/7] devfreq: move statistics to separate struct

[Bartlomiej Zolnierkiewicz]

Hi Chanwoo,

On 11/14/19 2:52 AM, Chanwoo Choi wrote:
> Hi Kamil,
> 
> The 'freq_table' and 'max_state' in the devfreq_dev_profile
> were used in the ARM Mali device driver[1][2][3]. Although ARM Mali
> device driver was posted to mainline kernel, they used
> them for a long time. It means that this patch break
> the compatibility. The ARM Mali drivers are very
> important devfreq device driver. 

This argument is not a a technical one and the official upstream
kernel policy is to not depend on out-of-tree drivers.

Besides the ARM Mali drivers are full of code like:

#if LINUX_VERSION_CODE >= KERNEL_VERSION(x, y, z)
...
#else
...
#endif

so few more instances of similar code won't do any harm.. ;-)

> [1] https://developer.arm.com/tools-and-software/graphics-and-gaming/mali-drivers/bifrost-kernel#
> [2] https://developer.arm.com/tools-and-software/graphics-and-gaming/mali-drivers/midgard-kernel
> [3] https://developer.arm.com/tools-and-software/graphics-and-gaming/mali-drivers/utgard-kernel

I took a look at ARM Mali drivers source code anyway and I fail to
see a rationale behind their behavior of doing 'freq_table' and
'max_state' initialization in the driver itself (instead of leaving
it up to the devfreq core code, like all in-kernel drivers are doing
already).

Could you please explain rationale behind ARM Mali drivers' special
needs?

[ Both ARM Mali and devfreq core code are using generic PM OPP code
  these days to do 'freq_table' and 'max_state' initialization, the
  only difference seems to be that ARM Mali creates the frequency
  table in the descending order (but there also seems to be no real
  need for it). ]

Maybe this is an opportunity to simplify also the ARM Mali driver?

> Also, the devfreq device driver specifies their own
> information and data into devfreq_dev_profile structure 
> before registering the devfreq device with devfreq_add_device().
> This patch breaks the basic usage rule of devfreq_dev_profile structure.

Well, 'struct devfreq_stats *stats' can be trivially moved out of
'struct devfreq_profile' to 'struct devfreq' if you prefer it that
way..

Best regards,
--
Bartlomiej Zolnierkiewicz
Samsung R&D Institute Poland
Samsung Electronics

> So, I can't agree this patch. Not ack.
> 
> Regards,
> Chanwoo Choi
> 
> On 11/13/19 6:13 PM, Kamil Konieczny wrote:
>> Count time and transitions between devfreq frequencies in separate struct
>> for improved code readability and maintenance.
>>
>> Signed-off-by: Kamil Konieczny <k.konieczny@xxxxxxxxxxx>
>> ---
>>  drivers/devfreq/devfreq.c          | 156 ++++++++++++++++-------------
>>  drivers/devfreq/exynos-bus.c       |   6 +-
>>  drivers/devfreq/governor_passive.c |  26 +++--
>>  include/linux/devfreq.h            |  43 ++++----
>>  4 files changed, 129 insertions(+), 102 deletions(-)
>>
>> diff --git a/drivers/devfreq/devfreq.c b/drivers/devfreq/devfreq.c
>> index d79412b0de59..d85867a91230 100644
>> --- a/drivers/devfreq/devfreq.c
>> +++ b/drivers/devfreq/devfreq.c
>> @@ -105,10 +105,11 @@ static unsigned long find_available_max_freq(struct devfreq *devfreq)
>>   */
>>  static int devfreq_get_freq_level(struct devfreq *devfreq, unsigned long freq)
>>  {
>> +	struct devfreq_stats *stats = devfreq->profile->stats;
>>  	int lev;
>>  
>> -	for (lev = 0; lev < devfreq->profile->max_state; lev++)
>> -		if (freq == devfreq->profile->freq_table[lev])
>> +	for (lev = 0; lev < stats->max_state; lev++)
>> +		if (freq == stats->freq_table[lev])
>>  			return lev;
>>  
>>  	return -EINVAL;
>> @@ -117,56 +118,64 @@ static int devfreq_get_freq_level(struct devfreq *devfreq, unsigned long freq)
>>  static int set_freq_table(struct devfreq *devfreq)
>>  {
>>  	struct devfreq_dev_profile *profile = devfreq->profile;
>> +	struct devfreq_stats *stats;
>>  	struct dev_pm_opp *opp;
>>  	unsigned long freq;
>> -	int i, count;
>> +	int i, count, err = -ENOMEM;
>>  
>>  	/* Initialize the freq_table from OPP table */
>>  	count = dev_pm_opp_get_opp_count(devfreq->dev.parent);
>>  	if (count <= 0)
>>  		return -EINVAL;
>>  
>> -	profile->max_state = count;
>> -	profile->freq_table = devm_kcalloc(devfreq->dev.parent,
>> -					count,
>> -					sizeof(*profile->freq_table),
>> -					GFP_KERNEL);
>> -	if (!profile->freq_table) {
>> -		profile->max_state = 0;
>> +	stats = devm_kzalloc(devfreq->dev.parent,
>> +			     sizeof(struct devfreq_stats), GFP_KERNEL);
>> +	if (!stats)
>>  		return -ENOMEM;
>> -	}
>>  
>> -	for (i = 0, freq = 0; i < profile->max_state; i++, freq++) {
>> +	profile->stats = stats;
>> +	stats->max_state = count;
>> +	stats->freq_table = devm_kcalloc(devfreq->dev.parent,
>> +					 count,
>> +					 sizeof(*stats->freq_table),
>> +					 GFP_KERNEL);
>> +	if (!stats->freq_table)
>> +		goto err_no_mem;
>> +
>> +	for (i = 0, freq = 0; i < count; i++, freq++) {
>>  		opp = dev_pm_opp_find_freq_ceil(devfreq->dev.parent, &freq);
>>  		if (IS_ERR(opp)) {
>> -			devm_kfree(devfreq->dev.parent, profile->freq_table);
>> -			profile->max_state = 0;
>> -			return PTR_ERR(opp);
>> +			devm_kfree(devfreq->dev.parent, stats->freq_table);
>> +			stats->max_state = 0;
>> +			err = PTR_ERR(opp);
>> +			goto err_no_mem;
>>  		}
>>  		dev_pm_opp_put(opp);
>> -		profile->freq_table[i] = freq;
>> +		stats->freq_table[i] = freq;
>>  	}
>>  
>> -	profile->trans_table = devm_kzalloc(devfreq->dev.parent,
>> -					    array3_size(sizeof(unsigned int),
>> -							count, count),
>> -					    GFP_KERNEL);
>> -	if (!profile->trans_table)
>> +	stats->trans_table = devm_kzalloc(devfreq->dev.parent,
>> +					  array3_size(sizeof(unsigned int),
>> +						      count, count),
>> +					  GFP_KERNEL);
>> +	if (!stats->trans_table)
>>  		goto err_no_mem;
>>  
>> -	profile->time_in_state = devm_kcalloc(devfreq->dev.parent, count,
>> -					      sizeof(*profile->time_in_state),
>> -					      GFP_KERNEL);
>> -	if (!profile->time_in_state)
>> +	stats->time_in_state = devm_kcalloc(devfreq->dev.parent, count,
>> +					    sizeof(*stats->time_in_state),
>> +					    GFP_KERNEL);
>> +	if (!stats->time_in_state)
>>  		goto err_no_mem;
>>  
>> -	profile->last_time = get_jiffies_64();
>> -	spin_lock_init(&profile->stats_lock);
>> +	stats->last_time = get_jiffies_64();
>> +	spin_lock_init(&stats->stats_lock);
>>  
>>  	return 0;
>>  err_no_mem:
>> -	profile->max_state = 0;
>> -	return -ENOMEM;
>> +	stats->max_state = 0;
>> +	devm_kfree(devfreq->dev.parent, profile->stats);
>> +	profile->stats = NULL;
>> +	return err;
>>  }
>>  
>>  /**
>> @@ -176,7 +185,7 @@ static int set_freq_table(struct devfreq *devfreq)
>>   */
>>  int devfreq_update_status(struct devfreq *devfreq, unsigned long freq)
>>  {
>> -	struct devfreq_dev_profile *profile = devfreq->profile;
>> +	struct devfreq_stats *stats = devfreq->profile->stats;
>>  	unsigned long long cur_time;
>>  	int lev, prev_lev, ret = 0;
>>  
>> @@ -184,22 +193,21 @@ int devfreq_update_status(struct devfreq *devfreq, unsigned long freq)
>>  
>>  	/* Immediately exit if previous_freq is not initialized yet. */
>>  	if (!devfreq->previous_freq) {
>> -		spin_lock(&profile->stats_lock);
>> -		profile->last_time = cur_time;
>> -		spin_unlock(&profile->stats_lock);
>> +		spin_lock(&stats->stats_lock);
>> +		stats->last_time = cur_time;
>> +		spin_unlock(&stats->stats_lock);
>>  		return 0;
>>  	}
>>  
>>  	prev_lev = devfreq_get_freq_level(devfreq, devfreq->previous_freq);
>>  
>> -	spin_lock(&profile->stats_lock);
>> +	spin_lock(&stats->stats_lock);
>>  	if (prev_lev < 0) {
>>  		ret = prev_lev;
>>  		goto out;
>>  	}
>>  
>> -	profile->time_in_state[prev_lev] +=
>> -			 cur_time - profile->last_time;
>> +	stats->time_in_state[prev_lev] += cur_time - stats->last_time;
>>  	lev = devfreq_get_freq_level(devfreq, freq);
>>  	if (lev < 0) {
>>  		ret = lev;
>> @@ -207,14 +215,14 @@ int devfreq_update_status(struct devfreq *devfreq, unsigned long freq)
>>  	}
>>  
>>  	if (lev != prev_lev) {
>> -		profile->trans_table[(prev_lev *
>> -				profile->max_state) + lev]++;
>> -		profile->total_trans++;
>> +		stats->trans_table[(prev_lev *
>> +				stats->max_state) + lev]++;
>> +		stats->total_trans++;
>>  	}
>>  
>>  out:
>> -	profile->last_time = cur_time;
>> -	spin_unlock(&profile->stats_lock);
>> +	stats->last_time = cur_time;
>> +	spin_unlock(&stats->stats_lock);
>>  	return ret;
>>  }
>>  EXPORT_SYMBOL(devfreq_update_status);
>> @@ -504,9 +512,9 @@ void devfreq_monitor_resume(struct devfreq *devfreq)
>>  		queue_delayed_work(devfreq_wq, &devfreq->work,
>>  			msecs_to_jiffies(profile->polling_ms));
>>  
>> -	spin_lock(&profile->stats_lock);
>> -	profile->last_time = get_jiffies_64();
>> -	spin_unlock(&profile->stats_lock);
>> +	spin_lock(&profile->stats->stats_lock);
>> +	profile->stats->last_time = get_jiffies_64();
>> +	spin_unlock(&profile->stats->stats_lock);
>>  	devfreq->stop_polling = false;
>>  
>>  	if (profile->get_cur_freq &&
>> @@ -677,7 +685,7 @@ struct devfreq *devfreq_add_device(struct device *dev,
>>  	devfreq->data = data;
>>  	devfreq->nb.notifier_call = devfreq_notifier_call;
>>  
>> -	if (!profile->max_state && !profile->freq_table) {
>> +	if (!profile->stats) {
>>  		mutex_unlock(&devfreq->lock);
>>  		err = set_freq_table(devfreq);
>>  		if (err < 0)
>> @@ -1282,6 +1290,7 @@ static ssize_t min_freq_store(struct device *dev, struct device_attribute *attr,
>>  			      const char *buf, size_t count)
>>  {
>>  	struct devfreq *df = to_devfreq(dev);
>> +	struct devfreq_stats *stats = df->profile->stats;
>>  	unsigned long value;
>>  	int ret;
>>  
>> @@ -1297,13 +1306,13 @@ static ssize_t min_freq_store(struct device *dev, struct device_attribute *attr,
>>  			goto unlock;
>>  		}
>>  	} else {
>> -		unsigned long *freq_table = df->profile->freq_table;
>> +		unsigned long *freq_table = stats->freq_table;
>>  
>>  		/* Get minimum frequency according to sorting order */
>> -		if (freq_table[0] < freq_table[df->profile->max_state - 1])
>> +		if (freq_table[0] < freq_table[stats->max_state - 1])
>>  			value = freq_table[0];
>>  		else
>> -			value = freq_table[df->profile->max_state - 1];
>> +			value = freq_table[stats->max_state - 1];
>>  	}
>>  
>>  	df->min_freq = value;
>> @@ -1326,6 +1335,7 @@ static ssize_t max_freq_store(struct device *dev, struct device_attribute *attr,
>>  			      const char *buf, size_t count)
>>  {
>>  	struct devfreq *df = to_devfreq(dev);
>> +	struct devfreq_stats *stats = df->profile->stats;
>>  	unsigned long value;
>>  	int ret;
>>  
>> @@ -1341,11 +1351,11 @@ static ssize_t max_freq_store(struct device *dev, struct device_attribute *attr,
>>  			goto unlock;
>>  		}
>>  	} else {
>> -		unsigned long *freq_table = df->profile->freq_table;
>> +		unsigned long *freq_table = stats->freq_table;
>>  
>>  		/* Get maximum frequency according to sorting order */
>> -		if (freq_table[0] < freq_table[df->profile->max_state - 1])
>> -			value = freq_table[df->profile->max_state - 1];
>> +		if (freq_table[0] < freq_table[stats->max_state - 1])
>> +			value = freq_table[stats->max_state - 1];
>>  		else
>>  			value = freq_table[0];
>>  	}
>> @@ -1373,14 +1383,15 @@ static ssize_t available_frequencies_show(struct device *d,
>>  					  char *buf)
>>  {
>>  	struct devfreq *df = to_devfreq(d);
>> +	struct devfreq_stats *stats = df->profile->stats;
>>  	ssize_t count = 0;
>>  	int i;
>>  
>>  	mutex_lock(&df->lock);
>>  
>> -	for (i = 0; i < df->profile->max_state; i++)
>> +	for (i = 0; i < stats->max_state; i++)
>>  		count += scnprintf(&buf[count], (PAGE_SIZE - count - 2),
>> -				"%lu ", df->profile->freq_table[i]);
>> +				"%lu ", stats->freq_table[i]);
>>  
>>  	mutex_unlock(&df->lock);
>>  	/* Truncate the trailing space */
>> @@ -1398,9 +1409,10 @@ static ssize_t trans_stat_show(struct device *dev,
>>  {
>>  	struct devfreq *devfreq = to_devfreq(dev);
>>  	struct devfreq_dev_profile *profile = devfreq->profile;
>> +	struct devfreq_stats *stats = profile->stats;
>> +	unsigned int max_state = stats->max_state;
>>  	ssize_t len;
>>  	int i, j;
>> -	unsigned int max_state = profile->max_state;
>>  
>>  	if (!devfreq->stop_polling &&
>>  			devfreq_update_status(devfreq, devfreq->previous_freq))
>> @@ -1411,45 +1423,45 @@ static ssize_t trans_stat_show(struct device *dev,
>>  	len = sprintf(buf, "     From  :   To\n");
>>  	len += sprintf(buf + len, "           :");
>>  
>> -	spin_lock(&profile->stats_lock);
>> +	spin_lock(&stats->stats_lock);
>>  	for (i = 0; i < max_state; i++)
>>  		len += sprintf(buf + len, "%10lu",
>> -				profile->freq_table[i]);
>> +				stats->freq_table[i]);
>>  
>>  	len += sprintf(buf + len, "   time(ms)\n");
>>  
>>  	for (i = 0; i < max_state; i++) {
>> -		if (profile->freq_table[i] == devfreq->previous_freq)
>> +		if (stats->freq_table[i] == devfreq->previous_freq)
>>  			len += sprintf(buf + len, "*");
>>  		else
>>  			len += sprintf(buf + len, " ");
>>  
>>  		len += sprintf(buf + len, "%10lu:",
>> -				profile->freq_table[i]);
>> +				stats->freq_table[i]);
>>  		for (j = 0; j < max_state; j++)
>>  			len += sprintf(buf + len, "%10u",
>> -				profile->trans_table[(i * max_state) + j]);
>> +				stats->trans_table[(i * max_state) + j]);
>>  		len += sprintf(buf + len, "%10llu\n", (u64)
>> -			jiffies64_to_msecs(profile->time_in_state[i]));
>> +			jiffies64_to_msecs(stats->time_in_state[i]));
>>  	}
>>  
>>  	len += sprintf(buf + len, "Total transition : %u\n",
>> -					profile->total_trans);
>> -	spin_unlock(&profile->stats_lock);
>> +					stats->total_trans);
>> +	spin_unlock(&stats->stats_lock);
>>  	return len;
>>  }
>>  static DEVICE_ATTR_RO(trans_stat);
>>  
>> -static void defvreq_stats_clear_table(struct devfreq_dev_profile *profile)
>> +static void defvreq_stats_clear_table(struct devfreq_stats *stats)
>>  {
>> -	unsigned int count = profile->max_state;
>> -
>> -	spin_lock(&profile->stats_lock);
>> -	memset(profile->time_in_state, 0, count * sizeof(u64));
>> -	memset(profile->trans_table, 0, count * count * sizeof(int));
>> -	profile->last_time = get_jiffies_64();
>> -	profile->total_trans = 0;
>> -	spin_unlock(&profile->stats_lock);
>> +	unsigned int count = stats->max_state;
>> +
>> +	spin_lock(&stats->stats_lock);
>> +	memset(stats->time_in_state, 0, count * sizeof(u64));
>> +	memset(stats->trans_table, 0, count * count * sizeof(int));
>> +	stats->last_time = get_jiffies_64();
>> +	stats->total_trans = 0;
>> +	spin_unlock(&stats->stats_lock);
>>  }
>>  
>>  static ssize_t trans_reset_store(struct device *dev,
>> @@ -1459,7 +1471,7 @@ static ssize_t trans_reset_store(struct device *dev,
>>  {
>>  	struct devfreq *devfreq = to_devfreq(dev);
>>  
>> -	defvreq_stats_clear_table(devfreq->profile);
>> +	defvreq_stats_clear_table(devfreq->profile->stats);
>>  
>>  	return count;
>>  }
>> diff --git a/drivers/devfreq/exynos-bus.c b/drivers/devfreq/exynos-bus.c
>> index d9f377912c10..b212aae2bb3e 100644
>> --- a/drivers/devfreq/exynos-bus.c
>> +++ b/drivers/devfreq/exynos-bus.c
>> @@ -496,9 +496,9 @@ static int exynos_bus_probe(struct platform_device *pdev)
>>  	}
>>  
>>  out:
>> -	max_state = bus->devfreq->profile->max_state;
>> -	min_freq = (bus->devfreq->profile->freq_table[0] / 1000);
>> -	max_freq = (bus->devfreq->profile->freq_table[max_state - 1] / 1000);
>> +	max_state = profile->stats->max_state;
>> +	min_freq = (profile->stats->freq_table[0] / 1000);
>> +	max_freq = (profile->stats->freq_table[max_state - 1] / 1000);
>>  	pr_info("exynos-bus: new bus device registered: %s (%6ld KHz ~ %6ld KHz)\n",
>>  			dev_name(dev), min_freq, max_freq);
>>  
>> diff --git a/drivers/devfreq/governor_passive.c b/drivers/devfreq/governor_passive.c
>> index 58308948b863..b2d87a88335c 100644
>> --- a/drivers/devfreq/governor_passive.c
>> +++ b/drivers/devfreq/governor_passive.c
>> @@ -18,6 +18,8 @@ static int devfreq_passive_get_target_freq(struct devfreq *devfreq,
>>  	struct devfreq_passive_data *p_data
>>  			= (struct devfreq_passive_data *)devfreq->data;
>>  	struct devfreq *parent_devfreq = (struct devfreq *)p_data->parent;
>> +	struct devfreq_stats *parent_stats = parent_devfreq->profile->stats;
>> +	struct devfreq_stats *stats;
>>  	unsigned long child_freq = ULONG_MAX;
>>  	struct dev_pm_opp *opp;
>>  	int i, count, ret = 0;
>> @@ -47,10 +49,14 @@ static int devfreq_passive_get_target_freq(struct devfreq *devfreq,
>>  	 * device. And then the index is used for getting the suitable
>>  	 * new frequency for passive devfreq device.
>>  	 */
>> -	if (!devfreq->profile || !devfreq->profile->freq_table
>> -		|| devfreq->profile->max_state <= 0)
>> +	if (!devfreq->profile || !devfreq->profile->stats ||
>> +	    devfreq->profile->stats->max_state <= 0 ||
>> +	    !parent_devfreq->profile ||	!parent_devfreq->profile->stats ||
>> +	    parent_devfreq->profile->stats->max_state <= 0)
>>  		return -EINVAL;
>>  
>> +	stats = devfreq->profile->stats;
>> +	parent_stats = parent_devfreq->profile->stats;
>>  	/*
>>  	 * The passive governor have to get the correct frequency from OPP
>>  	 * list of parent device. Because in this case, *freq is temporary
>> @@ -68,21 +74,21 @@ static int devfreq_passive_get_target_freq(struct devfreq *devfreq,
>>  	 * Get the OPP table's index of decided freqeuncy by governor
>>  	 * of parent device.
>>  	 */
>> -	for (i = 0; i < parent_devfreq->profile->max_state; i++)
>> -		if (parent_devfreq->profile->freq_table[i] == *freq)
>> +	for (i = 0; i < parent_stats->max_state; i++)
>> +		if (parent_stats->freq_table[i] == *freq)
>>  			break;
>>  
>> -	if (i == parent_devfreq->profile->max_state) {
>> +	if (i == parent_stats->max_state) {
>>  		ret = -EINVAL;
>>  		goto out;
>>  	}
>>  
>>  	/* Get the suitable frequency by using index of parent device. */
>> -	if (i < devfreq->profile->max_state) {
>> -		child_freq = devfreq->profile->freq_table[i];
>> +	if (i < stats->max_state) {
>> +		child_freq = stats->freq_table[i];
>>  	} else {
>> -		count = devfreq->profile->max_state;
>> -		child_freq = devfreq->profile->freq_table[count - 1];
>> +		count = stats->max_state;
>> +		child_freq = stats->freq_table[count - 1];
>>  	}
>>  
>>  	/* Return the suitable frequency for passive device. */
>> @@ -109,7 +115,7 @@ static int update_devfreq_passive(struct devfreq *devfreq, unsigned long freq)
>>  	if (ret < 0)
>>  		goto out;
>>  
>> -	if (devfreq->profile->freq_table
>> +	if (devfreq->profile->stats
>>  		&& (devfreq_update_status(devfreq, freq)))
>>  		dev_err(&devfreq->dev,
>>  			"Couldn't update frequency transition information.\n");
>> diff --git a/include/linux/devfreq.h b/include/linux/devfreq.h
>> index 4ceb2a517a9c..8459af1a1583 100644
>> --- a/include/linux/devfreq.h
>> +++ b/include/linux/devfreq.h
>> @@ -64,6 +64,30 @@ struct devfreq_dev_status {
>>   */
>>  #define DEVFREQ_FLAG_LEAST_UPPER_BOUND		0x1
>>  
>> +/**
>> + * struct devfreq_stats - Devfreq's transitions stats counters
>> + * @freq_table:		Optional list of frequencies to support statistics
>> + *			and freq_table must be generated in ascending order.
>> + * @max_state:		The size of freq_table.
>> + * @total_trans:	Number of devfreq transitions
>> + * @trans_table:	Statistics of devfreq transitions
>> + * @time_in_state:	Statistics of devfreq states
>> + * @last_time:		The last time stats were updated
>> + * @stats_lock:		Lock protecting trans_table, time_in_state,
>> + *			last_time and total_trans used for statistics
>> + */
>> +struct devfreq_stats {
>> +	unsigned long *freq_table;
>> +	unsigned int max_state;
>> +
>> +	/* information for device frequency transition */
>> +	unsigned int total_trans;
>> +	unsigned int *trans_table;
>> +	u64 *time_in_state;
>> +	unsigned long long last_time;
>> +	spinlock_t stats_lock;
>> +};
>> +
>>  /**
>>   * struct devfreq_dev_profile - Devfreq's user device profile
>>   * @initial_freq:	The operating frequency when devfreq_add_device() is
>> @@ -88,15 +112,7 @@ struct devfreq_dev_status {
>>   *			from devfreq_remove_device() call. If the user
>>   *			has registered devfreq->nb at a notifier-head,
>>   *			this is the time to unregister it.
>> - * @freq_table:		Optional list of frequencies to support statistics
>> - *			and freq_table must be generated in ascending order.
>> - * @max_state:		The size of freq_table.
>> - * @total_trans:	Number of devfreq transitions
>> - * @trans_table:	Statistics of devfreq transitions
>> - * @time_in_state:	Statistics of devfreq states
>> - * @last_time:		The last time stats were updated
>> - * @stats_lock:		Lock protecting trans_table, time_in_state,
>> - *			last_time and total_trans used for statistics
>> + * @stats:		Statistics of devfreq states and state transitions
>>   */
>>  struct devfreq_dev_profile {
>>  	unsigned long initial_freq;
>> @@ -108,14 +124,7 @@ struct devfreq_dev_profile {
>>  	int (*get_cur_freq)(struct device *dev, unsigned long *freq);
>>  	void (*exit)(struct device *dev);
>>  
>> -	unsigned long *freq_table;
>> -	unsigned int max_state;
>> -	/* information for device frequency transition */
>> -	unsigned int total_trans;
>> -	unsigned int *trans_table;
>> -	u64 *time_in_state;
>> -	unsigned long long last_time;
>> -	spinlock_t stats_lock;
>> +	struct devfreq_stats *stats;
>>  };
>>  
>>  /**
>>