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Subject: Re: [PATCH 7/7] devfreq: move statistics to separate struct
To:     Chanwoo Choi <cw00.choi@samsung.com>
Cc:     Kamil Konieczny <k.konieczny@samsung.com>,
        Krzysztof Kozlowski <krzk@kernel.org>,
        Kukjin Kim <kgene@kernel.org>,
        Kyungmin Park <kyungmin.park@samsung.com>,
        linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org,
        linux-pm@vger.kernel.org, linux-samsung-soc@vger.kernel.org,
        Marek Szyprowski <m.szyprowski@samsung.com>,
        MyungJoo Ham <myungjoo.ham@samsung.com>,
        Zhang Rui <rui.zhang@intel.com>,
        Eduardo Valentin <edubezval@gmail.com>,
        Javi Merino <javi.merino@arm.com>,
        =?UTF-8?Q?=c3=98rjan_Eide?= <orjan.eide@arm.com>
From:   Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
Message-ID: <d9d13537-f4c9-4420-c3bc-438bc87c5e6a@samsung.com>
Date:   Fri, 15 Nov 2019 13:40:39 +0100
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References: <20191113091336.5218-1-k.konieczny@samsung.com>
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        <38350d81-e916-b386-6727-f4c85689c172@samsung.com>
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        <4ed6b8bf-b415-c42d-33d6-d2ed0504eaf4@samsung.com>
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[ added Zhang, Eduardo, Ørjan and Javi to Cc: ]

On 11/15/19 7:21 AM, Chanwoo Choi wrote:
> Hi Bartlomiej,
> 
> On 11/15/19 12:25 PM, Chanwoo Choi wrote:
>> Hi Bartlomiej,
>>
>> On 11/15/19 3:01 AM, Bartlomiej Zolnierkiewicz wrote:
>>>
>>> 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://protect2.fireeye.com/url?k=909caa5c-cd52abe8-909d2113-000babdfecba-812f16576c3614a3&u=https://developer.arm.com/tools-and-software/graphics-and-gaming/mali-drivers/bifrost-kernel#
>>>> [2] https://protect2.fireeye.com/url?k=33265f96-6ee85e22-3327d4d9-000babdfecba-44c2daec328712e6&u=https://developer.arm.com/tools-and-software/graphics-and-gaming/mali-drivers/midgard-kernel
>>>> [3] https://protect2.fireeye.com/url?k=69bdcab0-3473cb04-69bc41ff-000babdfecba-4b576facf85e0208&u=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?
>>
>> OK. I agree to simplify them on this time.
>> For touching the 'freq_table' and 'max_state', need to fix
>> the descending order of freq_table. 
>>
>> The partition_enable_ops() in the drivers/thermal/devfreq_cooling.c 
>> requires the descending order of freq_table. Have to change it by using
>> the ascending time or support both ascending and descending order for freq_table.
>>
>> 1. Move freq_table, max_state of devfreq_dev_profile to struct devfreq
>> 2. Edit partition_enable_ops() in the drivers/thermal/devfreq_cooling.c 
>>    by using ascending order instead of descending order.
>>
> 
> After changed about 'freq_table' and 'max_state', the build error
> will happen on ARM mail driver because the initialization code of
> 'freq_table' in ARM mali driver, didn't check the kernel version.
> 
> The first devfreq patch provided the 'freq_table' as optional variable
> in the 'struct devfreq_dev_profile'. Even if ARM mali driver is out of mainline tree, 
> this change seems that break the usage rule of 'freq_table' in 'struct devfreq_dev_profile'.
> 
> So, if there are no any beneficial reason, I just keep the current status of 'freq_table'
> in order to keep the previous usage rule of 'freq_table' in 'struct devfreq_dev_profile'.
> 
> Frankly, I'm note sure that it is necessary. I don't want to make
> the side-effect without any useful reason.
> 
> But,
> Separately, have to fix the ordering issue of partition_enable_ops()
> in the drivers/thermal/devfreq_cooling.c.

Hmmm.. fixing partition_enable_opps() should be trivial but I wonder
why we are carrying devfreq_cooling.c code in upstream kernel at all?

It has been merged in the following commit:

commit a76caf55e5b356ba20a5a43ac4d9f7a04b20941d
Author: Ørjan Eide <orjan.eide@arm.com>
Date:   Thu Sep 10 18:09:30 2015 +0100

    thermal: Add devfreq cooling
    
    Add a generic thermal cooling device for devfreq, that is similar to
    cpu_cooling.
    
    The device must use devfreq.  In order to use the power extension of the
    cooling device, it must have registered its OPPs using the OPP library.
    
    Cc: Zhang Rui <rui.zhang@intel.com>
    Cc: Eduardo Valentin <edubezval@gmail.com>
    Signed-off-by: Javi Merino <javi.merino@arm.com>
    Signed-off-by: Ørjan Eide <orjan.eide@arm.com>
    Signed-off-by: Eduardo Valentin <edubezval@gmail.com>
...

but 4 years later there is still no single in-kernel user for this code?

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

>>>
>>>> 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@samsung.com>
>>>>> ---
>>>>>  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;
>>>>>  };
>>>>>  
>>>>>  /**
>>>>>