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Subject: Re: [PATCH v2 2/3] devfreq: add clearing transitions stats
To:     Chanwoo Choi <cw00.choi@samsung.com>
Cc:     Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>,
        Krzysztof Kozlowski <krzk@kernel.org>,
        Kyungmin Park <kyungmin.park@samsung.com>,
        linux-kernel@vger.kernel.org, linux-pm@vger.kernel.org,
        Marek Szyprowski <m.szyprowski@samsung.com>,
        MyungJoo Ham <myungjoo.ham@samsung.com>
From:   Kamil Konieczny <k.konieczny@samsung.com>
Message-ID: <2ca32866-e1f6-afcf-2700-89208587c19e@samsung.com>
Date:   Thu, 5 Dec 2019 11:33:10 +0100
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Hi Chanwoo,

On 05.12.2019 01:38, Chanwoo Choi wrote:
> On 12/5/19 12:00 AM, Kamil Konieczny wrote:
>> Add clearing transition table and time in states devfreq statistics
>> by writing to trans_stat file in devfreq sysfs.
> 
> Have to add command example how to reset the trans_stat via sysfs
> on patch description.
> 
> And, have to add how to do it on documentation file as following:
> On next version, please contain the following modification with this patch.
> 
> diff --git a/Documentation/ABI/testing/sysfs-class-devfreq b/Documentation/ABI/testing/sysfs-class-devfreq
> index 75897e2fde43..c172ff838643 100644
> --- a/Documentation/ABI/testing/sysfs-class-devfreq
> +++ b/Documentation/ABI/testing/sysfs-class-devfreq
> @@ -60,7 +60,10 @@ Description:
>                 the number of transitions between states.
>                 In order to activate this ABI, the devfreq target device
>                 driver should provide the list of available frequencies
> -               with its profile.
> +               with its profile. If need to reset the statistics of devfreq
> +               behavior on a specific device, enter 0(zero) to 'trans_stat'
> +               as following:
> +                       echo 0 > /sys/class/devfreq/.../trans_stat
>  
>  What:          /sys/class/devfreq/.../userspace/set_freq
>  Date:          September 2011

Thank you for spotting this and giving patch, I will include it with v3.

>>
>> Signed-off-by: Kamil Konieczny <k.konieczny@samsung.com>
>> ---
>> Changes in v2:
>>  instead of creating new sysfs file, add new functionality to trans_stat
>>  and clear stats when anything is writen to it
>>
>>  drivers/devfreq/devfreq.c | 22 +++++++++++++++++++++-
>>  1 file changed, 21 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/devfreq/devfreq.c b/drivers/devfreq/devfreq.c
>> index 0e2030403e4a..901af3b66a76 100644
>> --- a/drivers/devfreq/devfreq.c
>> +++ b/drivers/devfreq/devfreq.c
>> @@ -1478,7 +1478,27 @@ static ssize_t trans_stat_show(struct device *dev,
>>  					devfreq->total_trans);
>>  	return len;
>>  }
>> -static DEVICE_ATTR_RO(trans_stat);
>> +
>> +static ssize_t trans_stat_store(struct device *dev,
>> +				struct device_attribute *attr,
>> +				const char *buf, size_t count)
>> +{
>> +	struct devfreq *df = to_devfreq(dev);
>> +	unsigned int cnt = df->profile->max_state;
>> +
 
> Why don't you check the input value is whether value is 0(zero) or not?

I will follow your suggestion as this will help to avoid misuse

> If user enter the any value to 'trans_stat', devfreq core
> reset the statistics data. I want to decide the fixed value
> for the reset as following:
> 
> 	echo 0 > /sys/class/devfreq/devfreqX/trans_stat
> 

Thank you, I will add it to commit description.

>> +	if (cnt == 0)
>> +		return count;
>> +
>> +	mutex_lock(&df->lock);
>> +	memset(df->time_in_state, 0, cnt * sizeof(u64));
>> +	memset(df->trans_table, 0, cnt * cnt * sizeof(int));
>> +	df->last_stat_updated = get_jiffies_64();
>> +	df->total_trans = 0;
>> +	mutex_unlock(&df->lock);
>> +
>> +	return count;
>> +}
>> +static DEVICE_ATTR_RW(trans_stat);
>>  
>>  static struct attribute *devfreq_attrs[] = {
>>  	&dev_attr_name.attr,

-- 
Best regards,
Kamil Konieczny
Samsung R&D Institute Poland