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Subject: Re: [PATCH 3/7] devfreq: add clearing transitions stats in sysfs
To:     Chanwoo Choi <cw00.choi@samsung.com>,
        Kamil Konieczny <k.konieczny@samsung.com>
Cc:     Kamil Konieczny <k.konieczny@partner.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:   Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
Message-ID: <95813188-be4f-d3b3-459a-597be775f035@samsung.com>
Date:   Thu, 14 Nov 2019 19:23:03 +0100
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Hi Chanwoo,

On 11/13/19 10:41 AM, Chanwoo Choi wrote:
> Hi,
> 
> If user only want to use the transitions stats information
> from now, the user just read the sysfs twice and then
> can calculate them between the read data. It is enough

IOW you are suggesting that user should invest his valuable time
into actually doing such calculations (or implementing some extra
script to do the data parsing and calculations automatically)
instead of doing simple write to special sysfs file?

Also similar patch for cpufreq has been applied not so long ago:

commit ee7930ee27fe5240398cc302fa8eb4454725f188
Author: Markus Mayer <mmayer@broadcom.com>
Date:   Mon Nov 7 10:02:23 2016 -0800

    cpufreq: stats: New sysfs attribute for clearing statistics
    
    Allow CPUfreq statistics to be cleared by writing anything to
    /sys/.../cpufreq/stats/reset.
    
    Signed-off-by: Markus Mayer <mmayer@broadcom.com>
    Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
    Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
...

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

> to get the existing sysfs information. 
> 
> And I don't know the any other reason. So, I can't agree this patch.
> So, Not ack.
> 
> Regards,
> Chanwoo Choi
> 
> 
> On 11/13/19 6:13 PM, Kamil Konieczny wrote:
>> Add new function trans_reset in sysfs for clearing transition
>> table and time in states devfreq statistics.> 
>> Signed-off-by: Kamil Konieczny <k.konieczny@samsung.com>
>> ---
>>  drivers/devfreq/devfreq.c | 26 ++++++++++++++++++++++++++
>>  1 file changed, 26 insertions(+)
>>
>> diff --git a/drivers/devfreq/devfreq.c b/drivers/devfreq/devfreq.c
>> index ac04b5baef70..0a88055d1362 100644
>> --- a/drivers/devfreq/devfreq.c
>> +++ b/drivers/devfreq/devfreq.c
>> @@ -1445,6 +1445,31 @@ static ssize_t trans_stat_show(struct device *dev,
>>  }
>>  static DEVICE_ATTR_RO(trans_stat);
>>  
>> +static void defvreq_stats_clear_table(struct devfreq *devfreq)
>> +{
>> +	unsigned int count = devfreq->profile->max_state;
>> +
>> +	spin_lock(&devfreq->stats_lock);
>> +	memset(devfreq->time_in_state, 0, count * sizeof(u64));
>> +	memset(devfreq->trans_table, 0, count * count * sizeof(int));
>> +	devfreq->last_stat_updated = get_jiffies_64();
>> +	devfreq->total_trans = 0;
>> +	spin_unlock(&devfreq->stats_lock);
>> +}
>> +
>> +static ssize_t trans_reset_store(struct device *dev,
>> +				 struct device_attribute *attr,
>> +				 const char *buf,
>> +				 size_t count)
>> +{
>> +	struct devfreq *devfreq = to_devfreq(dev);
>> +
>> +	defvreq_stats_clear_table(devfreq);
>> +
>> +	return count;
>> +}
>> +static DEVICE_ATTR_WO(trans_reset);
>> +
>>  static struct attribute *devfreq_attrs[] = {
>>  	&dev_attr_governor.attr,
>>  	&dev_attr_available_governors.attr,
>> @@ -1455,6 +1480,7 @@ static struct attribute *devfreq_attrs[] = {
>>  	&dev_attr_min_freq.attr,
>>  	&dev_attr_max_freq.attr,
>>  	&dev_attr_trans_stat.attr,
>> +	&dev_attr_trans_reset.attr,
>>  	NULL,
>>  };
>>  ATTRIBUTE_GROUPS(devfreq);