linux-kernel - Re: [PATCH v2 2/3] devfreq: add clearing transitions stats

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Date:   Thu, 5 Dec 2019 09:38:05 +0900
From:   Chanwoo Choi <cw00.choi@...sung.com>
To:     Kamil Konieczny <k.konieczny@...sung.com>
Cc:     Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>,
        Krzysztof Kozlowski <krzk@...nel.org>,
        Kyungmin Park <kyungmin.park@...sung.com>,
        linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org,
        Marek Szyprowski <m.szyprowski@...sung.com>,
        MyungJoo Ham <myungjoo.ham@...sung.com>
Subject: Re: [PATCH v2 2/3] devfreq: add clearing transitions stats

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


> 
> Signed-off-by: Kamil Konieczny <k.konieczny@...sung.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?
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

> +	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,
Chanwoo Choi
Samsung Electronics