linux-kernel - RE: [PATCH v3 3/8] PM / devfreq: Show the available min/max frequency through sysfs node

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Date:   Wed, 11 Oct 2017 11:15:32 +0000
From:   MyungJoo Ham <myungjoo.ham@...sung.com>
To:     Chanwoo Choi <cw00.choi@...sung.com>,
        Kyungmin Park <kyungmin.park@...sung.com>
CC:     "rafael.j.wysocki@...el.com" <rafael.j.wysocki@...el.com>,
        "chanwoo@...nel.org" <chanwoo@...nel.org>,
        Inki Dae <inki.dae@...sung.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>
Subject: RE: [PATCH v3 3/8] PM / devfreq: Show the available min/max
 frequency through sysfs node

> The existing {min|max}_freq sysfs nodes don't consider whether min/max_freq
> are available or not. Those sysfs nodes show just the stored value
> in the struct devfreq.
> 
> The devfreq uses the OPP interface and then dev_pm_opp_{disable|add}()
> might change the state of the device's supported frequency. This patch
> shows the available minimum and maximum frequency through sysfs node.
> 
> Signed-off-by: Chanwoo Choi <cw00.choi@...sung.com>
> ---
>  drivers/devfreq/devfreq.c | 18 ++++++++++++++++--
>  1 file changed, 16 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/devfreq/devfreq.c b/drivers/devfreq/devfreq.c
> index 2ce1fd0a1324..799a0cf75d39 100644
> --- a/drivers/devfreq/devfreq.c
> +++ b/drivers/devfreq/devfreq.c
> @@ -1128,7 +1128,14 @@ static ssize_t min_freq_store(struct device *dev, struct device_attribute *attr,
>  static ssize_t min_freq_show(struct device *dev, struct device_attribute *attr,
>  			     char *buf)
>  {
> -	return sprintf(buf, "%lu\n", to_devfreq(dev)->min_freq);
> +	struct devfreq *df = to_devfreq(dev);
> +	unsigned long min_freq = to_devfreq(dev)->min_freq;
> +	unsigned long available_min_freq = find_available_min_freq(df);
> +
> +	if (available_min_freq != 0 && min_freq < available_min_freq)

nitpick:

If available_min_freq == 0,
it can't be min_freq < available_min_freq anyway;
it's unsigned.

> +		min_freq = available_min_freq;
> +
> +	return sprintf(buf, "%lu\n", min_freq);
>  }
>  
>  static ssize_t max_freq_store(struct device *dev, struct device_attribute *attr,
> @@ -1162,7 +1169,14 @@ static ssize_t max_freq_store(struct device *dev, struct device_attribute *attr,
>  static ssize_t max_freq_show(struct device *dev, struct device_attribute *attr,
>  			     char *buf)
>  {
> -	return sprintf(buf, "%lu\n", to_devfreq(dev)->max_freq);
> +	struct devfreq *df = to_devfreq(dev);
> +	unsigned long max_freq = to_devfreq(dev)->max_freq;
> +	unsigned long available_max_freq = find_available_max_freq(df);
> +
> +	if (available_max_freq != 0 && max_freq > available_max_freq)
> +		max_freq = available_max_freq;

similar here.

> +
> +	return sprintf(buf, "%lu\n", max_freq);
>  }
>  static DEVICE_ATTR_RW(max_freq);