linux-kernel - Re: [PATCH] PM / devfreq: Init user limits from OPP limits, not viceversa

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Message-id: <5AFCD5EC.5080200@samsung.com>
Date:   Thu, 17 May 2018 10:07:56 +0900
From:   Chanwoo Choi <cw00.choi@...sung.com>
To:     Matthias Kaehlcke <mka@...omium.org>,
        MyungJoo Ham <myungjoo.ham@...sung.com>,
        Kyungmin Park <kyungmin.park@...sung.com>
Cc:     linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org,
        Brian Norris <briannorris@...omium.org>,
        Douglas Anderson <dianders@...omium.org>
Subject: Re: [PATCH] PM / devfreq: Init user limits from OPP limits, not
 viceversa

Hi,

On 2018년 05월 17일 07:57, Matthias Kaehlcke wrote:
> Commit ab8f58ad72c4 ("PM / devfreq: Set min/max_freq when adding
> the devfreq device") introduced the initialization of the user
> limits min/max_freq from the lowest/highest available OPPs. Later
> commit f1d981eaecf8 ("PM / devfreq: Use the available min/max
> frequency") added scaling_min/max_freq, which actually represent
> the frequencies of the lowest/highest available OPP. scaling_min/
> max_freq are initialized with the values from min/max_freq, which
> is totally correct in the context, but a bit awkward to read.
> 
> Swap the initialization and assign scaling_min/max_freq with the
> OPP freqs and then the user limts min/max_freq with scaling_min/
> max_freq.
> 
> Needless to say that this change is a NOP, intended to improve
> readability.
> 
> Signed-off-by: Matthias Kaehlcke <mka@...omium.org>
> ---
> Additional context: I'm considering to introduce the concept of
> a devfreq policy, which would probably move min/max_freq inside
> of a struct policy, this would make the initialization even
> more awkward to read. If this moves forward I might also propose
> to rename scaling_min/max_freq to something like min/max_opp_freq
> to avoid confusion with the frequencies in the policy (cpufreq uses
> scaling_min/max_freq for the sysfs attributes of the policy
> limits).
> 
>  drivers/devfreq/devfreq.c | 12 ++++++------
>  1 file changed, 6 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/devfreq/devfreq.c b/drivers/devfreq/devfreq.c
> index fe2af6aa88fc..0057ef5b0a98 100644
> --- a/drivers/devfreq/devfreq.c
> +++ b/drivers/devfreq/devfreq.c
> @@ -604,21 +604,21 @@ struct devfreq *devfreq_add_device(struct device *dev,
>  		mutex_lock(&devfreq->lock);
>  	}
>  
> -	devfreq->min_freq = find_available_min_freq(devfreq);
> -	if (!devfreq->min_freq) {
> +	devfreq->scaling_min_freq = find_available_min_freq(devfreq);
> +	if (!devfreq->scaling_min_freq) {
>  		mutex_unlock(&devfreq->lock);
>  		err = -EINVAL;
>  		goto err_dev;
>  	}
> -	devfreq->scaling_min_freq = devfreq->min_freq;
> +	devfreq->min_freq = devfreq->scaling_min_freq;
>  
> -	devfreq->max_freq = find_available_max_freq(devfreq);
> -	if (!devfreq->max_freq) {
> +	devfreq->scaling_max_freq = find_available_max_freq(devfreq);
> +	if (!devfreq->scaling_max_freq) {
>  		mutex_unlock(&devfreq->lock);
>  		err = -EINVAL;
>  		goto err_dev;
>  	}
> -	devfreq->scaling_max_freq = devfreq->max_freq;
> +	devfreq->max_freq = devfreq->scaling_max_freq;
>  
>  	dev_set_name(&devfreq->dev, "devfreq%d",
>  				atomic_inc_return(&devfreq_no));
> 

This patch just clean-up codes related to min/max_freq and scaling_min/max_freq.
It seems be good.

Reviewed-by: Chanwoo Choi <cw00.choi@...sung.com>

But, I don't want to change the name from 'scaling_min/max_freq'
to 'min/max_opp_freq'. You can check the meaning of variables
in comment of struct devfreq.

-- 
Best Regards,
Chanwoo Choi
Samsung Electronics