linux-kernel - Re: [PATCH 2/6] devfreq: refactor set

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Message-ID: <9eef3348-e86f-1113-3691-39ba3a620fb8@partner.samsung.com>
Date:   Thu, 22 Nov 2018 11:40:09 +0100
From:   Lukasz Luba <l.luba@...tner.samsung.com>
To:     Chanwoo Choi <cw00.choi@...sung.com>,
        linux-arm-kernel@...ts.infradead.org,
        linux-samsung-soc@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-pm@...r.kernel.org, devicetree@...r.kernel.org
Cc:     tjakobi@...h.uni-bielefeld.de, myungjoo.ham@...sung.com,
        kyungmin.park@...sung.com, rjw@...ysocki.net, len.brown@...el.com,
        pavel@....cz, gregkh@...uxfoundation.org, keescook@...omium.org,
        anton@...msg.org, ccross@...roid.com, tony.luck@...el.com,
        robh+dt@...nel.org, mark.rutland@....com, kgene@...nel.org,
        krzk@...nel.org, m.szyprowski@...sung.com, b.zolnierkie@...sung.com
Subject: Re: [PATCH 2/6] devfreq: refactor set_target frequency function

Hi Chanwoo Choi

On 11/22/18 3:52 AM, Chanwoo Choi wrote:
> On 2018년 11월 22일 03:01, Lukasz Luba wrote:
>> The refactoring is needed for the new client in devfreq: suspend.
>> To avoid code duplication, move it to the new local function
>> devfreq_set_target.
>>
>> The patch draws on Tobias Jakobi's work posted ~2 years ago, who tried to
>> solve issue with devfreq device's frequency during suspend/resume.
>> During the discussion on LKML some corner cases and comments appeared
>> related to the design. This patch address them keeping in mind suggestions
>> from Chanwoo Choi.
> 
> As I commented on patch1, please remove it.
OK
> 
>>
>> Suggested-by: Tobias Jakobi <tjakobi@...h.uni-bielefeld.de>
>> Suggested-by: Chanwoo Choi <cw00.choi@...sung.com>
>> Signed-off-by: Lukasz Luba <l.luba@...tner.samsung.com>
>> ---
>>   drivers/devfreq/devfreq.c | 62 ++++++++++++++++++++++++++++-------------------
>>   1 file changed, 37 insertions(+), 25 deletions(-)
>>
>> diff --git a/drivers/devfreq/devfreq.c b/drivers/devfreq/devfreq.c
>> index e20e7e4..cf9c643 100644
>> --- a/drivers/devfreq/devfreq.c
>> +++ b/drivers/devfreq/devfreq.c
>> @@ -285,6 +285,42 @@ static int devfreq_notify_transition(struct devfreq *devfreq,
>>   	return 0;
>>   }
>>   
>> +static int devfreq_set_target(struct devfreq *devfreq, unsigned long new_freq,
>> +			      unsigned long *prev_freq, u32 flags)
> 
> Please remove the unused space in front of 'unsigned long *prev_freq'.
> Use tab only for indentation.
OK
> 
>> +{
>> +	struct devfreq_freqs freqs;
>> +	unsigned long cur_freq;
>> +	int err = 0;
>> +
>> +	if (devfreq->profile->get_cur_freq)
>> +		devfreq->profile->get_cur_freq(devfreq->dev.parent, &cur_freq);
>> +	else
>> +		cur_freq = devfreq->previous_freq;
>> +
>> +	freqs.old = cur_freq;
>> +	freqs.new = new_freq;
>> +	devfreq_notify_transition(devfreq, &freqs, DEVFREQ_PRECHANGE);
>> +
>> +	err = devfreq->profile->target(devfreq->dev.parent, &new_freq, flags);
>> +	if (err) {
>> +		freqs.new = cur_freq;
>> +		devfreq_notify_transition(devfreq, &freqs, DEVFREQ_POSTCHANGE);
>> +		return err;
>> +	}
>> +
>> +	freqs.new = new_freq;
>> +	devfreq_notify_transition(devfreq, &freqs, DEVFREQ_POSTCHANGE);
>> +
>> +	if (devfreq_update_status(devfreq, new_freq))
>> +		dev_err(&devfreq->dev,
>> +			"Couldn't update frequency transition information.\n");
>> +
>> +	devfreq->previous_freq = new_freq;
>> +	*prev_freq = cur_freq;
>> +
>> +	return err;
>> +}
>> +
>>   /* Load monitoring helper functions for governors use */
>>   
>>   /**
>> @@ -296,7 +332,6 @@ static int devfreq_notify_transition(struct devfreq *devfreq,
>>    */
>>   int update_devfreq(struct devfreq *devfreq)
>>   {
>> -	struct devfreq_freqs freqs;
>>   	unsigned long freq, cur_freq, min_freq, max_freq;
> 
> 
> cur_freq is not used after modification. Remove it.
> 
>>   	int err = 0;
>>   	u32 flags = 0;
>> @@ -333,31 +368,8 @@ int update_devfreq(struct devfreq *devfreq)
>>   		flags |= DEVFREQ_FLAG_LEAST_UPPER_BOUND; /* Use LUB */
>>   	}
>>   
>> -	if (devfreq->profile->get_cur_freq)
>> -		devfreq->profile->get_cur_freq(devfreq->dev.parent, &cur_freq);
>> -	else
>> -		cur_freq = devfreq->previous_freq;
>> -
>> -	freqs.old = cur_freq;
>> -	freqs.new = freq;
>> -	devfreq_notify_transition(devfreq, &freqs, DEVFREQ_PRECHANGE);
>> +	return devfreq_set_target(devfreq, freq, &cur_freq, flags);
> 
> You get the 'cur_freq' from devfreq_set_taget() for devfreq_suspend_device() on patch3.
> But, update_devfreq() and devfreq_resume_device() don't use the 'cur_freq' value
> from devfreq_set_target().
> 
> Instead, getting 'cur_freq' for 'devfreq->resume_freq' in the devfreq_set_target().
> Please remove the 'cur_freq' parameter from devfreq_set_target.

I can remove the 3rd parameter from devfreq_set_target(),
but it implies that patch 1 and 3 cannot be merged. The function 
devfreq_set_target will use 'devfreq->resume_freq' so it must be in 
devfreq struct.
So, in v2 version there will be still 6 patches, with the 1st patch 
defining needed fields in devfreq struct.
Do you agree for that?

> 
>>   
>> -	err = devfreq->profile->target(devfreq->dev.parent, &freq, flags);
>> -	if (err) {
>> -		freqs.new = cur_freq;
>> -		devfreq_notify_transition(devfreq, &freqs, DEVFREQ_POSTCHANGE);
>> -		return err;
>> -	}
>> -
>> -	freqs.new = freq;
>> -	devfreq_notify_transition(devfreq, &freqs, DEVFREQ_POSTCHANGE);
>> -
>> -	if (devfreq_update_status(devfreq, freq))
>> -		dev_err(&devfreq->dev,
>> -			"Couldn't update frequency transition information.\n");
>> -
>> -	devfreq->previous_freq = freq;
>> -	return err;
>>   }
>>   EXPORT_SYMBOL(update_devfreq);
>>   
>>
> 
> 

Regards,
Lukasz Luba