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Date:   Thu, 22 Nov 2018 11:54:50 +0900
From:   Chanwoo Choi <cw00.choi@samsung.com>
Organization: Samsung Electronics
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To:     Lukasz Luba <l.luba@partner.samsung.com>,
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Subject: Re: [PATCH 2/6] devfreq: refactor set_target frequency function
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On 2018년 11월 22일 11:52, 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.
> 
>>
>> Suggested-by: Tobias Jakobi <tjakobi@math.uni-bielefeld.de>
>> Suggested-by: Chanwoo Choi <cw00.choi@samsung.com>
>> Signed-off-by: Lukasz Luba <l.luba@partner.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.
> 
>> +{
>> +	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;
>> +}

You can change the devfreq_set_target as following:

 static int devfreq_set_target(struct devfreq *devfreq, unsigned long new_freq,
-                             unsigned long *prev_freq, u32 flags)
+                       u32 flags)
 {
        struct devfreq_freqs freqs;
        unsigned long cur_freq;
@@ -319,7 +319,9 @@ static int devfreq_set_target(struct devfreq *devfreq, unsigned long new_freq,
                        "Couldn't update frequency transition information.\n");
 
        devfreq->previous_freq = new_freq;
-       *prev_freq = cur_freq;


But, you have to add following new code on patch3 instead of patch2.

+
+       if (devfreq->suspend_freq)
+               devfreq->resume_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.
> 
>>  
>> -	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);
>>  
>>
> 
> 


-- 
Best Regards,
Chanwoo Choi
Samsung Electronics