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Date:   Fri, 23 Nov 2018 08:45:45 +0900
From:   Chanwoo Choi <cw00.choi@samsung.com>
Organization: Samsung Electronics
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To:     Lukasz Luba <l.luba@partner.samsung.com>,
        linux-arm-kernel@lists.infradead.org,
        linux-samsung-soc@vger.kernel.org, linux-kernel@vger.kernel.org,
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Cc:     tjakobi@math.uni-bielefeld.de, myungjoo.ham@samsung.com,
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        robh+dt@kernel.org, mark.rutland@arm.com, kgene@kernel.org,
        krzk@kernel.org, m.szyprowski@samsung.com, b.zolnierkie@samsung.com
Subject: Re: [PATCH 2/6] devfreq: refactor set_target frequency function
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Hi Lukasz,

On 2018년 11월 22일 19:40, Lukasz Luba wrote:
> 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@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.
> 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?

So, I replied again as following on my other reply[1] of patch2: 
[1] https://lkml.org/lkml/2018/11/22/507

But, you have to add following new code on patch3 instead of patch2.
patch2 doesn't contain the following codes and then
patch3 adds 'resume_freq' variable and adds the following code on patch3.

+
+       if (devfreq->suspend_freq)
+               devfreq->resume_freq = cur_freq;

> 
>>
>>>   
>>> -	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
> 
> 


-- 
Best Regards,
Chanwoo Choi
Samsung Electronics