Re: [PATCH 2/6] devfreq: refactor set_target frequency function

From: Lukasz Luba <l.luba@partner.samsung.com>
To: Chanwoo Choi <cw00.choi@samsung.com>,
	linux-arm-kernel@lists.infradead.org,
	linux-samsung-soc@vger.kernel.org, linux-kernel@vger.kernel.org,
	linux-pm@vger.kernel.org, devicetree@vger.kernel.org
Cc: tjakobi@math.uni-bielefeld.de, myungjoo.ham@samsung.com,
	kyungmin.park@samsung.com, rjw@rjwysocki.net,
	len.brown@intel.com, pavel@ucw.cz, gregkh@linuxfoundation.org,
	keescook@chromium.org, anton@enomsg.org, ccross@android.com,
	tony.luck@intel.com, 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
Date: Fri, 23 Nov 2018 10:58:35 +0100	[thread overview]
Message-ID: <1c3a4aad-99cb-9295-3a5e-ff7a3c5245a3@partner.samsung.com> (raw)
In-Reply-To: <5BF73FA9.7010402@samsung.com>

Hi Chanwoo Choi,

On 11/23/18 12:45 AM, Chanwoo Choi wrote:
> 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;
> 
OK, I will add that change to patch 3.

Regards,
Lukasz
>>
>>>
>>>>    
>>>> -	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
>>
>>
> 
> 