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Date: Fri, 23 Nov 2018 10:58:35 +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 11/23/18 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@...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?
>
> 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
>>
>>
>
>
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