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Date:   Thu, 12 Jul 2018 17:38:09 +0900
From:   Chanwoo Choi <cw00.choi@...sung.com>
To:     Matthias Kaehlcke <mka@...omium.org>
Cc:     MyungJoo Ham <myungjoo.ham@...sung.com>,
        Kyungmin Park <kyungmin.park@...sung.com>,
        Arnd Bergmann <arnd@...db.de>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>, linux-pm@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        Brian Norris <briannorris@...omium.org>,
        Douglas Anderson <dianders@...omium.org>,
        Enric Balletbo i Serra <enric.balletbo@...labora.com>,
        "Rafael J . Wysocki" <rjw@...ysocki.net>,
        Viresh Kumar <viresh.kumar@...aro.org>,
        Lee Jones <lee.jones@...aro.org>,
        Benson Leung <bleung@...omium.org>,
        Olof Johansson <olof@...om.net>
Subject: Re: [PATCH v5 04/12] PM / devfreq: Add struct devfreq_policy

Hi Matthias,

On 2018년 07월 07일 02:07, Matthias Kaehlcke wrote:
> Hi,
> 
> On Wed, Jul 04, 2018 at 11:51:30AM +0900, Chanwoo Choi wrote:
>> Hi,
>>
>> On 2018년 07월 04일 08:46, Matthias Kaehlcke wrote:
>>> Move variables related with devfreq policy changes from struct devfreq
>>> to the new struct devfreq_policy and add a policy field to struct devfreq.
>>>
>>> The following variables are moved:
>>>
>>> df->min/max_freq           =>   p->user.min/max_freq
>>> df->scaling_min/max_freq   =>   p->devinfo.min/max_freq
>>> df->governor               =>   p->governor
>>> df->governor_name          =>   p->governor_name
>>>
>>> Signed-off-by: Matthias Kaehlcke <mka@...omium.org>
>>> Reviewed-by: Brian Norris <briannorris@...omium.org>
>>> ---
>>> Changes in v5:
>>> - none
>>>
>>> Changes in v4:
>>> - added 'Reviewed-by: Brian Norris <briannorris@...omium.org>' tag
>>>
>>> Changes in v3:
>>> - none
>>>
>>> Changes in v2:
>>> - performance, powersave and simpleondemand governors don't need changes
>>>   with "PM / devfreq: Don't adjust to user limits in governors"
>>> - formatting fixes
>>> ---
>>>  drivers/devfreq/devfreq.c          | 137 ++++++++++++++++-------------
>>>  drivers/devfreq/governor_passive.c |   4 +-
>>>  include/linux/devfreq.h            |  38 +++++---
> 
> 
>>>  3 files changed, 103 insertions(+), 76 deletions(-)
>>>
>>
>> (skip)
>>
>>>  
>>> diff --git a/drivers/devfreq/governor_passive.c b/drivers/devfreq/governor_passive.c
>>> index 3bc29acbd54e..e0987c749ec2 100644
>>> --- a/drivers/devfreq/governor_passive.c
>>> +++ b/drivers/devfreq/governor_passive.c
>>> @@ -99,12 +99,12 @@ static int update_devfreq_passive(struct devfreq *devfreq, unsigned long freq)
>>>  {
>>>  	int ret;
>>>  
>>> -	if (!devfreq->governor)
>>> +	if (!devfreq->policy.governor)
>>>  		return -EINVAL;
>>>  
>>>  	mutex_lock_nested(&devfreq->lock, SINGLE_DEPTH_NESTING);
>>>  
>>> -	ret = devfreq->governor->get_target_freq(devfreq, &freq);
>>> +	ret = devfreq->policy.governor->get_target_freq(devfreq, &freq);
>>>  	if (ret < 0)
>>>  		goto out;
>>>  
>>> diff --git a/include/linux/devfreq.h b/include/linux/devfreq.h
>>> index 3aae5b3af87c..9bf23b976f4d 100644
>>> --- a/include/linux/devfreq.h
>>> +++ b/include/linux/devfreq.h
>>> @@ -109,6 +109,30 @@ struct devfreq_dev_profile {
>>>  	unsigned int max_state;
>>>  };
>>>  
>>> +/**
>>> + * struct devfreq_freq_limits - Devfreq frequency limits
>>> + * @min_freq:	minimum frequency
>>> + * @max_freq:	maximum frequency
>>> + */
>>> +struct devfreq_freq_limits {
>>> +	unsigned long min_freq;
>>> +	unsigned long max_freq;
>>> +};
>>> +
>>> +/**
>>> + * struct devfreq_policy - Devfreq policy
>>> + * @user:	frequency limits requested by the user
>>> + * @devinfo:	frequency limits of the device (available OPPs)
>>> + * @governor:	method how to choose frequency based on the usage.
>>
>> nitpick. remove '.' on the end of line.
> 
> Ok
> 
>>> + * @governor_name:	devfreq governor name for use with this devfreq
>>> + */
>>> +struct devfreq_policy {
>>> +	struct devfreq_freq_limits user;
>>> +	struct devfreq_freq_limits devinfo;
>>> +	const struct devfreq_governor *governor;
>>> +	char governor_name[DEVFREQ_NAME_LEN];
>>> +};
>>> +
>>>  /**
>>>   * struct devfreq - Device devfreq structure
>>>   * @node:	list node - contains the devices with devfreq that have been
>>> @@ -117,8 +141,6 @@ struct devfreq_dev_profile {
>>>   * @dev:	device registered by devfreq class. dev.parent is the device
>>>   *		using devfreq.
>>>   * @profile:	device-specific devfreq profile
>>> - * @governor:	method how to choose frequency based on the usage.
>>> - * @governor_name:	devfreq governor name for use with this devfreq
>>>   * @nb:		notifier block used to notify devfreq object that it should
>>>   *		reevaluate operable frequencies. Devfreq users may use
>>>   *		devfreq.nb to the corresponding register notifier call chain.
>>> @@ -126,10 +148,7 @@ struct devfreq_dev_profile {
>>>   * @previous_freq:	previously configured frequency value.
>>>   * @data:	Private data of the governor. The devfreq framework does not
>>>   *		touch this.
>>> - * @min_freq:	Limit minimum frequency requested by user (0: none)
>>> - * @max_freq:	Limit maximum frequency requested by user (0: none)
>>> - * @scaling_min_freq:	Limit minimum frequency requested by OPP interface
>>> - * @scaling_max_freq:	Limit maximum frequency requested by OPP interface
>>> + * @policy:		Policy for frequency adjustments
>>
>> The devfreq_policy contains the range of frequency and governor information.
>> But, this description focus on the frequency. You need to explain the more
>> correct description of 'policy'.
> 
> I wouldn't say that the focus is on 'frequency', but on 'frequency
> adjustments', and the governor is an integral part of them.

OK. I agree your original description.

> 
> I can change it to "Policy for frequency adjustments, including
> frequency limits and the governor" if you prefer. I'm open to other
> suggestions.

(snip)

-- 
Best Regards,
Chanwoo Choi
Samsung Electronics

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