linux-kernel - Re: [PATCH 4/6] devfreq: add devfreq

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Date:   Thu, 22 Nov 2018 12:02:04 +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 4/6] devfreq: add devfreq_suspend/resume() functions



On 11/22/18 4:07 AM, Chanwoo Choi wrote:
> Hi,
> 
> On 2018년 11월 22일 03:01, Lukasz Luba wrote:
>> This patch adds implementation for global suspend/resume for
>> devfreq framework. System suspend will next use these functions.
>>
>> 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.
> 
> Please remove the duplicate information about patch history.
> 
>>
>> 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 | 49 +++++++++++++++++++++++++++++++++++++++++++++++
>>   include/linux/devfreq.h   |  7 +++++++
>>   2 files changed, 56 insertions(+)
>>
>> diff --git a/drivers/devfreq/devfreq.c b/drivers/devfreq/devfreq.c
>> index 7e09de8..2f4391c 100644
>> --- a/drivers/devfreq/devfreq.c
>> +++ b/drivers/devfreq/devfreq.c
>> @@ -44,6 +44,9 @@ static LIST_HEAD(devfreq_governor_list);
>>   static LIST_HEAD(devfreq_list);
>>   static DEFINE_MUTEX(devfreq_list_lock);
>>   
>> +/* Flag showing state of suspend/resume */
>> +static bool devfreq_suspended;
> 
> Is it necessary? This patch just saves the 'true' or 'false' to this variable.
> And there are no any point to check the value of this variable.
> Please remove it.
> 
>> +
>>   /**
>>    * find_device_devfreq() - find devfreq struct using device pointer
>>    * @dev:	device pointer used to lookup device devfreq.
>> @@ -938,6 +941,52 @@ int devfreq_resume_device(struct devfreq *devfreq)
>>   EXPORT_SYMBOL(devfreq_resume_device);
>>   
>>   /**
>> + * devfreq_suspend() - Suspend devfreq governors and devices
>> + *
>> + * Called during system wide Suspend/Hibernate cycles for suspending governors
>> + * and devices preserving the state for resume. On some platforms the devfreq
>> + * device must have precise state (frequency) after resume in order to provide
>> + * fully operating setup.
>> + */
>> +void devfreq_suspend(void)
>> +{
>> +	struct devfreq *devfreq;
>> +	int ret;
>> +
>> +	mutex_lock(&devfreq_list_lock);
>> +	list_for_each_entry(devfreq, &devfreq_list, node) {
>> +		ret = devfreq_suspend_device(devfreq);
>> +		if (ret)
>> +			dev_warn(&devfreq->dev, "device suspend failed\n");
>> +	}
>> +	mutex_unlock(&devfreq_list_lock);
>> +
>> +	devfreq_suspended = true;
> 
> Remove it.
> 
>> +}
>> +
>> +/**
>> + * devfreq_resume() - Resume devfreq governors and devices
>> + *
>> + * Called during system wide Suspend/Hibernate cycle for resuming governors and
>> + * devices that are suspended with devfreq_suspend().
>> + */
>> +void devfreq_resume(void)
>> +{
>> +	struct devfreq *devfreq;
>> +	int ret;
>> +
>> +	devfreq_suspended = false;
> 
> Remove it.
> 
>> +
>> +	mutex_lock(&devfreq_list_lock);
>> +	list_for_each_entry(devfreq, &devfreq_list, node) {
>> +		ret = devfreq_resume_device(devfreq);
>> +		if (ret)
>> +			dev_warn(&devfreq->dev, "device resume failed\n");
>> +	}
>> +	mutex_unlock(&devfreq_list_lock);
>> +}
>> +
>> +/**
>>    * devfreq_add_governor() - Add devfreq governor
>>    * @governor:	the devfreq governor to be added
>>    */
>> diff --git a/include/linux/devfreq.h b/include/linux/devfreq.h
>> index 7fe96f9..4f0fea8 100644
>> --- a/include/linux/devfreq.h
>> +++ b/include/linux/devfreq.h
>> @@ -202,6 +202,10 @@ extern void devm_devfreq_remove_device(struct device *dev,
>>   extern int devfreq_suspend_device(struct devfreq *devfreq);
>>   extern int devfreq_resume_device(struct devfreq *devfreq);
>>   
>> +
> 
> Remove the blank line.
> 
>> +extern void devfreq_suspend(void);
>> +extern void devfreq_resume(void);
>> +
>>   /**
>>    * update_devfreq() - Reevaluate the device and configure frequency
>>    * @devfreq:	the devfreq device
>> @@ -396,6 +400,9 @@ static inline int devfreq_update_stats(struct devfreq *df)
>>   {
>>   	return -EINVAL;
>>   }
>> +
>> +static inline void devfreq_suspend(void) {}
>> +static inline void devfreq_resume(void) {}
> 
> You better to move the inline definitions
> under 'devfreq_resume_device' inline function.
OK, I will move it there.
> 
>>   #endif /* CONFIG_PM_DEVFREQ */
>>   
>>   #endif /* __LINUX_DEVFREQ_H__ */
>>
> 
>

Regards,
Lukasz Luba