Subject: Re: [PATCH v2 2/5] devfreq: add support for suspend/resume of a devfreq device

From: Chanwoo Choi <[email-masked]>
Date: Tue, 04 Dec 2018 14:43:42 +0900

Hi,

On 2018년 12월 04일 14:36, Chanwoo Choi wrote:
> Hi Lukasz,
> 
> Looks good to me. But, I add the some comments.
> If you will fix it, feel free to add my tag:
> Reviewed-by: Chanwoo choi <[email-masked]>

Sorry. Fix typo 'choi' to 'Choi' as following.
Reviewed-by: Chanwoo Choi <[email-masked]>

> 
> On 2018년 12월 03일 23:31, Lukasz Luba wrote:
>> The patch prepares devfreq device for handling suspend/resume
>> functionality.  The new fields will store needed information during this
> 
> nitpick. Remove unneeded space. There are two spaces between '.' and 'The new'. 
> 
>> process.  Devfreq framework handles opp-suspend DT entry and there is no
> 
> ditto.
> 
>> need of modyfications in the drivers code.  It uses atomic variables to
> 
> ditto.
> 
>> make sure no race condition affects the process.
>>
>> The patch is based on earlier work by Tobias Jakobi.
> 
> Please remove it from each patch description.
> 
>>
>> Suggested-by: Tobias Jakobi <[email-masked]>
>> Suggested-by: Chanwoo Choi <[email-masked]>
>> Signed-off-by: Lukasz Luba <[email-masked]>
>> ---
>>  drivers/devfreq/devfreq.c | 51 +++++++++++++++++++++++++++++++++++++++--------
>>  include/linux/devfreq.h   |  7 +++++++
>>  2 files changed, 50 insertions(+), 8 deletions(-)
>>
>> diff --git a/drivers/devfreq/devfreq.c b/drivers/devfreq/devfreq.c
>> index a9fd61b..36bed24 100644
>> --- a/drivers/devfreq/devfreq.c
>> +++ b/drivers/devfreq/devfreq.c
>> @@ -316,6 +316,10 @@ static int devfreq_set_target(struct devfreq *devfreq, unsigned long new_freq,
>>  			"Couldn't update frequency transition information.\n");
>>  
>>  	devfreq->previous_freq = new_freq;
>> +
>> +	if (devfreq->suspend_freq)
>> +		devfreq->resume_freq = cur_freq;
>> +
>>  	return err;
>>  }
>>  
>> @@ -667,6 +671,9 @@ struct devfreq *devfreq_add_device(struct device *dev,
>>  	}
>>  	devfreq->max_freq = devfreq->scaling_max_freq;
>>  
>> +	devfreq->suspend_freq = dev_pm_opp_get_suspend_opp_freq(dev);
>> +	atomic_set(&devfreq->suspend_count, 0);
>> +
>>  	dev_set_name(&devfreq->dev, "devfreq%d",
>>  				atomic_inc_return(&devfreq_no));
>>  	err = device_register(&devfreq->dev);
>> @@ -867,14 +874,28 @@ EXPORT_SYMBOL(devm_devfreq_remove_device);
>>   */
>>  int devfreq_suspend_device(struct devfreq *devfreq)
>>  {
>> +	int ret;
>> +
>>  	if (!devfreq)
>>  		return -EINVAL;
>>  
>> -	if (!devfreq->governor)
>> -		return 0;
>> +	if (devfreq->governor) {
>> +		ret = devfreq->governor->event_handler(devfreq,
>> +					DEVFREQ_GOV_SUSPEND, NULL);
>> +		if (ret)
>> +			return ret;
>> +	}
>> +
>> +	if (devfreq->suspend_freq) {
>> +		if (atomic_inc_return(&devfreq->suspend_count) > 1)
>> +			return 0;
>> +
>> +		ret = devfreq_set_target(devfreq, devfreq->suspend_freq, 0);
>> +		if (ret)
>> +			return ret;
>> +	}
>>  
>> -	return devfreq->governor->event_handler(devfreq,
>> -				DEVFREQ_GOV_SUSPEND, NULL);
>> +	return 0;
>>  }
>>  EXPORT_SYMBOL(devfreq_suspend_device);
>>  
>> @@ -888,14 +909,28 @@ EXPORT_SYMBOL(devfreq_suspend_device);
>>   */
>>  int devfreq_resume_device(struct devfreq *devfreq)
>>  {
>> +	int ret;
>> +
>>  	if (!devfreq)
>>  		return -EINVAL;
>>  
>> -	if (!devfreq->governor)
>> -		return 0;
>> +	if (devfreq->resume_freq) {
>> +		if (atomic_dec_return(&devfreq->suspend_count) >= 1)
>> +			return 0;
>>  
>> -	return devfreq->governor->event_handler(devfreq,
>> -				DEVFREQ_GOV_RESUME, NULL);
>> +		ret = devfreq_set_target(devfreq, devfreq->resume_freq, 0);
>> +		if (ret)
>> +			return ret;
>> +	}
>> +
>> +	if (devfreq->governor) {
>> +		ret = devfreq->governor->event_handler(devfreq,
>> +					DEVFREQ_GOV_RESUME, NULL);
>> +		if (ret)
>> +			return ret;
>> +	}
>> +
>> +	return 0;
>>  }
>>  EXPORT_SYMBOL(devfreq_resume_device);
>>  
>> diff --git a/include/linux/devfreq.h b/include/linux/devfreq.h
>> index e4963b0..d985199 100644
>> --- a/include/linux/devfreq.h
>> +++ b/include/linux/devfreq.h
>> @@ -131,6 +131,9 @@ struct devfreq_dev_profile {
>>   * @scaling_min_freq:	Limit minimum frequency requested by OPP interface
>>   * @scaling_max_freq:	Limit maximum frequency requested by OPP interface
>>   * @stop_polling:	 devfreq polling status of a device.
>> + * @suspend_freq:	 frequency of a device set during suspend phase.
>> + * @resume_freq:	 frequency of a device set in resume phase.
>> + * @suspend_count:	 suspend requests counter for a device.
>>   * @total_trans:	Number of devfreq transitions
>>   * @trans_table:	Statistics of devfreq transitions
>>   * @time_in_state:	Statistics of devfreq states
>> @@ -167,6 +170,10 @@ struct devfreq {
>>  	unsigned long scaling_max_freq;
>>  	bool stop_polling;
>>  
>> +	unsigned long suspend_freq;
>> +	unsigned long resume_freq;
>> +	atomic_t suspend_count;
>> +
>>  	/* information for device frequency transition */
>>  	unsigned int total_trans;
>>  	unsigned int *trans_table;
>>
> 
> 

-- 
Best Regards,
Chanwoo Choi
Samsung Electronics

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