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Subject: Re: [PATCH 07/11] PM / devfreq: check get_dev_status before start
 monitor
From:   Chanwoo Choi <cwchoi00@gmail.com>
To:     Dong Aisheng <aisheng.dong@nxp.com>, linux-pm@vger.kernel.org,
        linux-arm-kernel@lists.infradead.org
Cc:     dongas86@gmail.com, kernel@pengutronix.de, shawnguo@kernel.org,
        linux-imx@nxp.com, linux-kernel@vger.kernel.org,
        myungjoo.ham@samsung.com, kyungmin.park@samsung.com,
        cw00.choi@samsung.com, abel.vesa@nxp.com
References: <1615294733-22761-1-git-send-email-aisheng.dong@nxp.com>
 <1615294733-22761-8-git-send-email-aisheng.dong@nxp.com>
 <de25cd22-7f17-5902-21d3-881e3128dd31@gmail.com>
Message-ID: <a546248b-3946-c781-94a9-30f0c92f88d2@gmail.com>
Date:   Wed, 10 Mar 2021 01:12:40 +0900
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On 21. 3. 10. 오전 12:58, Chanwoo Choi wrote:
> On 21. 3. 9. 오후 9:58, Dong Aisheng wrote:
>> The devfreq monitor depends on the device to provide load information
>> by .get_dev_status() to calculate the next target freq.
>>
>> And this will cause changing governor to simple ondemand fail
>> if device can't support.
>>
>> Signed-off-by: Dong Aisheng <aisheng.dong@nxp.com>
>> ---
>>   drivers/devfreq/devfreq.c                 | 10 +++++++---
>>   drivers/devfreq/governor.h                |  2 +-
>>   drivers/devfreq/governor_simpleondemand.c |  3 +--
>>   3 files changed, 9 insertions(+), 6 deletions(-)
>>
>> diff --git a/drivers/devfreq/devfreq.c b/drivers/devfreq/devfreq.c
>> index 7231fe6862a2..d1787b6c7d7c 100644
>> --- a/drivers/devfreq/devfreq.c
>> +++ b/drivers/devfreq/devfreq.c
>> @@ -482,10 +482,13 @@ static void devfreq_monitor(struct work_struct 
>> *work)
>>    * to be called from governor in response to DEVFREQ_GOV_START
>>    * event when device is added to devfreq framework.
>>    */
>> -void devfreq_monitor_start(struct devfreq *devfreq)
>> +int devfreq_monitor_start(struct devfreq *devfreq)
>>   {
>>       if (IS_SUPPORTED_FLAG(devfreq->governor->flags, IRQ_DRIVEN))
>> -        return;
>> +        return 0;
>> +
>> +    if (!devfreq->profile->get_dev_status)
>> +        return -EINVAL;

Again, I think that get_dev_status is not used for all governors.
So that it cause the governor start fail. Don't check whether
.get_dev_status is NULL or not.

>>       switch (devfreq->profile->timer) {
>>       case DEVFREQ_TIMER_DEFERRABLE:
>> @@ -495,12 +498,13 @@ void devfreq_monitor_start(struct devfreq *devfreq)
>>           INIT_DELAYED_WORK(&devfreq->work, devfreq_monitor);
>>           break;
>>       default:
>> -        return;
>> +        return -EINVAL;
>>       }
>>       if (devfreq->profile->polling_ms)
>>           queue_delayed_work(devfreq_wq, &devfreq->work,
>>               msecs_to_jiffies(devfreq->profile->polling_ms));
>> +    return 0;
>>   }
>>   EXPORT_SYMBOL(devfreq_monitor_start);
>> diff --git a/drivers/devfreq/governor.h b/drivers/devfreq/governor.h
>> index 5cee3f64fe2b..31af6d072a10 100644
>> --- a/drivers/devfreq/governor.h
>> +++ b/drivers/devfreq/governor.h
>> @@ -75,7 +75,7 @@ struct devfreq_governor {
>>                   unsigned int event, void *data);
>>   };
>> -void devfreq_monitor_start(struct devfreq *devfreq);
>> +int devfreq_monitor_start(struct devfreq *devfreq);
>>   void devfreq_monitor_stop(struct devfreq *devfreq);
>>   void devfreq_monitor_suspend(struct devfreq *devfreq);
>>   void devfreq_monitor_resume(struct devfreq *devfreq);
>> diff --git a/drivers/devfreq/governor_simpleondemand.c 
>> b/drivers/devfreq/governor_simpleondemand.c
>> index d57b82a2b570..ea287b57cbf3 100644
>> --- a/drivers/devfreq/governor_simpleondemand.c
>> +++ b/drivers/devfreq/governor_simpleondemand.c
>> @@ -89,8 +89,7 @@ static int devfreq_simple_ondemand_handler(struct 
>> devfreq *devfreq,
>>   {
>>       switch (event) {
>>       case DEVFREQ_GOV_START:
>> -        devfreq_monitor_start(devfreq);
>> -        break;
>> +        return devfreq_monitor_start(devfreq);
>>       case DEVFREQ_GOV_STOP:
>>           devfreq_monitor_stop(devfreq);
>>
> 
> Need to handle the all points of devfreq_monitor_start() usage.
> please check the tegra30-devfreq.c for this update.
> 
> $ grep -rn "devfreq_monitor_start" drivers/
> drivers/devfreq/governor_simpleondemand.c:92: 
> devfreq_monitor_start(devfreq);
> drivers/devfreq/tegra30-devfreq.c:744:        
> devfreq_monitor_start(devfreq);
> ......
> 


-- 
Best Regards,
Samsung Electronics
Chanwoo Choi