linux-kernel - Re: [PATCH 3/3] PM / devfreq: account suspend/resume for stats

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Date:	Tue, 15 Jan 2013 17:16:54 +0530
From:	Rajagopal Venkat <rajagopal.venkat@...aro.org>
To:	myungjoo.ham@...il.com
Cc:	jonghwa3.lee@...sung.com, kyungmin.park@...sung.com,
	mturquette@...aro.org, rjw@...k.pl, patches@...aro.org,
	linaro-dev@...ts.linaro.org, linux-pm@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/3] PM / devfreq: account suspend/resume for stats

On 14 January 2013 20:18, MyungJoo Ham <myungjoo.ham@...sung.com> wrote:
> On Tue, Jan 8, 2013 at 2:50 PM, Rajagopal Venkat
> <rajagopal.venkat@...aro.org> wrote:
>> devfreq stats is not taking device suspend and resume into
>> account. Fix it.
>>
>> Signed-off-by: Rajagopal Venkat <rajagopal.venkat@...aro.org>
>
> With monitor_suspend(), we are suspending the DVFS mechanism of a
> device, not the device itself.
>
> Thus, the device may keep its frequency running and we may assume that
> the frequency is constant as the DVFS mechanism is in suspend.
>
> Why do you want to stop the statistics as well?
>

There seems to be misunderstanding of devfreq_monitor_suspend() and
devfreq_monitor_resume() apis usage.

Typically devfreq_monitor_suspend() would be called to suspend the device
devfreq when device is entering idle state by powering off(clocks and voltage).
When device itself is off, it's incorrect to allow stats to continue.

>
>
> Again, as in the other patch, this is about the semantics of the
> "devfreq statistics".
>
> It does not seem to be a problem of which is correct and which is not,
> but it seems to be a problem of which is more convenient.
>
> Could you please give me some cases where your semantics is more helpful?

When gpu is powered off, gpu devfreq should be suspended and hence the stats.

>
>
>
> I've been using the stat feature like this:
>
> # cat stat; run benchmark; cat stat
> and look at the differences with any ops done during "run benchmark".
>
>
>
> Cheers,
> MyungJoo.
>
>> ---
>>  drivers/devfreq/devfreq.c |   15 ++++++++++++---
>>  1 file changed, 12 insertions(+), 3 deletions(-)
>>
>> diff --git a/drivers/devfreq/devfreq.c b/drivers/devfreq/devfreq.c
>> index 2843a22..4c50235 100644
>> --- a/drivers/devfreq/devfreq.c
>> +++ b/drivers/devfreq/devfreq.c
>> @@ -297,6 +297,7 @@ void devfreq_monitor_suspend(struct devfreq *devfreq)
>>                 return;
>>         }
>>
>> +       devfreq_update_status(devfreq, devfreq->previous_freq);
>>         devfreq->stop_polling = true;
>>         mutex_unlock(&devfreq->lock);
>>         cancel_delayed_work_sync(&devfreq->work);
>> @@ -313,6 +314,8 @@ EXPORT_SYMBOL(devfreq_monitor_suspend);
>>   */
>>  void devfreq_monitor_resume(struct devfreq *devfreq)
>>  {
>> +       unsigned long freq;
>> +
>>         mutex_lock(&devfreq->lock);
>>         if (!devfreq->stop_polling)
>>                 goto out;
>> @@ -321,8 +324,14 @@ void devfreq_monitor_resume(struct devfreq *devfreq)
>>                         devfreq->profile->polling_ms)
>>                 queue_delayed_work(devfreq_wq, &devfreq->work,
>>                         msecs_to_jiffies(devfreq->profile->polling_ms));
>> +
>> +       devfreq->last_stat_updated = jiffies;
>>         devfreq->stop_polling = false;
>>
>> +       if (devfreq->profile->get_cur_freq &&
>> +               !devfreq->profile->get_cur_freq(devfreq->dev.parent, &freq))
>> +               devfreq->previous_freq = freq;
>> +
>>  out:
>>         mutex_unlock(&devfreq->lock);
>>  }
>> @@ -931,11 +940,11 @@ static ssize_t show_trans_table(struct device *dev, struct device_attribute *att
>>  {
>>         struct devfreq *devfreq = to_devfreq(dev);
>>         ssize_t len;
>> -       int i, j, err;
>> +       int i, j;
>>         unsigned int max_state = devfreq->profile->max_state;
>>
>> -       err = devfreq_update_status(devfreq, devfreq->previous_freq);
>> -       if (err)
>> +       if (!devfreq->stop_polling &&
>> +                       devfreq_update_status(devfreq, devfreq->previous_freq))
>>                 return 0;
>>
>>         len = sprintf(buf, "   From  :   To\n");
>> --
>> 1.7.10.4
>>
>> --
>> To unsubscribe from this list: send the line "unsubscribe linux-pm" in
>> the body of a message to majordomo@...r.kernel.org
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>
>
>
> --
> MyungJoo Ham, Ph.D.
> Mobile Software Platform Lab, DMC Business, Samsung Electronics



-- 
Regards,
Rajagopal
--
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