Hi Tobias,
On 2016년 11월 24일 10:34, Chanwoo Choi wrote:
> Hi Tobias,
>
> I like your suggestion. But I have some comment on below.
>
> On 2016년 11월 23일 22:51, Tobias Jakobi wrote:
>> This suspend/resume operations works analogous to the
>> cpufreq_{suspend,resume}() calls in the CPUFreq subsystem.
>>
>> Signed-off-by: Tobias Jakobi <tjakobi@xxxxxxxxxxxxxxxxxxxxx>
>> ---
>> drivers/devfreq/devfreq.c | 75 +++++++++++++++++++++++++++++++++++++++++++++++
>> include/linux/devfreq.h | 10 +++++++
>> 2 files changed, 85 insertions(+)
>>
>> diff --git a/drivers/devfreq/devfreq.c b/drivers/devfreq/devfreq.c
>> index bf3ea76..2f1aa83 100644
>> --- a/drivers/devfreq/devfreq.c
>> +++ b/drivers/devfreq/devfreq.c
>> @@ -785,6 +785,81 @@ int devfreq_resume_device(struct devfreq *devfreq)
>> EXPORT_SYMBOL(devfreq_resume_device);
>>
>> /**
>> + * devfreq_suspend() - Suspend DevFreq governors
>> + *
>> + * Called during system wide Suspend/Hibernate cycles for suspending governors
>> + * in the same fashion as cpufreq_suspend().
>> + */
>> +void devfreq_suspend(void)
>> +{
>> + struct devfreq *devfreq;
>> + unsigned long freq;
>> + int ret;
>> +
>> + mutex_lock(&devfreq_list_lock);
>> +
>> + list_for_each_entry(devfreq, &devfreq_list, node) {
>> + if (!devfreq->suspend_freq)
>> + continue;
>> +
>> + ret = devfreq_suspend_device(devfreq);
The devfreq_suspend_device() stop the monitoring of governors.
But, this function is exported. It means that each devfreq device.
can call the devfreq_suspend/resume_device() (e.g., int drivers/scsi/ufs/ufshcd.c)
So, you should consider following case:
- case :Before calling the devfreq_suspend() and specific devfreq already call
the devfreq_suspend_device(), how to support it?
In this case, the specific devfreq device don't want to call
the devfreq_resume_device() in the devfreq_resume().
>> + if (ret < 0) {
>> + dev_warn(&devfreq->dev, "%s: governor suspend failed\n", __func__);
>> + continue;
>> + }
>> +
>> + devfreq->resume_freq = 0;
>> + if (devfreq->profile->get_cur_freq) {
>> + ret = devfreq->profile->get_cur_freq(devfreq->dev.parent, &freq);
>> + if (ret >= 0)
>> + devfreq->resume_freq = freq;
>> + }
>> +
>> + freq = devfreq->suspend_freq;
>> + ret = devfreq->profile->target(devfreq->dev.parent, &freq, 0);
>
>
> DEVFREQ subsystem has the passive governor[2] and devfreq device using passive[1]
> governor depends on the parent devfreq device. The passive governor uses
> 'DEVFREQ_TRANSITION_NOTIFIER' notifier to track the changed state of
> parent devfreq device.
>
> When changing the clock/voltage of parent devfreq device,
> DEVFREQ subsystem have to notify the changed frequency
> to the passive devfreq device.
>
> So, you should call the devfreq_notifiy_transition()
> before/after 'devfreq->profile->target' as following:
> You can refer the update_devfreq() function
> that is how to use devfreq_notifiy_transition().
>
> For example,
> struct devfreq_freq freqs;
>
> if (devfreq->profile->get_cur_freq) {
> ret = devfreq->profile->get_cur_freq(devfreq->dev.parent, &freq);
> if (ret >= 0)
> devfreq->resume_freq = freq;
> } else {
> devfreq->resume_freq = devfreq_previous_freq;
> }
>
> freqs.old = devfreq->resume_freq;
> freqs.new = devfreq->suspend_freq;
> devfreq_notify_transition(devfreq, &freqs, DEVFREQ_PRECHANGE);
>
> freq = devfreq->suspend_freq;
> ret = devfreq->profile->target(devfreq->dev.parent, &freq, 0);
>
> freqs.new = freq;
> devfreq_notify_transition(devfreq, &freqs, DEVFREQ_POSTCHANGE);
>
> if (ret < 0)
> dev_warn(&devfreq->dev, "%s: setting suspend frequency failed\n", __func__);
> }
>
> [1] DEVFREQ_TRANSITION_NOTIFIER notifier
> - https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=0fe3a66410a3ba96679be903f1e287d7a0a264a9
> [2] DEVFREQ passive governor
> - https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=996133119f57334c38b020dbfaaac5b5eb127e29
>
>> +
>> + if (ret < 0)
>> + dev_warn(&devfreq->dev, "%s: setting suspend frequency failed\n", __func__);
>> + }
>> +
>> + mutex_unlock(&devfreq_list_lock);
>> +}
>> +
>> +/**
>> + * devfreq_resume() - Resume DevFreq governors
>> + *
>> + * Called during system wide Suspend/Hibernate cycle for resuming governors that
>> + * are suspended with devfreq_suspend().
>> + */
>> +void devfreq_resume(void)
>> +{
>> + struct devfreq *devfreq;
>> + unsigned long freq;
>> + int ret;
>> +
>> + mutex_lock(&devfreq_list_lock);
>> +
>> + list_for_each_entry(devfreq, &devfreq_list, node) {
>> + if (!devfreq->suspend_freq)
>> + continue;
>> +
>> + freq = devfreq->resume_freq;
>> + ret = devfreq->profile->target(devfreq->dev.parent, &freq, 0);
>
> ditto.
>
>> +
>> + if (ret < 0) {
>> + dev_warn(&devfreq->dev, "%s: setting resume frequency failed\n", __func__);
>> + continue;
>> + }
>> +
>> + ret = devfreq_resume_device(devfreq);
>> + if (ret < 0)
>> + dev_warn(&devfreq->dev, "%s: governor resume failed\n", __func__);
>> + }
>> +
>> + 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 2de4e2e..555d024 100644
>> --- a/include/linux/devfreq.h
>> +++ b/include/linux/devfreq.h
>> @@ -171,6 +171,9 @@ struct devfreq {
>> struct notifier_block nb;
>> struct delayed_work work;
>>
>> + unsigned long suspend_freq; /* freq during devfreq suspend */
>> + unsigned long resume_freq; /* freq restored after suspend cycle */
>> +
>> unsigned long previous_freq;
>> struct devfreq_dev_status last_status;
>>
>> @@ -211,6 +214,10 @@ 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);
>>
>> +/* Suspend/resume the entire Devfreq subsystem. */
>> +void devfreq_suspend(void);
>> +void devfreq_resume(void);
>> +
>> /* Helper functions for devfreq user device driver with OPP. */
>> extern struct dev_pm_opp *devfreq_recommended_opp(struct device *dev,
>> unsigned long *freq, u32 flags);
>> @@ -410,6 +417,9 @@ static inline int devfreq_update_stats(struct devfreq *df)
>> {
>> return -EINVAL;
>> }
>> +
>> +static inline void devfreq_suspend(void) {}
>> +static inline void devfreq_resume(void) {}
>> #endif /* CONFIG_PM_DEVFREQ */
>>
>> #endif /* __LINUX_DEVFREQ_H__ */
>>
>
>
Best Regards,
Chanwoo Choi
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