Re: Re: [PATCH v4 2/3] devfreq: Add suspend and resume apis

Re: Re: [PATCH v4 2/3] devfreq: Add suspend and resume apis

[MyungJoo Ham]

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> On 8 October 2012 03:31, Rafael J. Wysocki <rjw@sisk.pl> wrote:
> > On Thursday 04 of October 2012 14:58:33 Rajagopal Venkat wrote:
> >> Add devfreq suspend/resume apis for devfreq users. This patch
> >> supports suspend and resume of devfreq load monitoring, required
> >> for devices which can idle.
> >>
> >> Signed-off-by: Rajagopal Venkat <rajagopal.venkat@linaro.org>
> >> Acked-by: MyungJoo Ham <myungjoo.ham@samsung.com>
> >
> > Well, I wonder if this may be tied in to the runtime PM framework, so that,
> > for example, pm_runtime_suspend() will automatically suspend devfreq on
> > success (and the runtime resume of the device will resume devfreq)?
> 
> That's a good idea. If you agree, we can handle this as separate patch on
> top this patchset.

I guess implementing the idea may be not so obvious; thus, seperating
the patchset would be appropriate.

When we implement the idea, we may need to implement at the
pm_runtime core. Because devfreq->dev is a child of the target dev, not
a parent, runtime-pm event of the target dev does not automatically
invoke a cascaded action on the devfreq->dev.

Maybe either
1) capability to allow a child to monitor the power state of a parent
(I remember Inki Dae once suggested to add notifiers at runtime-pm, but
it seems to be not merged)
or
2) letting runtime-pm be aware of devfreq
(doesn't feel alright with this??)
is required?



> 
> >
> > Rafael
> >
> >
> >> ---
> >>  drivers/devfreq/devfreq.c                 | 28 ++++++++++++++++++++++++++++
> >>  drivers/devfreq/governor.h                |  2 ++
> >>  drivers/devfreq/governor_simpleondemand.c |  9 +++++++++
> >>  include/linux/devfreq.h                   | 12 ++++++++++++
> >>  4 files changed, 51 insertions(+)
> >>
> >> diff --git a/drivers/devfreq/devfreq.c b/drivers/devfreq/devfreq.c
> >> index 41a4099..63e075e 100644
> >> --- a/drivers/devfreq/devfreq.c
> >> +++ b/drivers/devfreq/devfreq.c
> >> @@ -428,6 +428,34 @@ int devfreq_remove_device(struct devfreq *devfreq)
> >>  }
> >>  EXPORT_SYMBOL(devfreq_remove_device);
> >>
> >> +/**
> >> + * devfreq_suspend_device() - Suspend devfreq of a device.
> >> + * @devfreq  the devfreq instance to be suspended
> >> + */
> >> +int devfreq_suspend_device(struct devfreq *devfreq)
> >> +{
> >> +     if (!devfreq)
> >> +             return -EINVAL;
> >> +
> >> +     return devfreq->governor->event_handler(devfreq,
> >> +                             DEVFREQ_GOV_SUSPEND, NULL);
> >> +}
> >> +EXPORT_SYMBOL(devfreq_suspend_device);
> >> +
> >> +/**
> >> + * devfreq_resume_device() - Resume devfreq of a device.
> >> + * @devfreq  the devfreq instance to be resumed
> >> + */
> >> +int devfreq_resume_device(struct devfreq *devfreq)
> >> +{
> >> +     if (!devfreq)
> >> +             return -EINVAL;
> >> +
> >> +     return devfreq->governor->event_handler(devfreq,
> >> +                             DEVFREQ_GOV_RESUME, NULL);
> >> +}
> >> +EXPORT_SYMBOL(devfreq_resume_device);
> >> +
> >>  static ssize_t show_governor(struct device *dev,
> >>                            struct device_attribute *attr, char *buf)
> >>  {
> >> diff --git a/drivers/devfreq/governor.h b/drivers/devfreq/governor.h
> >> index bb3aff3..26432ac 100644
> >> --- a/drivers/devfreq/governor.h
> >> +++ b/drivers/devfreq/governor.h
> >> @@ -22,6 +22,8 @@
> >>  #define DEVFREQ_GOV_START                    0x1
> >>  #define DEVFREQ_GOV_STOP                     0x2
> >>  #define DEVFREQ_GOV_INTERVAL                 0x3
> >> +#define DEVFREQ_GOV_SUSPEND                  0x4
> >> +#define DEVFREQ_GOV_RESUME                   0x5
> >>
> >>  /* Caution: devfreq->lock must be locked before calling update_devfreq */
> >>  extern int update_devfreq(struct devfreq *devfreq);
> >> diff --git a/drivers/devfreq/governor_simpleondemand.c b/drivers/devfreq/governor_simpleondemand.c
> >> index cf94218..a8ba78c 100644
> >> --- a/drivers/devfreq/governor_simpleondemand.c
> >> +++ b/drivers/devfreq/governor_simpleondemand.c
> >> @@ -104,6 +104,15 @@ int devfreq_simple_ondemand_handler(struct devfreq *devfreq,
> >>       case DEVFREQ_GOV_INTERVAL:
> >>               devfreq_interval_update(devfreq, (unsigned int *)data);
> >>               break;
> >> +
> >> +     case DEVFREQ_GOV_SUSPEND:
> >> +             devfreq_monitor_suspend(devfreq);
> >> +             break;
> >> +
> >> +     case DEVFREQ_GOV_RESUME:
> >> +             devfreq_monitor_resume(devfreq);
> >> +             break;
> >> +
> >>       default:
> >>               break;
> >>       }
> >> diff --git a/include/linux/devfreq.h b/include/linux/devfreq.h
> >> index 9cdffde..ee243a3 100644
> >> --- a/include/linux/devfreq.h
> >> +++ b/include/linux/devfreq.h
> >> @@ -158,6 +158,8 @@ extern struct devfreq *devfreq_add_device(struct device *dev,
> >>                                 const struct devfreq_governor *governor,
> >>                                 void *data);
> >>  extern int devfreq_remove_device(struct devfreq *devfreq);
> >> +extern int devfreq_suspend_device(struct devfreq *devfreq);
> >> +extern int devfreq_resume_device(struct devfreq *devfreq);
> >>
> >>  /* Helper functions for devfreq user device driver with OPP. */
> >>  extern struct opp *devfreq_recommended_opp(struct device *dev,
> >> @@ -211,6 +213,16 @@ static int devfreq_remove_device(struct devfreq *devfreq)
> >>       return 0;
> >>  }
> >>
> >> +static int devfreq_suspend_device(struct devfreq *devfreq)
> >> +{
> >> +     return 0;
> >> +}
> >> +
> >> +static int devfreq_resume_device(struct devfreq *devfreq)
> >> +{
> >> +     return 0;
> >> +}
> >> +
> >>  static struct opp *devfreq_recommended_opp(struct device *dev,
> >>                                          unsigned long *freq, u32 flags)
> >>  {
> >>
> > --
> > I speak only for myself.
> > Rafael J. Wysocki, Intel Open Source Technology Center.
> 
> 
> 
> -- 
> Regards,
> Rajagopal
> 
> 
> 
>        
>   
>          
> 
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Re: [PATCH v4 2/3] devfreq: Add suspend and resume apis

[Rafael J. Wysocki]

On Monday 08 of October 2012 10:48:24 MyungJoo Ham wrote:
> > On 8 October 2012 03:31, Rafael J. Wysocki <rjw@sisk.pl> wrote:
> > > On Thursday 04 of October 2012 14:58:33 Rajagopal Venkat wrote:
> > >> Add devfreq suspend/resume apis for devfreq users. This patch
> > >> supports suspend and resume of devfreq load monitoring, required
> > >> for devices which can idle.
> > >>
> > >> Signed-off-by: Rajagopal Venkat <rajagopal.venkat@linaro.org>
> > >> Acked-by: MyungJoo Ham <myungjoo.ham@samsung.com>
> > >
> > > Well, I wonder if this may be tied in to the runtime PM framework, so that,
> > > for example, pm_runtime_suspend() will automatically suspend devfreq on
> > > success (and the runtime resume of the device will resume devfreq)?
> > 
> > That's a good idea. If you agree, we can handle this as separate patch on
> > top this patchset.

Sure.

> I guess implementing the idea may be not so obvious; thus, seperating
> the patchset would be appropriate.
> 
> When we implement the idea, we may need to implement at the
> pm_runtime core. Because devfreq->dev is a child of the target dev, not
> a parent, runtime-pm event of the target dev does not automatically
> invoke a cascaded action on the devfreq->dev.

I'm not exactly sure what you mean, care to explain?

> Maybe either
> 1) capability to allow a child to monitor the power state of a parent
> (I remember Inki Dae once suggested to add notifiers at runtime-pm, but
> it seems to be not merged)
> or
> 2) letting runtime-pm be aware of devfreq
> (doesn't feel alright with this??)
> is required?

I'm not a big fan of notifiers, so I'd prefer to avoid using them, if
possible.

Thanks,
Rafael


-- 
I speak only for myself.
Rafael J. Wysocki, Intel Open Source Technology Center.

Re: Re: [PATCH v4 2/3] devfreq: Add suspend and resume apis

[MyungJoo Ham]

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> On Monday 08 of October 2012 10:48:24 MyungJoo Ham wrote:
> > > On 8 October 2012 03:31, Rafael J. Wysocki <rjw@sisk.pl> wrote:
> > > > On Thursday 04 of October 2012 14:58:33 Rajagopal Venkat wrote:
> > > >> Add devfreq suspend/resume apis for devfreq users. This patch
> > > >> supports suspend and resume of devfreq load monitoring, required
> > > >> for devices which can idle.
> > > >>
> > > >> Signed-off-by: Rajagopal Venkat <rajagopal.venkat@linaro.org>
> > > >> Acked-by: MyungJoo Ham <myungjoo.ham@samsung.com>
> > > >
> > > > Well, I wonder if this may be tied in to the runtime PM framework, so that,
> > > > for example, pm_runtime_suspend() will automatically suspend devfreq on
> > > > success (and the runtime resume of the device will resume devfreq)?
> > > 
> > > That's a good idea. If you agree, we can handle this as separate patch on
> > > top this patchset.
> 
> Sure.
> 
> > I guess implementing the idea may be not so obvious; thus, seperating
> > the patchset would be appropriate.
> > 
> > When we implement the idea, we may need to implement at the
> > pm_runtime core. Because devfreq->dev is a child of the target dev, not
> > a parent, runtime-pm event of the target dev does not automatically
> > invoke a cascaded action on the devfreq->dev.
> 
> I'm not exactly sure what you mean, care to explain?

When a device "p" creates devfreq, devfreq->dev->parent = p.
And, devfreq's functions need to react to the "p"'s runtime-pm events.

However, when "p"'s runtime-pm-suspend is being invoked,
devfreq->dev's runtime-pm-suspend won't be automatically invoked.

Thus, we will need a mechanism that invokes devfreq->dev's runtime-pm
callbacks when p's runtime-pm is invoked. (at the runtime-pm core)
Or
A mechanism that one can notify others (including its children) when
the one's runtime-pm is invoked. (probably at the runtime-pm core, too)

Without such support, it appears that the current implementation
(calling runtime-pm suspend/resume equivalent devfreq functions
manually at device drivers) seems to be inevitable.



Anyway, if devfreq->dev is a parent of "p", runtime-pm core will
do the required task automatically; however, it isn't and I don't
think it'd be appropriate.

> 
> > Maybe either
> > 1) capability to allow a child to monitor the power state of a parent
> > (I remember Inki Dae once suggested to add notifiers at runtime-pm, but
> > it seems to be not merged)
> > or
> > 2) letting runtime-pm be aware of devfreq
> > (doesn't feel alright with this??)
> > is required?
> 
> I'm not a big fan of notifiers, so I'd prefer to avoid using them, if
> possible.
> 
> Thanks,
> Rafael
> 
> 
> -- 
> I speak only for myself.
> Rafael J. Wysocki, Intel Open Source Technology Center.
> 

Cheers,
MyungJoo
ÿôèº{.nÇ+‰·Ÿ®‰­†+%ŠËÿ±éݶ\x17¥Šwÿº{.nÇ+‰·¥Š{±þG«éÿŠ{ayº\x1dʇڙë,j\a­¢f£¢·hšïêÿ‘êçz_è®\x03(­éšŽŠÝ¢j"ú\x1a¶^[m§ÿÿ¾\a«þG«éÿ¢¸?™¨è­Ú&£ø§~á¶iO•æ¬z·švØ^\x14\x04\x1a¶^[m§ÿÿÃ\fÿ¶ìÿ¢¸?–I¥