linux-kernel - Re: [RFC v3 1/3] PM/runtime: Add a new interface to get accounted time

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Message-ID: <CAPDyKFrSxX-eBsTiEvbrbjVpqkSuBnhxruCgtihH6hSvWSFD1g@mail.gmail.com>
Date:   Wed, 19 Dec 2018 11:20:33 +0100
From:   Ulf Hansson <ulf.hansson@...aro.org>
To:     Vincent Guittot <vincent.guittot@...aro.org>
Cc:     "open list:THERMAL" <linux-pm@...r.kernel.org>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Thara Gopinath <thara.gopinath@...aro.org>,
        jani.nikula@...ux.intel.com,
        Joonas Lahtinen <joonas.lahtinen@...ux.intel.com>,
        rodrigo.vivi@...el.com, David Airlie <airlied@...ux.ie>,
        "Intel graphics driver community testing & development" 
        <intel-gfx@...ts.freedesktop.org>,
        dri-devel <dri-devel@...ts.freedesktop.org>
Subject: Re: [RFC v3 1/3] PM/runtime: Add a new interface to get accounted time

On Wed, 19 Dec 2018 at 11:11, Vincent Guittot
<vincent.guittot@...aro.org> wrote:
>
> On Wed, 19 Dec 2018 at 10:58, Ulf Hansson <ulf.hansson@...aro.org> wrote:
> >
> > On Tue, 18 Dec 2018 at 15:55, Vincent Guittot
> > <vincent.guittot@...aro.org> wrote:
> > >
> > > Some drivers (like i915/drm) need to get the accounted suspended time.
> > > pm_runtime_accounted_time_get() will return the suspended or active
> > > accounted time until now.
> >
> > I suggest to leave the active accounted time out for now. At least
> > until we have some users.
>
> This is needed to keep same feature level for i915/drm

I don't follow. According to the changes in the drm driver in patch2,
we are only calling the new pm_runtime interface with RPM_SUSPENDED?

>
> >
> > That said, perhaps rename the function to something along the lines
> > of, pm_runtime_last_suspended_time(), to make it more clear.
> >
> > >
> > > Signed-off-by: Vincent Guittot <vincent.guittot@...aro.org>
> > > ---
> > >  drivers/base/power/runtime.c | 26 ++++++++++++++++++++++++++
> > >  include/linux/pm_runtime.h   |  2 ++
> > >  2 files changed, 28 insertions(+)
> > >
> > > diff --git a/drivers/base/power/runtime.c b/drivers/base/power/runtime.c
> > > index 7062469..6461469 100644
> > > --- a/drivers/base/power/runtime.c
> > > +++ b/drivers/base/power/runtime.c
> > > @@ -88,6 +88,32 @@ static void __update_runtime_status(struct device *dev, enum rpm_status status)
> > >         dev->power.runtime_status = status;
> > >  }
> > >
> > > +u64 pm_runtime_accounted_time_get(struct device *dev, enum rpm_status status, bool update)
> > > +{
> > > +       u64 now = ktime_to_ns(ktime_get());
> >
> > I think you should stay on jiffies here - and then switch to ktime in patch 3.
> >
> > > +       u64 delta = 0, time = 0;
> > > +       unsigned long flags;
> > > +
> > > +       spin_lock_irqsave(&dev->power.lock, flags);
> > > +
> > > +       if (dev->power.disable_depth > 0)
> > > +               goto unlock;
> > > +
> > > +       /* Add ongoing state  if requested */
> > > +       if (update && dev->power.runtime_status == status)
> > > +               delta = now - dev->power.accounting_timestamp;
> > > +
> >
> > Hmm. Do we really need to update the accounting timestamp? I would
> > rather avoid it if possible.
>
> i915/drm uses this to track ongoing suspended state. In fact they are
> mainly interested by this part

Again, sorry I don't follow.

My suggested changes below, would do exactly that; track the ongoing
suspended state.

The user can call the function several times while the device remains
RPM_SUSPENDED, and if needed the user could then compute the delta
in-between the calls, for whatever reason that may be needed.

>
> >
> > It seems like it should be sufficient to return the delta between
> > "now" and the "dev->power.accounting_timestamp", when
> > "dev->power.runtime_status == RPM_SUSPENDED".
> >
> > In other case, just return 0, because we are not in RPM_SUSPENDED state.
>
> only the RPM_SUSPENDED is used by i915/drm but wanted to provide a
> generic interface to get
> suspended or not suspend state

I see.

Although, unless Rafael thinks different, I would rather try to keep
this as simple as possible and expose only what is needed and nothing
more.

>
> >
> > > +       if (status == RPM_SUSPENDED)
> > > +               time = dev->power.suspended_time + delta;
> > > +       else
> > > +               time = dev->power.active_time + delta;
> > > +
> > > +unlock:
> > > +       spin_unlock_irqrestore(&dev->power.lock, flags);
> > > +
> > > +       return time;
> > > +}
> > > +
> > >  /**
> > >   * pm_runtime_deactivate_timer - Deactivate given device's suspend timer.
> > >   * @dev: Device to handle.
> > > diff --git a/include/linux/pm_runtime.h b/include/linux/pm_runtime.h
> > > index 54af4ee..86f21f9 100644
> > > --- a/include/linux/pm_runtime.h
> > > +++ b/include/linux/pm_runtime.h
> > > @@ -113,6 +113,8 @@ static inline bool pm_runtime_is_irq_safe(struct device *dev)
> > >         return dev->power.irq_safe;
> > >  }
> > >
> > > +extern u64 pm_runtime_accounted_time_get(struct device *dev, enum rpm_status status, bool update);
> > > +
> > >  #else /* !CONFIG_PM */
> > >
> > >  static inline bool queue_pm_work(struct work_struct *work) { return false; }
> > > --
> > > 2.7.4
> > >
> >
> > Kind regards
> > Uffe

Kind regards
Uffe