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

[Ulf Hansson]

On Wed, 19 Dec 2018 at 11:34, Vincent Guittot
<vincent.guittot@xxxxxxxxxx> wrote:
>
> On Wed, 19 Dec 2018 at 11:21, Ulf Hansson <ulf.hansson@xxxxxxxxxx> wrote:
> >
> > On Wed, 19 Dec 2018 at 11:11, Vincent Guittot
> > <vincent.guittot@xxxxxxxxxx> wrote:
> > >
> > > On Wed, 19 Dec 2018 at 10:58, Ulf Hansson <ulf.hansson@xxxxxxxxxx> wrote:
> > > >
> > > > On Tue, 18 Dec 2018 at 15:55, Vincent Guittot
> > > > <vincent.guittot@xxxxxxxxxx> 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?
>
> sorry I mix your question above and the one about  accounting_timestamp.
>
> So I agree that only RPM_SUSPENDED is used for now
>
> >
> > >
> > > >
> > > > 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@xxxxxxxxxx>
> > > > > ---
> > > > >  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.
>
> In fact we don't update dev->power.accounting_timestamp but only use
> it to get how much time has elapsed in the current state.
>
> >
> > 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.
>
> So I'm not sure to catch your question:
> Is your problem linked to status != RPM_SUSPENDED or the update
> parameter that compute delta ?

My intent was to keep things simple.

1. Only expose last suspended time, which means tracking the ongoing
suspended state. In other words, you can also remove "enum rpm_status
status" as the in-parameter to pm_runtime_accounted_time_get().
2. Don't allow the user of pm_runtime_accounted_time_get() to update
the current timestamp, in "dev->power.accounting_timestamp".

Is that okay for the drm driver, to do what it does today?

>
> >
> > >
> > > >
> > > > 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.
>
> I'm fine with both. Rafael ?
>
> >
> > >
> > > >
> > > > > +       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