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

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Message-ID: <CAPDyKFq6X8vJU=pK1fgirGkD2-GS=LryRP1No8bSgPNLbyvAEg@mail.gmail.com>
Date:   Wed, 19 Dec 2018 10:58:17 +0100
From:   Ulf Hansson <ulf.hansson@...aro.org>
To:     Vincent Guittot <vincent.guittot@...aro.org>
Cc:     Linux PM <linux-pm@...r.kernel.org>,
        Linux Kernel Mailing List <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 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.

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.

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.

> +       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