On Thu, 20 Dec 2018 at 23:03, Ulf Hansson <ulf.hansson@xxxxxxxxxx> wrote:
>
> On Thu, 20 Dec 2018 at 15:17, Vincent Guittot
> <vincent.guittot@xxxxxxxxxx> wrote:
> >
> > From: Thara Gopinath <thara.gopinath@xxxxxxxxxx>
> >
> > This patch replaces jiffies based accounting for runtime_active_time
> > and runtime_suspended_time with ktime base accounting. This makes the
> > runtime debug counters inline with genpd and other pm subsytems which
> > uses ktime based accounting.
> >
> > Signed-off-by: Thara Gopinath <thara.gopinath@xxxxxxxxxx>
> > [move from ktime to raw nsec]
> > Signed-off-by: Vincent Guittot <vincent.guittot@xxxxxxxxxx>
> > ---
> > drivers/base/power/runtime.c | 17 +++++++++--------
> > drivers/base/power/sysfs.c | 11 ++++++++---
> > include/linux/pm.h | 6 +++---
> > 3 files changed, 20 insertions(+), 14 deletions(-)
> >
> > diff --git a/drivers/base/power/runtime.c b/drivers/base/power/runtime.c
> > index e695544..f700524 100644
> > --- a/drivers/base/power/runtime.c
> > +++ b/drivers/base/power/runtime.c
> > @@ -64,8 +64,8 @@ static int rpm_suspend(struct device *dev, int rpmflags);
> > */
> > void update_pm_runtime_accounting(struct device *dev)
> > {
> > - unsigned long now = jiffies;
> > - unsigned long delta;
> > + u64 now = ktime_to_ns(ktime_get());
> > + u64 delta;
> >
> > delta = now - dev->power.accounting_timestamp;
> >
> > @@ -75,9 +75,9 @@ void update_pm_runtime_accounting(struct device *dev)
> > return;
> >
> > if (dev->power.runtime_status == RPM_SUSPENDED)
> > - dev->power.suspended_jiffies += delta;
> > + dev->power.suspended_time += delta;
> > else
> > - dev->power.active_jiffies += delta;
> > + dev->power.active_time += delta;
> > }
> >
> > static void __update_runtime_status(struct device *dev, enum rpm_status status)
> > @@ -88,17 +88,18 @@ static void __update_runtime_status(struct device *dev, enum rpm_status status)
> >
> > u64 pm_runtime_suspended_time(struct device *dev)
> > {
> > - unsigned long flags, time;
> > + u64 time;
> > + unsigned long flags;
> >
> > spin_lock_irqsave(&dev->power.lock, flags);
> >
> > update_pm_runtime_accounting(dev);
> >
> > - time = dev->power.suspended_jiffies;
> > + time = dev->power.suspended_time;
> >
> > spin_unlock_irqrestore(&dev->power.lock, flags);
> >
> > - return jiffies_to_nsecs(time);
> > + return time;
> > }
> > EXPORT_SYMBOL_GPL(pm_runtime_suspended_time);
> >
> > @@ -1503,7 +1504,7 @@ void pm_runtime_init(struct device *dev)
> > dev->power.request_pending = false;
> > dev->power.request = RPM_REQ_NONE;
> > dev->power.deferred_resume = false;
> > - dev->power.accounting_timestamp = jiffies;
> > + dev->power.accounting_timestamp = ktime_to_ns(ktime_get());
>
> This change worries me a bit, but it may not be a problem in practice.
>
> pm_runtime_init() is called when devices get initialized, via
> device_initialize(). If timekeeping has not been initialized prior a
> call to ktime_get() is done, it will fail and causing a NULL pointer
> deference or something along those lines.
>
> In other words, do we know that device_initialize() is always called
> after timekeeping has been initialized during boot?
That something we discussed at lpc and we should be safe
>
> [...]
>
> Kind regards
> Uffe
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