Date:	Wed, 4 Feb 2015 21:59:02 +0800
From:	Xunlei Pang <pang.xunlei@...aro.org>
To:	Xunlei Pang <pang.xunlei@...aro.org>
Cc:	lkml <linux-kernel@...r.kernel.org>,
	"rtc-linux@...glegroups.com" <rtc-linux@...glegroups.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Alessandro Zummo <a.zummo@...ertech.it>,
	John Stultz <john.stultz@...aro.org>,
	Arnd Bergmann <arnd.bergmann@...aro.org>
Subject: Re: [PATCH v3 1/2] time: Don't bother to run rtc_resume() for the
 nonstop clocksource

Ping ...

On 29 January 2015 at 23:59, Xunlei Pang <xlpang@....com> wrote:
> From: Xunlei Pang <pang.xunlei@...aro.org>
>
> If a system does not provide a persistent_clock(), the time
> will be updated on resume by rtc_resume(). With the addition
> of the non-stop clocksources for suspend timing, those systems
> set the time on resume in timekeeping_resume(), but may not
> provide a valid persistent_clock().
>
> This results in the rtc_resume() logic thinking no one has set
> the time and it then will over-write the suspend time again,
> which is not necessary and only increases clock error.
>
> So, fix this for rtc_resume().
>
> Signed-off-by: Xunlei Pang <pang.xunlei@...aro.org>
> ---
> v2->v3:
> Refine according to John's comments using internal variable.
>
>  drivers/rtc/class.c         |  2 +-
>  include/linux/timekeeping.h |  1 +
>  kernel/time/timekeeping.c   | 32 ++++++++++++++++++++------------
>  3 files changed, 22 insertions(+), 13 deletions(-)
>
> diff --git a/drivers/rtc/class.c b/drivers/rtc/class.c
> index 472a5ad..6100af5 100644
> --- a/drivers/rtc/class.c
> +++ b/drivers/rtc/class.c
> @@ -102,7 +102,7 @@ static int rtc_resume(struct device *dev)
>         struct timespec64       sleep_time;
>         int err;
>
> -       if (has_persistent_clock())
> +       if (timekeeping_sleeptime_injected())
>                 return 0;
>
>         rtc_hctosys_ret = -ENODEV;
> diff --git a/include/linux/timekeeping.h b/include/linux/timekeeping.h
> index 9b63d13..17a460d 100644
> --- a/include/linux/timekeeping.h
> +++ b/include/linux/timekeeping.h
> @@ -225,6 +225,7 @@ static inline void timekeeping_clocktai(struct timespec *ts)
>  /*
>   * RTC specific
>   */
> +extern bool timekeeping_sleeptime_injected(void);
>  extern void timekeeping_inject_sleeptime64(struct timespec64 *delta);
>
>  /*
> diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c
> index 6a93185..b02133e 100644
> --- a/kernel/time/timekeeping.c
> +++ b/kernel/time/timekeeping.c
> @@ -1125,12 +1125,26 @@ static void __timekeeping_inject_sleeptime(struct timekeeper *tk,
>         tk_debug_account_sleep_time(delta);
>  }
>
> +static bool sleeptime_inject;
> +
> +#if defined(CONFIG_RTC_CLASS) && \
> +       defined(CONFIG_PM_SLEEP) && \
> +       defined(CONFIG_RTC_HCTOSYS_DEVICE)
> +/**
> + * Used by rtc_resume().
> + */
> +bool timekeeping_sleeptime_injected(void)
> +{
> +       return sleeptime_inject;
> +}
> +
>  /**
>   * timekeeping_inject_sleeptime64 - Adds suspend interval to timeekeeping values
>   * @delta: pointer to a timespec64 delta value
>   *
>   * This hook is for architectures that cannot support read_persistent_clock
> - * because their RTC/persistent clock is only accessible when irqs are enabled.
> + * because their RTC/persistent clock is only accessible when irqs are enabled,
> + * and also don't have an effective nonstop clocksource.
>   *
>   * This function should only be called by rtc_resume(), and allows
>   * a suspend offset to be injected into the timekeeping values.
> @@ -1140,13 +1154,6 @@ void timekeeping_inject_sleeptime64(struct timespec64 *delta)
>         struct timekeeper *tk = &tk_core.timekeeper;
>         unsigned long flags;
>
> -       /*
> -        * Make sure we don't set the clock twice, as timekeeping_resume()
> -        * already did it
> -        */
> -       if (has_persistent_clock())
> -               return;
> -
>         raw_spin_lock_irqsave(&timekeeper_lock, flags);
>         write_seqcount_begin(&tk_core.seq);
>
> @@ -1162,6 +1169,7 @@ void timekeeping_inject_sleeptime64(struct timespec64 *delta)
>         /* signal hrtimers about time change */
>         clock_was_set();
>  }
> +#endif
>
>  /**
>   * timekeeping_resume - Resumes the generic timekeeping subsystem.
> @@ -1178,8 +1186,8 @@ static void timekeeping_resume(void)
>         struct timespec64 ts_new, ts_delta;
>         struct timespec tmp;
>         cycle_t cycle_now, cycle_delta;
> -       bool suspendtime_found = false;
>
> +       sleeptime_inject = false;
>         read_persistent_clock(&tmp);
>         ts_new = timespec_to_timespec64(tmp);
>
> @@ -1226,13 +1234,13 @@ static void timekeeping_resume(void)
>                 nsec += ((u64) cycle_delta * mult) >> shift;
>
>                 ts_delta = ns_to_timespec64(nsec);
> -               suspendtime_found = true;
> +               sleeptime_inject = true;
>         } else if (timespec64_compare(&ts_new, &timekeeping_suspend_time) > 0) {
>                 ts_delta = timespec64_sub(ts_new, timekeeping_suspend_time);
> -               suspendtime_found = true;
> +               sleeptime_inject = true;
>         }
>
> -       if (suspendtime_found)
> +       if (sleeptime_inject)
>                 __timekeeping_inject_sleeptime(tk, &ts_delta);
>
>         /* Re-base the last cycle value */
> --
> 1.9.1
>
>
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