linux-kernel - Re: [PATCH v3 1/2] time: Don't bother to run rtc

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Message-ID: <CALAqxLW5YGD1wY6OaYJ_G8JN5Afo_OF2C5SHOp0N=Um3KP8z=g@mail.gmail.com>
Date:	Wed, 11 Feb 2015 08:01:43 +0800
From:	John Stultz <john.stultz@...aro.org>
To:	Xunlei Pang <xlpang@....com>
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>,
	Arnd Bergmann <arnd.bergmann@...aro.org>,
	Xunlei Pang <pang.xunlei@...aro.org>
Subject: Re: [PATCH v3 1/2] time: Don't bother to run rtc_resume() for the
 nonstop clocksource

On Thu, Jan 29, 2015 at 11:59 PM, 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;

Took a closer look here.. So you're replacing has_persistent_clock()
in the resume side, but not the suspend... Can we not cleanup
has_persistent_clock and consolidate to one accessor for both sides of
the suspend?

>
>         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)

This change wasn't explained in the commit message. Its fine as a
small optimization, but probably should be split into its own patch.

thanks
-john
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