Re: [PATCH v3 1/2] time: Don't bother to run rtc_resume() for the nonstop clocksource

From: John Stultz
Date: Tue Feb 10 2015 - 19:01:53 EST


On Thu, Jan 29, 2015 at 11:59 PM, Xunlei Pang <xlpang@xxxxxxx> wrote:
> From: Xunlei Pang <pang.xunlei@xxxxxxxxxx>
>
> 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@xxxxxxxxxx>
> ---
> 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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