linux-kernel - Re: [PATCHv4 14/17] pps: capture MONOTONIC

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Date:	Thu, 18 Nov 2010 11:42:47 -0800
From:	john stultz <johnstul@...ibm.com>
To:	Alexander Gordeev <lasaine@....cs.msu.su>
Cc:	linux-kernel@...r.kernel.org,
	"Nikita V. Youshchenko" <yoush@...msu.su>,
	linuxpps@...enneenne.com, Rodolfo Giometti <giometti@...eenne.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	David Howells <dhowells@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>, Magnus Damm <damm@...nsource.se>,
	Jason Wessel <jason.wessel@...driver.com>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCHv4 14/17] pps: capture MONOTONIC_RAW timestamps as well

On Thu, 2010-11-18 at 19:01 +0300, Alexander Gordeev wrote:
> MONOTONIC_RAW clock timestamps are ideally suited for frequency
> calculation and also fit well into the original NTP hardpps design. Now
> phase and frequency can be adjusted separately: the former based on
> REALTIME clock and the latter based on MONOTONIC_RAW clock.
> A new function getnstime_raw_and_real is added to timekeeping subsystem
> to capture both timestamps at the same time and atomically.
> 
> Signed-off-by: Alexander Gordeev <lasaine@....cs.msu.su>

Acked-by: John Stultz <johnstul@...ibm.com>

> ---
>  include/linux/pps_kernel.h |    3 ++-
>  include/linux/time.h       |    2 ++
>  kernel/time/timekeeping.c  |   38 ++++++++++++++++++++++++++++++++++++++
>  3 files changed, 42 insertions(+), 1 deletions(-)
> 
> diff --git a/include/linux/pps_kernel.h b/include/linux/pps_kernel.h
> index 5af0498..39fc7125 100644
> --- a/include/linux/pps_kernel.h
> +++ b/include/linux/pps_kernel.h
> @@ -48,6 +48,7 @@ struct pps_source_info {
>  };
> 
>  struct pps_event_time {
> +	struct timespec ts_raw;
>  	struct timespec ts_real;
>  };
> 
> @@ -111,7 +112,7 @@ static inline void timespec_to_pps_ktime(struct pps_ktime *kt,
> 
>  static inline void pps_get_ts(struct pps_event_time *ts)
>  {
> -	getnstimeofday(&ts->ts_real);
> +	getnstime_raw_and_real(&ts->ts_raw, &ts->ts_real);
>  }
> 
>  #endif /* LINUX_PPS_KERNEL_H */
> diff --git a/include/linux/time.h b/include/linux/time.h
> index 9f15ac7..1e6d3b5 100644
> --- a/include/linux/time.h
> +++ b/include/linux/time.h
> @@ -158,6 +158,8 @@ extern unsigned int alarm_setitimer(unsigned int seconds);
>  extern int do_getitimer(int which, struct itimerval *value);
>  extern void getnstimeofday(struct timespec *tv);
>  extern void getrawmonotonic(struct timespec *ts);
> +extern void getnstime_raw_and_real(struct timespec *ts_raw,
> +		struct timespec *ts_real);
>  extern void getboottime(struct timespec *ts);
>  extern void monotonic_to_bootbased(struct timespec *ts);
> 
> diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c
> index 49010d8..947c7dc 100644
> --- a/kernel/time/timekeeping.c
> +++ b/kernel/time/timekeeping.c
> @@ -285,6 +285,44 @@ void ktime_get_ts(struct timespec *ts)
>  EXPORT_SYMBOL_GPL(ktime_get_ts);
> 
>  /**
> + * getnstime_raw_and_real - Returns both the time of day an raw
> + * monotonic time in a timespec format
> + * @ts_mono_raw:	pointer to the timespec to be set to raw
> + *			monotonic time
> + * @ts_real:		pointer to the timespec to be set to the time
> + *			of day
> + */
> +void getnstime_raw_and_real(struct timespec *ts_raw, struct timespec *ts_real)
> +{
> +	unsigned long seq;
> +	s64 nsecs_raw, nsecs_real;
> +
> +	WARN_ON_ONCE(timekeeping_suspended);
> +
> +	do {
> +		u32 arch_offset;
> +
> +		seq = read_seqbegin(&xtime_lock);
> +
> +		*ts_raw = raw_time;
> +		*ts_real = xtime;
> +
> +		nsecs_raw = timekeeping_get_ns_raw();
> +		nsecs_real = timekeeping_get_ns();
> +
> +		/* If arch requires, add in gettimeoffset() */
> +		arch_offset = arch_gettimeoffset();
> +		nsecs_raw += arch_offset;
> +		nsecs_real += arch_offset;
> +
> +	} while (read_seqretry(&xtime_lock, seq));
> +
> +	timespec_add_ns(ts_raw, nsecs_raw);
> +	timespec_add_ns(ts_real, nsecs_real);
> +}
> +EXPORT_SYMBOL(getnstime_raw_and_real);
> +
> +/**
>   * do_gettimeofday - Returns the time of day in a timeval
>   * @tv:		pointer to the timeval to be set
>   *


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