Re: Patch "time: Add cycles to nanoseconds translation" has been added to the 4.4-stable tree

[Richard Cochran <richardcochran@gmail.com>]

On Thu, Oct 13, 2016 at 05:35:54PM +0200, gregkh@linuxfoundation.org wrote:
> 
> This is a note to let you know that I've just added the patch titled
> 
>     time: Add cycles to nanoseconds translation
> 
> to the 4.4-stable tree which can be found at:
>     http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
> 
> The filename of the patch is:
>      time-add-cycles-to-nanoseconds-translation.patch
> and it can be found in the queue-4.4 subdirectory.
> 
> If you, or anyone else, feels it should not be added to the stable tree,
> please let <stable@vger.kernel.org> know about it.

IIRC, this one is not any kind of bug fix, but rather in support of
new functionality.

Thanks,
Richard


> From 6bd58f09e1d8cc6c50a824c00bf0d617919986a1 Mon Sep 17 00:00:00 2001
> From: "Christopher S. Hall" <christopher.s.hall@intel.com>
> Date: Mon, 22 Feb 2016 03:15:19 -0800
> Subject: time: Add cycles to nanoseconds translation
> 
> From: Christopher S. Hall <christopher.s.hall@intel.com>
> 
> commit 6bd58f09e1d8cc6c50a824c00bf0d617919986a1 upstream.
> 
> The timekeeping code does not currently provide a way to translate
> externally provided clocksource cycles to system time. The cycle count
> is always provided by the result clocksource read() method internal to
> the timekeeping code. The added function timekeeping_cycles_to_ns()
> calculated a nanosecond value from a cycle count that can be added to
> tk_read_base.base value yielding the current system time. This allows
> clocksource cycle values external to the timekeeping code to provide a
> cycle count that can be transformed to system time.
> 
> Cc: Prarit Bhargava <prarit@redhat.com>
> Cc: Richard Cochran <richardcochran@gmail.com>
> Cc: Thomas Gleixner <tglx@linutronix.de>
> Cc: Ingo Molnar <mingo@kernel.org>
> Cc: Andy Lutomirski <luto@amacapital.net>
> Cc: kevin.b.stanton@intel.com
> Cc: kevin.j.clarke@intel.com
> Cc: hpa@zytor.com
> Cc: jeffrey.t.kirsher@intel.com
> Cc: netdev@vger.kernel.org
> Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
> Signed-off-by: Christopher S. Hall <christopher.s.hall@intel.com>
> Signed-off-by: John Stultz <john.stultz@linaro.org>
> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> 
> ---
>  kernel/time/timekeeping.c |   25 +++++++++++++++++++++----
>  1 file changed, 21 insertions(+), 4 deletions(-)
> 
> --- a/kernel/time/timekeeping.c
> +++ b/kernel/time/timekeeping.c
> @@ -298,17 +298,34 @@ u32 (*arch_gettimeoffset)(void) = defaul
>  static inline u32 arch_gettimeoffset(void) { return 0; }
>  #endif
>  
> +static inline s64 timekeeping_delta_to_ns(struct tk_read_base *tkr,
> +					  cycle_t delta)
> +{
> +	s64 nsec;
> +
> +	nsec = delta * tkr->mult + tkr->xtime_nsec;
> +	nsec >>= tkr->shift;
> +
> +	/* If arch requires, add in get_arch_timeoffset() */
> +	return nsec + arch_gettimeoffset();
> +}
> +
>  static inline s64 timekeeping_get_ns(struct tk_read_base *tkr)
>  {
>  	cycle_t delta;
> -	s64 nsec;
>  
>  	delta = timekeeping_get_delta(tkr);
> +	return timekeeping_delta_to_ns(tkr, delta);
> +}
>  
> -	nsec = (delta * tkr->mult + tkr->xtime_nsec) >> tkr->shift;
> +static inline s64 timekeeping_cycles_to_ns(struct tk_read_base *tkr,
> +					    cycle_t cycles)
> +{
> +	cycle_t delta;
>  
> -	/* If arch requires, add in get_arch_timeoffset() */
> -	return nsec + arch_gettimeoffset();
> +	/* calculate the delta since the last update_wall_time */
> +	delta = clocksource_delta(cycles, tkr->cycle_last, tkr->mask);
> +	return timekeeping_delta_to_ns(tkr, delta);
>  }
>  
>  /**
> 
> 
> Patches currently in stable-queue which might be from christopher.s.hall@intel.com are
> 
> queue-4.4/time-add-cycles-to-nanoseconds-translation.patch