Subject: [PATCH] davinci: Implement sched_clock()

From: [email-masked] (Kevin Hilman)
Date: Thu, 07 Oct 2010 10:12:04 -0700

Andreas.Gaer at baslerweb.com writes:

> From: Andreas Gaeer <[email-masked]>
>
> Overwrite the default implementation of sched_clock that is based on
> jiffies by something more precise. This improves timestamps in ftrace.
> Implementation is copied from OMAP platform code.
>
> Signed-off-by: Andreas Gaeer <[email-masked]>

Thanks, applying to davinci git.  

Will queue for 2.6.38 (it's a bit too late for 2.6.37 as Linus only
wants real regression fixes after -rc6.)

Kevin

> ---
>  arch/arm/mach-davinci/time.c |   24 +++++++++++++++++++++++-
>  1 files changed, 23 insertions(+), 1 deletions(-)
>
> diff --git a/arch/arm/mach-davinci/time.c b/arch/arm/mach-davinci/time.c
> index 0f21c36..5d1eea0 100644
> --- a/arch/arm/mach-davinci/time.c
> +++ b/arch/arm/mach-davinci/time.c
> @@ -272,15 +272,36 @@ static cycle_t read_cycles(struct clocksource *cs)
>  	return (cycles_t)timer32_read(t);
>  }
>  
> +/*
> + * Kernel assumes that sched_clock can be called early but may not have
> + * things ready yet.
> + */
> +static cycle_t read_dummy(struct clocksource *cs)
> +{
> +	return 0;
> +}
> +
> +
>  static struct clocksource clocksource_davinci = {
>  	.rating		= 300,
> -	.read		= read_cycles,
> +	.read		= read_dummy,
>  	.mask		= CLOCKSOURCE_MASK(32),
>  	.shift		= 24,
>  	.flags		= CLOCK_SOURCE_IS_CONTINUOUS,
>  };
>  
>  /*
> + * Overwrite weak default sched_clock with something more precise
> + */
> +unsigned long long notrace sched_clock(void)
> +{
> +	const cycle_t cyc = clocksource_davinci.read(&clocksource_davinci);
> +
> +	return clocksource_cyc2ns(cyc, clocksource_davinci.mult,
> +				clocksource_davinci.shift);
> +}
> +
> +/*
>   * clockevent
>   */
>  static int davinci_set_next_event(unsigned long cycles,
> @@ -377,6 +398,7 @@ static void __init davinci_timer_init(void)
>  	davinci_clock_tick_rate = clk_get_rate(timer_clk);
>  
>  	/* setup clocksource */
> +	clocksource_davinci.read = read_cycles;
>  	clocksource_davinci.name = id_to_name[clocksource_id];
>  	clocksource_davinci.mult =
>  		clocksource_khz2mult(davinci_clock_tick_rate/1000,