[U-Boot] [PATCH 2/9] Exynos: Add timer_get_us function

[Simon Glass]

On Wed, Feb 27, 2013 at 2:02 AM, Akshay Saraswat <akshay.s at samsung.com> wrote:
> timer_get_us returns the time in microseconds since a certain reference
> point of history.  However, it does not guarantee to return an accurate
> time after a long period; instead, it wraps around (that is, the
> reference point is reset to some other point of history) after some
> periods. The frequency of wrapping around is about an hour (or 2^32
> microseconds).
>
> TEST=sf probe 1:0; time sf read 40008000 0 1000
> Try with different numbers of bytes and see that sane values are obtained
>
> Signed-off-by: Che-Liang Chiou <clchiou at chromium.org>
> Signed-off-by: Akshay Saraswat <akshay.s at samsung.com>

Acked-by: Simon Glass <sjg at chromium.org>

> ---
>  arch/arm/cpu/armv7/s5p-common/timer.c | 15 +++++++++++++++
>  1 file changed, 15 insertions(+)
>
> diff --git a/arch/arm/cpu/armv7/s5p-common/timer.c b/arch/arm/cpu/armv7/s5p-common/timer.c
> index c48a297..de61405 100644
> --- a/arch/arm/cpu/armv7/s5p-common/timer.c
> +++ b/arch/arm/cpu/armv7/s5p-common/timer.c
> @@ -90,6 +90,21 @@ unsigned long get_timer(unsigned long base)
>         return gd->arch.timer_reset_value / 1000 - base;
>  }
>
> +unsigned long timer_get_us(void)
> +{
> +       static unsigned long base_time_us;
> +
> +       struct s5p_timer *const timer =
> +               (struct s5p_timer *)samsung_get_base_timer();
> +       unsigned long now_downward_us = readl(&timer->tcnto4);
> +
> +       if (!base_time_us)
> +               base_time_us = now_downward_us;
> +
> +       /* Note that this timer counts downward. */
> +       return base_time_us - now_downward_us;
> +}
> +
>  /* delay x useconds */
>  void __udelay(unsigned long usec)
>  {
> --
> 1.8.0
>