Re: [Xen-devel] [PATCH 02 of 10] arm: implement udelay()

[David Vrabel <dvrabel@xxxxxxxxxx>]

On 23/02/12 17:40, Tim Deegan wrote:
> arm: implement udelay()
> 
> Signed-off-by: Tim Deegan <tim@xxxxxxx>
> 
[...]
> diff -r 4a7c14209131 -r ec051056db2b xen/arch/arm/time.c
> --- a/xen/arch/arm/time.c     Thu Feb 23 17:39:59 2012 +0000
> +++ b/xen/arch/arm/time.c     Thu Feb 23 17:39:59 2012 +0000
> @@ -171,6 +171,16 @@ void __cpuinit init_timer_interrupt(void
>      request_irq(30, timer_interrupt, 0, "phytimer", NULL);
>  }
>  
> +/* Wait a set number of microseconds */
> +void udelay(unsigned long usecs)
> +{
> +    s_time_t deadline = get_s_time() + 1000 * (s_time_t) usecs;
> +    do {
> +        dsb();
> +        isb();

What are these barriers for?

David

> +    } while ( get_s_time() - deadline < 0 );
> +}
> +
>  /*
>   * Local variables:
>   * mode: C

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