Re: [PATCH 33/36] AArch64: Generic timers support

[John Stultz]

On 07/13/2012 09:02 AM, Catalin Marinas wrote:
> On Fri, Jul 13, 2012 at 01:40:03PM +0100, Arnd Bergmann wrote:
> > Hmm, in the quest to eliminate CLOCK_TICK_RATE entirely, could we
> > make a Kconfig symbol that is selected for all architectures that
> > (may) rely on a periodic timer tick and require this to be set?
> >
> > Architectures that always have a working clock source would then just
> > not include the timex.h header and #define ACT_HZ HZ in common code.
>
> Would something like below be enough?

Looks interesting. Although I've not had a chance to follow through in 
more detail to see what that might impact.  But something like this 
seems like a good approach.


> Also, are there any implications if we boot with clocksource=jiffies?

You'd probably see an maximum error of:
	 (tick-device-granularity/2)/(1sec/HZ).

If that ends up larger then 100ppm you'd have a fairly poor clock, 
although NTP can correct for up to 500ppm.

thanks
-john

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