Re: [RFC][PATCH] Convert alpha to use clocksource

[john stultz <johnstul@us.ibm.com>]

On Thu, 2010-03-18 at 07:32 -0700, Richard Henderson wrote:
> On 03/17/2010 07:01 PM, John Stultz wrote:
> > Alpha has a tsc like rpcc counter that it uses to manage time.
> > This can be converted to an actual clocksource instead of utilizing
> > the arch_gettimeoffset method that is really only there for legacy
> > systems with no continuous counter.
> 
> With 8 seconds or less between roll-overs, do you actually consider
> this a continuous counter?  I don't.  I suggest this be left alone.

The timekeeping code handles this (although the shift value I picked may
need some adjustment - what is the expected counter freq range on
alpha?). The ACPI PM counter which is very common on x86 is only 24 bits
and rolls over in ~5 seconds. It works fine.

However, I'm not maintaining the arch, and this patch isn't limiting the
timekeeping core, so the call is really yours. I sent this out on a whim
since it looked easy to do.

However, while this change is totally optional, I suspect my suggestion
about moving to the clockevents code is going to rise in importance. The
triplicate timer code paths of non-converted, converted periodic and
converted one-shot is difficult to follow.

I'll try to find a good example of an easy conversion case (PIT on x86
is not it) and send it your way.

thanks
-john