RE: [PATCH 3/8] x86/apic: allow use of lapic timer early calibration result

Thomas Gleixner
2010-05-11T19:50:30Z

Jacob,

On Tue, 11 May 2010, Pan, Jacob jun wrote:

> Thanks for the review.
>
> > >
> > > lapic timer calibration can be combined with tsc in platform specific
> > > calibration functions. if such calibration result is obtained early,
> > > we can skip the redundent calibration loops.
> >
> > I'd rather move lapic calibration into TSC calibration in general as
> > we do the same thing twice for no good reason.
> >
> > That needs some code restructuring, but that's worth it.
> >
> I am trying to avoid the risks of completely remove the current lapic
> calibration code since there are so many platforms with different timer
> options. And I don't understand things like why pm timer is preferred.
> Why not use the rating in clocksource?

We do not have access to the clocksource at that point. But we do a
calibration loop for TSC and for lapic timer. There is no reason why
we can't do that in one go.

> > Aside of my general objection it'd be not a good idea to make this
> > global w/o renaming it to something sensible like
> > lapic_timer_frequency.
> >
> perhaps, the calibration data can directly be assigned to lapic timer
> clock_event_device.mult? There is no need for the device specific result
> scale (e.g. bus clocks per tick)

No. That needs an accessor function.

Thanks,

tglx