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SubjectRE: [PATCH][2.6][2/5]Support for HPET based timer
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> -----Original Message-----
> From: john stultz [mailto:johnstul@us.ibm.com]
>
> Well, the difficult part is deciding in time_init() if we are going to
> use HPET without touching the hardware (to say, check if its actually
> there).
>

Yes. But, currently we are using ACPI early table parse to look at HPET.
So we should be OK here.
Even if accessing HPET hardware fails later, in the late_time_init(),
we can fallback to PIT, as long as calibrate_delay() is done after
late_time_init().

> We could pick a simple time source (ie: PIT) that would get us through
> early boot, then choose the real time source in late_time_init(). That
> would also make implementing the ACPI PM time-source much simpler as
we
> could wait until after ACPI is up, letting us avoid having to parse
the
> tables by hand.
>
> However I'm not sure it would be trivial and bug free. ;)
>

Depending on multiple time sources may not be good idea, IMO. May be,
one day we will have a fully-legacy-free system with no PIT. :)

Thanks,
-Venkatesh
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