From: Dmitry Torokhov <dtor_core@ameritech.net>
To: john stultz <johnstul@us.ibm.com>
Subject: Re: [2.6.0-mm2] PM timer still has problems
Date: Wed, 7 Jan 2004 01:30:21 -0500
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       Arjan van de Ven <arjanv@redhat.com>, jw schultz <jw@pegasys.ws>
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On Tuesday 06 January 2004 03:31 am, john stultz wrote:
> On Sun, 2004-01-04 at 22:17, Dmitry Torokhov wrote:
> > I decided to go hpet way and use tsc in ACPI PM timer to do delay
> > stuff and monotonic clock.
>
> I think you have a valid point that as loops_per_jiffy isn't updated,
> delay_pmtmr() and delay_pit() are broken w/ CPUFREQ.
>
> However I don't understand using the TSC for montonic_clock. I have no
> clue why the HPET folks implemented it that way (likely my fault for
> not enough documentaiton), but I haven't had the time to try to clean
> up that code. And really, if your TSC is reliable enough for
> monotonic_clock, why are you using the pmtmr? :) Unless it specifically
> is resolving an issue, I'd drop that change.
>

I thought (it seems that I was mistaken) that the goal of monotonic_clock
is to privide high-resolution cheap timestamps that are guaranteed never
go back as there is no adjustments to the time. The normal clock it supposed
to be stable and accurate but probably give lower resolution. In case of
pmtmr vs. TSC seems to have higher resolution and is cheap so it was used.

Dmitry 

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