Re: [ACPI] X86_PM_TIMER: /proc/cpuinfo doesn't get updated

Dominik Brodowski
2004-03-18T09:06:54Z

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On Wed, Mar 17, 2004 at 02:56:27PM -0800, Nate Lawson wrote:
> On Wed, 17 Mar 2004, Dominik Brodowski wrote:
> > On Tue, Mar 16, 2004 at 11:40:57PM -0500, Dmitry Torokhov wrote:
> > > On Tuesday 16 March 2004 08:33 pm, Peter Chubb wrote:
> > > > >>>>> "Dmitry" == Dmitry Torokhov <dtor_core@ameritech.net> writes:
> > > >
> > > > Dmitry> On Tuesday 16 March 2004 07:13 pm, Karol Kozimor wrote:
> > > > >> Thus wrote john stultz: > Hmm. This is untested, but I think this
> > > > >> should do the trick.
> > > > >>
> > > > >> Hmm... without the patch, neither cpu MHz nor bogomips are updated,
> > > > >> with the patch cpu MHz value seems correct (both using acpi.ko and
> > > > >> speedstep-ich.ko, but the bogomips is still at its initial value.
> > > > >> Best regards,
> > > > >>
> > > >
> > > > Dmitry> Karol, do you have a P4? AFAIK P4's TSC is stable even if core
> > > > Dmitry> frequence changes so loop_per_juffy (== bogomips) need not be
> > > > Dmitry> updated.
> > > >
> > > > The TSC is variable rate for Pentium-IV if you're using clock
> > > > modulation.
> > > >
> > > > Peter C
> > > >
> > >
> > > I understand that by clock modulation you mean throttling as opposed to
> > > true SpeedStep... OK, that means that for P4+ we somehow need to figure
> > > out whether the CPU is throttled or not to correctly calculate delays.
> > > Is there a clean way to get this data?
> >
> > Hm, will have one patch to test it ready later today -- and a basic patch to
> > do this distinction is in the hiding of my notebook's harddisk already...
> > who's willing to do some testing on his SpeedStep-capable Pentium 4 - Mobile.
>
> Instead of all this gymnastics, how about:

It's not so much gymnastics -- implementing different handling for cpufreq
drivers which do not affect the TSC is easy. It's just difficult to get to
know what drivers/CPUs are affected... and the test run you did yesterday
helped in evaluating this. Thanks for doing so.

> 1. If using Px states, state is unknown until first "set" event.

Normally, when using cpufreq drivers the original state is known -- only the
ACPI spec has this severe flaw, but there are tries for a workaround [patch
is submitted]

> 2. Implement priorities for time source selection and a generic timer API.
> This gets around the need to get the clock rate correct to have system
> timers work. On FreeBSD, this is /sys/kern/kern_tc.c

IIRC, John Stultz intends to do a major upgrade of the timing code in 2.7.

Dominik

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