linux-kernel - Re: PMTMR running too fast

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Message-Id: <1165261226.5499.54.camel@localhost.localdomain>
Date:	Mon, 04 Dec 2006 19:40:26 +0000
From:	Ian Campbell <ijc@...lion.org.uk>
To:	john stultz <johnstul@...ibm.com>
Cc:	linux-kernel@...r.kernel.org, Andi Kleen <ak@...e.de>
Subject: Re: PMTMR running too fast

On Mon, 2006-12-04 at 11:19 -0800, john stultz wrote:
> On Sun, 2006-12-03 at 13:50 +0000, Ian Campbell wrote:
> > In older kernels arch/i386/kernel/timers/timer_pm.c:verify_pmtmr_rate
> > contained a check for sensible PMTMR rate and disabled that clocksource
> > if it was found to be out of spec[0]. This check seems to have been lost
> > in the transition to drivers/clocksource/acpi_pm.c, the removal is in
> > 61743fe445213b87fb55a389c8d073785323ca3e "Time: i386 Conversion - part
> > 4: Remove Old timer_opts Code"[1] and the check is not present in the
> > replacement 5d0cf410e94b1f1ff852c3f210d22cc6c5a27ffa "Time: i386
> > Clocksource Drivers"[2].
> 
> Fedora has a bug covering this:
> https://bugzilla.redhat.com/bugzilla/show_bug.cgi?id=211902

> > Is there a specific reason the check was removed (I couldn't see on in
> > the archives) or was it simply overlooked? Without it I need to pass
> > clocksource=tsc to have 2.6.18 work correctly on an older K6 system with
> > an Aladdin chipset (will dig out the precise details if required). Would
> > a patch to reintroduce the check be acceptable or would some sort of
> > blacklist based solution be more acceptable?
> 
> If I recall correctly, it was pulled because there was some question as
> to if it was actually needed (x86_64 didn't need it) and it slows down
> the boot time (although not by much). 
> 
> I'm fine just re-adding it. Although if the number of affected systems
> are small we could just blacklist it (Ian, mind sending dmidecode
> output?).

dmidecode.txt is attached.

Cheers,
Ian.

-- 
Ian Campbell

Felson's Law:
	To steal ideas from one person is plagiarism; to steal from
	many is research.

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