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From: Andi Kleen <ak@suse.de>
To: john stultz <johnstul@us.ibm.com>
Cc: Ian Campbell <ijc@hellion.org.uk>, linux-kernel@vger.kernel.org
Subject: Re: PMTMR running too fast
Date: Wed, 6 Dec 2006 17:44:47 +0100	[thread overview]
Message-ID: <200612061744.47249.ak@suse.de> (raw)
In-Reply-To: <1165259962.6152.5.camel@localhost.localdomain>


> 
> > 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?).
> 
> Andi, your thoughts?

Doing a check at boot time is fine for me. Just I don't want the
"read pmtmr three times at runtime" code anywhere near x86-64

I don't think the boot time check needs DMI guarding

But BTW the check is not necessarily enough -- there is at least one
NF3 machine around where the PIT timer ticks at a wrong frequency.
Safer would be probably to calibrate against RTC which is afaik used
by Windows too (so it's likely to be ok) 

-Andi

  parent reply	other threads:[~2006-12-06 17:44 UTC|newest]

Thread overview: 11+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2006-12-03 13:50 Ian Campbell
2006-12-04 19:19 ` john stultz
2006-12-04 19:40   ` Ian Campbell
2006-12-04 20:14     ` john stultz
2006-12-05  7:41       ` Ian Campbell
2006-12-05 19:34         ` john stultz
2006-12-06  8:14           ` Ian Campbell
2006-12-06 19:46           ` Ian Campbell
2006-12-06 16:44   ` Andi Kleen [this message]
2006-12-06 19:28     ` john stultz
2006-12-06 20:14       ` Andi Kleen

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