From: Andi Kleen <ak@suse.de>
Organization: SUSE Linux Products GmbH, Nuernberg, GF: Markus Rex, HRB 16746 (AG Nuernberg)
To: tglx@linutronix.de
Subject: Re: [PATCH] Blacklist Dell Optiplex 320 from using the HPET
Date: Sun, 6 May 2007 00:05:37 +0200
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       Andrew Morton <akpm@linux-foundation.org>,
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       lkml <linux-kernel@vger.kernel.org>
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On Saturday 05 May 2007 21:15:01 Thomas Gleixner wrote:
> On Sat, 2007-05-05 at 19:24 +0200, Andi Kleen wrote:
> > >  	if (!is_hpet_capable())
> > > @@ -278,6 +279,14 @@ int __init hpet_enable(void)
> > >  	/* Start the counter */
> > >  	hpet_start_counter();
> > >  
> > > +	/* Verify whether hpet counter works */
> > > +	t1 = hpet_read();
> > > +	udelay(50);
> > 
> > Are you sure udelay is calibrated at this point? I didn't think so.
> > In fact it needs the external clocks and it's a chicken and egg problem.
> 
> Oops. You are right. OTOH it does not matter whether it is accurate or
> not.

It might be very short if you're very unlucky and the CPU is fast
and then trigger the check incorrectly.

-Andi
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