Subject: Re: [PATCH] Blacklist Dell Optiplex 320 from using the HPET
From: Thomas Gleixner <tglx@linutronix.de>
Reply-To: tglx@linutronix.de
To: Andi Kleen <ak@suse.de>
Cc: john stultz <johnstul@us.ibm.com>,
       Andrew Morton <akpm@linux-foundation.org>,
       "Guilherme M. Schroeder" <guilherme@centralinf.com.br>,
       lkml <linux-kernel@vger.kernel.org>
In-Reply-To: <200705051924.14258.ak@suse.de>
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Date: Sat, 05 May 2007 21:15:01 +0200
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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 safer to use a long loop with io port accesses or similar.

Should work as well.

	tglx


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