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Subject: Re: + i386-lapic-timer-calibration.patch added to -mm tree
From: Thomas Gleixner <tglx@linutronix.de>
Reply-To: tglx@linutronix.de
To: Ingo Molnar <mingo@elte.hu>
Cc: linux-kernel@vger.kernel.org, mm-commits@vger.kernel.org,
       Andrew Morton <akpm@osdl.org>
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References: <200611012045.kA1KjM1p018949@shell0.pdx.osdl.net>
	 <20061108120914.GB19843@elte.hu>
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Date: Wed, 08 Nov 2006 13:27:10 +0100
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On Wed, 2006-11-08 at 13:09 +0100, Ingo Molnar wrote:
> one question:
> 
> > +	long tapic = apic_read(APIC_TMCCT);
> > +	unsigned long pm = acpi_pm_read_early();
> 
> is this function call safe if the box has no pm-timer?

That's in the pm-timer-allow-early-access.patch:

Subject: pmtimer: Allow early access to pm timer

+static inline u32 acpi_pm_read_early(void)
+{
+       if (!pmtmr_ioport)
+               return 0;
+       /* mask the output to 24 bits */
+       return acpi_pm_read_verified();
+}

If pmtmr is not available, the function returns 0, so the resulting
delta is 0 and therefor ignored. Same applies, when PMTIMER is disabled
in the config.

	tglx