linux-kernel - Re: + i386-lapic-timer-calibration.patch added to -mm tree

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Date:	Wed, 08 Nov 2006 13:27:10 +0100
From:	Thomas Gleixner <tglx@...utronix.de>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	linux-kernel@...r.kernel.org, mm-commits@...r.kernel.org,
	Andrew Morton <akpm@...l.org>
Subject: Re: + i386-lapic-timer-calibration.patch added to -mm tree

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


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