linux-kernel - Re: [PATCH] x86: let 64 bit to use 32 bit calibrate_apic

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Date:	Mon, 25 Aug 2008 13:05:49 -0700
From:	"Yinghai Lu" <yhlu.kernel@...il.com>
To:	"Cyrill Gorcunov" <gorcunov@...il.com>
Cc:	"Ingo Molnar" <mingo@...e.hu>,
	"Thomas Gleixner" <tglx@...utronix.de>,
	"H. Peter Anvin" <hpa@...or.com>,
	"Andrew Morton" <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] x86: let 64 bit to use 32 bit calibrate_apic_clock

On Mon, Aug 25, 2008 at 9:47 AM, Cyrill Gorcunov <gorcunov@...il.com> wrote:
> [Yinghai Lu - Mon, Aug 25, 2008 at 01:04:34AM -0700]
> | On Mon, Aug 25, 2008 at 12:47 AM, Ingo Molnar <mingo@...e.hu> wrote:
> | >
> | > * Yinghai Lu <yhlu.kernel@...il.com> wrote:
> | >
> | >> Signed-of-by: Yinghai Lu <yhlu.kernel@...il.com>
> | >
> | > applied to tip/irq/sparseirq - thanks Yinghai.
> | >
> | > btw., why was this bit needed:
> | >
> | >> @@ -659,6 +575,7 @@ static int __init calibrate_APIC_clock(v
> | >>       delta = lapic_cal_t1 - lapic_cal_t2;
> | >>       apic_printk(APIC_VERBOSE, "... lapic delta = %ld\n", delta);
> | >>
> | >> +#ifdef CONFIG_X86_PM_TIMER
> | >>       /* Check, if the PM timer is available */
> | >>       deltapm = lapic_cal_pm2 - lapic_cal_pm1;
> | >>       apic_printk(APIC_VERBOSE, "... PM timer delta = %ld\n", deltapm);
> | >> @@ -687,6 +604,7 @@ static int __init calibrate_APIC_clock(v
> | >>               }
> | >>               pm_referenced = 1;
> | >>       }
> | >> +#endif
> | >
> | > wouldnt this be a (small) fix for the pre-unification 32-bit side as
> | > well, which we should put into tip/x86/urgent as well?
> |
> | 64bit have those MACRO, it seems when CONFIG_EMBEDDED is set, could
> | reduce some size if pm is not selected.
> |
> | it seems not be urgent for 2.6.27.
> |
> | YH
> |
>
> Hey, APIC_DIVISOR is now wrong - it should be 16 for both modes

why?

calibration_result = (delta * APIC_DIVISOR) / LAPIC_CAL_LOOPS;

> then, shouldn't it? :)

could make for 64 to use 16 too.

YH
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