Commit e492c5ae authored by Yinghai Lu's avatar Yinghai Lu Committed by Ingo Molnar
Browse files

x86: let 64 bit to use 32 bit calibrate_apic_clock 



Use the 32-bit APIC calibration code - it's more mature.

Signed-of-by: default avatarYinghai Lu <yhlu.kernel@gmail.com>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent 0f611ffa

arch/x86/kernel/apic.c

+2 −86
Original line number Diff line number Diff line
@@ -478,90 +478,6 @@ static void __cpuinit setup_APIC_timer(void) 
	clockevents_register_device(levt);

}



#ifdef CONFIG_X86_64

/*

 * In this function we calibrate APIC bus clocks to the external

 * timer. Unfortunately we cannot use jiffies and the timer irq

 * to calibrate, since some later bootup code depends on getting

 * the first irq? Ugh.

 *

 * We want to do the calibration only once since we

 * want to have local timer irqs syncron. CPUs connected

 * by the same APIC bus have the very same bus frequency.

 * And we want to have irqs off anyways, no accidental

 * APIC irq that way.

 */



#define TICK_COUNT 100000000



static int __init calibrate_APIC_clock(void)

{

	unsigned apic, apic_start;

	unsigned long tsc, tsc_start;

	int result;



	local_irq_disable();



	/*

	 * Put whatever arbitrary (but long enough) timeout

	 * value into the APIC clock, we just want to get the

	 * counter running for calibration.

	 *

	 * No interrupt enable !

	 */

	__setup_APIC_LVTT(250000000, 0, 0);



	apic_start = apic_read(APIC_TMCCT);

#ifdef CONFIG_X86_PM_TIMER

	if (apic_calibrate_pmtmr && pmtmr_ioport) {

		pmtimer_wait(5000);  /* 5ms wait */

		apic = apic_read(APIC_TMCCT);

		result = (apic_start - apic) * 1000L / 5;

	} else

#endif

	{

		rdtscll(tsc_start);



		do {

			apic = apic_read(APIC_TMCCT);

			rdtscll(tsc);

		} while ((tsc - tsc_start) < TICK_COUNT &&

				(apic_start - apic) < TICK_COUNT);



		result = (apic_start - apic) * 1000L * tsc_khz /

					(tsc - tsc_start);

	}



	local_irq_enable();



	printk(KERN_DEBUG "APIC timer calibration result %d\n", result);



	printk(KERN_INFO "Detected %d.%03d MHz APIC timer.\n",

		result / 1000 / 1000, result / 1000 % 1000);



	/* Calculate the scaled math multiplication factor */

	lapic_clockevent.mult = div_sc(result, NSEC_PER_SEC,

				       lapic_clockevent.shift);

	lapic_clockevent.max_delta_ns =

		clockevent_delta2ns(0x7FFFFF, &lapic_clockevent);

	lapic_clockevent.min_delta_ns =

		clockevent_delta2ns(0xF, &lapic_clockevent);



	calibration_result = (result * APIC_DIVISOR) / HZ;



	/*

	 * Do a sanity check on the APIC calibration result

	 */

	if (calibration_result < (1000000 / HZ)) {

		printk(KERN_WARNING

			"APIC frequency too slow, disabling apic timer\n");

		return -1;

	}



	return 0;

}



#else

/*

 * In this functions we calibrate APIC bus clocks to the external timer.

 *
@@ -659,6 +575,7 @@ static int __init calibrate_APIC_clock(void) 
	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(void) 
		}

		pm_referenced = 1;

	}

#endif



	/* Calculate the scaled math multiplication factor */

	lapic_clockevent.mult = div_sc(delta, TICK_NSEC * LAPIC_CAL_LOOPS,
@@ -773,8 +691,6 @@ static int __init calibrate_APIC_clock(void) 
	return 0;

}



#endif



/*

 * Setup the boot APIC

 *