arch/i386/kernel/apic.c

/*
 *	Local APIC handling, local APIC timers
 *
 *	(c) 1999, 2000 Ingo Molnar <mingo@redhat.com>
 *
 *	Fixes
 *	Maciej W. Rozycki	:	Bits for genuine 82489DX APICs;
 *					thanks to Eric Gilmore
 *					and Rolf G. Tews
 *					for testing these extensively.
 *	Maciej W. Rozycki	:	Various updates and fixes.
 *	Mikael Pettersson	:	Power Management for UP-APIC.
 *	Pavel Machek and
 *	Mikael Pettersson	:	PM converted to driver model.
 */

#include <linux/init.h>

#include <linux/mm.h>
#include <linux/delay.h>
#include <linux/bootmem.h>
#include <linux/smp_lock.h>
#include <linux/interrupt.h>
#include <linux/mc146818rtc.h>
#include <linux/kernel_stat.h>
#include <linux/sysdev.h>
#include <linux/cpu.h>
#include <linux/clockchips.h>
#include <linux/acpi_pmtmr.h>
#include <linux/module.h>

#include <asm/atomic.h>
#include <asm/smp.h>
#include <asm/mtrr.h>
#include <asm/mpspec.h>
#include <asm/desc.h>
#include <asm/arch_hooks.h>
#include <asm/hpet.h>
#include <asm/i8253.h>
#include <asm/nmi.h>
#include <asm/idle.h>

#include <mach_apic.h>
#include <mach_apicdef.h>
#include <mach_ipi.h>

#include "io_ports.h"

/*
 * Sanity check
 */
#if (SPURIOUS_APIC_VECTOR & 0x0F) != 0x0F
# error SPURIOUS_APIC_VECTOR definition error
#endif

/*
 * Knob to control our willingness to enable the local APIC.
 *
 * -1=force-disable, +1=force-enable
 */
static int enable_local_apic __initdata = 0;

/* Local APIC timer verification ok */
static int local_apic_timer_verify_ok;

/*
 * Debug level, exported for io_apic.c
 */
int apic_verbosity;

static unsigned int calibration_result;

static int lapic_next_event(unsigned long delta,
			    struct clock_event_device *evt);
static void lapic_timer_setup(enum clock_event_mode mode,
			      struct clock_event_device *evt);
static void lapic_timer_broadcast(cpumask_t mask);
static void apic_pm_activate(void);

/*
 * The local apic timer can be used for any function which is CPU local.
 */
static struct clock_event_device lapic_clockevent = {
	.name		= "lapic",
	.features	= CLOCK_EVT_FEAT_PERIODIC | CLOCK_EVT_FEAT_ONESHOT
			| CLOCK_EVT_FEAT_C3STOP | CLOCK_EVT_FEAT_DUMMY,
	.shift		= 32,
	.set_mode	= lapic_timer_setup,
	.set_next_event	= lapic_next_event,
	.broadcast	= lapic_timer_broadcast,
	.rating		= 100,
	.irq		= -1,
};
static DEFINE_PER_CPU(struct clock_event_device, lapic_events);

/* Local APIC was disabled by the BIOS and enabled by the kernel */
static int enabled_via_apicbase;

/*
 * Get the LAPIC version
 */
static inline int lapic_get_version(void)
{
	return GET_APIC_VERSION(apic_read(APIC_LVR));
}

/*
 * Check, if the APIC is integrated or a seperate chip
 */
static inline int lapic_is_integrated(void)
{
	return APIC_INTEGRATED(lapic_get_version());
}

/*
 * Check, whether this is a modern or a first generation APIC
 */
static int modern_apic(void)
{
	/* AMD systems use old APIC versions, so check the CPU */
	if (boot_cpu_data.x86_vendor == X86_VENDOR_AMD &&
	    boot_cpu_data.x86 >= 0xf)
		return 1;
	return lapic_get_version() >= 0x14;
}

/**
 * enable_NMI_through_LVT0 - enable NMI through local vector table 0
 */
void enable_NMI_through_LVT0 (void * dummy)
{
	unsigned int v = APIC_DM_NMI;

	/* Level triggered for 82489DX */
	if (!lapic_is_integrated())
		v |= APIC_LVT_LEVEL_TRIGGER;
	apic_write_around(APIC_LVT0, v);
}

/**
 * get_physical_broadcast - Get number of physical broadcast IDs
 */
int get_physical_broadcast(void)
{
	return modern_apic() ? 0xff : 0xf;
}

/**
 * lapic_get_maxlvt - get the maximum number of local vector table entries
 */
int lapic_get_maxlvt(void)
{
	unsigned int v = apic_read(APIC_LVR);

	/* 82489DXs do not report # of LVT entries. */
	return APIC_INTEGRATED(GET_APIC_VERSION(v)) ? GET_APIC_MAXLVT(v) : 2;
}

/*
 * Local APIC timer
 */

/* Clock divisor is set to 16 */
#define APIC_DIVISOR 16

/*
 * This function sets up the local APIC timer, with a timeout of
 * 'clocks' APIC bus clock. During calibration we actually call
 * this function twice on the boot CPU, once with a bogus timeout
 * value, second time for real. The other (noncalibrating) CPUs
 * call this function only once, with the real, calibrated value.
 *
 * We do reads before writes even if unnecessary, to get around the
 * P5 APIC double write bug.
 */
static void __setup_APIC_LVTT(unsigned int clocks, int oneshot, int irqen)
{
	unsigned int lvtt_value, tmp_value;

	lvtt_value = LOCAL_TIMER_VECTOR;
	if (!oneshot)
		lvtt_value |= APIC_LVT_TIMER_PERIODIC;
	if (!lapic_is_integrated())
		lvtt_value |= SET_APIC_TIMER_BASE(APIC_TIMER_BASE_DIV);

	if (!irqen)
		lvtt_value |= APIC_LVT_MASKED;

	apic_write_around(APIC_LVTT, lvtt_value);

	/*
	 * Divide PICLK by 16
	 */
	tmp_value = apic_read(APIC_TDCR);
	apic_write_around(APIC_TDCR, (tmp_value
				& ~(APIC_TDR_DIV_1 | APIC_TDR_DIV_TMBASE))
				| APIC_TDR_DIV_16);

	if (!oneshot)
		apic_write_around(APIC_TMICT, clocks/APIC_DIVISOR);
}

/*
 * Program the next event, relative to now
 */
static int lapic_next_event(unsigned long delta,
			    struct clock_event_device *evt)
{
	apic_write_around(APIC_TMICT, delta);
	return 0;
}

/*
 * Setup the lapic timer in periodic or oneshot mode
 */
static void lapic_timer_setup(enum clock_event_mode mode,
			      struct clock_event_device *evt)
{
	unsigned long flags;
	unsigned int v;

	/* Lapic used for broadcast ? */
	if (!local_apic_timer_verify_ok)
		return;

	local_irq_save(flags);

	switch (mode) {
	case CLOCK_EVT_MODE_PERIODIC:
	case CLOCK_EVT_MODE_ONESHOT:
		__setup_APIC_LVTT(calibration_result,
				  mode != CLOCK_EVT_MODE_PERIODIC, 1);
		break;
	case CLOCK_EVT_MODE_UNUSED:
	case CLOCK_EVT_MODE_SHUTDOWN:
		v = apic_read(APIC_LVTT);
		v |= (APIC_LVT_MASKED | LOCAL_TIMER_VECTOR);
		apic_write_around(APIC_LVTT, v);
		break;
	}

	local_irq_restore(flags);
}

/*
 * Local APIC timer broadcast function
 */
static void lapic_timer_broadcast(cpumask_t mask)
{
#ifdef CONFIG_SMP
	send_IPI_mask(mask, LOCAL_TIMER_VECTOR);
#endif
}

/*
 * Setup the local APIC timer for this CPU. Copy the initilized values
 * of the boot CPU and register the clock event in the framework.
 */
static void __devinit setup_APIC_timer(void)
{
	struct clock_event_device *levt = &__get_cpu_var(lapic_events);

	memcpy(levt, &lapic_clockevent, sizeof(*levt));
	levt->cpumask = cpumask_of_cpu(smp_processor_id());

	clockevents_register_device(levt);
}

/*
 * In this functions we calibrate APIC bus clocks to the external timer.
 *
 * 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.
 *
 * This was previously done by reading the PIT/HPET and waiting for a wrap
 * around to find out, that a tick has elapsed. I have a box, where the PIT
 * readout is broken, so it never gets out of the wait loop again. This was
 * also reported by others.
 *
 * Monitoring the jiffies value is inaccurate and the clockevents
 * infrastructure allows us to do a simple substitution of the interrupt
 * handler.
 *
 * The calibration routine also uses the pm_timer when possible, as the PIT
 * happens to run way too slow (factor 2.3 on my VAIO CoreDuo, which goes
 * back to normal later in the boot process).
 */

#define LAPIC_CAL_LOOPS		(HZ/10)

static __initdata volatile int lapic_cal_loops = -1;
static __initdata long lapic_cal_t1, lapic_cal_t2;
static __initdata unsigned long long lapic_cal_tsc1, lapic_cal_tsc2;
static __initdata unsigned long lapic_cal_pm1, lapic_cal_pm2;
static __initdata unsigned long lapic_cal_j1, lapic_cal_j2;

/*
 * Temporary interrupt handler.
 */
static void __init lapic_cal_handler(struct clock_event_device *dev)
{
	unsigned long long tsc = 0;
	long tapic = apic_read(APIC_TMCCT);
	unsigned long pm = acpi_pm_read_early();

	if (cpu_has_tsc)
		rdtscll(tsc);

	switch (lapic_cal_loops++) {
	case 0:
		lapic_cal_t1 = tapic;
		lapic_cal_tsc1 = tsc;
		lapic_cal_pm1 = pm;
		lapic_cal_j1 = jiffies;
		break;

	case LAPIC_CAL_LOOPS:
		lapic_cal_t2 = tapic;
		lapic_cal_tsc2 = tsc;
		if (pm < lapic_cal_pm1)
			pm += ACPI_PM_OVRRUN;
		lapic_cal_pm2 = pm;
		lapic_cal_j2 = jiffies;
		break;
	}
}

/*
 * Setup the boot APIC
 *
 * Calibrate and verify the result.
 */
void __init setup_boot_APIC_clock(void)
{
	struct clock_event_device *levt = &__get_cpu_var(lapic_events);
	const long pm_100ms = PMTMR_TICKS_PER_SEC/10;
	const long pm_thresh = pm_100ms/100;
	void (*real_handler)(struct clock_event_device *dev);
	unsigned long deltaj;
	long delta, deltapm;

	apic_printk(APIC_VERBOSE, "Using local APIC timer interrupts.\n"
		    "calibrating APIC timer ...\n");

	local_irq_disable();

	/* Replace the global interrupt handler */
	real_handler = global_clock_event->event_handler;
	global_clock_event->event_handler = lapic_cal_handler;

	/*
	 * Setup the APIC counter to 1e9. There is no way the lapic
	 * can underflow in the 100ms detection time frame
	 */
	__setup_APIC_LVTT(1000000000, 0, 0);

	/* Let the interrupts run */
	local_irq_enable();

	while(lapic_cal_loops <= LAPIC_CAL_LOOPS);

	local_irq_disable();

	/* Restore the real event handler */
	global_clock_event->event_handler = real_handler;

	/* Build delta t1-t2 as apic timer counts down */
	delta = lapic_cal_t1 - lapic_cal_t2;
	apic_printk(APIC_VERBOSE, "... lapic delta = %ld\n", delta);

	/* Check, if the PM timer is available */
	deltapm = lapic_cal_pm2 - lapic_cal_pm1;
	apic_printk(APIC_VERBOSE, "... PM timer delta = %ld\n", deltapm);

	if (deltapm) {
		unsigned long mult;
		u64 res;

		mult = clocksource_hz2mult(PMTMR_TICKS_PER_SEC, 22);

		if (deltapm > (pm_100ms - pm_thresh) &&
		    deltapm < (pm_100ms + pm_thresh)) {
			apic_printk(APIC_VERBOSE, "... PM timer result ok\n");
		} else {
			res = (((u64) deltapm) *  mult) >> 22;
			do_div(res, 1000000);
			printk(KERN_WARNING "APIC calibration not consistent "
			       "with PM Timer: %ldms instead of 100ms\n",
			       (long)res);
			/* Correct the lapic counter value */
			res = (((u64) delta ) * pm_100ms);
			do_div(res, deltapm);
			printk(KERN_INFO "APIC delta adjusted to PM-Timer: "
			       "%lu (%ld)\n", (unsigned long) res, delta);
			delta = (long) res;
		}
	}

	/* Calculate the scaled math multiplication factor */
	lapic_clockevent.mult = div_sc(delta, TICK_NSEC * LAPIC_CAL_LOOPS, 32);
	lapic_clockevent.max_delta_ns =
		clockevent_delta2ns(0x7FFFFF, &lapic_clockevent);
	lapic_clockevent.min_delta_ns =
		clockevent_delta2ns(0xF, &lapic_clockevent);

	calibration_result = (delta * APIC_DIVISOR) / LAPIC_CAL_LOOPS;

	apic_printk(APIC_VERBOSE, "..... delta %ld\n", delta);
	apic_printk(APIC_VERBOSE, "..... mult: %ld\n", lapic_clockevent.mult);
	apic_printk(APIC_VERBOSE, "..... calibration result: %u\n",
		    calibration_result);

	if (cpu_has_tsc) {
		delta = (long)(lapic_cal_tsc2 - lapic_cal_tsc1);
		apic_printk(APIC_VERBOSE, "..... CPU clock speed is "
			    "%ld.%04ld MHz.\n",
			    (delta / LAPIC_CAL_LOOPS) / (1000000 / HZ),
			    (delta / LAPIC_CAL_LOOPS) % (1000000 / HZ));
	}

	apic_printk(APIC_VERBOSE, "..... host bus clock speed is "
		    "%u.%04u MHz.\n",
		    calibration_result / (1000000 / HZ),
		    calibration_result % (1000000 / HZ));


	apic_printk(APIC_VERBOSE, "... verify APIC timer\n");

	/*
	 * Setup the apic timer manually
	 */
	local_apic_timer_verify_ok = 1;
	levt->event_handler = lapic_cal_handler;
	lapic_timer_setup(CLOCK_EVT_MODE_PERIODIC, levt);
	lapic_cal_loops = -1;

	/* Let the interrupts run */
	local_irq_enable();

	while(lapic_cal_loops <= LAPIC_CAL_LOOPS);

	local_irq_disable();

	/* Stop the lapic timer */
	lapic_timer_setup(CLOCK_EVT_MODE_SHUTDOWN, levt);

	local_irq_enable();

	/* Jiffies delta */
	deltaj = lapic_cal_j2 - lapic_cal_j1;
	apic_printk(APIC_VERBOSE, "... jiffies delta = %lu\n", deltaj);

	/* Check, if the PM timer is available */
	deltapm = lapic_cal_pm2 - lapic_cal_pm1;
	apic_printk(APIC_VERBOSE, "... PM timer delta = %ld\n", deltapm);

	local_apic_timer_verify_ok = 0;

	if (deltapm) {
		if (deltapm > (pm_100ms - pm_thresh) &&
		    deltapm < (pm_100ms + pm_thresh)) {
			apic_printk(APIC_VERBOSE, "... PM timer result ok\n");
			/* Check, if the jiffies result is consistent */
			if (deltaj < LAPIC_CAL_LOOPS-2 ||
			    deltaj > LAPIC_CAL_LOOPS+2) {
				/*
				 * Not sure, what we can do about this one.
				 * When high resultion timers are active
				 * and the lapic timer does not stop in C3
				 * we are fine. Otherwise more trouble might
				 * be waiting. -- tglx
				 */
				printk(KERN_WARNING "Global event device %s "
				       "has wrong frequency "
				       "(%lu ticks instead of %d)\n",
				       global_clock_event->name, deltaj,
				       LAPIC_CAL_LOOPS);
			}
			local_apic_timer_verify_ok = 1;
		}
	} else {
		/* Check, if the jiffies result is consistent */
		if (deltaj >= LAPIC_CAL_LOOPS-2 &&
		    deltaj <= LAPIC_CAL_LOOPS+2) {
			apic_printk(APIC_VERBOSE, "... jiffies result ok\n");
			local_apic_timer_verify_ok = 1;
		}
	}

	if (!local_apic_timer_verify_ok) {
		printk(KERN_WARNING
		       "APIC timer disabled due to verification failure.\n");
		/* No broadcast on UP ! */
		if (num_possible_cpus() == 1)
			return;
	} else
		lapic_clockevent.features &= ~CLOCK_EVT_FEAT_DUMMY;

	/* Setup the lapic or request the broadcast */
	setup_APIC_timer();
}

void __devinit setup_secondary_APIC_clock(void)
{
	setup_APIC_timer();
}

/*
 * The guts of the apic timer interrupt
 */
static void local_apic_timer_interrupt(void)
{
	int cpu = smp_processor_id();
	struct clock_event_device *evt = &per_cpu(lapic_events, cpu);

	/*
	 * Normally we should not be here till LAPIC has been initialized but
	 * in some cases like kdump, its possible that there is a pending LAPIC
	 * timer interrupt from previous kernel's context and is delivered in
	 * new kernel the moment interrupts are enabled.
	 *
	 * Interrupts are enabled early and LAPIC is setup much later, hence
	 * its possible that when we get here evt->event_handler is NULL.
	 * Check for event_handler being NULL and discard the interrupt as
	 * spurious.
	 */
	if (!evt->event_handler) {
		printk(KERN_WARNING
		       "Spurious LAPIC timer interrupt on cpu %d\n", cpu);
		/* Switch it off */
		lapic_timer_setup(CLOCK_EVT_MODE_SHUTDOWN, evt);
		return;
	}

	per_cpu(irq_stat, cpu).apic_timer_irqs++;

	evt->event_handler(evt);
}

/*
 * Local APIC timer interrupt. This is the most natural way for doing
 * local interrupts, but local timer interrupts can be emulated by
 * broadcast interrupts too. [in case the hw doesn't support APIC timers]
 *
 * [ if a single-CPU system runs an SMP kernel then we call the local
 *   interrupt as well. Thus we cannot inline the local irq ... ]
 */

void fastcall smp_apic_timer_interrupt(struct pt_regs *regs)
{
	struct pt_regs *old_regs = set_irq_regs(regs);

	/*
	 * NOTE! We'd better ACK the irq immediately,
	 * because timer handling can be slow.
	 */
	ack_APIC_irq();
	/*
	 * update_process_times() expects us to have done irq_enter().
	 * Besides, if we don't timer interrupts ignore the global
	 * interrupt lock, which is the WrongThing (tm) to do.
	 */
	exit_idle();
	irq_enter();
	local_apic_timer_interrupt();
	irq_exit();

	set_irq_regs(old_regs);
}

int setup_profiling_timer(unsigned int multiplier)
{
	return -EINVAL;
}

/*
 * Local APIC start and shutdown
 */

/**
 * clear_local_APIC - shutdown the local APIC
 *
 * This is called, when a CPU is disabled and before rebooting, so the state of
 * the local APIC has no dangling leftovers. Also used to cleanout any BIOS
 * leftovers during boot.
 */
void clear_local_APIC(void)
{
	int maxlvt = lapic_get_maxlvt();
	unsigned long v;

	/*
	 * Masking an LVT entry can trigger a local APIC error
	 * if the vector is zero. Mask LVTERR first to prevent this.
	 */
	if (maxlvt >= 3) {
		v = ERROR_APIC_VECTOR; /* any non-zero vector will do */
		apic_write_around(APIC_LVTERR, v | APIC_LVT_MASKED);
	}
	/*
	 * Careful: we have to set masks only first to deassert
	 * any level-triggered sources.
	 */
	v = apic_read(APIC_LVTT);
	apic_write_around(APIC_LVTT, v | APIC_LVT_MASKED);
	v = apic_read(APIC_LVT0);
	apic_write_around(APIC_LVT0, v | APIC_LVT_MASKED);
	v = apic_read(APIC_LVT1);
	apic_write_around(APIC_LVT1, v | APIC_LVT_MASKED);
	if (maxlvt >= 4) {
		v = apic_read(APIC_LVTPC);
		apic_write_around(APIC_LVTPC, v | APIC_LVT_MASKED);
	}

	/* lets not touch this if we didn't frob it */
#ifdef CONFIG_X86_MCE_P4THERMAL
	if (maxlvt >= 5) {
		v = apic_read(APIC_LVTTHMR);
		apic_write_around(APIC_LVTTHMR, v | APIC_LVT_MASKED);
	}
#endif
	/*
	 * Clean APIC state for other OSs:
	 */
	apic_write_around(APIC_LVTT, APIC_LVT_MASKED);
	apic_write_around(APIC_LVT0, APIC_LVT_MASKED);
	apic_write_around(APIC_LVT1, APIC_LVT_MASKED);
	if (maxlvt >= 3)
		apic_write_around(APIC_LVTERR, APIC_LVT_MASKED);
	if (maxlvt >= 4)
		apic_write_around(APIC_LVTPC, APIC_LVT_MASKED);

#ifdef CONFIG_X86_MCE_P4THERMAL
	if (maxlvt >= 5)
		apic_write_around(APIC_LVTTHMR, APIC_LVT_MASKED);
#endif
	/* Integrated APIC (!82489DX) ? */
	if (lapic_is_integrated()) {
		if (maxlvt > 3)
			/* Clear ESR due to Pentium errata 3AP and 11AP */
			apic_write(APIC_ESR, 0);
		apic_read(APIC_ESR);
	}
}

/**
 * disable_local_APIC - clear and disable the local APIC
 */
void disable_local_APIC(void)
{
	unsigned long value;

	clear_local_APIC();

	/*
	 * Disable APIC (implies clearing of registers
	 * for 82489DX!).
	 */
	value = apic_read(APIC_SPIV);
	value &= ~APIC_SPIV_APIC_ENABLED;
	apic_write_around(APIC_SPIV, value);

	/*
	 * When LAPIC was disabled by the BIOS and enabled by the kernel,
	 * restore the disabled state.
	 */
	if (enabled_via_apicbase) {
		unsigned int l, h;

		rdmsr(MSR_IA32_APICBASE, l, h);
		l &= ~MSR_IA32_APICBASE_ENABLE;
		wrmsr(MSR_IA32_APICBASE, l, h);
	}
}

/*
 * If Linux enabled the LAPIC against the BIOS default disable it down before
 * re-entering the BIOS on shutdown.  Otherwise the BIOS may get confused and
 * not power-off.  Additionally clear all LVT entries before disable_local_APIC
 * for the case where Linux didn't enable the LAPIC.
 */
void lapic_shutdown(void)
{
	unsigned long flags;

	if (!cpu_has_apic)
		return;

	local_irq_save(flags);
	clear_local_APIC();

	if (enabled_via_apicbase)
		disable_local_APIC();

	local_irq_restore(flags);
}

/*
 * This is to verify that we're looking at a real local APIC.
 * Check these against your board if the CPUs aren't getting
 * started for no apparent reason.
 */
int __init verify_local_APIC(void)
{
	unsigned int reg0, reg1;

	/*
	 * The version register is read-only in a real APIC.
	 */
	reg0 = apic_read(APIC_LVR);
	apic_printk(APIC_DEBUG, "Getting VERSION: %x\n", reg0);
	apic_write(APIC_LVR, reg0 ^ APIC_LVR_MASK);
	reg1 = apic_read(APIC_LVR);
	apic_printk(APIC_DEBUG, "Getting VERSION: %x\n", reg1);

	/*
	 * The two version reads above should print the same
	 * numbers.  If the second one is different, then we
	 * poke at a non-APIC.
	 */
	if (reg1 != reg0)
		return 0;

	/*
	 * Check if the version looks reasonably.
	 */
	reg1 = GET_APIC_VERSION(reg0);
	if (reg1 == 0x00 || reg1 == 0xff)
		return 0;
	reg1 = lapic_get_maxlvt();
	if (reg1 < 0x02 || reg1 == 0xff)
		return 0;

	/*
	 * The ID register is read/write in a real APIC.
	 */
	reg0 = apic_read(APIC_ID);
	apic_printk(APIC_DEBUG, "Getting ID: %x\n", reg0);

	/*
	 * The next two are just to see if we have sane values.
	 * They're only really relevant if we're in Virtual Wire
	 * compatibility mode, but most boxes are anymore.
	 */
	reg0 = apic_read(APIC_LVT0);
	apic_printk(APIC_DEBUG, "Getting LVT0: %x\n", reg0);
	reg1 = apic_read(APIC_LVT1);
	apic_printk(APIC_DEBUG, "Getting LVT1: %x\n", reg1);

	return 1;
}

/**
 * sync_Arb_IDs - synchronize APIC bus arbitration IDs
 */
void __init sync_Arb_IDs(void)
{
	/*
	 * Unsupported on P4 - see Intel Dev. Manual Vol. 3, Ch. 8.6.1 And not
	 * needed on AMD.
	 */
	if (modern_apic())
		return;
	/*
	 * Wait for idle.
	 */
	apic_wait_icr_idle();

	apic_printk(APIC_DEBUG, "Synchronizing Arb IDs.\n");
	apic_write_around(APIC_ICR, APIC_DEST_ALLINC | APIC_INT_LEVELTRIG
				| APIC_DM_INIT);
}

/*
 * An initial setup of the virtual wire mode.
 */
void __init init_bsp_APIC(void)
{
	unsigned long value;

	/*
	 * Don't do the setup now if we have a SMP BIOS as the
	 * through-I/O-APIC virtual wire mode might be active.
	 */
	if (smp_found_config || !cpu_has_apic)
		return;

	/*
	 * Do not trust the local APIC being empty at bootup.
	 */
	clear_local_APIC();

	/*
	 * Enable APIC.
	 */
	value = apic_read(APIC_SPIV);
	value &= ~APIC_VECTOR_MASK;
	value |= APIC_SPIV_APIC_ENABLED;

	/* This bit is reserved on P4/Xeon and should be cleared */
	if ((boot_cpu_data.x86_vendor == X86_VENDOR_INTEL) &&
	    (boot_cpu_data.x86 == 15))
		value &= ~APIC_SPIV_FOCUS_DISABLED;
	else
		value |= APIC_SPIV_FOCUS_DISABLED;
	value |= SPURIOUS_APIC_VECTOR;
	apic_write_around(APIC_SPIV, value);

	/*
	 * Set up the virtual wire mode.
	 */
	apic_write_around(APIC_LVT0, APIC_DM_EXTINT);
	value = APIC_DM_NMI;
	if (!lapic_is_integrated())		/* 82489DX */
		value |= APIC_LVT_LEVEL_TRIGGER;
	apic_write_around(APIC_LVT1, value);
}

/**
 * setup_local_APIC - setup the local APIC
 */
void __devinit setup_local_APIC(void)
{
	unsigned long oldvalue, value, maxlvt, integrated;
	int i, j;

	/* Pound the ESR really hard over the head with a big hammer - mbligh */
	if (esr_disable) {
		apic_write(APIC_ESR, 0);
		apic_write(APIC_ESR, 0);
		apic_write(APIC_ESR, 0);
		apic_write(APIC_ESR, 0);
	}

	integrated = lapic_is_integrated();

	/*
	 * Double-check whether this APIC is really registered.
	 */
	if (!apic_id_registered())
		BUG();

	/*
	 * Intel recommends to set DFR, LDR and TPR before enabling
	 * an APIC.  See e.g. "AP-388 82489DX User's Manual" (Intel
	 * document number 292116).  So here it goes...
	 */
	init_apic_ldr();

	/*
	 * Set Task Priority to 'accept all'. We never change this
	 * later on.
	 */
	value = apic_read(APIC_TASKPRI);
	value &= ~APIC_TPRI_MASK;
	apic_write_around(APIC_TASKPRI, value);

	/*
	 * After a crash, we no longer service the interrupts and a pending
	 * interrupt from previous kernel might still have ISR bit set.
	 *
	 * Most probably by now CPU has serviced that pending interrupt and
	 * it might not have done the ack_APIC_irq() because it thought,
	 * interrupt came from i8259 as ExtInt. LAPIC did not get EOI so it
	 * does not clear the ISR bit and cpu thinks it has already serivced
	 * the interrupt. Hence a vector might get locked. It was noticed
	 * for timer irq (vector 0x31). Issue an extra EOI to clear ISR.
	 */
	for (i = APIC_ISR_NR - 1; i >= 0; i--) {
		value = apic_read(APIC_ISR + i*0x10);
		for (j = 31; j >= 0; j--) {
			if (value & (1<<j))
				ack_APIC_irq();
		}
	}

	/*
	 * Now that we are all set up, enable the APIC
	 */
	value = apic_read(APIC_SPIV);
	value &= ~APIC_VECTOR_MASK;
	/*
	 * Enable APIC
	 */
	value |= APIC_SPIV_APIC_ENABLED;

	/*
	 * Some unknown Intel IO/APIC (or APIC) errata is biting us with
	 * certain networking cards. If high frequency interrupts are
	 * happening on a particular IOAPIC pin, plus the IOAPIC routing
	 * entry is masked/unmasked at a high rate as well then sooner or
	 * later IOAPIC line gets 'stuck', no more interrupts are received
	 * from the device. If focus CPU is disabled then the hang goes
	 * away, oh well :-(
	 *
	 * [ This bug can be reproduced easily with a level-triggered
	 *   PCI Ne2000 networking cards and PII/PIII processors, dual
	 *   BX chipset. ]
	 */
	/*
	 * Actually disabling the focus CPU check just makes the hang less
	 * frequent as it makes the interrupt distributon model be more
	 * like LRU than MRU (the short-term load is more even across CPUs).
	 * See also the comment in end_level_ioapic_irq().  --macro
	 */

	/* Enable focus processor (bit==0) */
	value &= ~APIC_SPIV_FOCUS_DISABLED;

	/*
	 * Set spurious IRQ vector
	 */
	value |= SPURIOUS_APIC_VECTOR;
	apic_write_around(APIC_SPIV, value);

	/*
	 * Set up LVT0, LVT1:
	 *
	 * set up through-local-APIC on the BP's LINT0. This is not
	 * strictly necessery in pure symmetric-IO mode, but sometimes
	 * we delegate interrupts to the 8259A.
	 */
	/*
	 * TODO: set up through-local-APIC from through-I/O-APIC? --macro
	 */
	value = apic_read(APIC_LVT0) & APIC_LVT_MASKED;
	if (!smp_processor_id() && (pic_mode || !value)) {
		value = APIC_DM_EXTINT;
		apic_printk(APIC_VERBOSE, "enabled ExtINT on CPU#%d\n",
				smp_processor_id());
	} else {
		value = APIC_DM_EXTINT | APIC_LVT_MASKED;
		apic_printk(APIC_VERBOSE, "masked ExtINT on CPU#%d\n",
				smp_processor_id());
	}
	apic_write_around(APIC_LVT0, value);

	/*
	 * only the BP should see the LINT1 NMI signal, obviously.
	 */
	if (!smp_processor_id())
		value = APIC_DM_NMI;
	else
		value = APIC_DM_NMI | APIC_LVT_MASKED;
	if (!integrated)		/* 82489DX */
		value |= APIC_LVT_LEVEL_TRIGGER;
	apic_write_around(APIC_LVT1, value);

	if (integrated && !esr_disable) {		/* !82489DX */
		maxlvt = lapic_get_maxlvt();
		if (maxlvt > 3)		/* Due to the Pentium erratum 3AP. */
			apic_write(APIC_ESR, 0);
		oldvalue = apic_read(APIC_ESR);

		/* enables sending errors */
		value = ERROR_APIC_VECTOR;
		apic_write_around(APIC_LVTERR, value);
		/*
		 * spec says clear errors after enabling vector.
		 */
		if (maxlvt > 3)
			apic_write(APIC_ESR, 0);
		value = apic_read(APIC_ESR);
		if (value != oldvalue)
			apic_printk(APIC_VERBOSE, "ESR value before enabling "
				"vector: 0x%08lx  after: 0x%08lx\n",
				oldvalue, value);
	} else {
		if (esr_disable)
			/*
			 * Something untraceble is creating bad interrupts on
			 * secondary quads ... for the moment, just leave the
			 * ESR disabled - we can't do anything useful with the
			 * errors anyway - mbligh
			 */
			printk(KERN_INFO "Leaving ESR disabled.\n");
		else
			printk(KERN_INFO "No ESR for 82489DX.\n");
	}

	/* Disable the local apic timer */
	value = apic_read(APIC_LVTT);
	value |= (APIC_LVT_MASKED | LOCAL_TIMER_VECTOR);
	apic_write_around(APIC_LVTT, value);

	setup_apic_nmi_watchdog(NULL);
	apic_pm_activate();
}

/*
 * Detect and initialize APIC
 */
static int __init detect_init_APIC (void)
{
	u32 h, l, features;

	/* Disabled by kernel option? */
	if (enable_local_apic < 0)
		return -1;

	switch (boot_cpu_data.x86_vendor) {
	case X86_VENDOR_AMD:
		if ((boot_cpu_data.x86 == 6 && boot_cpu_data.x86_model > 1) ||
		    (boot_cpu_data.x86 == 15))
			break;
		goto no_apic;
	case X86_VENDOR_INTEL:
		if (boot_cpu_data.x86 == 6 || boot_cpu_data.x86 == 15 ||
		    (boot_cpu_data.x86 == 5 && cpu_has_apic))
			break;
		goto no_apic;
	default:
		goto no_apic;
	}

	if (!cpu_has_apic) {
		/*
		 * Over-ride BIOS and try to enable the local APIC only if
		 * "lapic" specified.
		 */
		if (enable_local_apic <= 0) {
			printk(KERN_INFO "Local APIC disabled by BIOS -- "
			       "you can enable it with \"lapic\"\n");
			return -1;
		}
		/*
		 * Some BIOSes disable the local APIC in the APIC_BASE
		 * MSR. This can only be done in software for Intel P6 or later
		 * and AMD K7 (Model > 1) or later.
		 */
		rdmsr(MSR_IA32_APICBASE, l, h);
		if (!(l & MSR_IA32_APICBASE_ENABLE)) {
			printk(KERN_INFO
			       "Local APIC disabled by BIOS -- reenabling.\n");
			l &= ~MSR_IA32_APICBASE_BASE;
			l |= MSR_IA32_APICBASE_ENABLE | APIC_DEFAULT_PHYS_BASE;
			wrmsr(MSR_IA32_APICBASE, l, h);
			enabled_via_apicbase = 1;
		}
	}
	/*
	 * The APIC feature bit should now be enabled
	 * in `cpuid'
	 */
	features = cpuid_edx(1);
	if (!(features & (1 << X86_FEATURE_APIC))) {
		printk(KERN_WARNING "Could not enable APIC!\n");
		return -1;
	}
	set_bit(X86_FEATURE_APIC, boot_cpu_data.x86_capability);
	mp_lapic_addr = APIC_DEFAULT_PHYS_BASE;

	/* The BIOS may have set up the APIC at some other address */
	rdmsr(MSR_IA32_APICBASE, l, h);
	if (l & MSR_IA32_APICBASE_ENABLE)
		mp_lapic_addr = l & MSR_IA32_APICBASE_BASE;

	if (nmi_watchdog != NMI_NONE)
		nmi_watchdog = NMI_LOCAL_APIC;

	printk(KERN_INFO "Found and enabled local APIC!\n");

	apic_pm_activate();

	return 0;

no_apic:
	printk(KERN_INFO "No local APIC present or hardware disabled\n");
	return -1;
}

/**
 * init_apic_mappings - initialize APIC mappings
 */
void __init init_apic_mappings(void)
{
	unsigned long apic_phys;

	/*
	 * If no local APIC can be found then set up a fake all
	 * zeroes page to simulate the local APIC and another
	 * one for the IO-APIC.
	 */
	if (!smp_found_config && detect_init_APIC()) {
		apic_phys = (unsigned long) alloc_bootmem_pages(PAGE_SIZE);
		apic_phys = __pa(apic_phys);
	} else
		apic_phys = mp_lapic_addr;

	set_fixmap_nocache(FIX_APIC_BASE, apic_phys);
	printk(KERN_DEBUG "mapped APIC to %08lx (%08lx)\n", APIC_BASE,
	       apic_phys);

	/*
	 * Fetch the APIC ID of the BSP in case we have a
	 * default configuration (or the MP table is broken).
	 */
	if (boot_cpu_physical_apicid == -1U)
		boot_cpu_physical_apicid = GET_APIC_ID(apic_read(APIC_ID));

#ifdef CONFIG_X86_IO_APIC
	{
		unsigned long ioapic_phys, idx = FIX_IO_APIC_BASE_0;
		int i;

		for (i = 0; i < nr_ioapics; i++) {
			if (smp_found_config) {
				ioapic_phys = mp_ioapics[i].mpc_apicaddr;
				if (!ioapic_phys) {
					printk(KERN_ERR
					       "WARNING: bogus zero IO-APIC "
					       "address found in MPTABLE, "
					       "disabling IO/APIC support!\n");
					smp_found_config = 0;
					skip_ioapic_setup = 1;
					goto fake_ioapic_page;
				}
			} else {
fake_ioapic_page:
				ioapic_phys = (unsigned long)
					      alloc_bootmem_pages(PAGE_SIZE);
				ioapic_phys = __pa(ioapic_phys);
			}
			set_fixmap_nocache(idx, ioapic_phys);
			printk(KERN_DEBUG "mapped IOAPIC to %08lx (%08lx)\n",
			       __fix_to_virt(idx), ioapic_phys);
			idx++;
		}
	}
#endif
}

/*
 * This initializes the IO-APIC and APIC hardware if this is
 * a UP kernel.
 */
int __init APIC_init_uniprocessor (void)
{
	if (enable_local_apic < 0)
		clear_bit(X86_FEATURE_APIC, boot_cpu_data.x86_capability);

	if (!smp_found_config && !cpu_has_apic)
		return -1;

	/*
	 * Complain if the BIOS pretends there is one.
	 */
	if (!cpu_has_apic &&
	    APIC_INTEGRATED(apic_version[boot_cpu_physical_apicid])) {
		printk(KERN_ERR "BIOS bug, local APIC #%d not detected!...\n",
		       boot_cpu_physical_apicid);
		clear_bit(X86_FEATURE_APIC, boot_cpu_data.x86_capability);
		return -1;
	}

	verify_local_APIC();

	connect_bsp_APIC();

	/*
	 * Hack: In case of kdump, after a crash, kernel might be booting
	 * on a cpu with non-zero lapic id. But boot_cpu_physical_apicid
	 * might be zero if read from MP tables. Get it from LAPIC.
	 */
#ifdef CONFIG_CRASH_DUMP
	boot_cpu_physical_apicid = GET_APIC_ID(apic_read(APIC_ID));
#endif
	phys_cpu_present_map = physid_mask_of_physid(boot_cpu_physical_apicid);

	setup_local_APIC();

#ifdef CONFIG_X86_IO_APIC
	if (smp_found_config)
		if (!skip_ioapic_setup && nr_ioapics)
			setup_IO_APIC();
#endif
	setup_boot_clock();

	return 0;
}

/*
 * APIC command line parameters
 */
static int __init parse_lapic(char *arg)
{
	enable_local_apic = 1;
	return 0;
}
early_param("lapic", parse_lapic);

static int __init parse_nolapic(char *arg)
{
	enable_local_apic = -1;
	clear_bit(X86_FEATURE_APIC, boot_cpu_data.x86_capability);
	return 0;
}
early_param("nolapic", parse_nolapic);

static int __init apic_set_verbosity(char *str)
{
	if (strcmp("debug", str) == 0)
		apic_verbosity = APIC_DEBUG;
	else if (strcmp("verbose", str) == 0)
		apic_verbosity = APIC_VERBOSE;
	return 1;
}

__setup("apic=", apic_set_verbosity);


/*
 * Local APIC interrupts
 */

/*
 * This interrupt should _never_ happen with our APIC/SMP architecture
 */
void smp_spurious_interrupt(struct pt_regs *regs)
{
	unsigned long v;

	exit_idle();
	irq_enter();
	/*
	 * Check if this really is a spurious interrupt and ACK it
	 * if it is a vectored one.  Just in case...
	 * Spurious interrupts should not be ACKed.
	 */
	v = apic_read(APIC_ISR + ((SPURIOUS_APIC_VECTOR & ~0x1f) >> 1));
	if (v & (1 << (SPURIOUS_APIC_VECTOR & 0x1f)))
		ack_APIC_irq();

	/* see sw-dev-man vol 3, chapter 7.4.13.5 */
	printk(KERN_INFO "spurious APIC interrupt on CPU#%d, "
	       "should never happen.\n", smp_processor_id());
	irq_exit();
}

/*
 * This interrupt should never happen with our APIC/SMP architecture
 */
void smp_error_interrupt(struct pt_regs *regs)
{
	unsigned long v, v1;

	exit_idle();
	irq_enter();
	/* First tickle the hardware, only then report what went on. -- REW */
	v = apic_read(APIC_ESR);
	apic_write(APIC_ESR, 0);
	v1 = apic_read(APIC_ESR);
	ack_APIC_irq();
	atomic_inc(&irq_err_count);

	/* Here is what the APIC error bits mean:
	   0: Send CS error
	   1: Receive CS error
	   2: Send accept error
	   3: Receive accept error
	   4: Reserved
	   5: Send illegal vector
	   6: Received illegal vector
	   7: Illegal register address
	*/
	printk (KERN_DEBUG "APIC error on CPU%d: %02lx(%02lx)\n",
		smp_processor_id(), v , v1);
	irq_exit();
}

/*
 * Initialize APIC interrupts
 */
void __init apic_intr_init(void)
{
#ifdef CONFIG_SMP
	smp_intr_init();
#endif
	/* self generated IPI for local APIC timer */
	set_intr_gate(LOCAL_TIMER_VECTOR, apic_timer_interrupt);

	/* IPI vectors for APIC spurious and error interrupts */
	set_intr_gate(SPURIOUS_APIC_VECTOR, spurious_interrupt);
	set_intr_gate(ERROR_APIC_VECTOR, error_interrupt);

	/* thermal monitor LVT interrupt */
#ifdef CONFIG_X86_MCE_P4THERMAL
	set_intr_gate(THERMAL_APIC_VECTOR, thermal_interrupt);
#endif
}

/**
 * connect_bsp_APIC - attach the APIC to the interrupt system
 */
void __init connect_bsp_APIC(void)
{
	if (pic_mode) {
		/*
		 * Do not trust the local APIC being empty at bootup.
		 */
		clear_local_APIC();
		/*
		 * PIC mode, enable APIC mode in the IMCR, i.e.  connect BSP's
		 * local APIC to INT and NMI lines.
		 */
		apic_printk(APIC_VERBOSE, "leaving PIC mode, "
				"enabling APIC mode.\n");
		outb(0x70, 0x22);
		outb(0x01, 0x23);
	}
	enable_apic_mode();
}

/**
 * disconnect_bsp_APIC - detach the APIC from the interrupt system
 * @virt_wire_setup:	indicates, whether virtual wire mode is selected
 *
 * Virtual wire mode is necessary to deliver legacy interrupts even when the
 * APIC is disabled.
 */
void disconnect_bsp_APIC(int virt_wire_setup)
{
	if (pic_mode) {
		/*
		 * Put the board back into PIC mode (has an effect only on
		 * certain older boards).  Note that APIC interrupts, including
		 * IPIs, won't work beyond this point!  The only exception are
		 * INIT IPIs.
		 */
		apic_printk(APIC_VERBOSE, "disabling APIC mode, "
				"entering PIC mode.\n");
		outb(0x70, 0x22);
		outb(0x00, 0x23);
	} else {
		/* Go back to Virtual Wire compatibility mode */
		unsigned long value;

		/* For the spurious interrupt use vector F, and enable it */
		value = apic_read(APIC_SPIV);
		value &= ~APIC_VECTOR_MASK;
		value |= APIC_SPIV_APIC_ENABLED;
		value |= 0xf;
		apic_write_around(APIC_SPIV, value);

		if (!virt_wire_setup) {
			/*
			 * For LVT0 make it edge triggered, active high,
			 * external and enabled
			 */
			value = apic_read(APIC_LVT0);
			value &= ~(APIC_MODE_MASK | APIC_SEND_PENDING |
				APIC_INPUT_POLARITY | APIC_LVT_REMOTE_IRR |
				APIC_LVT_LEVEL_TRIGGER | APIC_LVT_MASKED );
			value |= APIC_LVT_REMOTE_IRR | APIC_SEND_PENDING;
			value = SET_APIC_DELIVERY_MODE(value, APIC_MODE_EXTINT);
			apic_write_around(APIC_LVT0, value);
		} else {
			/* Disable LVT0 */
			apic_write_around(APIC_LVT0, APIC_LVT_MASKED);
		}

		/*
		 * For LVT1 make it edge triggered, active high, nmi and
		 * enabled
		 */
		value = apic_read(APIC_LVT1);
		value &= ~(
			APIC_MODE_MASK | APIC_SEND_PENDING |
			APIC_INPUT_POLARITY | APIC_LVT_REMOTE_IRR |
			APIC_LVT_LEVEL_TRIGGER | APIC_LVT_MASKED);
		value |= APIC_LVT_REMOTE_IRR | APIC_SEND_PENDING;
		value = SET_APIC_DELIVERY_MODE(value, APIC_MODE_NMI);
		apic_write_around(APIC_LVT1, value);
	}
}

/*
 * Power management
 */
#ifdef CONFIG_PM

static struct {
	int active;
	/* r/w apic fields */
	unsigned int apic_id;
	unsigned int apic_taskpri;
	unsigned int apic_ldr;
	unsigned int apic_dfr;
	unsigned int apic_spiv;
	unsigned int apic_lvtt;
	unsigned int apic_lvtpc;
	unsigned int apic_lvt0;
	unsigned int apic_lvt1;
	unsigned int apic_lvterr;
	unsigned int apic_tmict;
	unsigned int apic_tdcr;
	unsigned int apic_thmr;
} apic_pm_state;

static int lapic_suspend(struct sys_device *dev, pm_message_t state)
{
	unsigned long flags;
	int maxlvt;

	if (!apic_pm_state.active)
		return 0;

	maxlvt = lapic_get_maxlvt();

	apic_pm_state.apic_id = apic_read(APIC_ID);
	apic_pm_state.apic_taskpri = apic_read(APIC_TASKPRI);
	apic_pm_state.apic_ldr = apic_read(APIC_LDR);
	apic_pm_state.apic_dfr = apic_read(APIC_DFR);
	apic_pm_state.apic_spiv = apic_read(APIC_SPIV);
	apic_pm_state.apic_lvtt = apic_read(APIC_LVTT);
	if (maxlvt >= 4)
		apic_pm_state.apic_lvtpc = apic_read(APIC_LVTPC);
	apic_pm_state.apic_lvt0 = apic_read(APIC_LVT0);
	apic_pm_state.apic_lvt1 = apic_read(APIC_LVT1);
	apic_pm_state.apic_lvterr = apic_read(APIC_LVTERR);
	apic_pm_state.apic_tmict = apic_read(APIC_TMICT);
	apic_pm_state.apic_tdcr = apic_read(APIC_TDCR);
#ifdef CONFIG_X86_MCE_P4THERMAL
	if (maxlvt >= 5)
		apic_pm_state.apic_thmr = apic_read(APIC_LVTTHMR);
#endif

	local_irq_save(flags);
	disable_local_APIC();
	local_irq_restore(flags);
	return 0;
}

static int lapic_resume(struct sys_device *dev)
{
	unsigned int l, h;
	unsigned long flags;
	int maxlvt;

	if (!apic_pm_state.active)
		return 0;

	maxlvt = lapic_get_maxlvt();

	local_irq_save(flags);

	/*
	 * Make sure the APICBASE points to the right address
	 *
	 * FIXME! This will be wrong if we ever support suspend on
	 * SMP! We'll need to do this as part of the CPU restore!
	 */
	rdmsr(MSR_IA32_APICBASE, l, h);
	l &= ~MSR_IA32_APICBASE_BASE;
	l |= MSR_IA32_APICBASE_ENABLE | mp_lapic_addr;
	wrmsr(MSR_IA32_APICBASE, l, h);

	apic_write(APIC_LVTERR, ERROR_APIC_VECTOR | APIC_LVT_MASKED);
	apic_write(APIC_ID, apic_pm_state.apic_id);
	apic_write(APIC_DFR, apic_pm_state.apic_dfr);
	apic_write(APIC_LDR, apic_pm_state.apic_ldr);
	apic_write(APIC_TASKPRI, apic_pm_state.apic_taskpri);
	apic_write(APIC_SPIV, apic_pm_state.apic_spiv);
	apic_write(APIC_LVT0, apic_pm_state.apic_lvt0);
	apic_write(APIC_LVT1, apic_pm_state.apic_lvt1);
#ifdef CONFIG_X86_MCE_P4THERMAL
	if (maxlvt >= 5)
		apic_write(APIC_LVTTHMR, apic_pm_state.apic_thmr);
#endif
	if (maxlvt >= 4)
		apic_write(APIC_LVTPC, apic_pm_state.apic_lvtpc);
	apic_write(APIC_LVTT, apic_pm_state.apic_lvtt);
	apic_write(APIC_TDCR, apic_pm_state.apic_tdcr);
	apic_write(APIC_TMICT, apic_pm_state.apic_tmict);
	apic_write(APIC_ESR, 0);
	apic_read(APIC_ESR);
	apic_write(APIC_LVTERR, apic_pm_state.apic_lvterr);
	apic_write(APIC_ESR, 0);
	apic_read(APIC_ESR);
	local_irq_restore(flags);
	return 0;
}

/*
 * This device has no shutdown method - fully functioning local APICs
 * are needed on every CPU up until machine_halt/restart/poweroff.
 */

static struct sysdev_class lapic_sysclass = {
	set_kset_name("lapic"),
	.resume		= lapic_resume,
	.suspend	= lapic_suspend,
};

static struct sys_device device_lapic = {
	.id	= 0,
	.cls	= &lapic_sysclass,
};

static void __devinit apic_pm_activate(void)
{
	apic_pm_state.active = 1;
}

static int __init init_lapic_sysfs(void)
{
	int error;

	if (!cpu_has_apic)
		return 0;
	/* XXX: remove suspend/resume procs if !apic_pm_state.active? */

	error = sysdev_class_register(&lapic_sysclass);
	if (!error)
		error = sysdev_register(&device_lapic);
	return error;
}
device_initcall(init_lapic_sysfs);

#else	/* CONFIG_PM */

static void apic_pm_activate(void) { }

#endif	/* CONFIG_PM */