linux/arch/x86_64/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/config.h>
#include <linux/init.h>

#include <linux/mm.h>
#include <linux/irq.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 <asm/atomic.h>
#include <asm/smp.h>
#include <asm/mtrr.h>
#include <asm/mpspec.h>
#include <asm/pgalloc.h>
#include <asm/mach_apic.h>
#include <asm/nmi.h>

int apic_verbosity;

int disable_apic_timer __initdata;

/* Using APIC to generate smp_local_timer_interrupt? */
int using_apic_timer = 0;

static DEFINE_PER_CPU(int, prof_multiplier) = 1;
static DEFINE_PER_CPU(int, prof_old_multiplier) = 1;
static DEFINE_PER_CPU(int, prof_counter) = 1;

static void apic_pm_activate(void);

void enable_NMI_through_LVT0 (void * dummy)
{
	unsigned int v, ver;
	
	ver = apic_read(APIC_LVR);
	ver = GET_APIC_VERSION(ver);
	v = APIC_DM_NMI;                        /* unmask and set to NMI */
	apic_write_around(APIC_LVT0, v);
}

int get_maxlvt(void)
{
	unsigned int v, ver, maxlvt;

	v = apic_read(APIC_LVR);
	ver = GET_APIC_VERSION(v);
	maxlvt = GET_APIC_MAXLVT(v);
	return maxlvt;
}

void clear_local_APIC(void)
{
	int maxlvt;
	unsigned int v;

	maxlvt = get_maxlvt();

	/*
	 * Masking an LVT entry on a P6 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);
	}

	/*
	 * 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);
	v = GET_APIC_VERSION(apic_read(APIC_LVR));
	if (APIC_INTEGRATED(v)) {	/* !82489DX */
		if (maxlvt > 3)		/* Due to Pentium errata 3AP and 11AP. */
			apic_write(APIC_ESR, 0);
		apic_read(APIC_ESR);
	}
}

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);
	}
}

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_QUIET, "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);
	}
}

void disable_local_APIC(void)
{
	unsigned int 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);
}

/*
 * 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 = 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);
	apic_write(APIC_ID, reg0 ^ APIC_ID_MASK);
	reg1 = apic_read(APIC_ID);
	apic_printk(APIC_DEBUG, "Getting ID: %x\n", reg1);
	apic_write(APIC_ID, reg0);
	if (reg1 != (reg0 ^ APIC_ID_MASK))
		return 0;

	/*
	 * 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;
}

void __init sync_Arb_IDs(void)
{
	/* Unsupported on P4 - see Intel Dev. Manual Vol. 3, Ch. 8.6.1 */
	unsigned int ver = GET_APIC_VERSION(apic_read(APIC_LVR));
	if (ver >= 0x14)	/* P4 or higher */
		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);
}

extern void __error_in_apic_c (void);

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

	/*
	 * 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;

	value = apic_read(APIC_LVR);
	ver = GET_APIC_VERSION(value);

	/*
	 * 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;
	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 (!APIC_INTEGRATED(ver))		/* 82489DX */
		value |= APIC_LVT_LEVEL_TRIGGER;
	apic_write_around(APIC_LVT1, value);
}

void __cpuinit setup_local_APIC (void)
{
	unsigned int value, ver, maxlvt;

	/* 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);
	}

	value = apic_read(APIC_LVR);
	ver = GET_APIC_VERSION(value);

	if ((SPURIOUS_APIC_VECTOR & 0x0f) != 0x0f)
		__error_in_apic_c();

	/*
	 * Double-check whether this APIC is really registered.
	 * This is meaningless in clustered apic mode, so we skip it.
	 */
	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);

	/*
	 * 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
	 */
#if 1
	/* Enable focus processor (bit==0) */
	value &= ~APIC_SPIV_FOCUS_DISABLED;
#else
	/* Disable focus processor (bit==1) */
	value |= APIC_SPIV_FOCUS_DISABLED;
#endif
	/*
	 * 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 necessary 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 (!APIC_INTEGRATED(ver))		/* 82489DX */
		value |= APIC_LVT_LEVEL_TRIGGER;
	apic_write_around(APIC_LVT1, value);

	if (APIC_INTEGRATED(ver) && !esr_disable) {		/* !82489DX */
		unsigned oldvalue;
		maxlvt = get_maxlvt();
		if (maxlvt > 3)		/* Due to the Pentium erratum 3AP. */
			apic_write(APIC_ESR, 0);
		oldvalue = apic_read(APIC_ESR);
		value = ERROR_APIC_VECTOR;      // enables sending errors
		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 after enabling vector: %08x, after %08x\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
			 */
			apic_printk(APIC_DEBUG, "Leaving ESR disabled.\n");
		else 
			apic_printk(APIC_DEBUG, "No ESR for 82489DX.\n");
	}

	nmi_watchdog_default();
	if (nmi_watchdog == NMI_LOCAL_APIC)
		setup_apic_nmi_watchdog();
	apic_pm_activate();
}

#ifdef CONFIG_PM

static struct {
	/* 'active' is true if the local APIC was enabled by us and
	   not the BIOS; this signifies that we are also responsible
	   for disabling it before entering apm/acpi suspend */
	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;

	if (!apic_pm_state.active)
		return 0;

	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);
	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);
	apic_pm_state.apic_thmr = apic_read(APIC_LVTTHMR);
	local_save_flags(flags);
	local_irq_disable();
	disable_local_APIC();
	local_irq_restore(flags);
	return 0;
}

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

	if (!apic_pm_state.active)
		return 0;

	/* XXX: Pavel needs this for S3 resume, but can't explain why */
	set_fixmap_nocache(FIX_APIC_BASE, APIC_DEFAULT_PHYS_BASE);

	local_irq_save(flags);
	rdmsr(MSR_IA32_APICBASE, l, h);
	l &= ~MSR_IA32_APICBASE_BASE;
	l |= MSR_IA32_APICBASE_ENABLE | APIC_DEFAULT_PHYS_BASE;
	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);
	apic_write(APIC_LVTTHMR, apic_pm_state.apic_thmr);
	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;
}

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 __cpuinit 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 */

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;
	else
		printk(KERN_WARNING "APIC Verbosity level %s not recognised"
				" use apic=verbose or apic=debug", str);

	return 0;
}

__setup("apic=", apic_set_verbosity);

/*
 * Detect and enable local APICs on non-SMP boards.
 * Original code written by Keir Fraser.
 * On AMD64 we trust the BIOS - if it says no APIC it is likely
 * not correctly set up (usually the APIC timer won't work etc.) 
 */

static int __init detect_init_APIC (void)
{
	if (!cpu_has_apic) {
		printk(KERN_INFO "No local APIC present\n");
		return -1;
	}

	mp_lapic_addr = APIC_DEFAULT_PHYS_BASE;
	boot_cpu_id = 0;
	return 0;
}

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);
	apic_printk(APIC_VERBOSE,"mapped APIC to %16lx (%16lx)\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_id == -1U)
		boot_cpu_id = 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;
			} else {
				ioapic_phys = (unsigned long) alloc_bootmem_pages(PAGE_SIZE);
				ioapic_phys = __pa(ioapic_phys);
			}
			set_fixmap_nocache(idx, ioapic_phys);
			apic_printk(APIC_VERBOSE,"mapped IOAPIC to %016lx (%016lx)\n",
					__fix_to_virt(idx), ioapic_phys);
			idx++;
		}
	}
#endif
}

/*
 * 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.
 */

#define APIC_DIVISOR 16

static void __setup_APIC_LVTT(unsigned int clocks)
{
	unsigned int lvtt_value, tmp_value, ver;

	ver = GET_APIC_VERSION(apic_read(APIC_LVR));
	lvtt_value = APIC_LVT_TIMER_PERIODIC | LOCAL_TIMER_VECTOR;
	if (!APIC_INTEGRATED(ver))
		lvtt_value |= SET_APIC_TIMER_BASE(APIC_TIMER_BASE_DIV);
	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);

	apic_write_around(APIC_TMICT, clocks/APIC_DIVISOR);
}

static void setup_APIC_timer(unsigned int clocks)
{
	unsigned long flags;

	local_irq_save(flags);

	/* For some reasons this doesn't work on Simics, so fake it for now */ 
	if (!strstr(boot_cpu_data.x86_model_id, "Screwdriver")) { 
	__setup_APIC_LVTT(clocks);
		return;
	} 

	/* wait for irq slice */
 	if (vxtime.hpet_address) {
 		int trigger = hpet_readl(HPET_T0_CMP);
 		while (hpet_readl(HPET_COUNTER) >= trigger)
 			/* do nothing */ ;
 		while (hpet_readl(HPET_COUNTER) <  trigger)
 			/* do nothing */ ;
 	} else {
		int c1, c2;
		outb_p(0x00, 0x43);
		c2 = inb_p(0x40);
		c2 |= inb_p(0x40) << 8;
	do {
			c1 = c2;
			outb_p(0x00, 0x43);
			c2 = inb_p(0x40);
			c2 |= inb_p(0x40) << 8;
		} while (c2 - c1 < 300);
	}

	__setup_APIC_LVTT(clocks);

	local_irq_restore(flags);
}

/*
 * 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)
{
	int apic, apic_start, tsc, tsc_start;
	int result;
	/*
	 * Put whatever arbitrary (but long enough) timeout
	 * value into the APIC clock, we just want to get the
	 * counter running for calibration.
	 */
	__setup_APIC_LVTT(1000000000);

	apic_start = apic_read(APIC_TMCCT);
	rdtscl(tsc_start);

	do {
		apic = apic_read(APIC_TMCCT);
		rdtscl(tsc);
	} while ((tsc - tsc_start) < TICK_COUNT && (apic - apic_start) < TICK_COUNT);

	result = (apic_start - apic) * 1000L * cpu_khz / (tsc - tsc_start);

	printk(KERN_INFO "Detected %d.%03d MHz APIC timer.\n",
		result / 1000 / 1000, result / 1000 % 1000);

	return result * APIC_DIVISOR / HZ;
}

static unsigned int calibration_result;

void __init setup_boot_APIC_clock (void)
{
	if (disable_apic_timer) { 
		printk(KERN_INFO "Disabling APIC timer\n"); 
		return; 
	} 

	printk(KERN_INFO "Using local APIC timer interrupts.\n");
	using_apic_timer = 1;

	local_irq_disable();

	calibration_result = calibrate_APIC_clock();
	/*
	 * Now set up the timer for real.
	 */
	setup_APIC_timer(calibration_result);

	local_irq_enable();
}

void __cpuinit setup_secondary_APIC_clock(void)
{
	local_irq_disable(); /* FIXME: Do we need this? --RR */
	setup_APIC_timer(calibration_result);
	local_irq_enable();
}

void __cpuinit disable_APIC_timer(void)
{
	if (using_apic_timer) {
		unsigned long v;

		v = apic_read(APIC_LVTT);
		apic_write_around(APIC_LVTT, v | APIC_LVT_MASKED);
	}
}

void enable_APIC_timer(void)
{
	if (using_apic_timer) {
		unsigned long v;

		v = apic_read(APIC_LVTT);
		apic_write_around(APIC_LVTT, v & ~APIC_LVT_MASKED);
	}
}

/*
 * the frequency of the profiling timer can be changed
 * by writing a multiplier value into /proc/profile.
 */
int setup_profiling_timer(unsigned int multiplier)
{
	int i;

	/*
	 * Sanity check. [at least 500 APIC cycles should be
	 * between APIC interrupts as a rule of thumb, to avoid
	 * irqs flooding us]
	 */
	if ( (!multiplier) || (calibration_result/multiplier < 500))
		return -EINVAL;

	/* 
	 * Set the new multiplier for each CPU. CPUs don't start using the
	 * new values until the next timer interrupt in which they do process
	 * accounting. At that time they also adjust their APIC timers
	 * accordingly.
	 */
	for (i = 0; i < NR_CPUS; ++i)
		per_cpu(prof_multiplier, i) = multiplier;

	return 0;
}

#undef APIC_DIVISOR

/*
 * Local timer interrupt handler. It does both profiling and
 * process statistics/rescheduling.
 *
 * We do profiling in every local tick, statistics/rescheduling
 * happen only every 'profiling multiplier' ticks. The default
 * multiplier is 1 and it can be changed by writing the new multiplier
 * value into /proc/profile.
 */

void smp_local_timer_interrupt(struct pt_regs *regs)
{
	int cpu = smp_processor_id();

	profile_tick(CPU_PROFILING, regs);
	if (--per_cpu(prof_counter, cpu) <= 0) {
		/*
		 * The multiplier may have changed since the last time we got
		 * to this point as a result of the user writing to
		 * /proc/profile. In this case we need to adjust the APIC
		 * timer accordingly.
		 *
		 * Interrupts are already masked off at this point.
		 */
		per_cpu(prof_counter, cpu) = per_cpu(prof_multiplier, cpu);
		if (per_cpu(prof_counter, cpu) != 
		    per_cpu(prof_old_multiplier, cpu)) {
			__setup_APIC_LVTT(calibration_result/
					per_cpu(prof_counter, cpu));
			per_cpu(prof_old_multiplier, cpu) =
				per_cpu(prof_counter, cpu);
		}

#ifdef CONFIG_SMP
		update_process_times(user_mode(regs));
#endif
	}

	/*
	 * We take the 'long' return path, and there every subsystem
	 * grabs the appropriate locks (kernel lock/ irq lock).
	 *
	 * we might want to decouple profiling from the 'long path',
	 * and do the profiling totally in assembly.
	 *
	 * Currently this isn't too much of an issue (performance wise),
	 * we can take more than 100K local irqs per second on a 100 MHz P5.
	 */
}

/*
 * 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 smp_apic_timer_interrupt(struct pt_regs *regs)
{
	/*
	 * the NMI deadlock-detector uses this.
	 */
	add_pda(apic_timer_irqs, 1);

	/*
	 * 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.
	 */
	irq_enter();
	smp_local_timer_interrupt(regs);
	irq_exit();
}

/*
 * oem_force_hpet_timer -- force HPET mode for some boxes.
 *
 * Thus far, the major user of this is IBM's Summit2 series:
 *
 * Clustered boxes may have unsynced TSC problems if they are
 * multi-chassis. Use available data to take a good guess.
 * If in doubt, go HPET.
 */
__init int oem_force_hpet_timer(void)
{
	int i, clusters, zeros;
	unsigned id;
	DECLARE_BITMAP(clustermap, NUM_APIC_CLUSTERS);

	bitmap_zero(clustermap, NUM_APIC_CLUSTERS);

	for (i = 0; i < NR_CPUS; i++) {
		id = bios_cpu_apicid[i];
		if (id != BAD_APICID)
			__set_bit(APIC_CLUSTERID(id), clustermap);
	}

	/* Problem:  Partially populated chassis may not have CPUs in some of
	 * the APIC clusters they have been allocated.  Only present CPUs have
	 * bios_cpu_apicid entries, thus causing zeroes in the bitmap.  Since
	 * clusters are allocated sequentially, count zeros only if they are
	 * bounded by ones.
	 */
	clusters = 0;
	zeros = 0;
	for (i = 0; i < NUM_APIC_CLUSTERS; i++) {
		if (test_bit(i, clustermap)) {
			clusters += 1 + zeros;
			zeros = 0;
		} else
			++zeros;
	}

	/*
	 * If clusters > 2, then should be multi-chassis.  Return 1 for HPET.
	 * Else return 0 to use TSC.
	 * May have to revisit this when multi-core + hyperthreaded CPUs come
	 * out, but AFAIK this will work even for them.
	 */
	return (clusters > 2);
}

/*
 * This interrupt should _never_ happen with our APIC/SMP architecture
 */
asmlinkage void smp_spurious_interrupt(void)
{
	unsigned int v;
	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();

#if 0
	static unsigned long last_warning; 
	static unsigned long skipped; 

	/* see sw-dev-man vol 3, chapter 7.4.13.5 */
	if (time_before(last_warning+30*HZ,jiffies)) { 
		printk(KERN_INFO "spurious APIC interrupt on CPU#%d, %ld skipped.\n",
		       smp_processor_id(), skipped);
		last_warning = jiffies; 
		skipped = 0;
	} else { 
		skipped++; 
	} 
#endif 
	irq_exit();
}

/*
 * This interrupt should never happen with our APIC/SMP architecture
 */

asmlinkage void smp_error_interrupt(void)
{
	unsigned int v, v1;

	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: %02x(%02x)\n",
	        smp_processor_id(), v , v1);
	irq_exit();
}

int disable_apic; 

/*
 * This initializes the IO-APIC and APIC hardware if this is
 * a UP kernel.
 */
int __init APIC_init_uniprocessor (void)
{
	if (disable_apic) { 
		printk(KERN_INFO "Apic disabled\n");
		return -1; 
	}
	if (!cpu_has_apic) { 
		disable_apic = 1;
		printk(KERN_INFO "Apic disabled by BIOS\n");
		return -1;
	}

	verify_local_APIC();

	connect_bsp_APIC();

	phys_cpu_present_map = physid_mask_of_physid(0);
	apic_write_around(APIC_ID, boot_cpu_id);

	setup_local_APIC();

#ifdef CONFIG_X86_IO_APIC
	if (smp_found_config && !skip_ioapic_setup && nr_ioapics)
			setup_IO_APIC();
	else
		nr_ioapics = 0;
#endif
	setup_boot_APIC_clock();
	check_nmi_watchdog();
	return 0;
}

static __init int setup_disableapic(char *str) 
{ 
	disable_apic = 1;
	return 0;
} 

static __init int setup_nolapic(char *str) 
{ 
	disable_apic = 1;
	return 0;
} 

static __init int setup_noapictimer(char *str) 
{ 
	disable_apic_timer = 1;
	return 0;
} 

/* dummy parsing: see setup.c */

__setup("disableapic", setup_disableapic); 
__setup("nolapic", setup_nolapic);  /* same as disableapic, for compatibility */

__setup("noapictimer", setup_noapictimer); 

/* no "lapic" flag - we only use the lapic when the BIOS tells us so. */