/*
 *      Intel IO-APIC support for multi-Pentium hosts.
 *
 *      Copyright (C) 1997, 1998, 1999, 2000 Ingo Molnar, Hajnalka Szabo
 *
 *      Many thanks to Stig Venaas for trying out countless experimental
 *      patches and reporting/debugging problems patiently!
 *
 *      (c) 1999, Multiple IO-APIC support, developed by
 *      Ken-ichi Yaku <yaku@css1.kbnes.nec.co.jp> and
 *      Hidemi Kishimoto <kisimoto@css1.kbnes.nec.co.jp>,
 *      further tested and cleaned up by Zach Brown <zab@redhat.com>
 *      and 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
 */

#include <linux/mm.h>
#include <linux/irq.h>
#include <linux/interrupt.h>
#include <linux/init.h>
#include <linux/delay.h>
#include <linux/sched.h>
#include <linux/config.h>
#include <linux/smp_lock.h>
#include <linux/mc146818rtc.h>

#include <asm/io.h>
#include <asm/smp.h>
#include <asm/desc.h>
#include <asm/smpboot.h>

#undef APIC_LOCKUP_DEBUG

#define APIC_LOCKUP_DEBUG

static spinlock_t ioapic_lock = SPIN_LOCK_UNLOCKED;

unsigned int int_dest_addr_mode = APIC_DEST_LOGICAL;
unsigned char int_delivery_mode = dest_LowestPrio;


/*
 * # of IRQ routing registers
 */
int nr_ioapic_registers[MAX_IO_APICS];

/*
 * Rough estimation of how many shared IRQs there are, can
 * be changed anytime.
 */
#define MAX_PLUS_SHARED_IRQS NR_IRQS
#define PIN_MAP_SIZE (MAX_PLUS_SHARED_IRQS + NR_IRQS)

/*
 * This is performance-critical, we want to do it O(1)
 *
 * the indexing order of this array favors 1:1 mappings
 * between pins and IRQs.
 */

static struct irq_pin_list {
        int apic, pin, next;
} irq_2_pin[PIN_MAP_SIZE];

/*
 * The common case is 1:1 IRQ<->pin mappings. Sometimes there are
 * shared ISA-space IRQs, so we have to support them. We are super
 * fast in the common case, and fast for shared ISA-space IRQs.
 */
static void __init add_pin_to_irq(unsigned int irq, int apic, int pin)
{
        static int first_free_entry = NR_IRQS;
        struct irq_pin_list *entry = irq_2_pin + irq;

        while (entry->next)
                entry = irq_2_pin + entry->next;

        if (entry->pin != -1) {
                entry->next = first_free_entry;
                entry = irq_2_pin + entry->next;
                if (++first_free_entry >= PIN_MAP_SIZE)
                        panic("io_apic.c: whoops");
        }
        entry->apic = apic;
        entry->pin = pin;
}

/*
 * Reroute an IRQ to a different pin.
 */
static void __init replace_pin_at_irq(unsigned int irq,
                                      int oldapic, int oldpin,
                                      int newapic, int newpin)
{
        struct irq_pin_list *entry = irq_2_pin + irq;

        while (1) {
                if (entry->apic == oldapic && entry->pin == oldpin) {
                        entry->apic = newapic;
                        entry->pin = newpin;
                }
                if (!entry->next)
                        break;
                entry = irq_2_pin + entry->next;
        }
}

#define __DO_ACTION(R, ACTION, FINAL)                                   \
                                                                        \
{                                                                       \
        int pin;                                                        \
        struct irq_pin_list *entry = irq_2_pin + irq;                   \
                                                                        \
        for (;;) {                                                      \
                unsigned int reg;                                       \
                pin = entry->pin;                                       \
                if (pin == -1)                                          \
                        break;                                          \
                reg = io_apic_read(entry->apic, 0x10 + R + pin*2);      \
                reg ACTION;                                             \
                io_apic_modify(entry->apic, reg);                       \
                if (!entry->next)                                       \
                        break;                                          \
                entry = irq_2_pin + entry->next;                        \
        }                                                               \
        FINAL;                                                          \
}

#define DO_ACTION(name,R,ACTION, FINAL)                                 \
                                                                        \
        static void name##_IO_APIC_irq (unsigned int irq)               \
        __DO_ACTION(R, ACTION, FINAL)

DO_ACTION( __mask,             0, |= 0x00010000, io_apic_sync(entry->apic) )
                                                /* mask = 1 */
DO_ACTION( __unmask,           0, &= 0xfffeffff, )
                                                /* mask = 0 */
DO_ACTION( __mask_and_edge,    0, = (reg & 0xffff7fff) | 0x00010000, )
                                                /* mask = 1, trigger = 0 */
DO_ACTION( __unmask_and_level, 0, = (reg & 0xfffeffff) | 0x00008000, )
                                                /* mask = 0, trigger = 1 */

static void mask_IO_APIC_irq (unsigned int irq)
{
        unsigned long flags;

        spin_lock_irqsave(&ioapic_lock, flags);
        __mask_IO_APIC_irq(irq);
        spin_unlock_irqrestore(&ioapic_lock, flags);
}

static void unmask_IO_APIC_irq (unsigned int irq)
{
        unsigned long flags;

        spin_lock_irqsave(&ioapic_lock, flags);
        __unmask_IO_APIC_irq(irq);
        spin_unlock_irqrestore(&ioapic_lock, flags);
}

void clear_IO_APIC_pin(unsigned int apic, unsigned int pin)
{
        struct IO_APIC_route_entry entry;
        unsigned long flags;

        /*
         * Disable it in the IO-APIC irq-routing table:
         */
        memset(&entry, 0, sizeof(entry));
        entry.mask = 1;
        spin_lock_irqsave(&ioapic_lock, flags);
        io_apic_write(apic, 0x10 + 2 * pin, *(((int *)&entry) + 0));
        io_apic_write(apic, 0x11 + 2 * pin, *(((int *)&entry) + 1));
        spin_unlock_irqrestore(&ioapic_lock, flags);
}

static void clear_IO_APIC (void)
{
        int apic, pin;

        for (apic = 0; apic < nr_ioapics; apic++)
                for (pin = 0; pin < nr_ioapic_registers[apic]; pin++)
                        clear_IO_APIC_pin(apic, pin);
}

/*
 * support for broken MP BIOSs, enables hand-redirection of PIRQ0-7 to
 * specific CPU-side IRQs.
 */

#define MAX_PIRQS 8
int pirq_entries [MAX_PIRQS];
int pirqs_enabled;
int skip_ioapic_setup;

static int __init noioapic_setup(char *str)
{
        skip_ioapic_setup = 1;
        return 1;
}

__setup("noapic", noioapic_setup);

static int __init ioapic_setup(char *str)
{
        skip_ioapic_setup = 0;
        return 1;
}

__setup("apic", ioapic_setup);

static int __init ioapic_pirq_setup(char *str)
{
        int i, max;
        int ints[MAX_PIRQS+1];

        get_options(str, ARRAY_SIZE(ints), ints);

        for (i = 0; i < MAX_PIRQS; i++)
                pirq_entries[i] = -1;

        pirqs_enabled = 1;
        printk(KERN_INFO "PIRQ redirection, working around broken MP-BIOS.\n");
        max = MAX_PIRQS;
        if (ints[0] < MAX_PIRQS)
                max = ints[0];

        for (i = 0; i < max; i++) {
                printk(KERN_DEBUG "... PIRQ%d -> IRQ %d\n", i, ints[i+1]);
                /*
                 * PIRQs are mapped upside down, usually.
                 */
                pirq_entries[MAX_PIRQS-i-1] = ints[i+1];
        }
        return 1;
}

__setup("pirq=", ioapic_pirq_setup);

/*
 * Find the IRQ entry number of a certain pin.
 */
static int __init find_irq_entry(int apic, int pin, int type)
{
        int i;

        for (i = 0; i < mp_irq_entries; i++)
                if (mp_irqs[i].mpc_irqtype == type &&
                    (mp_irqs[i].mpc_dstapic == mp_ioapics[apic].mpc_apicid ||
                     mp_irqs[i].mpc_dstapic == MP_APIC_ALL) &&
                    mp_irqs[i].mpc_dstirq == pin)
                        return i;

        return -1;
}

/*
 * Find the pin to which IRQ[irq] (ISA) is connected
 */
static int __init find_isa_irq_pin(int irq, int type)
{
        int i;

        for (i = 0; i < mp_irq_entries; i++) {
                int lbus = mp_irqs[i].mpc_srcbus;

                if ((mp_bus_id_to_type[lbus] == MP_BUS_ISA ||
                     mp_bus_id_to_type[lbus] == MP_BUS_EISA ||
                     mp_bus_id_to_type[lbus] == MP_BUS_MCA) &&
                    (mp_irqs[i].mpc_irqtype == type) &&
                    (mp_irqs[i].mpc_srcbusirq == irq))

                        return mp_irqs[i].mpc_dstirq;
        }
        return -1;
}

/*
 * Find a specific PCI IRQ entry.
 * Not an __init, possibly needed by modules
 */
static int pin_2_irq(int idx, int apic, int pin);

int IO_APIC_get_PCI_irq_vector(int bus, int slot, int pin)
{
        int apic, i, best_guess = -1;

        Dprintk("querying PCI -> IRQ mapping bus:%d, slot:%d, pin:%d.\n",
                bus, slot, pin);
        if ((mp_bus_id_to_pci_bus==NULL) || (mp_bus_id_to_pci_bus[bus] == -1)) {
                printk(KERN_WARNING "PCI BIOS passed nonexistent PCI bus %d!\n", bus);
                return -1;
        }
        for (i = 0; i < mp_irq_entries; i++) {
                int lbus = mp_irqs[i].mpc_srcbus;

                for (apic = 0; apic < nr_ioapics; apic++)
                        if (mp_ioapics[apic].mpc_apicid == mp_irqs[i].mpc_dstapic ||
                            mp_irqs[i].mpc_dstapic == MP_APIC_ALL)
                                break;

                if ((mp_bus_id_to_type[lbus] == MP_BUS_PCI) &&
                    !mp_irqs[i].mpc_irqtype &&
                    (bus == lbus) &&
                    (slot == ((mp_irqs[i].mpc_srcbusirq >> 2) & 0x1f))) {
                        int irq = pin_2_irq(i,apic,mp_irqs[i].mpc_dstirq);

                        if (!(apic || IO_APIC_IRQ(irq)))
                                continue;

                        if (pin == (mp_irqs[i].mpc_srcbusirq & 3))
                                return irq;
                        /*
                         * Use the first all-but-pin matching entry as a
                         * best-guess fuzzy result for broken mptables.
                         */
                        if (best_guess < 0)
                                best_guess = irq;
                }
        }
        return best_guess;
}

/*
 * EISA Edge/Level control register, ELCR
 */
static int __init EISA_ELCR(unsigned int irq)
{
        if (irq < 16) {
                unsigned int port = 0x4d0 + (irq >> 3);
                return (inb(port) >> (irq & 7)) & 1;
        }
        printk(KERN_INFO "Broken MPtable reports ISA irq %d\n", irq);
        return 0;
}

/* EISA interrupts are always polarity zero and can be edge or level
 * trigger depending on the ELCR value.  If an interrupt is listed as
 * EISA conforming in the MP table, that means its trigger type must
 * be read in from the ELCR */

#define default_EISA_trigger(idx)       (EISA_ELCR(mp_irqs[idx].mpc_srcbusirq))
#define default_EISA_polarity(idx)      (0)

/* ISA interrupts are always polarity zero edge triggered,
 * when listed as conforming in the MP table. */

#define default_ISA_trigger(idx)        (0)
#define default_ISA_polarity(idx)       (0)

/* PCI interrupts are always polarity one level triggered,
 * when listed as conforming in the MP table. */

#define default_PCI_trigger(idx)        (1)
#define default_PCI_polarity(idx)       (1)

/* MCA interrupts are always polarity zero level triggered,
 * when listed as conforming in the MP table. */

#define default_MCA_trigger(idx)        (1)
#define default_MCA_polarity(idx)       (0)

static int __init MPBIOS_polarity(int idx)
{
        int bus = mp_irqs[idx].mpc_srcbus;
        int polarity;

        /*
         * Determine IRQ line polarity (high active or low active):
         */
        switch (mp_irqs[idx].mpc_irqflag & 3)
        {
                case 0: /* conforms, ie. bus-type dependent polarity */
                {
                        switch (mp_bus_id_to_type[bus])
                        {
                                case MP_BUS_ISA: /* ISA pin */
                                {
                                        polarity = default_ISA_polarity(idx);
                                        break;
                                }
                                case MP_BUS_EISA: /* EISA pin */
                                {
                                        polarity = default_EISA_polarity(idx);
                                        break;
                                }
                                case MP_BUS_PCI: /* PCI pin */
                                {
                                        polarity = default_PCI_polarity(idx);
                                        break;
                                }
                                case MP_BUS_MCA: /* MCA pin */
                                {
                                        polarity = default_MCA_polarity(idx);
                                        break;
                                }
                                default:
                                {
                                        printk(KERN_WARNING "broken BIOS!!\n");
                                        polarity = 1;
                                        break;
                                }
                        }
                        break;
                }
                case 1: /* high active */
                {
                        polarity = 0;
                        break;
                }
                case 2: /* reserved */
                {
                        printk(KERN_WARNING "broken BIOS!!\n");
                        polarity = 1;
                        break;
                }
                case 3: /* low active */
                {
                        polarity = 1;
                        break;
                }
                default: /* invalid */
                {
                        printk(KERN_WARNING "broken BIOS!!\n");
                        polarity = 1;
                        break;
                }
        }
        return polarity;
}

static int __init MPBIOS_trigger(int idx)
{
        int bus = mp_irqs[idx].mpc_srcbus;
        int trigger;

        /*
         * Determine IRQ trigger mode (edge or level sensitive):
         */
        switch ((mp_irqs[idx].mpc_irqflag>>2) & 3)
        {
                case 0: /* conforms, ie. bus-type dependent */
                {
                        switch (mp_bus_id_to_type[bus])
                        {
                                case MP_BUS_ISA: /* ISA pin */
                                {
                                        trigger = default_ISA_trigger(idx);
                                        break;
                                }
                                case MP_BUS_EISA: /* EISA pin */
                                {
                                        trigger = default_EISA_trigger(idx);
                                        break;
                                }
                                case MP_BUS_PCI: /* PCI pin */
                                {
                                        trigger = default_PCI_trigger(idx);
                                        break;
                                }
                                case MP_BUS_MCA: /* MCA pin */
                                {
                                        trigger = default_MCA_trigger(idx);
                                        break;
                                }
                                default:
                                {
                                        printk(KERN_WARNING "broken BIOS!!\n");
                                        trigger = 1;
                                        break;
                                }
                        }
                        break;
                }
                case 1: /* edge */
                {
                        trigger = 0;
                        break;
                }
                case 2: /* reserved */
                {
                        printk(KERN_WARNING "broken BIOS!!\n");
                        trigger = 1;
                        break;
                }
                case 3: /* level */
                {
                        trigger = 1;
                        break;
                }
                default: /* invalid */
                {
                        printk(KERN_WARNING "broken BIOS!!\n");
                        trigger = 0;
                        break;
                }
        }
        return trigger;
}

static inline int irq_polarity(int idx)
{
        return MPBIOS_polarity(idx);
}

static inline int irq_trigger(int idx)
{
        return MPBIOS_trigger(idx);
}

static int pin_2_irq(int idx, int apic, int pin)
{
        int irq, i;
        int bus = mp_irqs[idx].mpc_srcbus;

        /*
         * Debugging check, we are in big trouble if this message pops up!
         */
        if (mp_irqs[idx].mpc_dstirq != pin)
                printk(KERN_ERR "broken BIOS or MPTABLE parser, ayiee!!\n");

        switch (mp_bus_id_to_type[bus])
        {
                case MP_BUS_ISA: /* ISA pin */
                case MP_BUS_EISA:
                case MP_BUS_MCA:
                {
                        irq = mp_irqs[idx].mpc_srcbusirq;
                        break;
                }
                case MP_BUS_PCI: /* PCI pin */
                {
                        /*
                         * PCI IRQs are mapped in order
                         */
                        i = irq = 0;
                        while (i < apic)
                                irq += nr_ioapic_registers[i++];
                        irq += pin;
                        break;
                }
                default:
                {
                        printk(KERN_ERR "unknown bus type %d.\n",bus); 
                        irq = 0;
                        break;
                }
        }

        /*
         * PCI IRQ command line redirection. Yes, limits are hardcoded.
         */
        if ((pin >= 16) && (pin <= 23)) {
                if (pirq_entries[pin-16] != -1) {
                        if (!pirq_entries[pin-16]) {
                                printk(KERN_DEBUG "disabling PIRQ%d\n", pin-16);
                        } else {
                                irq = pirq_entries[pin-16];
                                printk(KERN_DEBUG "using PIRQ%d -> IRQ %d\n",
                                                pin-16, irq);
                        }
                }
        }
        return irq;
}

static inline int IO_APIC_irq_trigger(int irq)
{
        int apic, idx, pin;

        for (apic = 0; apic < nr_ioapics; apic++) {
                for (pin = 0; pin < nr_ioapic_registers[apic]; pin++) {
                        idx = find_irq_entry(apic,pin,mp_INT);
                        if ((idx != -1) && (irq == pin_2_irq(idx,apic,pin)))
                                return irq_trigger(idx);
                }
        }
        /*
         * nonexistent IRQs are edge default
         */
        return 0;
}

int irq_vector[NR_IRQS] = { FIRST_DEVICE_VECTOR , 0 };

static int __init assign_irq_vector(int irq)
{
        static int current_vector = FIRST_DEVICE_VECTOR, offset = 0;
        if (IO_APIC_VECTOR(irq) > 0)
                return IO_APIC_VECTOR(irq);
next:
        current_vector += 8;
        if (current_vector == SYSCALL_VECTOR)
                goto next;

        if (current_vector > FIRST_SYSTEM_VECTOR) {
                offset++;
                current_vector = FIRST_DEVICE_VECTOR + offset;
        }

        if (current_vector == FIRST_SYSTEM_VECTOR)
                panic("ran out of interrupt sources!");

        IO_APIC_VECTOR(irq) = current_vector;
        return current_vector;
}

extern void (*interrupt[NR_IRQS])(void);
static struct hw_interrupt_type ioapic_level_irq_type;
static struct hw_interrupt_type ioapic_edge_irq_type;

void __init setup_IO_APIC_irqs(void)
{
        struct IO_APIC_route_entry entry;
        int apic, pin, idx, irq, first_notcon = 1, vector;
        unsigned long flags;

        printk(KERN_DEBUG "init IO_APIC IRQs\n");

        for (apic = 0; apic < nr_ioapics; apic++) {
        for (pin = 0; pin < nr_ioapic_registers[apic]; pin++) {

                /*
                 * add it to the IO-APIC irq-routing table:
                 */
                memset(&entry,0,sizeof(entry));

                entry.delivery_mode = INT_DELIVERY_MODE;
                entry.dest_mode = (INT_DEST_ADDR_MODE != 0);
                entry.mask = 0;                         /* enable IRQ */
                entry.dest.logical.logical_dest = target_cpus();

                idx = find_irq_entry(apic,pin,mp_INT);
                if (idx == -1) {
                        if (first_notcon) {
                                printk(KERN_DEBUG " IO-APIC (apicid-pin) %d-%d", mp_ioapics[apic].mpc_apicid, pin);
                                first_notcon = 0;
                        } else
                                printk(", %d-%d", mp_ioapics[apic].mpc_apicid, pin);
                        continue;
                }

                entry.trigger = irq_trigger(idx);
                entry.polarity = irq_polarity(idx);

                if (irq_trigger(idx)) {
                        entry.trigger = 1;
                        entry.mask = 1;
                }

                irq = pin_2_irq(idx, apic, pin);
                /*
                 * skip adding the timer int on secondary nodes, which causes
                 * a small but painful rift in the time-space continuum
                 */
                if ((clustered_apic_mode == CLUSTERED_APIC_NUMAQ) 
                        && (apic != 0) && (irq == 0))
                        continue;
                else
                        add_pin_to_irq(irq, apic, pin);

                if (!apic && !IO_APIC_IRQ(irq))
                        continue;

                if (IO_APIC_IRQ(irq)) {
                        vector = assign_irq_vector(irq);
                        entry.vector = vector;

                        if (IO_APIC_irq_trigger(irq))
                                irq_desc[irq].handler = &ioapic_level_irq_type;
                        else
                                irq_desc[irq].handler = &ioapic_edge_irq_type;

                        set_intr_gate(vector, interrupt[irq]);
                
                        if (!apic && (irq < 16))
                                disable_8259A_irq(irq);
                }
                spin_lock_irqsave(&ioapic_lock, flags);
                io_apic_write(apic, 0x11+2*pin, *(((int *)&entry)+1));
                io_apic_write(apic, 0x10+2*pin, *(((int *)&entry)+0));
                spin_unlock_irqrestore(&ioapic_lock, flags);
        }
        }

        if (!first_notcon)
                printk(" not connected.\n");
}

/*
 * Set up the 8259A-master output pin as broadcast to all
 * CPUs.
 */
void __init setup_ExtINT_IRQ0_pin(unsigned int pin, int vector)
{
        struct IO_APIC_route_entry entry;
        unsigned long flags;

        memset(&entry,0,sizeof(entry));

        disable_8259A_irq(0);

        /* mask LVT0 */
        apic_write_around(APIC_LVT0, APIC_LVT_MASKED | APIC_DM_EXTINT);

        /*
         * We use logical delivery to get the timer IRQ
         * to the first CPU.
         */
        entry.dest_mode = (INT_DEST_ADDR_MODE != 0);
        entry.mask = 0;                                 /* unmask IRQ now */
        entry.dest.logical.logical_dest = target_cpus();
        entry.delivery_mode = INT_DELIVERY_MODE;
        entry.polarity = 0;
        entry.trigger = 0;
        entry.vector = vector;

        /*
         * The timer IRQ doesn't have to know that behind the
         * scene we have a 8259A-master in AEOI mode ...
         */
        irq_desc[0].handler = &ioapic_edge_irq_type;

        /*
         * Add it to the IO-APIC irq-routing table:
         */
        spin_lock_irqsave(&ioapic_lock, flags);
        io_apic_write(0, 0x11+2*pin, *(((int *)&entry)+1));
        io_apic_write(0, 0x10+2*pin, *(((int *)&entry)+0));
        spin_unlock_irqrestore(&ioapic_lock, flags);

        enable_8259A_irq(0);
}

void __init UNEXPECTED_IO_APIC(void)
{
        printk(KERN_WARNING 
                "An unexpected IO-APIC was found. If this kernel release is less than\n"
                "three months old please report this to linux-smp@vger.kernel.org\n");
}

void __init print_IO_APIC(void)
{
        int apic, i;
        struct IO_APIC_reg_00 reg_00;
        struct IO_APIC_reg_01 reg_01;
        struct IO_APIC_reg_02 reg_02;
        unsigned long flags;

        printk(KERN_DEBUG "number of MP IRQ sources: %d.\n", mp_irq_entries);
        for (i = 0; i < nr_ioapics; i++)
                printk(KERN_DEBUG "number of IO-APIC #%d registers: %d.\n",
                       mp_ioapics[i].mpc_apicid, nr_ioapic_registers[i]);

        /*
         * We are a bit conservative about what we expect.  We have to
         * know about every hardware change ASAP.
         */
        printk(KERN_INFO "testing the IO APIC.......................\n");

        for (apic = 0; apic < nr_ioapics; apic++) {

        spin_lock_irqsave(&ioapic_lock, flags);
        *(int *)&reg_00 = io_apic_read(apic, 0);
        *(int *)&reg_01 = io_apic_read(apic, 1);
        if (reg_01.version >= 0x10)
                *(int *)&reg_02 = io_apic_read(apic, 2);
        spin_unlock_irqrestore(&ioapic_lock, flags);

        printk("\n");
        printk(KERN_DEBUG "IO APIC #%d......\n", mp_ioapics[apic].mpc_apicid);
        printk(KERN_DEBUG ".... register #00: %08X\n", *(int *)&reg_00);
        printk(KERN_DEBUG ".......    : physical APIC id: %02X\n", reg_00.ID);
        printk(KERN_DEBUG ".......    : Delivery Type: %X\n", reg_00.delivery_type);
        printk(KERN_DEBUG ".......    : LTS          : %X\n", reg_00.LTS);
        if (reg_00.__reserved_0 || reg_00.__reserved_1 || reg_00.__reserved_2)
                UNEXPECTED_IO_APIC();

        printk(KERN_DEBUG ".... register #01: %08X\n", *(int *)&reg_01);
        printk(KERN_DEBUG ".......     : max redirection entries: %04X\n", reg_01.entries);
        if (    (reg_01.entries != 0x0f) && /* older (Neptune) boards */
                (reg_01.entries != 0x17) && /* typical ISA+PCI boards */
                (reg_01.entries != 0x1b) && /* Compaq Proliant boards */
                (reg_01.entries != 0x1f) && /* dual Xeon boards */
                (reg_01.entries != 0x22) && /* bigger Xeon boards */
                (reg_01.entries != 0x2E) &&
                (reg_01.entries != 0x3F)
        )
                UNEXPECTED_IO_APIC();

        printk(KERN_DEBUG ".......     : PRQ implemented: %X\n", reg_01.PRQ);
        printk(KERN_DEBUG ".......     : IO APIC version: %04X\n", reg_01.version);
        if (    (reg_01.version != 0x01) && /* 82489DX IO-APICs */
                (reg_01.version != 0x02) && /* VIA */
                (reg_01.version != 0x03) && /* later VIA */
                (reg_01.version != 0x10) && /* oldest IO-APICs */
                (reg_01.version != 0x11) && /* Pentium/Pro IO-APICs */
                (reg_01.version != 0x13) && /* Xeon IO-APICs */
                (reg_01.version != 0x20)    /* Intel P64H (82806 AA) */
        )
                UNEXPECTED_IO_APIC();
        if (reg_01.__reserved_1 || reg_01.__reserved_2)
                UNEXPECTED_IO_APIC();

        if (reg_01.version >= 0x10) {
                printk(KERN_DEBUG ".... register #02: %08X\n", *(int *)&reg_02);
                printk(KERN_DEBUG ".......     : arbitration: %02X\n", reg_02.arbitration);
                if (reg_02.__reserved_1 || reg_02.__reserved_2)
                        UNEXPECTED_IO_APIC();
        }

        printk(KERN_DEBUG ".... IRQ redirection table:\n");

        printk(KERN_DEBUG " NR Log Phy Mask Trig IRR Pol"
                          " Stat Dest Deli Vect:   \n");

        for (i = 0; i <= reg_01.entries; i++) {
                struct IO_APIC_route_entry entry;

                spin_lock_irqsave(&ioapic_lock, flags);
                *(((int *)&entry)+0) = io_apic_read(apic, 0x10+i*2);
                *(((int *)&entry)+1) = io_apic_read(apic, 0x11+i*2);
                spin_unlock_irqrestore(&ioapic_lock, flags);

                printk(KERN_DEBUG " %02x %03X %02X  ",
                        i,
                        entry.dest.logical.logical_dest,
                        entry.dest.physical.physical_dest
                );

                printk("%1d    %1d    %1d   %1d   %1d    %1d    %1d    %02X\n",
                        entry.mask,
                        entry.trigger,
                        entry.irr,
                        entry.polarity,
                        entry.delivery_status,
                        entry.dest_mode,
                        entry.delivery_mode,
                        entry.vector
                );
        }
        }
        printk(KERN_DEBUG "IRQ to pin mappings:\n");
        for (i = 0; i < NR_IRQS; i++) {
                struct irq_pin_list *entry = irq_2_pin + i;
                if (entry->pin < 0)
                        continue;
                printk(KERN_DEBUG "IRQ%d ", i);
                for (;;) {
                        printk("-> %d:%d", entry->apic, entry->pin);
                        if (!entry->next)
                                break;
                        entry = irq_2_pin + entry->next;
                }
                printk("\n");
        }

        printk(KERN_INFO ".................................... done.\n");

        return;
}

static void print_APIC_bitfield (int base)
{
        unsigned int v;
        int i, j;

        printk(KERN_DEBUG "0123456789abcdef0123456789abcdef\n" KERN_DEBUG);
        for (i = 0; i < 8; i++) {
                v = apic_read(base + i*0x10);
                for (j = 0; j < 32; j++) {
                        if (v & (1<<j))
                                printk("1");
                        else
                                printk("0");
                }
                printk("\n");
        }
}

void /*__init*/ print_local_APIC(void * dummy)
{
        unsigned int v, ver, maxlvt;

        printk("\n" KERN_DEBUG "printing local APIC contents on CPU#%d/%d:\n",
                smp_processor_id(), hard_smp_processor_id());
        v = apic_read(APIC_ID);
        printk(KERN_INFO "... APIC ID:      %08x (%01x)\n", v, GET_APIC_ID(v));
        v = apic_read(APIC_LVR);
        printk(KERN_INFO "... APIC VERSION: %08x\n", v);
        ver = GET_APIC_VERSION(v);
        maxlvt = get_maxlvt();

        v = apic_read(APIC_TASKPRI);
        printk(KERN_DEBUG "... APIC TASKPRI: %08x (%02x)\n", v, v & APIC_TPRI_MASK);

        if (APIC_INTEGRATED(ver)) {                     /* !82489DX */
                v = apic_read(APIC_ARBPRI);
                printk(KERN_DEBUG "... APIC ARBPRI: %08x (%02x)\n", v,
                        v & APIC_ARBPRI_MASK);
                v = apic_read(APIC_PROCPRI);
                printk(KERN_DEBUG "... APIC PROCPRI: %08x\n", v);
        }

        v = apic_read(APIC_EOI);
        printk(KERN_DEBUG "... APIC EOI: %08x\n", v);
        v = apic_read(APIC_RRR);
        printk(KERN_DEBUG "... APIC RRR: %08x\n", v);
        v = apic_read(APIC_LDR);
        printk(KERN_DEBUG "... APIC LDR: %08x\n", v);
        v = apic_read(APIC_DFR);
        printk(KERN_DEBUG "... APIC DFR: %08x\n", v);
        v = apic_read(APIC_SPIV);
        printk(KERN_DEBUG "... APIC SPIV: %08x\n", v);

        printk(KERN_DEBUG "... APIC ISR field:\n");
        print_APIC_bitfield(APIC_ISR);
        printk(KERN_DEBUG "... APIC TMR field:\n");
        print_APIC_bitfield(APIC_TMR);
        printk(KERN_DEBUG "... APIC IRR field:\n");
        print_APIC_bitfield(APIC_IRR);

        if (APIC_INTEGRATED(ver)) {             /* !82489DX */
                if (maxlvt > 3)         /* Due to the Pentium erratum 3AP. */
                        apic_write(APIC_ESR, 0);
                v = apic_read(APIC_ESR);
                printk(KERN_DEBUG "... APIC ESR: %08x\n", v);
        }

        v = apic_read(APIC_ICR);
        printk(KERN_DEBUG "... APIC ICR: %08x\n", v);
        v = apic_read(APIC_ICR2);
        printk(KERN_DEBUG "... APIC ICR2: %08x\n", v);

        v = apic_read(APIC_LVTT);
        printk(KERN_DEBUG "... APIC LVTT: %08x\n", v);

        if (maxlvt > 3) {                       /* PC is LVT#4. */
                v = apic_read(APIC_LVTPC);
                printk(KERN_DEBUG "... APIC LVTPC: %08x\n", v);
        }
        v = apic_read(APIC_LVT0);
        printk(KERN_DEBUG "... APIC LVT0: %08x\n", v);
        v = apic_read(APIC_LVT1);
        printk(KERN_DEBUG "... APIC LVT1: %08x\n", v);

        if (maxlvt > 2) {                       /* ERR is LVT#3. */
                v = apic_read(APIC_LVTERR);
                printk(KERN_DEBUG "... APIC LVTERR: %08x\n", v);
        }

        v = apic_read(APIC_TMICT);
        printk(KERN_DEBUG "... APIC TMICT: %08x\n", v);
        v = apic_read(APIC_TMCCT);
        printk(KERN_DEBUG "... APIC TMCCT: %08x\n", v);
        v = apic_read(APIC_TDCR);
        printk(KERN_DEBUG "... APIC TDCR: %08x\n", v);
        printk("\n");
}

void print_all_local_APICs (void)
{
        smp_call_function(print_local_APIC, NULL, 1, 1);
        print_local_APIC(NULL);
}

void /*__init*/ print_PIC(void)
{
        extern spinlock_t i8259A_lock;
        unsigned int v, flags;

        printk(KERN_DEBUG "\nprinting PIC contents\n");

        spin_lock_irqsave(&i8259A_lock, flags);

        v = inb(0xa1) << 8 | inb(0x21);
        printk(KERN_DEBUG "... PIC  IMR: %04x\n", v);

        v = inb(0xa0) << 8 | inb(0x20);
        printk(KERN_DEBUG "... PIC  IRR: %04x\n", v);

        outb(0x0b,0xa0);
        outb(0x0b,0x20);
        v = inb(0xa0) << 8 | inb(0x20);
        outb(0x0a,0xa0);
        outb(0x0a,0x20);

        spin_unlock_irqrestore(&i8259A_lock, flags);

        printk(KERN_DEBUG "... PIC  ISR: %04x\n", v);

        v = inb(0x4d1) << 8 | inb(0x4d0);
        printk(KERN_DEBUG "... PIC ELCR: %04x\n", v);
}

static void __init enable_IO_APIC(void)
{
        struct IO_APIC_reg_01 reg_01;
        int i;
        unsigned long flags;

        for (i = 0; i < PIN_MAP_SIZE; i++) {
                irq_2_pin[i].pin = -1;
                irq_2_pin[i].next = 0;
        }
        if (!pirqs_enabled)
                for (i = 0; i < MAX_PIRQS; i++)
                        pirq_entries[i] = -1;

        /*
         * The number of IO-APIC IRQ registers (== #pins):
         */
        for (i = 0; i < nr_ioapics; i++) {
                spin_lock_irqsave(&ioapic_lock, flags);
                *(int *)&reg_01 = io_apic_read(i, 1);
                spin_unlock_irqrestore(&ioapic_lock, flags);
                nr_ioapic_registers[i] = reg_01.entries+1;
        }

        /*
         * Do not trust the IO-APIC being empty at bootup
         */
        clear_IO_APIC();
}

/*
 * Not an __init, needed by the reboot code
 */
void disable_IO_APIC(void)
{
        /*
         * Clear the IO-APIC before rebooting:
         */
        clear_IO_APIC();

        disconnect_bsp_APIC();
}

/*
 * function to set the IO-APIC physical IDs based on the
 * values stored in the MPC table.
 *
 * by Matt Domsch <Matt_Domsch@dell.com>  Tue Dec 21 12:25:05 CST 1999
 */

static void __init setup_ioapic_ids_from_mpc (void)
{
        struct IO_APIC_reg_00 reg_00;
        unsigned long phys_id_present_map = phys_cpu_present_map;
        int apic;
        int i;
        unsigned char old_id;
        unsigned long flags;

        if (clustered_apic_mode)
                /* We don't have a good way to do this yet - hack */
                phys_id_present_map = (u_long) 0xf;
        /*
         * Set the IOAPIC ID to the value stored in the MPC table.
         */
        for (apic = 0; apic < nr_ioapics; apic++) {

                /* Read the register 0 value */
                spin_lock_irqsave(&ioapic_lock, flags);
                *(int *)&reg_00 = io_apic_read(apic, 0);
                spin_unlock_irqrestore(&ioapic_lock, flags);
                
                old_id = mp_ioapics[apic].mpc_apicid;

                if (mp_ioapics[apic].mpc_apicid >= apic_broadcast_id) {
                        printk(KERN_ERR "BIOS bug, IO-APIC#%d ID is %d in the MPC table!...\n",
                                apic, mp_ioapics[apic].mpc_apicid);
                        printk(KERN_ERR "... fixing up to %d. (tell your hw vendor)\n",
                                reg_00.ID);
                        mp_ioapics[apic].mpc_apicid = reg_00.ID;
                }

                /*
                 * Sanity check, is the ID really free? Every APIC in a
                 * system must have a unique ID or we get lots of nice
                 * 'stuck on smp_invalidate_needed IPI wait' messages.
                 * I/O APIC IDs no longer have any meaning for xAPICs and SAPICs.
                 */
                if ((clustered_apic_mode != CLUSTERED_APIC_XAPIC) &&
                    (phys_id_present_map & (1 << mp_ioapics[apic].mpc_apicid))) {
                        printk(KERN_ERR "BIOS bug, IO-APIC#%d ID %d is already used!...\n",
                                apic, mp_ioapics[apic].mpc_apicid);
                        for (i = 0; i < 0xf; i++)
                                if (!(phys_id_present_map & (1 << i)))
                                        break;
                        if (i >= apic_broadcast_id)
                                panic("Max APIC ID exceeded!\n");
                        printk(KERN_ERR "... fixing up to %d. (tell your hw vendor)\n",
                                i);
                        phys_id_present_map |= 1 << i;
                        mp_ioapics[apic].mpc_apicid = i;
                } else {
                        printk("Setting %d in the phys_id_present_map\n", mp_ioapics[apic].mpc_apicid);
                        phys_id_present_map |= 1 << mp_ioapics[apic].mpc_apicid;
                }


                /*
                 * We need to adjust the IRQ routing table
                 * if the ID changed.
                 */
                if (old_id != mp_ioapics[apic].mpc_apicid)
                        for (i = 0; i < mp_irq_entries; i++)
                                if (mp_irqs[i].mpc_dstapic == old_id)
                                        mp_irqs[i].mpc_dstapic
                                                = mp_ioapics[apic].mpc_apicid;

                /*
                 * Read the right value from the MPC table and
                 * write it into the ID register.
                 */
                printk(KERN_INFO "...changing IO-APIC physical APIC ID to %d ...",
                                        mp_ioapics[apic].mpc_apicid);

                reg_00.ID = mp_ioapics[apic].mpc_apicid;
                spin_lock_irqsave(&ioapic_lock, flags);
                io_apic_write(apic, 0, *(int *)&reg_00);
                spin_unlock_irqrestore(&ioapic_lock, flags);

                /*
                 * Sanity check
                 */
                spin_lock_irqsave(&ioapic_lock, flags);
                *(int *)&reg_00 = io_apic_read(apic, 0);
                spin_unlock_irqrestore(&ioapic_lock, flags);
                if (reg_00.ID != mp_ioapics[apic].mpc_apicid)
                        panic("could not set ID!\n");
                else
                        printk(" ok.\n");
        }
}

/*
 * There is a nasty bug in some older SMP boards, their mptable lies
 * about the timer IRQ. We do the following to work around the situation:
 *
 *      - timer IRQ defaults to IO-APIC IRQ
 *      - if this function detects that timer IRQs are defunct, then we fall
 *        back to ISA timer IRQs
 */
static int __init timer_irq_works(void)
{
        unsigned int t1 = jiffies;

        sti();
        /* Let ten ticks pass... */
        mdelay((10 * 1000) / HZ);

        /*
         * Expect a few ticks at least, to be sure some possible
         * glue logic does not lock up after one or two first
         * ticks in a non-ExtINT mode.  Also the local APIC
         * might have cached one ExtINT interrupt.  Finally, at
         * least one tick may be lost due to delays.
         */
        if (jiffies - t1 > 4)
                return 1;

        return 0;
}

/*
 * In the SMP+IOAPIC case it might happen that there are an unspecified
 * number of pending IRQ events unhandled. These cases are very rare,
 * so we 'resend' these IRQs via IPIs, to the same CPU. It's much
 * better to do it this way as thus we do not have to be aware of
 * 'pending' interrupts in the IRQ path, except at this point.
 */
/*
 * Edge triggered needs to resend any interrupt
 * that was delayed but this is now handled in the device
 * independent code.
 */
#define enable_edge_ioapic_irq unmask_IO_APIC_irq

static void disable_edge_ioapic_irq (unsigned int irq) { /* nothing */ }

/*
 * Starting up a edge-triggered IO-APIC interrupt is
 * nasty - we need to make sure that we get the edge.
 * If it is already asserted for some reason, we need
 * return 1 to indicate that is was pending.
 *
 * This is not complete - we should be able to fake
 * an edge even if it isn't on the 8259A...
 */

static unsigned int startup_edge_ioapic_irq(unsigned int irq)
{
        int was_pending = 0;
        unsigned long flags;

        spin_lock_irqsave(&ioapic_lock, flags);
        if (irq < 16) {
                disable_8259A_irq(irq);
                if (i8259A_irq_pending(irq))
                        was_pending = 1;
        }
        __unmask_IO_APIC_irq(irq);
        spin_unlock_irqrestore(&ioapic_lock, flags);

        return was_pending;
}

#define shutdown_edge_ioapic_irq        disable_edge_ioapic_irq

/*
 * Once we have recorded IRQ_PENDING already, we can mask the
 * interrupt for real. This prevents IRQ storms from unhandled
 * devices.
 */
static void ack_edge_ioapic_irq(unsigned int irq)
{
        if ((irq_desc[irq].status & (IRQ_PENDING | IRQ_DISABLED))
                                        == (IRQ_PENDING | IRQ_DISABLED))
                mask_IO_APIC_irq(irq);
        ack_APIC_irq();
}

static void end_edge_ioapic_irq (unsigned int i) { /* nothing */ }


/*
 * Level triggered interrupts can just be masked,
 * and shutting down and starting up the interrupt
 * is the same as enabling and disabling them -- except
 * with a startup need to return a "was pending" value.
 *
 * Level triggered interrupts are special because we
 * do not touch any IO-APIC register while handling
 * them. We ack the APIC in the end-IRQ handler, not
 * in the start-IRQ-handler. Protection against reentrance
 * from the same interrupt is still provided, both by the
 * generic IRQ layer and by the fact that an unacked local
 * APIC does not accept IRQs.
 */
static unsigned int startup_level_ioapic_irq (unsigned int irq)
{
        unmask_IO_APIC_irq(irq);

        return 0; /* don't check for pending */
}

#define shutdown_level_ioapic_irq       mask_IO_APIC_irq
#define enable_level_ioapic_irq         unmask_IO_APIC_irq
#define disable_level_ioapic_irq        mask_IO_APIC_irq

static void end_level_ioapic_irq (unsigned int irq)
{
        unsigned long v;
        int i;

/*
 * It appears there is an erratum which affects at least version 0x11
 * of I/O APIC (that's the 82093AA and cores integrated into various
 * chipsets).  Under certain conditions a level-triggered interrupt is
 * erroneously delivered as edge-triggered one but the respective IRR
 * bit gets set nevertheless.  As a result the I/O unit expects an EOI
 * message but it will never arrive and further interrupts are blocked
 * from the source.  The exact reason is so far unknown, but the
 * phenomenon was observed when two consecutive interrupt requests
 * from a given source get delivered to the same CPU and the source is
 * temporarily disabled in between.
 *
 * A workaround is to simulate an EOI message manually.  We achieve it
 * by setting the trigger mode to edge and then to level when the edge
 * trigger mode gets detected in the TMR of a local APIC for a
 * level-triggered interrupt.  We mask the source for the time of the
 * operation to prevent an edge-triggered interrupt escaping meanwhile.
 * The idea is from Manfred Spraul.  --macro
 */
        i = IO_APIC_VECTOR(irq);
        v = apic_read(APIC_TMR + ((i & ~0x1f) >> 1));

        ack_APIC_irq();

        if (!(v & (1 << (i & 0x1f)))) {
#ifdef APIC_LOCKUP_DEBUG
                struct irq_pin_list *entry;
#endif

#ifdef APIC_MISMATCH_DEBUG
                atomic_inc(&irq_mis_count);
#endif
                spin_lock(&ioapic_lock);
                __mask_and_edge_IO_APIC_irq(irq);
#ifdef APIC_LOCKUP_DEBUG
                for (entry = irq_2_pin + irq;;) {
                        unsigned int reg;

                        if (entry->pin == -1)
                                break;
                        reg = io_apic_read(entry->apic, 0x10 + entry->pin * 2);
                        if (reg & 0x00004000)
                                printk(KERN_CRIT "Aieee!!!  Remote IRR"
                                        " still set after unlock!\n");
                        if (!entry->next)
                                break;
                        entry = irq_2_pin + entry->next;
                }
#endif
                __unmask_and_level_IO_APIC_irq(irq);
                spin_unlock(&ioapic_lock);
        }
}

static void mask_and_ack_level_ioapic_irq (unsigned int irq) { /* nothing */ }

static void set_ioapic_affinity (unsigned int irq, unsigned long mask)
{
        unsigned long flags;
        /*
         * Only the first 8 bits are valid.
         */
        mask = mask << 24;

        spin_lock_irqsave(&ioapic_lock, flags);
        __DO_ACTION(1, = mask, )
        spin_unlock_irqrestore(&ioapic_lock, flags);
}

/*
 * Level and edge triggered IO-APIC interrupts need different handling,
 * so we use two separate IRQ descriptors. Edge triggered IRQs can be
 * handled with the level-triggered descriptor, but that one has slightly
 * more overhead. Level-triggered interrupts cannot be handled with the
 * edge-triggered handler, without risking IRQ storms and other ugly
 * races.
 */

static struct hw_interrupt_type ioapic_edge_irq_type = {
        "IO-APIC-edge",
        startup_edge_ioapic_irq,
        shutdown_edge_ioapic_irq,
        enable_edge_ioapic_irq,
        disable_edge_ioapic_irq,
        ack_edge_ioapic_irq,
        end_edge_ioapic_irq,
        set_ioapic_affinity,
};

static struct hw_interrupt_type ioapic_level_irq_type = {
        "IO-APIC-level",
        startup_level_ioapic_irq,
        shutdown_level_ioapic_irq,
        enable_level_ioapic_irq,
        disable_level_ioapic_irq,
        mask_and_ack_level_ioapic_irq,
        end_level_ioapic_irq,
        set_ioapic_affinity,
};

static inline void init_IO_APIC_traps(void)
{
        int irq;

        /*
         * NOTE! The local APIC isn't very good at handling
         * multiple interrupts at the same interrupt level.
         * As the interrupt level is determined by taking the
         * vector number and shifting that right by 4, we
         * want to spread these out a bit so that they don't
         * all fall in the same interrupt level.
         *
         * Also, we've got to be careful not to trash gate
         * 0x80, because int 0x80 is hm, kind of importantish. ;)
         */
        for (irq = 0; irq < NR_IRQS ; irq++) {
                if (IO_APIC_IRQ(irq) && !IO_APIC_VECTOR(irq)) {
                        /*
                         * Hmm.. We don't have an entry for this,
                         * so default to an old-fashioned 8259
                         * interrupt if we can..
                         */
                        if (irq < 16)
                                make_8259A_irq(irq);
                        else
                                /* Strange. Oh, well.. */
                                irq_desc[irq].handler = &no_irq_type;
                }
        }
}

static void enable_lapic_irq (unsigned int irq)
{
        unsigned long v;

        v = apic_read(APIC_LVT0);
        apic_write_around(APIC_LVT0, v & ~APIC_LVT_MASKED);
}

static void disable_lapic_irq (unsigned int irq)
{
        unsigned long v;

        v = apic_read(APIC_LVT0);
        apic_write_around(APIC_LVT0, v | APIC_LVT_MASKED);
}

static void ack_lapic_irq (unsigned int irq)
{
        ack_APIC_irq();
}

static void end_lapic_irq (unsigned int i) { /* nothing */ }

static struct hw_interrupt_type lapic_irq_type = {
        "local-APIC-edge",
        NULL, /* startup_irq() not used for IRQ0 */
        NULL, /* shutdown_irq() not used for IRQ0 */
        enable_lapic_irq,
        disable_lapic_irq,
        ack_lapic_irq,
        end_lapic_irq
};

static 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 */
        if (!APIC_INTEGRATED(ver))              /* 82489DX */
                v |= APIC_LVT_LEVEL_TRIGGER;
        apic_write_around(APIC_LVT0, v);
}

static void setup_nmi (void)
{
        /*
         * Dirty trick to enable the NMI watchdog ...
         * We put the 8259A master into AEOI mode and
         * unmask on all local APICs LVT0 as NMI.
         *
         * The idea to use the 8259A in AEOI mode ('8259A Virtual Wire')
         * is from Maciej W. Rozycki - so we do not have to EOI from
         * the NMI handler or the timer interrupt.
         */ 
        printk(KERN_INFO "activating NMI Watchdog ...");

        smp_call_function(enable_NMI_through_LVT0, NULL, 1, 1);
        enable_NMI_through_LVT0(NULL);

        printk(" done.\n");
}

/*
 * This looks a bit hackish but it's about the only one way of sending
 * a few INTA cycles to 8259As and any associated glue logic.  ICR does
 * not support the ExtINT mode, unfortunately.  We need to send these
 * cycles as some i82489DX-based boards have glue logic that keeps the
 * 8259A interrupt line asserted until INTA.  --macro
 */
static inline void unlock_ExtINT_logic(void)
{
        int pin, i;
        struct IO_APIC_route_entry entry0, entry1;
        unsigned char save_control, save_freq_select;
        unsigned long flags;

        pin = find_isa_irq_pin(8, mp_INT);
        if (pin == -1)
                return;

        spin_lock_irqsave(&ioapic_lock, flags);
        *(((int *)&entry0) + 1) = io_apic_read(0, 0x11 + 2 * pin);
        *(((int *)&entry0) + 0) = io_apic_read(0, 0x10 + 2 * pin);
        spin_unlock_irqrestore(&ioapic_lock, flags);
        clear_IO_APIC_pin(0, pin);

        memset(&entry1, 0, sizeof(entry1));

        entry1.dest_mode = 0;                   /* physical delivery */
        entry1.mask = 0;                        /* unmask IRQ now */
        entry1.dest.physical.physical_dest = hard_smp_processor_id();
        entry1.delivery_mode = dest_ExtINT;
        entry1.polarity = entry0.polarity;
        entry1.trigger = 0;
        entry1.vector = 0;

        spin_lock_irqsave(&ioapic_lock, flags);
        io_apic_write(0, 0x11 + 2 * pin, *(((int *)&entry1) + 1));
        io_apic_write(0, 0x10 + 2 * pin, *(((int *)&entry1) + 0));
        spin_unlock_irqrestore(&ioapic_lock, flags);

        save_control = CMOS_READ(RTC_CONTROL);
        save_freq_select = CMOS_READ(RTC_FREQ_SELECT);
        CMOS_WRITE((save_freq_select & ~RTC_RATE_SELECT) | 0x6,
                   RTC_FREQ_SELECT);
        CMOS_WRITE(save_control | RTC_PIE, RTC_CONTROL);

        i = 100;
        while (i-- > 0) {
                mdelay(10);
                if ((CMOS_READ(RTC_INTR_FLAGS) & RTC_PF) == RTC_PF)
                        i -= 10;
        }

        CMOS_WRITE(save_control, RTC_CONTROL);
        CMOS_WRITE(save_freq_select, RTC_FREQ_SELECT);
        clear_IO_APIC_pin(0, pin);

        spin_lock_irqsave(&ioapic_lock, flags);
        io_apic_write(0, 0x11 + 2 * pin, *(((int *)&entry0) + 1));
        io_apic_write(0, 0x10 + 2 * pin, *(((int *)&entry0) + 0));
        spin_unlock_irqrestore(&ioapic_lock, flags);
}

/*
 * This code may look a bit paranoid, but it's supposed to cooperate with
 * a wide range of boards and BIOS bugs.  Fortunately only the timer IRQ
 * is so screwy.  Thanks to Brian Perkins for testing/hacking this beast
 * fanatically on his truly buggy board.
 */
static inline void check_timer(void)
{
        extern int timer_ack;
        int pin1, pin2;
        int vector;

        /*
         * get/set the timer IRQ vector:
         */
        disable_8259A_irq(0);
        vector = assign_irq_vector(0);
        set_intr_gate(vector, interrupt[0]);

        /*
         * Subtle, code in do_timer_interrupt() expects an AEOI
         * mode for the 8259A whenever interrupts are routed
         * through I/O APICs.  Also IRQ0 has to be enabled in
         * the 8259A which implies the virtual wire has to be
         * disabled in the local APIC.
         */
        apic_write_around(APIC_LVT0, APIC_LVT_MASKED | APIC_DM_EXTINT);
        init_8259A(1);
        timer_ack = 1;
        enable_8259A_irq(0);

        pin1 = find_isa_irq_pin(0, mp_INT);
        pin2 = find_isa_irq_pin(0, mp_ExtINT);

        printk(KERN_INFO "..TIMER: vector=0x%02X pin1=%d pin2=%d\n", vector, pin1, pin2);

        if (pin1 != -1) {
                /*
                 * Ok, does IRQ0 through the IOAPIC work?
                 */
                unmask_IO_APIC_irq(0);
                if (timer_irq_works()) {
                        if (nmi_watchdog == NMI_IO_APIC) {
                                disable_8259A_irq(0);
                                setup_nmi();
                                enable_8259A_irq(0);
                                check_nmi_watchdog();
                        }
                        return;
                }
                clear_IO_APIC_pin(0, pin1);
                printk(KERN_ERR "..MP-BIOS bug: 8254 timer not connected to IO-APIC\n");
        }

        printk(KERN_INFO "...trying to set up timer (IRQ0) through the 8259A ... ");
        if (pin2 != -1) {
                printk("\n..... (found pin %d) ...", pin2);
                /*
                 * legacy devices should be connected to IO APIC #0
                 */
                setup_ExtINT_IRQ0_pin(pin2, vector);
                if (timer_irq_works()) {
                        printk("works.\n");
                        if (pin1 != -1)
                                replace_pin_at_irq(0, 0, pin1, 0, pin2);
                        else
                                add_pin_to_irq(0, 0, pin2);
                        if (nmi_watchdog == NMI_IO_APIC) {
                                setup_nmi();
                                check_nmi_watchdog();
                        }
                        return;
                }
                /*
                 * Cleanup, just in case ...
                 */
                clear_IO_APIC_pin(0, pin2);
        }
        printk(" failed.\n");

        if (nmi_watchdog) {
                printk(KERN_WARNING "timer doesn't work through the IO-APIC - disabling NMI Watchdog!\n");
                nmi_watchdog = 0;
        }

        printk(KERN_INFO "...trying to set up timer as Virtual Wire IRQ...");

        disable_8259A_irq(0);
        irq_desc[0].handler = &lapic_irq_type;
        apic_write_around(APIC_LVT0, APIC_DM_FIXED | vector);   /* Fixed mode */
        enable_8259A_irq(0);

        if (timer_irq_works()) {
                printk(" works.\n");
                return;
        }
        apic_write_around(APIC_LVT0, APIC_LVT_MASKED | APIC_DM_FIXED | vector);
        printk(" failed.\n");

        printk(KERN_INFO "...trying to set up timer as ExtINT IRQ...");

        init_8259A(0);
        make_8259A_irq(0);
        apic_write_around(APIC_LVT0, APIC_DM_EXTINT);

        unlock_ExtINT_logic();

        if (timer_irq_works()) {
                printk(" works.\n");
                return;
        }
        printk(" failed :(.\n");
        panic("IO-APIC + timer doesn't work! pester mingo@redhat.com");
}

/*
 *
 * IRQ's that are handled by the old PIC in all cases:
 * - IRQ2 is the cascade IRQ, and cannot be a io-apic IRQ.
 *   Linux doesn't really care, as it's not actually used
 *   for any interrupt handling anyway.
 * - There used to be IRQ13 here as well, but all
 *   MPS-compliant must not use it for FPU coupling and we
 *   want to use exception 16 anyway.  And there are
 *   systems who connect it to an I/O APIC for other uses.
 *   Thus we don't mark it special any longer.
 *
 * Additionally, something is definitely wrong with irq9
 * on PIIX4 boards.
 */
#define PIC_IRQS        (1<<2)

void __init setup_IO_APIC(void)
{
        enable_IO_APIC();

        io_apic_irqs = ~PIC_IRQS;
        printk("ENABLING IO-APIC IRQs\n");

        /*
         * Set up the IO-APIC IRQ routing table by parsing the MP-BIOS
         * mptable:
         */
        setup_ioapic_ids_from_mpc();
        sync_Arb_IDs();
        setup_IO_APIC_irqs();
        init_IO_APIC_traps();
        check_timer();
        print_IO_APIC();
}