Import 2.1.116pre2

[davej-history.git] / arch / i386 / kernel / io_apic.c

/*
 *      Intel IO-APIC support for multi-Pentium hosts.
 *
 *      Copyright (C) 1997, 1998 Ingo Molnar, Hajnalka Szabo
 *
 *      Many thanks to Stig Venaas for trying out countless experimental
 *      patches and reporting/debugging problems patiently!
 */

#include <linux/sched.h>
#include <linux/smp_lock.h>
#include <linux/init.h>
#include <linux/delay.h>
#include <asm/io.h>

#include "irq.h"

/*
 * volatile is justified in this case, IO-APIC register contents
 * might change spontaneously, GCC should not cache it
 */
#define IO_APIC_BASE ((volatile int *)fix_to_virt(FIX_IO_APIC_BASE))

/*
 * The structure of the IO-APIC:
 */

struct IO_APIC_reg_00 {
        __u32   __reserved_2    : 24,
                ID              :  4,
                __reserved_1    :  4;
} __attribute__ ((packed));

struct IO_APIC_reg_01 {
        __u32   version         :  8,
                __reserved_2    :  8,
                entries         :  8,
                __reserved_1    :  8;
} __attribute__ ((packed));

struct IO_APIC_reg_02 {
        __u32   __reserved_2    : 24,
                arbitration     :  4,
                __reserved_1    :  4;
} __attribute__ ((packed));

/*
 * # of IRQ routing registers
 */
int nr_ioapic_registers = 0;

enum ioapic_irq_destination_types {
        dest_Fixed = 0,
        dest_LowestPrio = 1,
        dest_ExtINT = 7
};

struct IO_APIC_route_entry {
        __u32   vector          :  8,
                delivery_mode   :  3,   /* 000: FIXED
                                         * 001: lowest prio
                                         * 111: ExtINT
                                         */
                dest_mode       :  1,   /* 0: physical, 1: logical */
                delivery_status :  1,
                polarity        :  1,
                irr             :  1,
                trigger         :  1,   /* 0: edge, 1: level */
                mask            :  1,   /* 0: enabled, 1: disabled */
                __reserved_2    : 15;

        union {         struct { __u32
                                        __reserved_1    : 24,
                                        physical_dest   :  4,
                                        __reserved_2    :  4;
                        } physical;

                        struct { __u32
                                        __reserved_1    : 24,
                                        logical_dest    :  8;
                        } logical;
        } dest;

} __attribute__ ((packed));

/*
 * MP-BIOS irq configuration table structures:
 */

enum mp_irq_source_types {
        mp_INT = 0,
        mp_NMI = 1,
        mp_SMI = 2,
        mp_ExtINT = 3
};

int mp_irq_entries = 0;                         /* # of MP IRQ source entries */
struct mpc_config_intsrc mp_irqs[MAX_IRQ_SOURCES];
                                                /* MP IRQ source entries */
int mpc_default_type = 0;                       /* non-0 if default (table-less)
                                                   MP configuration */


/*
 * This is performance-critical, we want to do it O(1)
 */
static int irq_2_pin[NR_IRQS];

static inline unsigned int io_apic_read(unsigned int reg)
{
        *IO_APIC_BASE = reg;
        return *(IO_APIC_BASE+4);
}

static inline void io_apic_write(unsigned int reg, unsigned int value)
{
        *IO_APIC_BASE = reg;
        *(IO_APIC_BASE+4) = value;
}

/*
 * Synchronize the IO-APIC and the CPU by doing
 * a dummy read from the IO-APIC
 */
static inline void io_apic_sync(void)
{
        (void) *(IO_APIC_BASE+4);
}

/*
 * We disable IO-APIC IRQs by setting their 'destination CPU mask' to
 * zero. Trick, trick.
 */
static inline void disable_IO_APIC_irq(unsigned int irq)
{
        int pin = irq_2_pin[irq];
        struct IO_APIC_route_entry entry;

        if (pin != -1) {
                *(((int *)&entry) + 1) = io_apic_read(0x11 + pin * 2);
                entry.dest.logical.logical_dest = 0x0;
                io_apic_write(0x11 + 2 * pin, *(((int *)&entry) + 1));
                io_apic_sync();
        }
}

static inline void enable_IO_APIC_irq(unsigned int irq)
{
        int pin = irq_2_pin[irq];
        struct IO_APIC_route_entry entry;

        if (pin != -1) {
                *(((int *)&entry) + 1) = io_apic_read(0x11 + pin * 2);
                entry.dest.logical.logical_dest = 0xff;
                io_apic_write(0x11 + 2 * pin, *(((int *)&entry) + 1));
        }
}

static inline void mask_IO_APIC_irq(unsigned int irq)
{
        int pin = irq_2_pin[irq];
        struct IO_APIC_route_entry entry;

        if (pin != -1) {
                *(((int *)&entry) + 0) = io_apic_read(0x10 + pin * 2);
                entry.mask = 1;
                io_apic_write(0x10 + 2 * pin, *(((int *)&entry) + 0));
                io_apic_sync();
        }
}

static inline void unmask_IO_APIC_irq(unsigned int irq)
{
        int pin = irq_2_pin[irq];
        struct IO_APIC_route_entry entry;

        if (pin != -1) {
                *(((int *)&entry) + 0) = io_apic_read(0x10 + pin * 2);
                entry.mask = 0;
                io_apic_write(0x10 + 2 * pin, *(((int *)&entry) + 0));
        }
}

static void __init clear_IO_APIC_pin(unsigned int pin)
{
        struct IO_APIC_route_entry entry;

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


/*
 * 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;

void __init ioapic_pirq_setup(char *str, int *ints)
{
        int i, max;

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

        if (!ints) {
                pirqs_enabled = 0;
                printk("PIRQ redirection, trusting MP-BIOS.\n");

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

/*
 * Find the IRQ entry number of a certain pin.
 */
static int __init find_irq_entry(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_dstirq == pin))

                        return i;

        return -1;
}

/*
 * Find the pin to which IRQ0 (ISA) is connected
 */
static int __init find_timer_pin(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_irqs[i].mpc_irqtype == type) &&
                    (mp_irqs[i].mpc_srcbusirq == 0x00))

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

/*
 * Find a specific PCI IRQ entry.
 * Not an initfunc, possibly needed by modules
 */
int IO_APIC_get_PCI_irq_vector(int bus, int slot, int pci_pin)
{
        int i;

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

                if (IO_APIC_IRQ(mp_irqs[i].mpc_dstirq) &&
                    (mp_bus_id_to_type[lbus] == MP_BUS_PCI) &&
                    !mp_irqs[i].mpc_irqtype &&
                    (bus == mp_bus_id_to_pci_bus[mp_irqs[i].mpc_srcbus]) &&
                    (slot == ((mp_irqs[i].mpc_srcbusirq >> 2) & 0x1f)) &&
                    (pci_pin == (mp_irqs[i].mpc_srcbusirq & 3)))

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

/*
 * There are broken mptables which register ISA+high-active+level IRQs,
 * these are illegal and are converted here to ISA+high-active+edge
 * IRQ sources. Careful, ISA+low-active+level is another broken entry
 * type, it represents PCI IRQs 'embedded into an ISA bus', they have
 * to be accepted. Yes, ugh.
 */

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 = 0;
                                        break;
                                }
                                case MP_BUS_PCI: /* PCI pin */
                                {
                                        polarity = 1;
                                        break;
                                }
                                default:
                                {
                                        printk("broken BIOS!!\n");
                                        polarity = 1;
                                        break;
                                }
                        }
                        break;
                }
                case 1: /* high active */
                {
                        polarity = 0;
                        break;
                }
                case 2: /* reserved */
                {
                        printk("broken BIOS!!\n");
                        polarity = 1;
                        break;
                }
                case 3: /* low active */
                {
                        polarity = 1;
                        break;
                }
                default: /* invalid */
                {
                        printk("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, edge */
                                {
                                        trigger = 0;
                                        break;
                                }
                                case MP_BUS_PCI: /* PCI pin, level */
                                {
                                        trigger = 1;
                                        break;
                                }
                                default:
                                {
                                        printk("broken BIOS!!\n");
                                        trigger = 1;
                                        break;
                                }
                        }
                        break;
                }
                case 1: /* edge */
                {
                        trigger = 0;
                        break;
                }
                case 2: /* reserved */
                {
                        printk("broken BIOS!!\n");
                        trigger = 1;
                        break;
                }
                case 3: /* level */
                {
                        trigger = 1;
                        break;
                }
                default: /* invalid */
                {
                        printk("broken BIOS!!\n");
                        trigger = 0;
                        break;
                }
        }
        return trigger;
}

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

        if ( (mp_bus_id_to_type[bus] == MP_BUS_ISA) &&
                (polarity == 0) /* active-high */ &&
                (trigger == 1) /* level */ )

                return 1; /* broken */

        return 0;
}

static inline int irq_polarity(int idx)
{
        /*
         * There are no known BIOS bugs wrt polarity.                yet.
         */
        return MPBIOS_polarity(idx);
}

static inline int irq_trigger(int idx)
{
        int trigger = MPBIOS_trigger(idx);

        if (trigger_flag_broken(idx))
                trigger = 0;
        return trigger;
}

static int __init pin_2_irq(int idx, int pin)
{
        int irq;
        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("broken BIOS or MPTABLE parser, ayiee!!\n");

        switch (mp_bus_id_to_type[bus])
        {
                case MP_BUS_ISA: /* ISA pin */
                {
                        irq = mp_irqs[idx].mpc_srcbusirq;
                        break;
                }
                case MP_BUS_PCI: /* PCI pin */
                {
                        /*
                         * PCI IRQs are 'directly mapped'
                         */
                        irq = pin;
                        break;
                }
                default:
                {
                        printk("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("disabling PIRQ%d\n", pin-16);
                        } else {
                                irq = pirq_entries[pin-16];
                                printk("using PIRQ%d -> IRQ %d\n",
                                                pin-16, irq);
                        }
                }
        }
        return irq;
}

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

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

static int __init assign_irq_vector(int irq)
{
        static int current_vector = IRQ0_TRAP_VECTOR, offset = 0;
        if (IO_APIC_VECTOR(irq) > 0)
                return IO_APIC_VECTOR(irq);
        current_vector += 8;
        if (current_vector > 0xFE) {
                offset++;
                current_vector = IRQ0_TRAP_VECTOR + offset;
                printk("WARNING: ASSIGN_IRQ_VECTOR wrapped back to %02X\n",
                       current_vector);
        }
        IO_APIC_VECTOR(irq) = current_vector;
        return current_vector;
}

void __init setup_IO_APIC_irqs(void)
{
        struct IO_APIC_route_entry entry;
        int pin, idx, bus, irq, first_notcon = 1;

        printk("init IO_APIC IRQs\n");

        for (pin = 0; pin < nr_ioapic_registers; pin++) {

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

                entry.delivery_mode = dest_LowestPrio;
                entry.dest_mode = 1;                    /* logical delivery */
                entry.mask = 0;                         /* enable IRQ */
                entry.dest.logical.logical_dest = 0xff; /* all CPUs */

                idx = find_irq_entry(pin,mp_INT);
                if (idx == -1) {
                        if (first_notcon) {
                                printk(" IO-APIC pin %d", pin);
                                first_notcon = 0;
                        } else
                                printk(", %d", pin);
                        continue;
                }

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

                irq = pin_2_irq(idx,pin);
                irq_2_pin[irq] = pin;

                if (!IO_APIC_IRQ(irq))
                        continue;

                entry.vector = assign_irq_vector(irq);

                bus = mp_irqs[idx].mpc_srcbus;

                if (trigger_flag_broken (idx))
                        printk("broken BIOS, changing pin %d to edge\n", pin);

                io_apic_write(0x10+2*pin, *(((int *)&entry)+0));
                io_apic_write(0x11+2*pin, *(((int *)&entry)+1));
        }

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

void __init setup_IO_APIC_irq_ISA_default(unsigned int irq)
{
        struct IO_APIC_route_entry entry;

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

        entry.delivery_mode = dest_LowestPrio;          /* lowest prio */
        entry.dest_mode = 1;                            /* logical delivery */
        entry.mask = 0;                                 /* unmask IRQ now */
        entry.dest.logical.logical_dest = 0xff;         /* all CPUs */

        entry.vector = assign_irq_vector(irq);

        entry.polarity = 0;
        entry.trigger = 0;

        io_apic_write(0x10+2*irq, *(((int *)&entry)+0));
        io_apic_write(0x11+2*irq, *(((int *)&entry)+1));
}

/*
 * Set up a certain pin as ExtINT delivered interrupt
 */
void __init setup_ExtINT_pin(unsigned int pin)
{
        struct IO_APIC_route_entry entry;

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

        entry.delivery_mode = dest_ExtINT;
        entry.dest_mode = 1;                            /* logical delivery */
        entry.mask = 0;                                 /* unmask IRQ now */
        entry.dest.logical.logical_dest = 0x01;         /* all CPUs */

        entry.vector = 0;                               /* it's ignored */

        entry.polarity = 0;
        entry.trigger = 0;

        io_apic_write(0x10+2*pin, *(((int *)&entry)+0));
        io_apic_write(0x11+2*pin, *(((int *)&entry)+1));
}

void __init UNEXPECTED_IO_APIC(void)
{
        printk(" WARNING: unexpected IO-APIC, please mail\n");
        printk("          to linux-smp@vger.rutgers.edu\n");
}

void __init print_IO_APIC(void)
{
        int i;
        struct IO_APIC_reg_00 reg_00;
        struct IO_APIC_reg_01 reg_01;
        struct IO_APIC_reg_02 reg_02;

        printk("number of MP IRQ sources: %d.\n", mp_irq_entries);
        printk("number of IO-APIC registers: %d.\n", nr_ioapic_registers);

        *(int *)&reg_00 = io_apic_read(0);
        *(int *)&reg_01 = io_apic_read(1);
        *(int *)&reg_02 = io_apic_read(2);

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

        printk(".... register #00: %08X\n", *(int *)&reg_00);
        printk(".......    : physical APIC id: %02X\n", reg_00.ID);
        if (reg_00.__reserved_1 || reg_00.__reserved_2)
                UNEXPECTED_IO_APIC();

        printk(".... register #01: %08X\n", *(int *)&reg_01);
        printk(".......     : max redirection entries: %04X\n", reg_01.entries);
        if (    (reg_01.entries != 0x0f) && /* ISA-only Neptune boards */
                (reg_01.entries != 0x17)    /* ISA+PCI boards */
        )
                UNEXPECTED_IO_APIC();
        if (reg_01.entries == 0x0f)
                printk(".......       [IO-APIC cannot route PCI PIRQ 0-3]\n");

        printk(".......     : IO APIC version: %04X\n", reg_01.version);
        if (    (reg_01.version != 0x10) && /* oldest IO-APICs */
                (reg_01.version != 0x11)  /* my IO-APIC */
        )
                UNEXPECTED_IO_APIC();
        if (reg_01.__reserved_1 || reg_01.__reserved_2)
                UNEXPECTED_IO_APIC();

        printk(".... register #02: %08X\n", *(int *)&reg_02);
        printk(".......     : arbitration: %02X\n", reg_02.arbitration);
        if (reg_02.__reserved_1 || reg_02.__reserved_2)
                UNEXPECTED_IO_APIC();

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

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

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

                *(((int *)&entry)+0) = io_apic_read(0x10+i*2);
                *(((int *)&entry)+1) = io_apic_read(0x11+i*2);

                printk(" %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("IRQ to pin mappings:\n");
        for (i = 0; i < NR_IRQS; i++)
                printk("%d->%d ", i, irq_2_pin[i]);
        printk("\n");

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

        return;
}

static void __init init_sym_mode(void)
{
        int i, pin;

        for (i = 0; i < NR_IRQS; i++)
                irq_2_pin[i] = -1;
        if (!pirqs_enabled)
                for (i = 0; i < MAX_PIRQS; i++)
                        pirq_entries[i] =- 1;

        printk("enabling symmetric IO mode... ");

        outb(0x70, 0x22);
        outb(0x01, 0x23);

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

        /*
         * The number of IO-APIC IRQ registers (== #pins):
         */
        {
                struct IO_APIC_reg_01 reg_01;

                *(int *)&reg_01 = io_apic_read(1);
                nr_ioapic_registers = reg_01.entries+1;
        }

        /*
         * Do not trust the IO-APIC being empty at bootup
         */
        for (pin = 0; pin < nr_ioapic_registers; pin++)
                clear_IO_APIC_pin(pin);
}

/*
 * Not an initfunc, needed by the reboot code
 */
void init_pic_mode(void)
{
        printk("disabling symmetric IO mode... ");
                outb_p(0x70, 0x22);
                outb_p(0x00, 0x23);
        printk("...done.\n");
}

char ioapic_OEM_ID [16];
char ioapic_Product_ID [16];

struct ioapic_list_entry {
        char * oem_id;
        char * product_id;
};

struct ioapic_list_entry __initdata ioapic_whitelist [] = {

        { "INTEL   "    ,       "PR440FX     "  },
        { "INTEL   "    ,       "82440FX     "  },
        { "AIR     "    ,       "KDI         "  },
        { 0             ,       0               }
};

struct ioapic_list_entry __initdata ioapic_blacklist [] = {

        { "OEM00000"    ,       "PROD00000000"  },
        { 0             ,       0               }
};

static int __init in_ioapic_list(struct ioapic_list_entry * table)
{
        for ( ; table->oem_id ; table++)
                if ((!strcmp(table->oem_id,ioapic_OEM_ID)) &&
                    (!strcmp(table->product_id,ioapic_Product_ID)))
                        return 1;
        return 0;
}

static int __init ioapic_whitelisted(void)
{
/*
 * Right now, whitelist everything to see whether the new parsing
 * routines really do work for everybody.
 */
#if 1
        return 1;
#else
        return in_ioapic_list(ioapic_whitelist);
#endif
}

static int __init ioapic_blacklisted(void)
{
        return in_ioapic_list(ioapic_blacklist);
}

static void __init setup_ioapic_id(void)
{
        struct IO_APIC_reg_00 reg_00;

        /*
         * 'default' mptable configurations mean a hardwired setup,
         * 2 CPUs, 16 APIC registers. IO-APIC ID is usually set to 0,
         * setting it to ID 2 should be fine.
         */

        /*
         * Sanity check, is ID 2 really free? Every APIC in the
         * system must have a unique ID or we get lots of nice
         * 'stuck on smp_invalidate_needed IPI wait' messages.
         */
        if (cpu_present_map & (1<<0x2))
                panic("APIC ID 2 already used");

        /*
         * Set the ID
         */
        *(int *)&reg_00 = io_apic_read(0);
        printk("...changing IO-APIC physical APIC ID to 2...\n");
        reg_00.ID = 0x2;
        io_apic_write(0, *(int *)&reg_00);

        /*
         * Sanity check
         */
        *(int *)&reg_00 = io_apic_read(0);
        if (reg_00.ID != 0x2)
                panic("could not set ID");
}

static void __init construct_default_ISA_mptable(void)
{
        int i, pos = 0;

        for (i = 0; i < 16; i++) {
                if (!IO_APIC_IRQ(i))
                        continue;

                mp_irqs[pos].mpc_irqtype = 0;
                mp_irqs[pos].mpc_irqflag = 0;
                mp_irqs[pos].mpc_srcbus = 0;
                mp_irqs[pos].mpc_srcbusirq = i;
                mp_irqs[pos].mpc_dstapic = 0;
                mp_irqs[pos].mpc_dstirq = i;
                pos++;
        }
        mp_irq_entries = pos;
        mp_bus_id_to_type[0] = MP_BUS_ISA;

        /*
         * MP specification 1.4 defines some extra rules for default
         * configurations, fix them up here:
         */
        
        switch (mpc_default_type)
        {
                case 2:
                        break;
                default:
                /*
                 * pin 2 is IRQ0:
                 */
                        mp_irqs[0].mpc_dstirq = 2;
        }

        setup_ioapic_id();
}

/*
 * 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();
        udelay(10*10000);

        if (jiffies-t1>1)
                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.
 */
static inline void self_IPI(unsigned int irq)
{
        irq_desc_t *desc = irq_desc + irq;

        if (desc->events && !desc->ipi) {
                desc->ipi = 1;
                send_IPI(APIC_DEST_SELF, IO_APIC_VECTOR(irq));
        }
}

/*
 * Edge triggered needs to resend any interrupt
 * that was delayed.
 */
static void enable_edge_ioapic_irq(unsigned int irq)
{
        self_IPI(irq);
        enable_IO_APIC_irq(irq);
}

static void disable_edge_ioapic_irq(unsigned int irq)
{
        disable_IO_APIC_irq(irq);
}

/*
 * Level triggered interrupts can just be masked.
 */
static void enable_level_ioapic_irq(unsigned int irq)
{
        unmask_IO_APIC_irq(irq);
}

static void disable_level_ioapic_irq(unsigned int irq)
{
        mask_IO_APIC_irq(irq);
}

static void do_edge_ioapic_IRQ(unsigned int irq, int cpu, struct pt_regs * regs)
{
        irq_desc_t *desc = irq_desc + irq;
        struct irqaction * action;

        spin_lock(&irq_controller_lock);

        /*
         * Edge triggered IRQs can be acknowledged immediately
         * and do not need to be masked.
         */
        ack_APIC_irq();
        desc->ipi = 0;
        desc->events = 1;

        /*
         * If the IRQ is disabled for whatever reason, we cannot
         * use the action we have.
         */
        action = NULL;
        if (!(desc->status & (IRQ_DISABLED | IRQ_INPROGRESS))) {
                action = desc->action;
                desc->status = IRQ_INPROGRESS;
                desc->events = 0;
        }
        spin_unlock(&irq_controller_lock);

        /*
         * If there is no IRQ handler or it was disabled, exit early.
         */
        if (!action)
                return;

        irq_enter(cpu, irq);

        /*
         * Edge triggered interrupts need to remember
         * pending events.
         */
        for (;;) {
                int pending;

                handle_IRQ_event(irq, regs);

                spin_lock(&irq_controller_lock);
                pending = desc->events;
                desc->events = 0;
                if (!pending)
                        break;
                spin_unlock(&irq_controller_lock);
        }
        desc->status &= IRQ_DISABLED;
        spin_unlock(&irq_controller_lock);

        irq_exit(cpu, irq);
}

static void do_level_ioapic_IRQ(unsigned int irq, int cpu,
                                struct pt_regs * regs)
{
        irq_desc_t *desc = irq_desc + irq;
        struct irqaction * action;

        spin_lock(&irq_controller_lock);
        /*
         * In the level triggered case we first disable the IRQ
         * in the IO-APIC, then we 'early ACK' the IRQ, then we
         * handle it and enable the IRQ when finished.
         *
         * disable has to happen before the ACK, to avoid IRQ storms.
         * So this all has to be within the spinlock.
         */
        mask_IO_APIC_irq(irq);

        desc->ipi = 0;

        /*
         * If the IRQ is disabled for whatever reason, we must
         * not enter the IRQ action.
         */
        action = NULL;
        if (!(desc->status & (IRQ_DISABLED | IRQ_INPROGRESS))) {
                action = desc->action;
                desc->status = IRQ_INPROGRESS;
        }

        ack_APIC_irq();
        spin_unlock(&irq_controller_lock);

        /* Exit early if we had no action or it was disabled */
        if (!action)
                return;

        irq_enter(cpu, irq);

        handle_IRQ_event(irq, regs);

        spin_lock(&irq_controller_lock);
        desc->status &= ~IRQ_INPROGRESS;
        if (!desc->status)
                unmask_IO_APIC_irq(irq);
        spin_unlock(&irq_controller_lock);

        irq_exit(cpu, irq);
}

/*
 * 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",
        do_edge_ioapic_IRQ,
        enable_edge_ioapic_irq,
        disable_edge_ioapic_irq
};

static struct hw_interrupt_type ioapic_level_irq_type = {
        "IO-APIC-level",
        do_level_ioapic_IRQ,
        enable_level_ioapic_irq,
        disable_level_ioapic_irq
};

static inline void init_IO_APIC_traps(void)
{
        int i;
        /*
         * 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 (i = 0; i < NR_IRQS ; i++) {
                if (IO_APIC_IRQ(i)) {
                        if (IO_APIC_irq_trigger(i))
                                irq_desc[i].handler = &ioapic_level_irq_type;
                        else
                                irq_desc[i].handler = &ioapic_edge_irq_type;
                        /*
                         * disable it in the 8259A:
                         */
                        if (i < 16)
                                disable_8259A_irq(i);
                }
        }
}

/*
 * 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)
{
        int pin1, pin2;

        pin1 = find_timer_pin(mp_INT);
        pin2 = find_timer_pin(mp_ExtINT);

        if (!timer_irq_works()) {
                if (pin1 != -1)
                        printk("..MP-BIOS bug: 8254 timer not connected to IO-APIC\n");
                printk("...trying to set up timer as ExtINT... ");

                if (pin2 != -1) {
                        printk(".. (found pin %d) ...", pin2);
                        setup_ExtINT_pin(pin2);
                        make_8259A_irq(0);
                }

                if (!timer_irq_works()) {
                        printk(" failed.\n");
                        printk("...trying to set up timer as BP IRQ...");
                        /*
                         * Just in case ...
                         */
                        if (pin1 != -1)
                                clear_IO_APIC_pin(pin1);
                        if (pin2 != -1)
                                clear_IO_APIC_pin(pin2);

                        make_8259A_irq(0);

                        if (!timer_irq_works()) {
                                printk(" failed.\n");
                                panic("IO-APIC + timer doesn't work!");
                        }
                }
                printk(" works.\n");
        }
}

void __init setup_IO_APIC(void)
{
        init_sym_mode();

        /*
         * Determine the range of IRQs handled by the IO-APIC. The
         * following boards can be fully enabled:
         *
         * - whitelisted ones
         * - those which have no PCI pins connected
         * - those for which the user has specified a pirq= parameter
         */
        if (    ioapic_whitelisted() ||
                (nr_ioapic_registers == 16) ||
                pirqs_enabled)
        {
                printk("ENABLING IO-APIC IRQs\n");
                io_apic_irqs = ~((1<<2)|(1<<9)|(1<<13));
        } else {
                if (ioapic_blacklisted())
                        printk(" blacklisted board, DISABLING IO-APIC IRQs\n");
                else
                        printk(" unlisted board, DISABLING IO-APIC IRQs\n");

                printk(" see Documentation/IO-APIC.txt to enable them\n");
                io_apic_irqs = 0;
        }

        /*
         * If there are no explicit MP IRQ entries, it's either one of the
         * default configuration types or we are broken. In both cases it's
         * fine to set up most of the low 16 IO-APIC pins to ISA defaults.
         */
        if (!mp_irq_entries) {
                printk("no explicit IRQ entries, using default mptable\n");
                construct_default_ISA_mptable();
        }

        init_IO_APIC_traps();

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