io_apic.c

/*
 *	Intel IO-APIC support for multi-Pentium hosts.
 *
 *	Copyright (C) 1997, 1998, 1999, 2000, 2009 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
 *	Paul Diefenbaugh	:	Added full ACPI support
 */

#include <linux/mm.h>
#include <linux/interrupt.h>
#include <linux/init.h>
#include <linux/delay.h>
#include <linux/sched.h>
#include <linux/pci.h>
#include <linux/mc146818rtc.h>
#include <linux/compiler.h>
#include <linux/acpi.h>
#include <linux/module.h>
#include <linux/sysdev.h>
#include <linux/msi.h>
#include <linux/htirq.h>
#include <linux/freezer.h>
#include <linux/kthread.h>
#include <linux/jiffies.h>	/* time_after() */
#include <linux/slab.h>
#ifdef CONFIG_ACPI
#include <acpi/acpi_bus.h>
#endif
#include <linux/bootmem.h>
#include <linux/dmar.h>
#include <linux/hpet.h>

#include <asm/idle.h>
#include <asm/io.h>
#include <asm/smp.h>
#include <asm/cpu.h>
#include <asm/desc.h>
#include <asm/proto.h>
#include <asm/acpi.h>
#include <asm/dma.h>
#include <asm/timer.h>
#include <asm/i8259.h>
#include <asm/nmi.h>
#include <asm/msidef.h>
#include <asm/hypertransport.h>
#include <asm/setup.h>
#include <asm/irq_remapping.h>
#include <asm/hpet.h>
#include <asm/hw_irq.h>

#include <asm/apic.h>

#define __apicdebuginit(type) static type __init
#define for_each_irq_pin(entry, head) \
	for (entry = head; entry; entry = entry->next)

/*
 *      Is the SiS APIC rmw bug present ?
 *      -1 = don't know, 0 = no, 1 = yes
 */
int sis_apic_bug = -1;

static DEFINE_RAW_SPINLOCK(ioapic_lock);
static DEFINE_RAW_SPINLOCK(vector_lock);

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

/* I/O APIC entries */
struct mpc_ioapic mp_ioapics[MAX_IO_APICS];
int nr_ioapics;

/* IO APIC gsi routing info */
struct mp_ioapic_gsi  mp_gsi_routing[MAX_IO_APICS];

/* The one past the highest gsi number used */
u32 gsi_top;

/* MP IRQ source entries */
struct mpc_intsrc mp_irqs[MAX_IRQ_SOURCES];

/* # of MP IRQ source entries */
int mp_irq_entries;

/* GSI interrupts */
static int nr_irqs_gsi = NR_IRQS_LEGACY;

#if defined (CONFIG_MCA) || defined (CONFIG_EISA)
int mp_bus_id_to_type[MAX_MP_BUSSES];
#endif

DECLARE_BITMAP(mp_bus_not_pci, MAX_MP_BUSSES);

int skip_ioapic_setup;

void arch_disable_smp_support(void)
{
#ifdef CONFIG_PCI
	noioapicquirk = 1;
	noioapicreroute = -1;
#endif
	skip_ioapic_setup = 1;
}

static int __init parse_noapic(char *str)
{
	/* disable IO-APIC */
	arch_disable_smp_support();
	return 0;
}
early_param("noapic", parse_noapic);

struct irq_pin_list {
	int apic, pin;
	struct irq_pin_list *next;
};

static struct irq_pin_list *get_one_free_irq_2_pin(int node)
{
	struct irq_pin_list *pin;

	pin = kzalloc_node(sizeof(*pin), GFP_ATOMIC, node);

	return pin;
}

/* irq_cfg is indexed by the sum of all RTEs in all I/O APICs. */
#ifdef CONFIG_SPARSE_IRQ
static struct irq_cfg irq_cfgx[NR_IRQS_LEGACY];
#else
static struct irq_cfg irq_cfgx[NR_IRQS];
#endif

int __init arch_early_irq_init(void)
{
	struct irq_cfg *cfg;
	struct irq_desc *desc;
	int count;
	int node;
	int i;

	if (!legacy_pic->nr_legacy_irqs) {
		nr_irqs_gsi = 0;
		io_apic_irqs = ~0UL;
	}

	cfg = irq_cfgx;
	count = ARRAY_SIZE(irq_cfgx);
	node = cpu_to_node(0);

	for (i = 0; i < count; i++) {
		desc = irq_to_desc(i);
		desc->chip_data = &cfg[i];
		zalloc_cpumask_var_node(&cfg[i].domain, GFP_NOWAIT, node);
		zalloc_cpumask_var_node(&cfg[i].old_domain, GFP_NOWAIT, node);
		/*
		 * For legacy IRQ's, start with assigning irq0 to irq15 to
		 * IRQ0_VECTOR to IRQ15_VECTOR on cpu 0.
		 */
		if (i < legacy_pic->nr_legacy_irqs) {
			cfg[i].vector = IRQ0_VECTOR + i;
			cpumask_set_cpu(0, cfg[i].domain);
		}
	}

	return 0;
}

#ifdef CONFIG_SPARSE_IRQ
struct irq_cfg *irq_cfg(unsigned int irq)
{
	struct irq_cfg *cfg = NULL;
	struct irq_desc *desc;

	desc = irq_to_desc(irq);
	if (desc)
		cfg = get_irq_desc_chip_data(desc);

	return cfg;
}

static struct irq_cfg *get_one_free_irq_cfg(int node)
{
	struct irq_cfg *cfg;

	cfg = kzalloc_node(sizeof(*cfg), GFP_ATOMIC, node);
	if (cfg) {
		if (!zalloc_cpumask_var_node(&cfg->domain, GFP_ATOMIC, node)) {
			kfree(cfg);
			cfg = NULL;
		} else if (!zalloc_cpumask_var_node(&cfg->old_domain,
							  GFP_ATOMIC, node)) {
			free_cpumask_var(cfg->domain);
			kfree(cfg);
			cfg = NULL;
		}
	}

	return cfg;
}

int arch_init_chip_data(struct irq_desc *desc, int node)
{
	struct irq_cfg *cfg;

	cfg = get_irq_desc_chip_data(desc);
	if (!cfg) {
		cfg = get_one_free_irq_cfg(node);
		desc->chip_data = cfg;
		if (!cfg) {
			printk(KERN_ERR "can not alloc irq_cfg\n");
			BUG_ON(1);
		}
	}

	return 0;
}

/* for move_irq_desc */
static void
init_copy_irq_2_pin(struct irq_cfg *old_cfg, struct irq_cfg *cfg, int node)
{
	struct irq_pin_list *old_entry, *head, *tail, *entry;

	cfg->irq_2_pin = NULL;
	old_entry = old_cfg->irq_2_pin;
	if (!old_entry)
		return;

	entry = get_one_free_irq_2_pin(node);
	if (!entry)
		return;

	entry->apic	= old_entry->apic;
	entry->pin	= old_entry->pin;
	head		= entry;
	tail		= entry;
	old_entry	= old_entry->next;
	while (old_entry) {
		entry = get_one_free_irq_2_pin(node);
		if (!entry) {
			entry = head;
			while (entry) {
				head = entry->next;
				kfree(entry);
				entry = head;
			}
			/* still use the old one */
			return;
		}
		entry->apic	= old_entry->apic;
		entry->pin	= old_entry->pin;
		tail->next	= entry;
		tail		= entry;
		old_entry	= old_entry->next;
	}

	tail->next = NULL;
	cfg->irq_2_pin = head;
}

static void free_irq_2_pin(struct irq_cfg *old_cfg, struct irq_cfg *cfg)
{
	struct irq_pin_list *entry, *next;

	if (old_cfg->irq_2_pin == cfg->irq_2_pin)
		return;

	entry = old_cfg->irq_2_pin;

	while (entry) {
		next = entry->next;
		kfree(entry);
		entry = next;
	}
	old_cfg->irq_2_pin = NULL;
}

void arch_init_copy_chip_data(struct irq_desc *old_desc,
				 struct irq_desc *desc, int node)
{
	struct irq_cfg *cfg;
	struct irq_cfg *old_cfg;

	cfg = get_one_free_irq_cfg(node);

	if (!cfg)
		return;

	desc->chip_data = cfg;

	old_cfg = old_desc->chip_data;

	cfg->vector = old_cfg->vector;
	cfg->move_in_progress = old_cfg->move_in_progress;
	cpumask_copy(cfg->domain, old_cfg->domain);
	cpumask_copy(cfg->old_domain, old_cfg->old_domain);

	init_copy_irq_2_pin(old_cfg, cfg, node);
}

static void free_irq_cfg(struct irq_cfg *cfg)
{
	free_cpumask_var(cfg->domain);
	free_cpumask_var(cfg->old_domain);
	kfree(cfg);
}

void arch_free_chip_data(struct irq_desc *old_desc, struct irq_desc *desc)
{
	struct irq_cfg *old_cfg, *cfg;

	old_cfg = get_irq_desc_chip_data(old_desc);
	cfg = get_irq_desc_chip_data(desc);

	if (old_cfg == cfg)
		return;

	if (old_cfg) {
		free_irq_2_pin(old_cfg, cfg);
		free_irq_cfg(old_cfg);
		old_desc->chip_data = NULL;
	}
}
/* end for move_irq_desc */

#else
struct irq_cfg *irq_cfg(unsigned int irq)
{
	return irq < nr_irqs ? irq_cfgx + irq : NULL;
}

#endif

struct io_apic {
	unsigned int index;
	unsigned int unused[3];
	unsigned int data;
	unsigned int unused2[11];
	unsigned int eoi;
};

static __attribute_const__ struct io_apic __iomem *io_apic_base(int idx)
{
	return (void __iomem *) __fix_to_virt(FIX_IO_APIC_BASE_0 + idx)
		+ (mp_ioapics[idx].apicaddr & ~PAGE_MASK);
}

static inline void io_apic_eoi(unsigned int apic, unsigned int vector)
{
	struct io_apic __iomem *io_apic = io_apic_base(apic);
	writel(vector, &io_apic->eoi);
}

static inline unsigned int io_apic_read(unsigned int apic, unsigned int reg)
{
	struct io_apic __iomem *io_apic = io_apic_base(apic);
	writel(reg, &io_apic->index);
	return readl(&io_apic->data);
}

static inline void io_apic_write(unsigned int apic, unsigned int reg, unsigned int value)
{
	struct io_apic __iomem *io_apic = io_apic_base(apic);
	writel(reg, &io_apic->index);
	writel(value, &io_apic->data);
}

/*
 * Re-write a value: to be used for read-modify-write
 * cycles where the read already set up the index register.
 *
 * Older SiS APIC requires we rewrite the index register
 */
static inline void io_apic_modify(unsigned int apic, unsigned int reg, unsigned int value)
{
	struct io_apic __iomem *io_apic = io_apic_base(apic);

	if (sis_apic_bug)
		writel(reg, &io_apic->index);
	writel(value, &io_apic->data);
}

static bool io_apic_level_ack_pending(struct irq_cfg *cfg)
{
	struct irq_pin_list *entry;
	unsigned long flags;

	raw_spin_lock_irqsave(&ioapic_lock, flags);
	for_each_irq_pin(entry, cfg->irq_2_pin) {
		unsigned int reg;
		int pin;

		pin = entry->pin;
		reg = io_apic_read(entry->apic, 0x10 + pin*2);
		/* Is the remote IRR bit set? */
		if (reg & IO_APIC_REDIR_REMOTE_IRR) {
			raw_spin_unlock_irqrestore(&ioapic_lock, flags);
			return true;
		}
	}
	raw_spin_unlock_irqrestore(&ioapic_lock, flags);

	return false;
}

union entry_union {
	struct { u32 w1, w2; };
	struct IO_APIC_route_entry entry;
};

static struct IO_APIC_route_entry ioapic_read_entry(int apic, int pin)
{
	union entry_union eu;
	unsigned long flags;
	raw_spin_lock_irqsave(&ioapic_lock, flags);
	eu.w1 = io_apic_read(apic, 0x10 + 2 * pin);
	eu.w2 = io_apic_read(apic, 0x11 + 2 * pin);
	raw_spin_unlock_irqrestore(&ioapic_lock, flags);
	return eu.entry;
}

/*
 * When we write a new IO APIC routing entry, we need to write the high
 * word first! If the mask bit in the low word is clear, we will enable
 * the interrupt, and we need to make sure the entry is fully populated
 * before that happens.
 */
static void
__ioapic_write_entry(int apic, int pin, struct IO_APIC_route_entry e)
{
	union entry_union eu = {{0, 0}};

	eu.entry = e;
	io_apic_write(apic, 0x11 + 2*pin, eu.w2);
	io_apic_write(apic, 0x10 + 2*pin, eu.w1);
}

void ioapic_write_entry(int apic, int pin, struct IO_APIC_route_entry e)
{
	unsigned long flags;
	raw_spin_lock_irqsave(&ioapic_lock, flags);
	__ioapic_write_entry(apic, pin, e);
	raw_spin_unlock_irqrestore(&ioapic_lock, flags);
}

/*
 * When we mask an IO APIC routing entry, we need to write the low
 * word first, in order to set the mask bit before we change the
 * high bits!
 */
static void ioapic_mask_entry(int apic, int pin)
{
	unsigned long flags;
	union entry_union eu = { .entry.mask = 1 };

	raw_spin_lock_irqsave(&ioapic_lock, flags);
	io_apic_write(apic, 0x10 + 2*pin, eu.w1);
	io_apic_write(apic, 0x11 + 2*pin, eu.w2);
	raw_spin_unlock_irqrestore(&ioapic_lock, flags);
}

/*
 * 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 int
add_pin_to_irq_node_nopanic(struct irq_cfg *cfg, int node, int apic, int pin)
{
	struct irq_pin_list **last, *entry;

	/* don't allow duplicates */
	last = &cfg->irq_2_pin;
	for_each_irq_pin(entry, cfg->irq_2_pin) {
		if (entry->apic == apic && entry->pin == pin)
			return 0;
		last = &entry->next;
	}

	entry = get_one_free_irq_2_pin(node);
	if (!entry) {
		printk(KERN_ERR "can not alloc irq_pin_list (%d,%d,%d)\n",
				node, apic, pin);
		return -ENOMEM;
	}
	entry->apic = apic;
	entry->pin = pin;

	*last = entry;
	return 0;
}

static void add_pin_to_irq_node(struct irq_cfg *cfg, int node, int apic, int pin)
{
	if (add_pin_to_irq_node_nopanic(cfg, node, apic, pin))
		panic("IO-APIC: failed to add irq-pin. Can not proceed\n");
}

/*
 * Reroute an IRQ to a different pin.
 */
static void __init replace_pin_at_irq_node(struct irq_cfg *cfg, int node,
					   int oldapic, int oldpin,
					   int newapic, int newpin)
{
	struct irq_pin_list *entry;

	for_each_irq_pin(entry, cfg->irq_2_pin) {
		if (entry->apic == oldapic && entry->pin == oldpin) {
			entry->apic = newapic;
			entry->pin = newpin;
			/* every one is different, right? */
			return;
		}
	}

	/* old apic/pin didn't exist, so just add new ones */
	add_pin_to_irq_node(cfg, node, newapic, newpin);
}

static void __io_apic_modify_irq(struct irq_pin_list *entry,
				 int mask_and, int mask_or,
				 void (*final)(struct irq_pin_list *entry))
{
	unsigned int reg, pin;

	pin = entry->pin;
	reg = io_apic_read(entry->apic, 0x10 + pin * 2);
	reg &= mask_and;
	reg |= mask_or;
	io_apic_modify(entry->apic, 0x10 + pin * 2, reg);
	if (final)
		final(entry);
}

static void io_apic_modify_irq(struct irq_cfg *cfg,
			       int mask_and, int mask_or,
			       void (*final)(struct irq_pin_list *entry))
{
	struct irq_pin_list *entry;

	for_each_irq_pin(entry, cfg->irq_2_pin)
		__io_apic_modify_irq(entry, mask_and, mask_or, final);
}

static void __mask_and_edge_IO_APIC_irq(struct irq_pin_list *entry)
{
	__io_apic_modify_irq(entry, ~IO_APIC_REDIR_LEVEL_TRIGGER,
			     IO_APIC_REDIR_MASKED, NULL);
}

static void __unmask_and_level_IO_APIC_irq(struct irq_pin_list *entry)
{
	__io_apic_modify_irq(entry, ~IO_APIC_REDIR_MASKED,
			     IO_APIC_REDIR_LEVEL_TRIGGER, NULL);
}

static void io_apic_sync(struct irq_pin_list *entry)
{
	/*
	 * Synchronize the IO-APIC and the CPU by doing
	 * a dummy read from the IO-APIC
	 */
	struct io_apic __iomem *io_apic;
	io_apic = io_apic_base(entry->apic);
	readl(&io_apic->data);
}

static void mask_ioapic(struct irq_cfg *cfg)
{
	unsigned long flags;

	raw_spin_lock_irqsave(&ioapic_lock, flags);
	io_apic_modify_irq(cfg, ~0, IO_APIC_REDIR_MASKED, &io_apic_sync);
	raw_spin_unlock_irqrestore(&ioapic_lock, flags);
}

static void mask_ioapic_irq(struct irq_data *data)
{
	mask_ioapic(data->chip_data);
}

static void __unmask_ioapic(struct irq_cfg *cfg)
{
	io_apic_modify_irq(cfg, ~IO_APIC_REDIR_MASKED, 0, NULL);
}

static void unmask_ioapic(struct irq_cfg *cfg)
{
	unsigned long flags;

	raw_spin_lock_irqsave(&ioapic_lock, flags);
	__unmask_ioapic(cfg);
	raw_spin_unlock_irqrestore(&ioapic_lock, flags);
}

static void unmask_ioapic_irq(struct irq_data *data)
{
	unmask_ioapic(data->chip_data);
}

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

	/* Check delivery_mode to be sure we're not clearing an SMI pin */
	entry = ioapic_read_entry(apic, pin);
	if (entry.delivery_mode == dest_SMI)
		return;
	/*
	 * Disable it in the IO-APIC irq-routing table:
	 */
	ioapic_mask_entry(apic, pin);
}

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);
}

#ifdef CONFIG_X86_32
/*
 * support for broken MP BIOSs, enables hand-redirection of PIRQ0-7 to
 * specific CPU-side IRQs.
 */

#define MAX_PIRQS 8
static int pirq_entries[MAX_PIRQS] = {
	[0 ... MAX_PIRQS - 1] = -1
};

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

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

	apic_printk(APIC_VERBOSE, 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++) {
		apic_printk(APIC_VERBOSE, 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);
#endif /* CONFIG_X86_32 */

struct IO_APIC_route_entry **alloc_ioapic_entries(void)
{
	int apic;
	struct IO_APIC_route_entry **ioapic_entries;

	ioapic_entries = kzalloc(sizeof(*ioapic_entries) * nr_ioapics,
				GFP_ATOMIC);
	if (!ioapic_entries)
		return 0;

	for (apic = 0; apic < nr_ioapics; apic++) {
		ioapic_entries[apic] =
			kzalloc(sizeof(struct IO_APIC_route_entry) *
				nr_ioapic_registers[apic], GFP_ATOMIC);
		if (!ioapic_entries[apic])
			goto nomem;
	}

	return ioapic_entries;

nomem:
	while (--apic >= 0)
		kfree(ioapic_entries[apic]);
	kfree(ioapic_entries);

	return 0;
}

/*
 * Saves all the IO-APIC RTE's
 */
int save_IO_APIC_setup(struct IO_APIC_route_entry **ioapic_entries)
{
	int apic, pin;

	if (!ioapic_entries)
		return -ENOMEM;

	for (apic = 0; apic < nr_ioapics; apic++) {
		if (!ioapic_entries[apic])
			return -ENOMEM;

		for (pin = 0; pin < nr_ioapic_registers[apic]; pin++)
			ioapic_entries[apic][pin] =
				ioapic_read_entry(apic, pin);
	}

	return 0;
}

/*
 * Mask all IO APIC entries.
 */
void mask_IO_APIC_setup(struct IO_APIC_route_entry **ioapic_entries)
{
	int apic, pin;

	if (!ioapic_entries)
		return;

	for (apic = 0; apic < nr_ioapics; apic++) {
		if (!ioapic_entries[apic])
			break;

		for (pin = 0; pin < nr_ioapic_registers[apic]; pin++) {
			struct IO_APIC_route_entry entry;

			entry = ioapic_entries[apic][pin];
			if (!entry.mask) {
				entry.mask = 1;
				ioapic_write_entry(apic, pin, entry);
			}
		}
	}
}

/*
 * Restore IO APIC entries which was saved in ioapic_entries.
 */
int restore_IO_APIC_setup(struct IO_APIC_route_entry **ioapic_entries)
{
	int apic, pin;

	if (!ioapic_entries)
		return -ENOMEM;

	for (apic = 0; apic < nr_ioapics; apic++) {
		if (!ioapic_entries[apic])
			return -ENOMEM;

		for (pin = 0; pin < nr_ioapic_registers[apic]; pin++)
			ioapic_write_entry(apic, pin,
					ioapic_entries[apic][pin]);
	}
	return 0;
}

void free_ioapic_entries(struct IO_APIC_route_entry **ioapic_entries)
{
	int apic;

	for (apic = 0; apic < nr_ioapics; apic++)
		kfree(ioapic_entries[apic]);

	kfree(ioapic_entries);
}

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

	for (i = 0; i < mp_irq_entries; i++)
		if (mp_irqs[i].irqtype == type &&
		    (mp_irqs[i].dstapic == mp_ioapics[apic].apicid ||
		     mp_irqs[i].dstapic == MP_APIC_ALL) &&
		    mp_irqs[i].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].srcbus;

		if (test_bit(lbus, mp_bus_not_pci) &&
		    (mp_irqs[i].irqtype == type) &&
		    (mp_irqs[i].srcbusirq == irq))

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

static int __init find_isa_irq_apic(int irq, int type)
{
	int i;

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

		if (test_bit(lbus, mp_bus_not_pci) &&
		    (mp_irqs[i].irqtype == type) &&
		    (mp_irqs[i].srcbusirq == irq))
			break;
	}
	if (i < mp_irq_entries) {
		int apic;
		for(apic = 0; apic < nr_ioapics; apic++) {
			if (mp_ioapics[apic].apicid == mp_irqs[i].dstapic)
				return apic;
		}
	}

	return -1;
}

#if defined(CONFIG_EISA) || defined(CONFIG_MCA)
/*
 * EISA Edge/Level control register, ELCR
 */
static int EISA_ELCR(unsigned int irq)
{
	if (irq < legacy_pic->nr_legacy_irqs) {
		unsigned int port = 0x4d0 + (irq >> 3);
		return (inb(port) >> (irq & 7)) & 1;
	}
	apic_printk(APIC_VERBOSE, KERN_INFO
			"Broken MPtable reports ISA irq %d\n", irq);
	return 0;
}

#endif

/* 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)

/* 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].srcbusirq))
#define default_EISA_polarity(idx)	default_ISA_polarity(idx)

/* 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)	default_ISA_polarity(idx)

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

	/*
	 * Determine IRQ line polarity (high active or low active):
	 */
	switch (mp_irqs[idx].irqflag & 3)
	{
		case 0: /* conforms, ie. bus-type dependent polarity */
			if (test_bit(bus, mp_bus_not_pci))
				polarity = default_ISA_polarity(idx);
			else
				polarity = default_PCI_polarity(idx);
			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 MPBIOS_trigger(int idx)
{
	int bus = mp_irqs[idx].srcbus;
	int trigger;

	/*
	 * Determine IRQ trigger mode (edge or level sensitive):
	 */
	switch ((mp_irqs[idx].irqflag>>2) & 3)
	{
		case 0: /* conforms, ie. bus-type dependent */
			if (test_bit(bus, mp_bus_not_pci))
				trigger = default_ISA_trigger(idx);
			else
				trigger = default_PCI_trigger(idx);
#if defined(CONFIG_EISA) || defined(CONFIG_MCA)
			switch (mp_bus_id_to_type[bus]) {
				case MP_BUS_ISA: /* ISA pin */
				{
					/* set before the switch */
					break;
				}
				case MP_BUS_EISA: /* EISA pin */
				{
					trigger = default_EISA_trigger(idx);
					break;
				}
				case MP_BUS_PCI: /* PCI pin */
				{
					/* set before the switch */
					break;
				}
				case MP_BUS_MCA: /* MCA pin */
				{
					trigger = default_MCA_trigger(idx);
					break;
				}
				default:
				{
					printk(KERN_WARNING "broken BIOS!!\n");
					trigger = 1;
					break;
				}
			}
#endif
			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;