/*
 *	linux/arch/mips/kernel/irq.c
 *
 *	Copyright (C) 1992 Linus Torvalds
 *
 * This file contains the code used by various IRQ handling routines:
 * asking for different IRQ's should be done through these routines
 * instead of just grabbing them. Thus setups with different IRQ numbers
 * shouldn't result in any weird surprises, and installing new handlers
 * should be easier.
 */

/*
 * IRQ's are in fact implemented a bit like signal handlers for the kernel.
 * Naturally it's not a 1:1 relation, but there are similarities.
 */

#include <linux/ptrace.h>
#include <linux/errno.h>
#include <linux/kernel_stat.h>
#include <linux/signal.h>
#include <linux/sched.h>
#include <linux/interrupt.h>
#include <linux/timex.h>

#include <asm/system.h>
#include <asm/io.h>
#include <asm/irq.h>
#include <asm/bitops.h>

unsigned char cache_21 = 0xff;
unsigned char cache_A1 = 0xff;

unsigned long spurious_count = 0;

void disable_irq(unsigned int irq_nr)
{
	unsigned long flags;
	unsigned char mask;

	mask = 1 << (irq_nr & 7);
	save_flags(flags);
	if (irq_nr < 8) {
		cli();
		cache_21 |= mask;
		outb(cache_21,0x21);
		restore_flags(flags);
		return;
	}
	cli();
	cache_A1 |= mask;
	outb(cache_A1,0xA1);
	restore_flags(flags);
}

void enable_irq(unsigned int irq_nr)
{
	unsigned long flags;
	unsigned char mask;

	mask = ~(1 << (irq_nr & 7));
	save_flags(flags);
	if (irq_nr < 8) {
		cli();
		cache_21 &= mask;
		outb(cache_21,0x21);
		restore_flags(flags);
		return;
	}
	cli();
	cache_A1 &= mask;
	outb(cache_A1,0xA1);
	restore_flags(flags);
}

/*
 * Pointers to the low-level handlers: first the general ones, then the
 * fast ones, then the bad ones.
 */
extern void interrupt(void);
extern void fast_interrupt(void);
extern void bad_interrupt(void);

/*
 * Initial irq handlers.
 */
struct irqaction {
	void (*handler)(int, struct pt_regs *);
	unsigned long flags;
	unsigned long mask;
	const char *name;
};

static struct irqaction irq_action[16] = {
	{ NULL, 0, 0, NULL }, { NULL, 0, 0, NULL },
	{ NULL, 0, 0, NULL }, { NULL, 0, 0, NULL },
	{ NULL, 0, 0, NULL }, { NULL, 0, 0, NULL },
	{ NULL, 0, 0, NULL }, { NULL, 0, 0, NULL },
	{ NULL, 0, 0, NULL }, { NULL, 0, 0, NULL },
	{ NULL, 0, 0, NULL }, { NULL, 0, 0, NULL },
	{ NULL, 0, 0, NULL }, { NULL, 0, 0, NULL },
	{ NULL, 0, 0, NULL }, { NULL, 0, 0, NULL }
};

int get_irq_list(char *buf)
{
	int i, len = 0;
	struct irqaction * action = irq_action;

	for (i = 0 ; i < 16 ; i++, action++) {
		if (!action->handler)
			continue;
		len += sprintf(buf+len, "%2d: %8d %c %s\n",
			i, kstat.interrupts[i],
			(action->flags & SA_INTERRUPT) ? '+' : ' ',
			action->name);
	}
	return len;
}

/*
 * do_IRQ handles IRQ's that have been installed without the
 * SA_INTERRUPT flag: it uses the full signal-handling return
 * and runs with other interrupts enabled. All relatively slow
 * IRQ's should use this format: notably the keyboard/timer
 * routines.
 */
asmlinkage void do_IRQ(int irq, struct pt_regs * regs)
{
	struct irqaction * action = irq + irq_action;

	kstat.interrupts[irq]++;
	action->handler(irq, regs);
}

/*
 * do_fast_IRQ handles IRQ's that don't need the fancy interrupt return
 * stuff - the handler is also running with interrupts disabled unless
 * it explicitly enables them later.
 */
asmlinkage void do_fast_IRQ(int irq)
{
	struct irqaction * action = irq + irq_action;

	kstat.interrupts[irq]++;
	action->handler(irq, NULL);
}

#define SA_PROBE SA_ONESHOT

int request_irq(unsigned int irq, void (*handler)(int, struct pt_regs *),
	unsigned long irqflags, const char * devname)
{
	struct irqaction * action;
	unsigned long flags;

	if (irq > 15)
		return -EINVAL;
	action = irq + irq_action;
	if (action->handler)
		return -EBUSY;
	if (!handler)
		return -EINVAL;
	save_flags(flags);
	cli();
	action->handler = handler;
	action->flags = irqflags;
	action->mask = 0;
	action->name = devname;
	if (!(action->flags & SA_PROBE)) { /* SA_ONESHOT is used by probing */
		/*
		 * FIXME: Does the SA_INTERRUPT flag make any sense on MIPS???
		 */
		if (action->flags & SA_INTERRUPT)
			set_intr_gate(irq,fast_interrupt);
		else
			set_intr_gate(irq,interrupt);
	}
	if (irq < 8) {
		cache_21 &= ~(1<<irq);
		outb(cache_21,0x21);
	} else {
		cache_21 &= ~(1<<2);
		cache_A1 &= ~(1<<(irq-8));
		outb(cache_21,0x21);
		outb(cache_A1,0xA1);
	}
	restore_flags(flags);
	return 0;
}

void free_irq(unsigned int irq)
{
	struct irqaction * action = irq + irq_action;
	unsigned long flags;

	if (irq > 15) {
		printk("Trying to free IRQ%d\n",irq);
		return;
	}
	if (!action->handler) {
		printk("Trying to free free IRQ%d\n",irq);
		return;
	}
	save_flags(flags);
	cli();
	if (irq < 8) {
		cache_21 |= 1 << irq;
		outb(cache_21,0x21);
	} else {
		cache_A1 |= 1 << (irq-8);
		outb(cache_A1,0xA1);
	}
	set_intr_gate(irq,bad_interrupt);
	action->handler = NULL;
	action->flags = 0;
	action->mask = 0;
	action->name = NULL;
	restore_flags(flags);
}

static void no_action(int cpl, struct pt_regs * regs) { }

unsigned int probe_irq_on (void)
{
	unsigned int i, irqs = 0, irqmask;
	unsigned long delay;

	/* first, snaffle up any unassigned irqs */
	for (i = 15; i > 0; i--) {
		if (!request_irq(i, no_action, SA_PROBE, "probe")) {
			enable_irq(i);
			irqs |= (1 << i);
		}
	}

	/* wait for spurious interrupts to mask themselves out again */
	for (delay = jiffies + 2; delay > jiffies; );	/* min 10ms delay */

	/* now filter out any obviously spurious interrupts */
	irqmask = (((unsigned int)cache_A1)<<8) | (unsigned int)cache_21;
	for (i = 15; i > 0; i--) {
		if (irqs & (1 << i) & irqmask) {
			irqs ^= (1 << i);
			free_irq(i);
		}
	}
#ifdef DEBUG
	printk("probe_irq_on:  irqs=0x%04x irqmask=0x%04x\n", irqs, irqmask);
#endif
	return irqs;
}

int probe_irq_off (unsigned int irqs)
{
	unsigned int i, irqmask;

	irqmask = (((unsigned int)cache_A1)<<8) | (unsigned int)cache_21;
	for (i = 15; i > 0; i--) {
		if (irqs & (1 << i)) {
			free_irq(i);
		}
	}
#ifdef DEBUG
	printk("probe_irq_off: irqs=0x%04x irqmask=0x%04x\n", irqs, irqmask);
#endif
	irqs &= irqmask;
	if (!irqs)
		return 0;
	i = ffz(~irqs);
	if (irqs != (irqs & (1 << i)))
		i = -i;
	return i;
}

void init_IRQ(void)
{
	int i;

	/* set the clock to 100 Hz */
	outb_p(0x34,0x43);		/* binary, mode 2, LSB/MSB, ch 0 */
	outb_p(LATCH & 0xff , 0x40);	/* LSB */
	outb(LATCH >> 8 , 0x40);	/* MSB */
	for (i = 0; i < 16 ; i++)
		set_intr_gate(i, bad_interrupt);
	if (request_irq(2, no_action, SA_INTERRUPT, "cascade"))
		printk("Unable to get IRQ2 for cascade\n");

	/* initialize the bottom half routines. */
	for (i = 0; i < 32; i++) {
		bh_base[i].routine = NULL;
		bh_base[i].data = NULL;
	}
	bh_active = 0;
	intr_count = 0;
}
