irq.c

来自「linux-2.4.29操作系统的源码」· C语言 代码 · 共 707 行 · 第 1/2 页

/*
 * This file is subject to the terms and conditions of the GNU General Public
 * License.  See the file "COPYING" in the main directory of this archive
 * for more details.
 *
 * arch/sh64/kernel/irq.c
 *
 * Copyright (C) 2000, 2001  Paolo Alberelli
 *
 */

/*
 * IRQs 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/config.h>
#include <linux/ptrace.h>
#include <linux/errno.h>
#include <linux/kernel_stat.h>
#include <linux/signal.h>
#include <linux/sched.h>
#include <linux/ioport.h>
#include <linux/interrupt.h>
#include <linux/timex.h>
#include <linux/slab.h>
#include <linux/random.h>
#include <linux/smp.h>
#include <linux/smp_lock.h>
#include <linux/init.h>

#include <asm/system.h>
#include <asm/io.h>
#include <asm/bitops.h>
#include <asm/smp.h>
#include <asm/pgalloc.h>
#include <asm/delay.h>
#include <asm/irq.h>
#include <linux/irq.h>

/*
 * Controller mappings for all interrupt sources:
 */
irq_desc_t irq_desc[NR_IRQS] __cacheline_aligned =
	{ [0 ... NR_IRQS-1] = { 0, &no_irq_type, NULL, 0, SPIN_LOCK_UNLOCKED}};

/*
 * Special irq handlers.
 */

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

/*
 * Generic no controller code
 */

static void enable_none(unsigned int irq) { }
static unsigned int startup_none(unsigned int irq) { return 0; }
static void disable_none(unsigned int irq) { }
static void ack_none(unsigned int irq)
{
/*
 * 'what should we do if we get a hw irq event on an illegal vector'.
 * each architecture has to answer this themselves, it doesnt deserve
 * a generic callback i think.
 */
	printk("unexpected IRQ trap at irq %02x\n", irq);
}

/* startup is the same as "enable", shutdown is same as "disable" */
#define shutdown_none	disable_none
#define end_none	enable_none

struct hw_interrupt_type no_irq_type = {
	"none",
	startup_none,
	shutdown_none,
	enable_none,
	disable_none,
	ack_none,
	end_none
};


/*
 * do_NMI handles all Non-Maskable Interrupts.
 */
asmlinkage void do_NMI(unsigned long vector_num, struct pt_regs * regs)
{	
	if (regs->sr & 0x40000000)
		printk("unexpected NMI trap in system mode\n");
	else
		printk("unexpected NMI trap in user mode\n");

	/* No statistics */
}


/*
 * Generic, controller-independent functions:
 */
#if defined(CONFIG_PROC_FS) && defined(CONFIG_SYSCTL)
int get_irq_list(char *buf)
{
	int i, j;
	struct irqaction * action;
	char *p = buf;

	p += sprintf(p, "           ");
	for (j=0; j<smp_num_cpus; j++)
		p += sprintf(p, "CPU%d       ",j);
	*p++ = '\n';

	for (i = 0 ; i < NR_IRQS ; i++) {
		action = irq_desc[i].action;
		if (!action) 
			continue;
		p += sprintf(p, "%3d: ",i);
		p += sprintf(p, "%10u ", kstat_irqs(i));
		p += sprintf(p, " %14s", irq_desc[i].handler->typename);
		p += irq_describe(p, i);
		p += sprintf(p, "  %s", action->name);

		for (action=action->next; action; action = action->next)
			p += sprintf(p, ", %s", action->name);
		*p++ = '\n';
	}
#if 0
	p += sprintf(p, "NMI: ");
	for (j = 0; j < smp_num_cpus; j++)
		p += sprintf(p, "%10u ",
			atomic_read(&nmi_counter(cpu_logical_map(j))));
	p += sprintf(p, "\n");
#endif

	return p - buf;
}
#endif

/*
 * This should really return information about whether
 * we should do bottom half handling etc. Right now we
 * end up _always_ checking the bottom half, which is a
 * waste of time and is not what some drivers would
 * prefer.
 */
int handle_IRQ_event(unsigned int irq, struct pt_regs * regs, struct irqaction * action)
{
	int status;
	int cpu = smp_processor_id();

	irq_enter(cpu, irq);

	status = 1;	/* Force the "do bottom halves" bit */

        if (!(action->flags & SA_INTERRUPT))
                __sti();

	do {
		status |= action->flags;
		action->handler(irq, action->dev_id, regs);
		action = action->next;
	} while (action);
	if (status & SA_SAMPLE_RANDOM)
		add_interrupt_randomness(irq);

	__cli();

	irq_exit(cpu, irq);

	return status;
}

/*
 * Generic enable/disable code: this just calls
 * down into the PIC-specific version for the actual
 * hardware disable after having gotten the irq
 * controller lock. 
 */

/**
 *	disable_irq_nosync - disable an irq without waiting
 *	@irq: Interrupt to disable
 *
 *	Disable the selected interrupt line. Disables of an interrupt
 *	stack. Unlike disable_irq(), this function does not ensure existing
 *	instances of the IRQ handler have completed before returning.
 *
 *	This function may be called from IRQ context.
 */
void disable_irq_nosync(unsigned int irq)
{
	irq_desc_t *desc = irq_desc + irq;
	unsigned long flags;

	spin_lock_irqsave(&desc->lock, flags);
	if (!desc->depth++) {
		desc->status |= IRQ_DISABLED;
		desc->handler->disable(irq);
	}
	spin_unlock_irqrestore(&desc->lock, flags);
}

/**
 *	disable_irq - disable an irq and wait for completion
 *	@irq: Interrupt to disable
 *
 *	Disable the selected interrupt line. Disables of an interrupt
 *	stack. That is for two disables you need two enables. This
 *	function waits for any pending IRQ handlers for this interrupt
 *	to complete before returning. If you use this function while
 *	holding a resource the IRQ handler may need you will deadlock.
 *
 *	This function may be called - with care - from IRQ context.
 */
void disable_irq(unsigned int irq)
{
	disable_irq_nosync(irq);

	if (!local_irq_count(smp_processor_id())) {
		do {
			barrier();
		} while (irq_desc[irq].status & IRQ_INPROGRESS);
	}
}

/**
 *	enable_irq - enable interrupt handling on an irq
 *	@irq: Interrupt to enable
 *
 *	Re-enables the processing of interrupts on this IRQ line
 *	providing no disable_irq calls are now in effect.
 *
 *	This function may be called from IRQ context.
 */
void enable_irq(unsigned int irq)
{
	irq_desc_t *desc = irq_desc + irq;
	unsigned long flags;

	spin_lock_irqsave(&desc->lock, flags);
	switch (desc->depth) {
	case 1: {
		unsigned int status = desc->status & ~IRQ_DISABLED;
		desc->status = status;
		if ((status & (IRQ_PENDING | IRQ_REPLAY)) == IRQ_PENDING) {
			desc->status = status | IRQ_REPLAY;
			hw_resend_irq(desc->handler,irq);
		}
		desc->handler->enable(irq);
		/* fall-through */
	}
	default:
		desc->depth--;
		break;
	case 0:
		printk("enable_irq() unbalanced from %p\n",
		       __builtin_return_address(0));
	}
	spin_unlock_irqrestore(&desc->lock, flags);
}

/*
 * do_IRQ handles all normal device IRQ's.
 */
asmlinkage int do_IRQ(unsigned long vector_num, struct pt_regs * regs)
{	
	/* 
	 * We ack quickly, we don't want the irq controller
	 * thinking we're snobs just because some other CPU has
	 * disabled global interrupts (we have already done the
	 * INT_ACK cycles, it's too late to try to pretend to the
	 * controller that we aren't taking the interrupt).
	 *
	 * 0 return value means that this irq is already being
	 * handled by some other CPU. (or is disabled)
	 */
	int irq;
	int cpu = smp_processor_id();
	irq_desc_t *desc;
	struct irqaction * action;
	unsigned int status;

	irq = irq_demux(vector_num);

	/*
	 * Should never happen, if it does check
	 * vectorN_to_IRQ[] against trap_jtable[].
	 */
	if (irq == -1) {
		printk("unexpected IRQ trap at vector %03lx\n", vector_num);
		return 1;
	}

	desc = irq_desc + irq;

	kstat.irqs[cpu][irq]++;
	spin_lock(&desc->lock);
	desc->handler->ack(irq);
	/*
	   REPLAY is when Linux resends an IRQ that was dropped earlier
	   WAITING is used by probe to mark irqs that are being tested
	   */
	status = desc->status & ~(IRQ_REPLAY | IRQ_WAITING | IRQ_INPROGRESS);
	status |= IRQ_PENDING; /* we _want_ to handle it */

	/*
	 * If the IRQ is disabled for whatever reason, we cannot
	 * use the action we have.
	 */
	action = NULL;
	if (!(status & (IRQ_DISABLED | IRQ_INPROGRESS))) {
		action = desc->action;
		status &= ~IRQ_PENDING; /* we commit to handling */
		status |= IRQ_INPROGRESS; /* we are handling it */
	}
	desc->status = status;

	/*
	 * If there is no IRQ handler or it was disabled, exit early.
	   Since we set PENDING, if another processor is handling
	   a different instance of this same irq, the other processor
	   will take care of it.
	 */
	if (!action)
		goto out;

	/*
	 * Edge triggered interrupts need to remember
	 * pending events.
	 * This applies to any hw interrupts that allow a second
	 * instance of the same irq to arrive while we are in do_IRQ
	 * or in the handler. But the code here only handles the _second_
	 * instance of the irq, not the third or fourth. So it is mostly
	 * useful for irq hardware that does not mask cleanly in an
	 * SMP environment.
	 */
	for (;;) {
		spin_unlock(&desc->lock);
		handle_IRQ_event(irq, regs, action);
		spin_lock(&desc->lock);

		if (!(desc->status & IRQ_PENDING))
			break;
		desc->status &= ~IRQ_PENDING;
	}
	desc->status &= ~IRQ_INPROGRESS;
out:
	/*
	 * The ->end() handler has to deal with interrupts which got
	 * disabled while the handler was running.
	 */
	desc->handler->end(irq);
	spin_unlock(&desc->lock);