irq.c

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/*
 *  linux/arch/alpha/kernel/irq.c
 *
 *  Copyright (C) 1995 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.
 */

#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/errno.h>
#include <linux/kernel_stat.h>
#include <linux/signal.h>
#include <linux/sched.h>
#include <linux/ptrace.h>
#include <linux/interrupt.h>
#include <linux/random.h>
#include <linux/init.h>
#include <linux/irq.h>
#include <linux/proc_fs.h>
#include <linux/seq_file.h>
#include <linux/profile.h>
#include <linux/bitops.h>

#include <asm/io.h>
#include <asm/uaccess.h>

volatile unsigned long irq_err_count;
DEFINE_PER_CPU(unsigned long, irq_pmi_count);

void ack_bad_irq(unsigned int irq)
{
    irq_err_count++;
    printk(KERN_CRIT "Unexpected IRQ trap at vector %u\n", irq);
}

#ifdef CONFIG_SMP 
static char irq_user_affinity[NR_IRQS];

int irq_select_affinity(unsigned int irq)
{
    struct irq_data *data = irq_get_irq_data(irq);
    struct irq_chip *chip;
    static int last_cpu;
    int cpu = last_cpu + 1;

    if (!data)
        return 1;
    chip = irq_data_get_irq_chip(data);

    if (!chip->irq_set_affinity || irq_user_affinity[irq])
        return 1;

    while (!cpu_possible(cpu) ||
           !cpumask_test_cpu(cpu, irq_default_affinity))
        cpu = (cpu < (NR_CPUS-1) ? cpu + 1 : 0);
    last_cpu = cpu;

    cpumask_copy(data->affinity, cpumask_of(cpu));
    chip->irq_set_affinity(data, cpumask_of(cpu), false);
    return 0;
}
#endif /* CONFIG_SMP */

int arch_show_interrupts(struct seq_file *p, int prec)
{
    int j;

#ifdef CONFIG_SMP
    seq_puts(p, "IPI: ");
    for_each_online_cpu(j)
        seq_printf(p, "%10lu ", cpu_data[j].ipi_count);
    seq_putc(p, '\n');
#endif
    seq_puts(p, "PMI: ");
    for_each_online_cpu(j)
        seq_printf(p, "%10lu ", per_cpu(irq_pmi_count, j));
    seq_puts(p, "          Performance Monitoring\n");
    seq_printf(p, "ERR: %10lu\n", irq_err_count);
    return 0;
}

/*
 * handle_irq handles all normal device IRQ's (the special
 * SMP cross-CPU interrupts have their own specific
 * handlers).
 */

#define MAX_ILLEGAL_IRQS 16

void
handle_irq(int irq)
{   
    /* 
     * 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)
     */
    static unsigned int illegal_count=0;
    struct irq_desc *desc = irq_to_desc(irq);
    
    if (!desc || ((unsigned) irq > ACTUAL_NR_IRQS &&
        illegal_count < MAX_ILLEGAL_IRQS)) {
        irq_err_count++;
        illegal_count++;
        printk(KERN_CRIT "device_interrupt: invalid interrupt %d\n",
               irq);
        return;
    }

    /*
     * From here we must proceed with IPL_MAX. Note that we do not
     * explicitly enable interrupts afterwards - some MILO PALcode
     * (namely LX164 one) seems to have severe problems with RTI
     * at IPL 0.
     */
    local_irq_disable();
    irq_enter();
    generic_handle_irq_desc(irq, desc);
    irq_exit();
}