i8259.c

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/*
 * 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.
 *
 * Code to handle x86 style IRQs plus some generic interrupt stuff.
 *
 * Copyright (C) 1992 Linus Torvalds
 * Copyright (C) 1994 - 2000 Ralf Baechle
 */
#include <linux/delay.h>
#include <linux/init.h>
#include <linux/ioport.h>
#include <linux/interrupt.h>
#include <linux/kernel.h>
#include <linux/spinlock.h>
#include <linux/syscore_ops.h>
#include <linux/irq.h>

#include <asm/i8259.h>
#include <asm/io.h>

/*
 * This is the 'legacy' 8259A Programmable Interrupt Controller,
 * present in the majority of PC/AT boxes.
 * plus some generic x86 specific things if generic specifics makes
 * any sense at all.
 * this file should become arch/i386/kernel/irq.c when the old irq.c
 * moves to arch independent land
 */

static int i8259A_auto_eoi = -1;
DEFINE_RAW_SPINLOCK(i8259A_lock);
static void disable_8259A_irq(struct irq_data *d);
static void enable_8259A_irq(struct irq_data *d);
static void mask_and_ack_8259A(struct irq_data *d);
static void init_8259A(int auto_eoi);

static struct irq_chip i8259A_chip = {
    .name           = "XT-PIC",
    .irq_mask       = disable_8259A_irq,
    .irq_disable        = disable_8259A_irq,
    .irq_unmask     = enable_8259A_irq,
    .irq_mask_ack       = mask_and_ack_8259A,
#ifdef CONFIG_MIPS_MT_SMTC_IRQAFF
    .irq_set_affinity   = plat_set_irq_affinity,
#endif /* CONFIG_MIPS_MT_SMTC_IRQAFF */
};

/*
 * 8259A PIC functions to handle ISA devices:
 */

/*
 * This contains the irq mask for both 8259A irq controllers,
 */
static unsigned int cached_irq_mask = 0xffff;

#define cached_master_mask  (cached_irq_mask)
#define cached_slave_mask   (cached_irq_mask >> 8)

static void disable_8259A_irq(struct irq_data *d)
{
    unsigned int mask, irq = d->irq - I8259A_IRQ_BASE;
    unsigned long flags;

    mask = 1 << irq;
    raw_spin_lock_irqsave(&i8259A_lock, flags);
    cached_irq_mask |= mask;
    if (irq & 8)
        outb(cached_slave_mask, PIC_SLAVE_IMR);
    else
        outb(cached_master_mask, PIC_MASTER_IMR);
    raw_spin_unlock_irqrestore(&i8259A_lock, flags);
}

static void enable_8259A_irq(struct irq_data *d)
{
    unsigned int mask, irq = d->irq - I8259A_IRQ_BASE;
    unsigned long flags;

    mask = ~(1 << irq);
    raw_spin_lock_irqsave(&i8259A_lock, flags);
    cached_irq_mask &= mask;
    if (irq & 8)
        outb(cached_slave_mask, PIC_SLAVE_IMR);
    else
        outb(cached_master_mask, PIC_MASTER_IMR);
    raw_spin_unlock_irqrestore(&i8259A_lock, flags);
}

int i8259A_irq_pending(unsigned int irq)
{
    unsigned int mask;
    unsigned long flags;
    int ret;

    irq -= I8259A_IRQ_BASE;
    mask = 1 << irq;
    raw_spin_lock_irqsave(&i8259A_lock, flags);
    if (irq < 8)
        ret = inb(PIC_MASTER_CMD) & mask;
    else
        ret = inb(PIC_SLAVE_CMD) & (mask >> 8);
    raw_spin_unlock_irqrestore(&i8259A_lock, flags);

    return ret;
}

void make_8259A_irq(unsigned int irq)
{
    disable_irq_nosync(irq);
    irq_set_chip_and_handler(irq, &i8259A_chip, handle_level_irq);
    enable_irq(irq);
}

/*
 * This function assumes to be called rarely. Switching between
 * 8259A registers is slow.
 * This has to be protected by the irq controller spinlock
 * before being called.
 */
static inline int i8259A_irq_real(unsigned int irq)
{
    int value;
    int irqmask = 1 << irq;

    if (irq < 8) {
        outb(0x0B, PIC_MASTER_CMD); /* ISR register */
        value = inb(PIC_MASTER_CMD) & irqmask;
        outb(0x0A, PIC_MASTER_CMD); /* back to the IRR register */
        return value;
    }
    outb(0x0B, PIC_SLAVE_CMD);  /* ISR register */
    value = inb(PIC_SLAVE_CMD) & (irqmask >> 8);
    outb(0x0A, PIC_SLAVE_CMD);  /* back to the IRR register */
    return value;
}

/*
 * Careful! The 8259A is a fragile beast, it pretty
 * much _has_ to be done exactly like this (mask it
 * first, _then_ send the EOI, and the order of EOI
 * to the two 8259s is important!
 */
static void mask_and_ack_8259A(struct irq_data *d)
{
    unsigned int irqmask, irq = d->irq - I8259A_IRQ_BASE;
    unsigned long flags;

    irqmask = 1 << irq;
    raw_spin_lock_irqsave(&i8259A_lock, flags);
    /*
     * Lightweight spurious IRQ detection. We do not want
     * to overdo spurious IRQ handling - it's usually a sign
     * of hardware problems, so we only do the checks we can
     * do without slowing down good hardware unnecessarily.
     *
     * Note that IRQ7 and IRQ15 (the two spurious IRQs
     * usually resulting from the 8259A-1|2 PICs) occur
     * even if the IRQ is masked in the 8259A. Thus we
     * can check spurious 8259A IRQs without doing the
     * quite slow i8259A_irq_real() call for every IRQ.
     * This does not cover 100% of spurious interrupts,
     * but should be enough to warn the user that there
     * is something bad going on ...
     */
    if (cached_irq_mask & irqmask)
        goto spurious_8259A_irq;
    cached_irq_mask |= irqmask;

handle_real_irq:
    if (irq & 8) {
        inb(PIC_SLAVE_IMR); /* DUMMY - (do we need this?) */
        outb(cached_slave_mask, PIC_SLAVE_IMR);
        outb(0x60+(irq&7), PIC_SLAVE_CMD);/* 'Specific EOI' to slave */
        outb(0x60+PIC_CASCADE_IR, PIC_MASTER_CMD); /* 'Specific EOI' to master-IRQ2 */
    } else {
        inb(PIC_MASTER_IMR);    /* DUMMY - (do we need this?) */
        outb(cached_master_mask, PIC_MASTER_IMR);
        outb(0x60+irq, PIC_MASTER_CMD); /* 'Specific EOI to master */
    }
    smtc_im_ack_irq(irq);
    raw_spin_unlock_irqrestore(&i8259A_lock, flags);
    return;

spurious_8259A_irq:
    /*
     * this is the slow path - should happen rarely.
     */
    if (i8259A_irq_real(irq))
        /*
         * oops, the IRQ _is_ in service according to the
         * 8259A - not spurious, go handle it.
         */
        goto handle_real_irq;

    {
        static int spurious_irq_mask;
        /*
         * At this point we can be sure the IRQ is spurious,
         * lets ACK and report it. [once per IRQ]
         */
        if (!(spurious_irq_mask & irqmask)) {
            printk(KERN_DEBUG "spurious 8259A interrupt: IRQ%d.\n", irq);
            spurious_irq_mask |= irqmask;
        }
        atomic_inc(&irq_err_count);
        /*
         * Theoretically we do not have to handle this IRQ,
         * but in Linux this does not cause problems and is
         * simpler for us.
         */
        goto handle_real_irq;
    }
}

static void i8259A_resume(void)
{
    if (i8259A_auto_eoi >= 0)
        init_8259A(i8259A_auto_eoi);
}

static void i8259A_shutdown(void)
{
    /* Put the i8259A into a quiescent state that
     * the kernel initialization code can get it
     * out of.
     */
    if (i8259A_auto_eoi >= 0) {
        outb(0xff, PIC_MASTER_IMR); /* mask all of 8259A-1 */
        outb(0xff, PIC_SLAVE_IMR);  /* mask all of 8259A-2 */
    }
}

static struct syscore_ops i8259_syscore_ops = {
    .resume = i8259A_resume,
    .shutdown = i8259A_shutdown,
};

static int __init i8259A_init_sysfs(void)
{
    register_syscore_ops(&i8259_syscore_ops);
    return 0;
}

device_initcall(i8259A_init_sysfs);

static void init_8259A(int auto_eoi)
{
    unsigned long flags;

    i8259A_auto_eoi = auto_eoi;

    raw_spin_lock_irqsave(&i8259A_lock, flags);

    outb(0xff, PIC_MASTER_IMR); /* mask all of 8259A-1 */
    outb(0xff, PIC_SLAVE_IMR);  /* mask all of 8259A-2 */

    /*
     * outb_p - this has to work on a wide range of PC hardware.
     */
    outb_p(0x11, PIC_MASTER_CMD);   /* ICW1: select 8259A-1 init */
    outb_p(I8259A_IRQ_BASE + 0, PIC_MASTER_IMR);    /* ICW2: 8259A-1 IR0 mapped to I8259A_IRQ_BASE + 0x00 */
    outb_p(1U << PIC_CASCADE_IR, PIC_MASTER_IMR);   /* 8259A-1 (the master) has a slave on IR2 */
    if (auto_eoi)   /* master does Auto EOI */
        outb_p(MASTER_ICW4_DEFAULT | PIC_ICW4_AEOI, PIC_MASTER_IMR);
    else        /* master expects normal EOI */
        outb_p(MASTER_ICW4_DEFAULT, PIC_MASTER_IMR);

    outb_p(0x11, PIC_SLAVE_CMD);    /* ICW1: select 8259A-2 init */
    outb_p(I8259A_IRQ_BASE + 8, PIC_SLAVE_IMR); /* ICW2: 8259A-2 IR0 mapped to I8259A_IRQ_BASE + 0x08 */
    outb_p(PIC_CASCADE_IR, PIC_SLAVE_IMR);  /* 8259A-2 is a slave on master's IR2 */
    outb_p(SLAVE_ICW4_DEFAULT, PIC_SLAVE_IMR); /* (slave's support for AEOI in flat mode is to be investigated) */
    if (auto_eoi)
        /*
         * In AEOI mode we just have to mask the interrupt
         * when acking.
         */
        i8259A_chip.irq_mask_ack = disable_8259A_irq;
    else
        i8259A_chip.irq_mask_ack = mask_and_ack_8259A;

    udelay(100);        /* wait for 8259A to initialize */

    outb(cached_master_mask, PIC_MASTER_IMR); /* restore master IRQ mask */
    outb(cached_slave_mask, PIC_SLAVE_IMR);   /* restore slave IRQ mask */

    raw_spin_unlock_irqrestore(&i8259A_lock, flags);
}

/*
 * IRQ2 is cascade interrupt to second interrupt controller
 */
static struct irqaction irq2 = {
    .handler = no_action,
    .name = "cascade",
    .flags = IRQF_NO_THREAD,
};

static struct resource pic1_io_resource = {
    .name = "pic1",
    .start = PIC_MASTER_CMD,
    .end = PIC_MASTER_IMR,
    .flags = IORESOURCE_BUSY
};

static struct resource pic2_io_resource = {
    .name = "pic2",
    .start = PIC_SLAVE_CMD,
    .end = PIC_SLAVE_IMR,
    .flags = IORESOURCE_BUSY
};

/*
 * On systems with i8259-style interrupt controllers we assume for
 * driver compatibility reasons interrupts 0 - 15 to be the i8259
 * interrupts even if the hardware uses a different interrupt numbering.
 */
void __init init_i8259_irqs(void)
{
    int i;

    insert_resource(&ioport_resource, &pic1_io_resource);
    insert_resource(&ioport_resource, &pic2_io_resource);

    init_8259A(0);

    for (i = I8259A_IRQ_BASE; i < I8259A_IRQ_BASE + 16; i++) {
        irq_set_chip_and_handler(i, &i8259A_chip, handle_level_irq);
        irq_set_probe(i);
    }

    setup_irq(I8259A_IRQ_BASE + PIC_CASCADE_IR, &irq2);
}