#include <linux/linkage.h>
#include <linux/errno.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/init.h>
#include <linux/kernel_stat.h>
#include <linux/sysdev.h>
#include <linux/bitops.h>
#include <linux/acpi.h>
#include <linux/io.h>
#include <linux/delay.h>

#include <asm/atomic.h>
#include <asm/system.h>
#include <asm/timer.h>
#include <asm/hw_irq.h>
#include <asm/pgtable.h>
#include <asm/desc.h>
#include <asm/apic.h>
#include <asm/i8259.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.
 */

static int i8259A_auto_eoi;
DEFINE_SPINLOCK(i8259A_lock);
static void mask_and_ack_8259A(unsigned int);

struct irq_chip i8259A_chip = {
        .name           = "XT-PIC",
        .mask           = disable_8259A_irq,
        .disable        = disable_8259A_irq,
        .unmask         = enable_8259A_irq,
        .mask_ack       = mask_and_ack_8259A,
};

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

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

/*
 * Not all IRQs can be routed through the IO-APIC, eg. on certain (older)
 * boards the timer interrupt is not really connected to any IO-APIC pin,
 * it's fed to the master 8259A's IR0 line only.
 *
 * Any '1' bit in this mask means the IRQ is routed through the IO-APIC.
 * this 'mixed mode' IRQ handling costs nothing because it's only used
 * at IRQ setup time.
 */
unsigned long io_apic_irqs;

void disable_8259A_irq(unsigned int irq)
{
        unsigned int mask = 1 << irq;
        unsigned long flags;

        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);
        spin_unlock_irqrestore(&i8259A_lock, flags);
}

void enable_8259A_irq(unsigned int irq)
{
        unsigned int mask = ~(1 << irq);
        unsigned long flags;

        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);
        spin_unlock_irqrestore(&i8259A_lock, flags);
}

int i8259A_irq_pending(unsigned int irq)
{
        unsigned int mask = 1<<irq;
        unsigned long flags;
        int ret;

        spin_lock_irqsave(&i8259A_lock, flags);
        if (irq < 8)
                ret = inb(PIC_MASTER_CMD) & mask;
        else
                ret = inb(PIC_SLAVE_CMD) & (mask >> 8);
        spin_unlock_irqrestore(&i8259A_lock, flags);

        return ret;
}

void make_8259A_irq(unsigned int irq)
{
        disable_irq_nosync(irq);
        io_apic_irqs &= ~(1<<irq);
        set_irq_chip_and_handler_name(irq, &i8259A_chip, handle_level_irq,
                                      "XT");
        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(unsigned int irq)
{
        unsigned int irqmask = 1 << irq;
        unsigned long flags;

        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);
                /* 'Specific EOI' to slave */
                outb(0x60+(irq&7), PIC_SLAVE_CMD);
                 /* 'Specific EOI' to master-IRQ2 */
                outb(0x60+PIC_CASCADE_IR, PIC_MASTER_CMD);
        } 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 */
        }
        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 char irq_trigger[2];
/**
 * ELCR registers (0x4d0, 0x4d1) control edge/level of IRQ
 */
static void restore_ELCR(char *trigger)
{
        outb(trigger[0], 0x4d0);
        outb(trigger[1], 0x4d1);
}

static void save_ELCR(char *trigger)
{
        /* IRQ 0,1,2,8,13 are marked as reserved */
        trigger[0] = inb(0x4d0) & 0xF8;
        trigger[1] = inb(0x4d1) & 0xDE;
}

static int i8259A_resume(struct sys_device *dev)
{
        init_8259A(i8259A_auto_eoi);
        restore_ELCR(irq_trigger);
        return 0;
}

static int i8259A_suspend(struct sys_device *dev, pm_message_t state)
{
        save_ELCR(irq_trigger);
        return 0;
}

static int i8259A_shutdown(struct sys_device *dev)
{
        /* Put the i8259A into a quiescent state that
         * the kernel initialization code can get it
         * out of.
         */
        outb(0xff, PIC_MASTER_IMR);     /* mask all of 8259A-1 */
        outb(0xff, PIC_SLAVE_IMR);      /* mask all of 8259A-1 */
        return 0;
}

static struct sysdev_class i8259_sysdev_class = {
        .name = "i8259",
        .suspend = i8259A_suspend,
        .resume = i8259A_resume,
        .shutdown = i8259A_shutdown,
};

static struct sys_device device_i8259A = {
        .id     = 0,
        .cls    = &i8259_sysdev_class,
};

static int __init i8259A_init_sysfs(void)
{
        int error = sysdev_class_register(&i8259_sysdev_class);
        if (!error)
                error = sysdev_register(&device_i8259A);
        return error;
}

device_initcall(i8259A_init_sysfs);

void mask_8259A(void)
{
        unsigned long flags;

        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 */

        spin_unlock_irqrestore(&i8259A_lock, flags);
}

void unmask_8259A(void)
{
        unsigned long flags;

        spin_lock_irqsave(&i8259A_lock, flags);

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

        spin_unlock_irqrestore(&i8259A_lock, flags);
}

void init_8259A(int auto_eoi)
{
        unsigned long flags;

        i8259A_auto_eoi = auto_eoi;

        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_pic - this has to work on a wide range of PC hardware.
         */
        outb_pic(0x11, PIC_MASTER_CMD); /* ICW1: select 8259A-1 init */

        /* ICW2: 8259A-1 IR0-7 mapped to 0x30-0x37 on x86-64,
           to 0x20-0x27 on i386 */
        outb_pic(IRQ0_VECTOR, PIC_MASTER_IMR);

        /* 8259A-1 (the master) has a slave on IR2 */
        outb_pic(1U << PIC_CASCADE_IR, PIC_MASTER_IMR);

        if (auto_eoi)   /* master does Auto EOI */
                outb_pic(MASTER_ICW4_DEFAULT | PIC_ICW4_AEOI, PIC_MASTER_IMR);
        else            /* master expects normal EOI */
                outb_pic(MASTER_ICW4_DEFAULT, PIC_MASTER_IMR);

        outb_pic(0x11, PIC_SLAVE_CMD);  /* ICW1: select 8259A-2 init */

        /* ICW2: 8259A-2 IR0-7 mapped to IRQ8_VECTOR */
        outb_pic(IRQ8_VECTOR, PIC_SLAVE_IMR);
        /* 8259A-2 is a slave on master's IR2 */
        outb_pic(PIC_CASCADE_IR, PIC_SLAVE_IMR);
        /* (slave's support for AEOI in flat mode is to be investigated) */
        outb_pic(SLAVE_ICW4_DEFAULT, PIC_SLAVE_IMR);

        if (auto_eoi)
                /*
                 * In AEOI mode we just have to mask the interrupt
                 * when acking.
                 */
                i8259A_chip.mask_ack = disable_8259A_irq;
        else
                i8259A_chip.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 */

        spin_unlock_irqrestore(&i8259A_lock, flags);
}