/*
 *  linux/arch/arm/kernel/irq.c
 *
 *  Copyright (C) 1992 Linus Torvalds
 *  Modifications for ARM processor Copyright (C) 1995-2000 Russell King.
 *  'Borrowed' for ARM26 and (C) 2003 Ian Molton.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 *
 *  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/config.h>
#include <linux/module.h>
#include <linux/ptrace.h>
#include <linux/kernel_stat.h>
#include <linux/signal.h>
#include <linux/sched.h>
#include <linux/ioport.h>
#include <linux/interrupt.h>
#include <linux/slab.h>
#include <linux/random.h>
#include <linux/smp.h>
#include <linux/init.h>
#include <linux/seq_file.h>
#include <linux/errno.h>

#include <asm/irq.h>
#include <asm/system.h>
#include <asm/irqchip.h>

//FIXME - this ought to be in a header IMO
void __init arc_init_irq(void);

/*
 * Maximum IRQ count.  Currently, this is arbitary.  However, it should
 * not be set too low to prevent false triggering.  Conversely, if it
 * is set too high, then you could miss a stuck IRQ.
 *
 * FIXME Maybe we ought to set a timer and re-enable the IRQ at a later time?
 */
#define MAX_IRQ_CNT     100000

static volatile unsigned long irq_err_count;
static DEFINE_SPINLOCK(irq_controller_lock);

struct irqdesc irq_desc[NR_IRQS];

/*
 * Dummy mask/unmask handler
 */
void dummy_mask_unmask_irq(unsigned int irq)
{
}

void do_bad_IRQ(unsigned int irq, struct irqdesc *desc, struct pt_regs *regs)
{
        irq_err_count += 1;
        printk(KERN_ERR "IRQ: spurious interrupt %d\n", irq);
}

static struct irqchip bad_chip = {
        .ack    = dummy_mask_unmask_irq,
        .mask   = dummy_mask_unmask_irq,
        .unmask = dummy_mask_unmask_irq,
};

static struct irqdesc bad_irq_desc = {
        .chip   = &bad_chip,
        .handle = do_bad_IRQ,
        .depth  = 1,
};

/**
 *      disable_irq - disable an irq and wait for completion
 *      @irq: Interrupt to disable
 *
 *      Disable the selected interrupt line.  We do this lazily.
 *
 *      This function may be called from IRQ context.
 */
void disable_irq(unsigned int irq)
{
        struct irqdesc *desc = irq_desc + irq;
        unsigned long flags;
        spin_lock_irqsave(&irq_controller_lock, flags);
        if (!desc->depth++)
                desc->enabled = 0;
        spin_unlock_irqrestore(&irq_controller_lock, flags);
}

/**
 *      enable_irq - enable interrupt handling on an irq
 *      @irq: Interrupt to enable
 *
 *      Re-enables the processing of interrupts on this IRQ line.
 *      Note that this may call the interrupt handler, so you may
 *      get unexpected results if you hold IRQs disabled.
 *
 *      This function may be called from IRQ context.
 */
void enable_irq(unsigned int irq)
{
        struct irqdesc *desc = irq_desc + irq;
        unsigned long flags;
        int pending = 0;

        spin_lock_irqsave(&irq_controller_lock, flags);
        if (unlikely(!desc->depth)) {
                printk("enable_irq(%u) unbalanced from %p\n", irq,
                        __builtin_return_address(0)); //FIXME bum addresses reported - why?
        } else if (!--desc->depth) {
                desc->probing = 0;
                desc->enabled = 1;
                desc->chip->unmask(irq);
                pending = desc->pending;
                desc->pending = 0;
                /*
                 * If the interrupt was waiting to be processed,
                 * retrigger it.
                 */
                if (pending)
                        desc->chip->rerun(irq);
        }
        spin_unlock_irqrestore(&irq_controller_lock, flags);
}

int show_interrupts(struct seq_file *p, void *v)
{
        int i = *(loff_t *) v;
        struct irqaction * action;

        if (i < NR_IRQS) {
                action = irq_desc[i].action;
                if (!action)
                        continue;
                seq_printf(p, "%3d: %10u ", i, kstat_irqs(i));
                seq_printf(p, "  %s", action->name);
                for (action = action->next; action; action = action->next) {
                        seq_printf(p, ", %s", action->name);
                }
                seq_putc(p, '\n');
        } else if (i == NR_IRQS) {
                show_fiq_list(p, v);
                seq_printf(p, "Err: %10lu\n", irq_err_count);
        }
        return 0;
}

/*
 * IRQ lock detection.
 *
 * Hopefully, this should get us out of a few locked situations.
 * However, it may take a while for this to happen, since we need
 * a large number if IRQs to appear in the same jiffie with the
 * same instruction pointer (or within 2 instructions).
 */
static int check_irq_lock(struct irqdesc *desc, int irq, struct pt_regs *regs)
{
        unsigned long instr_ptr = instruction_pointer(regs);

        if (desc->lck_jif == jiffies &&
            desc->lck_pc >= instr_ptr && desc->lck_pc < instr_ptr + 8) {
                desc->lck_cnt += 1;

                if (desc->lck_cnt > MAX_IRQ_CNT) {
                        printk(KERN_ERR "IRQ LOCK: IRQ%d is locking the system, disabled\n", irq);
                        return 1;
                }
        } else {
                desc->lck_cnt = 0;
                desc->lck_pc  = instruction_pointer(regs);
                desc->lck_jif = jiffies;
        }
        return 0;
}

static void
__do_irq(unsigned int irq, struct irqaction *action, struct pt_regs *regs)
{
        unsigned int status;
        int ret;

        spin_unlock(&irq_controller_lock);
        if (!(action->flags & SA_INTERRUPT))
                local_irq_enable();

        status = 0;
        do {
                ret = action->handler(irq, action->dev_id, regs);
                if (ret == IRQ_HANDLED)
                        status |= action->flags;
                action = action->next;
        } while (action);

        if (status & SA_SAMPLE_RANDOM)
                add_interrupt_randomness(irq);

        spin_lock_irq(&irq_controller_lock);
}

/*
 * This is for software-decoded IRQs.  The caller is expected to
 * handle the ack, clear, mask and unmask issues.
 */
void
do_simple_IRQ(unsigned int irq, struct irqdesc *desc, struct pt_regs *regs)
{
        struct irqaction *action;
        const int cpu = smp_processor_id();

        desc->triggered = 1;

        kstat_cpu(cpu).irqs[irq]++;

        action = desc->action;
        if (action)
                __do_irq(irq, desc->action, regs);
}

/*
 * Most edge-triggered IRQ implementations seem to take a broken
 * approach to this.  Hence the complexity.
 */
void
do_edge_IRQ(unsigned int irq, struct irqdesc *desc, struct pt_regs *regs)
{
        const int cpu = smp_processor_id();

        desc->triggered = 1;

        /*
         * If we're currently running this IRQ, or its disabled,
         * we shouldn't process the IRQ.  Instead, turn on the
         * hardware masks.
         */
        if (unlikely(desc->running || !desc->enabled))
                goto running;

        /*
         * Acknowledge and clear the IRQ, but don't mask it.
         */
        desc->chip->ack(irq);

        /*
         * Mark the IRQ currently in progress.
         */
        desc->running = 1;

        kstat_cpu(cpu).irqs[irq]++;

        do {
                struct irqaction *action;

                action = desc->action;
                if (!action)
                        break;

                if (desc->pending && desc->enabled) {
                        desc->pending = 0;
                        desc->chip->unmask(irq);
                }

                __do_irq(irq, action, regs);
        } while (desc->pending);

        desc->running = 0;

        /*
         * If we were disabled or freed, shut down the handler.
         */
        if (likely(desc->action && !check_irq_lock(desc, irq, regs)))
                return;

 running:
        /*
         * We got another IRQ while this one was masked or
         * currently running.  Delay it.
         */
        desc->pending = 1;
        desc->chip->mask(irq);
        desc->chip->ack(irq);
}

/*
 * Level-based IRQ handler.  Nice and simple.
 */
void
do_level_IRQ(unsigned int irq, struct irqdesc *desc, struct pt_regs *regs)
{
        struct irqaction *action;
        const int cpu = smp_processor_id();

        desc->triggered = 1;

        /*
         * Acknowledge, clear _AND_ disable the interrupt.
         */
        desc->chip->ack(irq);

        if (likely(desc->enabled)) {
                kstat_cpu(cpu).irqs[irq]++;

                /*
                 * Return with this interrupt masked if no action
                 */
                action = desc->action;
                if (action) {
                        __do_irq(irq, desc->action, regs);

                        if (likely(desc->enabled &&
                                   !check_irq_lock(desc, irq, regs)))
                                desc->chip->unmask(irq);
                }
        }
}

/*
 * do_IRQ handles all hardware IRQ's.  Decoded IRQs should not
 * come via this function.  Instead, they should provide their
 * own 'handler'
 */
asmlinkage void asm_do_IRQ(int irq, struct pt_regs *regs)
{
        struct irqdesc *desc = irq_desc + irq;

        /*
         * Some hardware gives randomly wrong interrupts.  Rather
         * than crashing, do something sensible.
         */
        if (irq >= NR_IRQS)
                desc = &bad_irq_desc;

        irq_enter();
        spin_lock(&irq_controller_lock);
        desc->handle(irq, desc, regs);
        spin_unlock(&irq_controller_lock);
        irq_exit();
}

void __set_irq_handler(unsigned int irq, irq_handler_t handle, int is_chained)
{
        struct irqdesc *desc;
        unsigned long flags;

        if (irq >= NR_IRQS) {
                printk(KERN_ERR "Trying to install handler for IRQ%d\n", irq);
                return;
        }

        if (handle == NULL)
                handle = do_bad_IRQ;

        desc = irq_desc + irq;

        if (is_chained && desc->chip == &bad_chip)
                printk(KERN_WARNING "Trying to install chained handler for IRQ%d\n", irq);

        spin_lock_irqsave(&irq_controller_lock, flags);
        if (handle == do_bad_IRQ) {
                desc->chip->mask(irq);
                desc->chip->ack(irq);
                desc->depth = 1;
                desc->enabled = 0;
        }
        desc->handle = handle;
        if (handle != do_bad_IRQ && is_chained) {
                desc->valid = 0;
                desc->probe_ok = 0;
                desc->depth = 0;
                desc->chip->unmask(irq);
        }
        spin_unlock_irqrestore(&irq_controller_lock, flags);
}

void set_irq_chip(unsigned int irq, struct irqchip *chip)
{
        struct irqdesc *desc;
        unsigned long flags;

        if (irq >= NR_IRQS) {
                printk(KERN_ERR "Trying to install chip for IRQ%d\n", irq);
                return;
        }

        if (chip == NULL)
                chip = &bad_chip;

        desc = irq_desc + irq;
        spin_lock_irqsave(&irq_controller_lock, flags);
        desc->chip = chip;
        spin_unlock_irqrestore(&irq_controller_lock, flags);
}

int set_irq_type(unsigned int irq, unsigned int type)
{
        struct irqdesc *desc;
        unsigned long flags;
        int ret = -ENXIO;

        if (irq >= NR_IRQS) {
                printk(KERN_ERR "Trying to set irq type for IRQ%d\n", irq);
                return -ENODEV;
        }

        desc = irq_desc + irq;
        if (desc->chip->type) {
                spin_lock_irqsave(&irq_controller_lock, flags);
                ret = desc->chip->type(irq, type);
                spin_unlock_irqrestore(&irq_controller_lock, flags);
        }

        return ret;
}

void set_irq_flags(unsigned int irq, unsigned int iflags)
{
        struct irqdesc *desc;
        unsigned long flags;

        if (irq >= NR_IRQS) {
                printk(KERN_ERR "Trying to set irq flags for IRQ%d\n", irq);
                return;
        }

        desc = irq_desc + irq;
        spin_lock_irqsave(&irq_controller_lock, flags);
        desc->valid = (iflags & IRQF_VALID) != 0;
        desc->probe_ok = (iflags & IRQF_PROBE) != 0;
        desc->noautoenable = (iflags & IRQF_NOAUTOEN) != 0;
        spin_unlock_irqrestore(&irq_controller_lock, flags);
}

int setup_irq(unsigned int irq, struct irqaction *new)
{
        int shared = 0;
        struct irqaction *old, **p;
        unsigned long flags;
        struct irqdesc *desc;

        /*
         * Some drivers like serial.c use request_irq() heavily,
         * so we have to be careful not to interfere with a
         * running system.
         */
        if (new->flags & SA_SAMPLE_RANDOM) {
                /*
                 * This function might sleep, we want to call it first,
                 * outside of the atomic block.
                 * Yes, this might clear the entropy pool if the wrong
                 * driver is attempted to be loaded, without actually
                 * installing a new handler, but is this really a problem,
                 * only the sysadmin is able to do this.
                 */
                rand_initialize_irq(irq);
        }

        /*
         * The following block of code has to be executed atomically
         */
        desc = irq_desc + irq;
        spin_lock_irqsave(&irq_controller_lock, flags);
        p = &desc->action;
        if ((old = *p) != NULL) {
                /* Can't share interrupts unless both agree to */
                if (!(old->flags & new->flags & SA_SHIRQ)) {
                        spin_unlock_irqrestore(&irq_controller_lock, flags);
                        return -EBUSY;
                }

                /* add new interrupt at end of irq queue */
                do {
                        p = &old->next;
                        old = *p;
                } while (old);
                shared = 1;
        }

        *p = new;

        if (!shared) {
                desc->probing = 0;
                desc->running = 0;
                desc->pending = 0;
                desc->depth = 1;
                if (!desc->noautoenable) {
                        desc->depth = 0;
                        desc->enabled = 1;
                        desc->chip->unmask(irq);
                }
        }

        spin_unlock_irqrestore(&irq_controller_lock, flags);
        return 0;
}

/**
 *      request_irq - allocate an interrupt line
 *      @irq: Interrupt line to allocate
 *      @handler: Function to be called when the IRQ occurs
 *      @irqflags: Interrupt type flags
 *      @devname: An ascii name for the claiming device
 *      @dev_id: A cookie passed back to the handler function
 *
 *      This call allocates interrupt resources and enables the
 *      interrupt line and IRQ handling. From the point this
 *      call is made your handler function may be invoked. Since
 *      your handler function must clear any interrupt the board
 *      raises, you must take care both to initialise your hardware
 *      and to set up the interrupt handler in the right order.
 *
 *      Dev_id must be globally unique. Normally the address of the
 *      device data structure is used as the cookie. Since the handler
 *      receives this value it makes sense to use it.
 *
 *      If your interrupt is shared you must pass a non NULL dev_id
 *      as this is required when freeing the interrupt.
 *
 *      Flags:
 *
 *      SA_SHIRQ                Interrupt is shared
 *
 *      SA_INTERRUPT            Disable local interrupts while processing
 *
 *      SA_SAMPLE_RANDOM        The interrupt can be used for entropy
 *
 */

//FIXME - handler used to return void - whats the significance of the change?
int request_irq(unsigned int irq, irqreturn_t (*handler)(int, void *, struct pt_regs *),
                 unsigned long irq_flags, const char * devname, void *dev_id)
{
        unsigned long retval;
        struct irqaction *action;

        if (irq >= NR_IRQS || !irq_desc[irq].valid || !handler ||
            (irq_flags & SA_SHIRQ && !dev_id))
                return -EINVAL;

        action = (struct irqaction *)kmalloc(sizeof(struct irqaction), GFP_KERNEL);
        if (!action)
                return -ENOMEM;

        action->handler = handler;
        action->flags = irq_flags;
        cpus_clear(action->mask);
        action->name = devname;
        action->next = NULL;
        action->dev_id = dev_id;

        retval = setup_irq(irq, action);

        if (retval)
                kfree(action);
        return retval;
}

EXPORT_SYMBOL(request_irq);

/**
 *      free_irq - free an interrupt
 *      @irq: Interrupt line to free
 *      @dev_id: Device identity to free
 *
 *      Remove an interrupt handler. The handler is removed and if the
 *      interrupt line is no longer in use by any driver it is disabled.
 *      On a shared IRQ the caller must ensure the interrupt is disabled
 *      on the card it drives before calling this function.
 *
 *      This function may be called from interrupt context.
 */
void free_irq(unsigned int irq, void *dev_id)
{
        struct irqaction * action, **p;
        unsigned long flags;

        if (irq >= NR_IRQS || !irq_desc[irq].valid) {
                printk(KERN_ERR "Trying to free IRQ%d\n",irq);
#ifdef CONFIG_DEBUG_ERRORS
                __backtrace();
#endif
                return;
        }

        spin_lock_irqsave(&irq_controller_lock, flags);
        for (p = &irq_desc[irq].action; (action = *p) != NULL; p = &action->next) {
                if (action->dev_id != dev_id)
                        continue;

                /* Found it - now free it */
                *p = action->next;
                kfree(action);
                goto out;
        }
        printk(KERN_ERR "Trying to free free IRQ%d\n",irq);
#ifdef CONFIG_DEBUG_ERRORS
        __backtrace();
#endif
out:
        spin_unlock_irqrestore(&irq_controller_lock, flags);
}

EXPORT_SYMBOL(free_irq);

/* Start the interrupt probing.  Unlike other architectures,
 * we don't return a mask of interrupts from probe_irq_on,
 * but return the number of interrupts enabled for the probe.
 * The interrupts which have been enabled for probing is
 * instead recorded in the irq_desc structure.
 */
unsigned long probe_irq_on(void)
{
        unsigned int i, irqs = 0;
        unsigned long delay;

        /*
         * first snaffle up any unassigned but
         * probe-able interrupts
         */
        spin_lock_irq(&irq_controller_lock);
        for (i = 0; i < NR_IRQS; i++) {
                if (!irq_desc[i].probe_ok || irq_desc[i].action)
                        continue;

                irq_desc[i].probing = 1;
                irq_desc[i].triggered = 0;
                if (irq_desc[i].chip->type)
                        irq_desc[i].chip->type(i, IRQT_PROBE);
                irq_desc[i].chip->unmask(i);
                irqs += 1;
        }
        spin_unlock_irq(&irq_controller_lock);

        /*
         * wait for spurious interrupts to mask themselves out again
         */
        for (delay = jiffies + HZ/10; time_before(jiffies, delay); )
                /* min 100ms delay */;

        /*
         * now filter out any obviously spurious interrupts
         */
        spin_lock_irq(&irq_controller_lock);
        for (i = 0; i < NR_IRQS; i++) {
                if (irq_desc[i].probing && irq_desc[i].triggered) {
                        irq_desc[i].probing = 0;
                        irqs -= 1;
                }
        }
        spin_unlock_irq(&irq_controller_lock);

        return irqs;
}

EXPORT_SYMBOL(probe_irq_on);

/*
 * Possible return values:
 *  >= 0 - interrupt number
 *    -1 - no interrupt/many interrupts
 */
int probe_irq_off(unsigned long irqs)
{
        unsigned int i;
        int irq_found = NO_IRQ;

        /*
         * look at the interrupts, and find exactly one
         * that we were probing has been triggered
         */
        spin_lock_irq(&irq_controller_lock);
        for (i = 0; i < NR_IRQS; i++) {
                if (irq_desc[i].probing &&
                    irq_desc[i].triggered) {
                        if (irq_found != NO_IRQ) {
                                irq_found = NO_IRQ;
                                goto out;
                        }
                        irq_found = i;
                }
        }

        if (irq_found == -1)
                irq_found = NO_IRQ;
out:
        spin_unlock_irq(&irq_controller_lock);

        return irq_found;
}

EXPORT_SYMBOL(probe_irq_off);

void __init init_irq_proc(void)
{
}

void __init init_IRQ(void)
{
        struct irqdesc *desc;
        extern void init_dma(void);
        int irq;

        for (irq = 0, desc = irq_desc; irq < NR_IRQS; irq++, desc++)
                *desc = bad_irq_desc;

        arc_init_irq();
        init_dma();
}