irq.c

/*
 *  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/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);
}
EXPORT_SYMBOL(disable_irq);

void disable_irq_nosync(unsigned int irq) __attribute__((alias("disable_irq")));

EXPORT_SYMBOL(disable_irq_nosync);

/**
 *	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);
}
EXPORT_SYMBOL(enable_irq);

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)
			goto out;
		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);
	}
out:
	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 & IRQF_DISABLED))
		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 & IRQF_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 & IRQF_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 & IRQF_SHARED)) {
			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:
 *
 *	IRQF_SHARED		Interrupt is shared
 *
 *	IRQF_DISABLED	Disable local interrupts while processing
 *
 *	IRQF_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 & IRQF_SHARED && !dev_id))
		return -EINVAL;

	action = 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();
}