irq.c

该文件是rt_linux

/*
 * SMP flags value to restore to:
 * 0 - global cli
 * 1 - global sti
 * 2 - local cli
 * 3 - local sti
 */
unsigned long __global_save_flags(void)
{
	int retval;
	int local_enabled;
	unsigned long flags;
	int cpu = smp_processor_id();

	__save_flags(flags);
#ifdef CONFIG_IA64
	local_enabled = (flags & IA64_PSR_I) != 0;
#else
	local_enabled = (flags >> EFLAGS_IF_SHIFT) & 1;
#endif
	/* default to local */
	retval = 2 + local_enabled;

	/* check for global flags if we're not in an interrupt */
	if (!really_local_irq_count()) {
		if (local_enabled)
			retval = 1;
		if (global_irq_holder == cpu)
			retval = 0;
	}
	return retval;
}

void __global_restore_flags(unsigned long flags)
{
	switch (flags) {
	case 0:
		__global_cli();
		break;
	case 1:
		__global_sti();
		break;
	case 2:
		__cli();
		break;
	case 3:
		__sti();
		break;
	default:
		printk("global_restore_flags: %08lx (%08lx)\n",
			flags, (&flags)[-1]);
	}
}

#endif

/*
 * This should really return information about whether
 * we should do bottom half handling etc. Right now we
 * end up _always_ checking the bottom half, which is a
 * waste of time and is not what some drivers would
 * prefer.
 */
int handle_IRQ_event(unsigned int irq, struct pt_regs * regs, struct irqaction * action)
{
	int status;

	local_irq_enter(irq);

	status = 1;	/* Force the "do bottom halves" bit */

	if (!(action->flags & SA_INTERRUPT))
		__sti();

	do {
		status |= action->flags;
		action->handler(irq, action->dev_id, regs);
		action = action->next;
	} while (action);
	if (status & SA_SAMPLE_RANDOM)
		add_interrupt_randomness(irq);
	__cli();

	local_irq_exit(irq);

	return status;
}

/**
 *	disable_irq_nosync - disable an irq without waiting
 *	@irq: Interrupt to disable
 *
 *	Disable the selected interrupt line.  Disables and Enables are
 *	nested.
 *	Unlike disable_irq(), this function does not ensure existing
 *	instances of the IRQ handler have completed before returning.
 *
 *	This function may be called from IRQ context.
 */

inline void disable_irq_nosync(unsigned int irq)
{
	irq_desc_t *desc = irq_desc(irq);
	unsigned long flags;

	spin_lock_irqsave(&desc->lock, flags);
	if (!desc->depth++) {
		desc->status |= IRQ_DISABLED;
		desc->handler->disable(irq);
	}
	spin_unlock_irqrestore(&desc->lock, flags);
}

/**
 *	disable_irq - disable an irq and wait for completion
 *	@irq: Interrupt to disable
 *
 *	Disable the selected interrupt line.  Enables and Disables are
 *	nested.
 *	This function waits for any pending IRQ handlers for this interrupt
 *	to complete before returning. If you use this function while
 *	holding a resource the IRQ handler may need you will deadlock.
 *
 *	This function may be called - with care - from IRQ context.
 */

void disable_irq(unsigned int irq)
{
	disable_irq_nosync(irq);

#ifdef CONFIG_SMP
	if (!really_local_irq_count()) {
		do {
			barrier();
		} while (irq_desc(irq)->status & IRQ_INPROGRESS);
	}
#endif
}

/**
 *	enable_irq - enable handling of an irq
 *	@irq: Interrupt to enable
 *
 *	Undoes the effect of one call to disable_irq().  If this
 *	matches the last disable, processing of interrupts on this
 *	IRQ line is re-enabled.
 *
 *	This function may be called from IRQ context.
 */

void enable_irq(unsigned int irq)
{
	irq_desc_t *desc = irq_desc(irq);
	unsigned long flags;

	spin_lock_irqsave(&desc->lock, flags);
	switch (desc->depth) {
	case 1: {
		unsigned int status = desc->status & ~IRQ_DISABLED;
		desc->status = status;
		if ((status & (IRQ_PENDING | IRQ_REPLAY)) == IRQ_PENDING) {
			desc->status = status | IRQ_REPLAY;
			hw_resend_irq(desc->handler,irq);
		}
		desc->handler->enable(irq);
		/* fall-through */
	}
	default:
		desc->depth--;
		break;
	case 0:
		printk("enable_irq(%u) unbalanced from %p\n",
		       irq, (void *) __builtin_return_address(0));
	}
	spin_unlock_irqrestore(&desc->lock, flags);
}

/*
 * do_IRQ handles all normal device IRQ's (the special
 * SMP cross-CPU interrupts have their own specific
 * handlers).
 */
unsigned int do_IRQ(unsigned long irq, struct pt_regs *regs)
{
	/*
	 * 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)
	 */
	int cpu = smp_processor_id();
	irq_desc_t *desc = irq_desc(irq);
	struct irqaction * action;
	unsigned int status;

	kstat.irqs[cpu][irq]++;

	if (desc->status & IRQ_PER_CPU) {
		/* no locking required for CPU-local interrupts: */
		desc->handler->ack(irq);
		handle_IRQ_event(irq, regs, desc->action);
		desc->handler->end(irq);
	} else {
		spin_lock(&desc->lock);
		desc->handler->ack(irq);
		/*
		 * REPLAY is when Linux resends an IRQ that was dropped earlier
		 * WAITING is used by probe to mark irqs that are being tested
		 */
		status = desc->status & ~(IRQ_REPLAY | IRQ_WAITING);
		status |= IRQ_PENDING; /* we _want_ to handle it */

		/*
		 * If the IRQ is disabled for whatever reason, we cannot
		 * use the action we have.
		 */
		action = NULL;
		if (!(status & (IRQ_DISABLED | IRQ_INPROGRESS))) {
			action = desc->action;
			status &= ~IRQ_PENDING; /* we commit to handling */
			status |= IRQ_INPROGRESS; /* we are handling it */
		}
		desc->status = status;

		/*
		 * If there is no IRQ handler or it was disabled, exit early.
		 * Since we set PENDING, if another processor is handling
		 * a different instance of this same irq, the other processor
		 * will take care of it.
		 */
		if (!action)
			goto out;

		/*
		 * Edge triggered interrupts need to remember
		 * pending events.
		 * This applies to any hw interrupts that allow a second
		 * instance of the same irq to arrive while we are in do_IRQ
		 * or in the handler. But the code here only handles the _second_
		 * instance of the irq, not the third or fourth. So it is mostly
		 * useful for irq hardware that does not mask cleanly in an
		 * SMP environment.
		 */
		for (;;) {
			spin_unlock(&desc->lock);
			handle_IRQ_event(irq, regs, action);
			spin_lock(&desc->lock);

			if (!(desc->status & IRQ_PENDING))
				break;
			desc->status &= ~IRQ_PENDING;
		}
		desc->status &= ~IRQ_INPROGRESS;
	  out:
		/*
		 * The ->end() handler has to deal with interrupts which got
		 * disabled while the handler was running.
		 */
		desc->handler->end(irq);
		spin_unlock(&desc->lock);
	}
	return 1;
}

/**
 *	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
 *
 */

int request_irq(unsigned int irq,
		void (*handler)(int, void *, struct pt_regs *),
		unsigned long irqflags,
		const char * devname,
		void *dev_id)
{
	int retval;
	struct irqaction * action;

#if 1
	/*
	 * Sanity-check: shared interrupts should REALLY pass in
	 * a real dev-ID, otherwise we'll have trouble later trying
	 * to figure out which interrupt is which (messes up the
	 * interrupt freeing logic etc).
	 */
	if (irqflags & SA_SHIRQ) {
		if (!dev_id)
			printk("Bad boy: %s called us without a dev_id!\n", devname);
	}
#endif

	if (irq >= NR_IRQS)
		return -EINVAL;
	if (!handler)
		return -EINVAL;

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

	action->handler = handler;
	action->flags = irqflags;
	action->mask = 0;
	action->name = devname;
	action->next = NULL;
	action->dev_id = dev_id;

	retval = setup_irq(irq, action);
	if (retval)
		kfree(action);
	return retval;
}

/**
 *	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. The function
 *	does not return until any executing interrupts for this IRQ
 *	have completed.
 *
 *	This function may be called from interrupt context. 
 *
 *	Bugs: Attempting to free an irq in a handler for the same irq hangs
 *	      the machine.
 */

void free_irq(unsigned int irq, void *dev_id)
{
	irq_desc_t *desc;
	struct irqaction **p;
	unsigned long flags;

	if (irq >= NR_IRQS)
		return;

	desc = irq_desc(irq);
	spin_lock_irqsave(&desc->lock,flags);
	p = &desc->action;
	for (;;) {
		struct irqaction * action = *p;
		if (action) {
			struct irqaction **pp = p;
			p = &action->next;
			if (action->dev_id != dev_id)
				continue;

			/* Found it - now remove it from the list of entries */
			*pp = action->next;
			if (!desc->action) {
				desc->status |= IRQ_DISABLED;
				desc->handler->shutdown(irq);
			}
			spin_unlock_irqrestore(&desc->lock,flags);

#ifdef CONFIG_SMP
			/* Wait to make sure it's not being used on another CPU */
			while (desc->status & IRQ_INPROGRESS)
				barrier();
#endif
			kfree(action);
			return;
		}
		printk("Trying to free free IRQ%d\n",irq);
		spin_unlock_irqrestore(&desc->lock,flags);
		return;
	}
}

/*
 * IRQ autodetection code..
 *
 * This depends on the fact that any interrupt that
 * comes in on to an unassigned handler will get stuck
 * with "IRQ_WAITING" cleared and the interrupt
 * disabled.
 */

static DECLARE_MUTEX(probe_sem);

/**
 *	probe_irq_on	- begin an interrupt autodetect
 *
 *	Commence probing for an interrupt. The interrupts are scanned