/*
   * linux/kernel/irq/spurious.c
   *
   * Copyright (C) 1992, 1998-2004 Linus Torvalds, Ingo Molnar
   *
   * This file contains spurious interrupt handling.
   */

  #include <linux/jiffies.h>

  #include <linux/irq.h>
  #include <linux/module.h>
  #include <linux/kallsyms.h>
  #include <linux/interrupt.h>

  #include <linux/moduleparam.h>

  #include <linux/timer.h>

  #include "internals.h"

  static int irqfixup __read_mostly;

  #define POLL_SPURIOUS_IRQ_INTERVAL (HZ/10)
  static void poll_spurious_irqs(unsigned long dummy);
  static DEFINE_TIMER(poll_spurious_irq_timer, poll_spurious_irqs, 0, 0);

  static int irq_poll_cpu;
  static atomic_t irq_poll_active;

  /*

   * We wait here for a poller to finish.
   *
   * If the poll runs on this CPU, then we yell loudly and return
   * false. That will leave the interrupt line disabled in the worst
   * case, but it should never happen.
   *
   * We wait until the poller is done and then recheck disabled and
   * action (about to be disabled). Only if it's still active, we return
   * true and let the handler run.
   */
  bool irq_wait_for_poll(struct irq_desc *desc)
  {
  	if (WARN_ONCE(irq_poll_cpu == smp_processor_id(),
  		      "irq poll in progress on cpu %d for irq %d
  ",
  		      smp_processor_id(), desc->irq_data.irq))
  		return false;
  
  #ifdef CONFIG_SMP
  	do {
  		raw_spin_unlock(&desc->lock);

  		while (irqd_irq_inprogress(&desc->irq_data))

  			cpu_relax();
  		raw_spin_lock(&desc->lock);

  	} while (irqd_irq_inprogress(&desc->irq_data));

  	/* Might have been disabled in meantime */

  	return !irqd_irq_disabled(&desc->irq_data) && desc->action;

  #else
  	return false;
  #endif
  }

  /*

   * Recovery handler for misrouted interrupts.
   */

  static int try_one_irq(int irq, struct irq_desc *desc, bool force)

  {

  	irqreturn_t ret = IRQ_NONE;

  	struct irqaction *action;

  	raw_spin_lock(&desc->lock);

  
  	/* PER_CPU and nested thread interrupts are never polled */

  	if (irq_settings_is_per_cpu(desc) || irq_settings_is_nested_thread(desc))

  		goto out;
  
  	/*
  	 * Do not poll disabled interrupts unless the spurious
  	 * disabled poller asks explicitely.
  	 */

  	if (irqd_irq_disabled(&desc->irq_data) && !force)

  		goto out;
  
  	/*
  	 * All handlers must agree on IRQF_SHARED, so we test just the
  	 * first. Check for action->next as well.
  	 */
  	action = desc->action;
  	if (!action || !(action->flags & IRQF_SHARED) ||

  	    (action->flags & __IRQF_TIMER) ||
  	    (action->handler(irq, action->dev_id) == IRQ_HANDLED) ||
  	    !action->next)

  		goto out;

  	/* Already running on another processor */

  	if (irqd_irq_inprogress(&desc->irq_data)) {

  		/*
  		 * Already running: If it is shared get the other
  		 * CPU to go looking for our mystery interrupt too
  		 */

  		desc->istate |= IRQS_PENDING;

  		goto out;

  	}

  	/* Mark it poll in progress */

  	desc->istate |= IRQS_POLL_INPROGRESS;

  	do {

  		if (handle_irq_event(desc) == IRQ_HANDLED)
  			ret = IRQ_HANDLED;

  		action = desc->action;

  	} while ((desc->istate & IRQS_PENDING) && action);

  	desc->istate &= ~IRQS_POLL_INPROGRESS;

  out:
  	raw_spin_unlock(&desc->lock);

  	return ret == IRQ_HANDLED;

  }
  
  static int misrouted_irq(int irq)
  {

  	struct irq_desc *desc;

  	int i, ok = 0;

  	if (atomic_inc_return(&irq_poll_active) != 1)

  		goto out;
  
  	irq_poll_cpu = smp_processor_id();

  	for_each_irq_desc(i, desc) {
  		if (!i)
  			 continue;

  
  		if (i == irq)	/* Already tried */
  			continue;

  		if (try_one_irq(i, desc, false))

  			ok = 1;

  	}

  out:
  	atomic_dec(&irq_poll_active);

  	/* So the caller can adjust the irq error counts */
  	return ok;
  }

  static void poll_spurious_irqs(unsigned long dummy)

  {

  	struct irq_desc *desc;

  	int i;

  	if (atomic_inc_return(&irq_poll_active) != 1)
  		goto out;
  	irq_poll_cpu = smp_processor_id();

  	for_each_irq_desc(i, desc) {

  		unsigned int state;

  		if (!i)
  			 continue;

  		/* Racy but it doesn't matter */

  		state = desc->istate;

  		barrier();

  		if (!(state & IRQS_SPURIOUS_DISABLED))

  			continue;

  		local_irq_disable();

  		try_one_irq(i, desc, true);

  		local_irq_enable();

  	}

  out:
  	atomic_dec(&irq_poll_active);

  	mod_timer(&poll_spurious_irq_timer,
  		  jiffies + POLL_SPURIOUS_IRQ_INTERVAL);

  }

  static inline int bad_action_ret(irqreturn_t action_ret)
  {
  	if (likely(action_ret <= (IRQ_HANDLED | IRQ_WAKE_THREAD)))
  		return 0;
  	return 1;
  }

  /*
   * If 99,900 of the previous 100,000 interrupts have not been handled
   * then assume that the IRQ is stuck in some manner. Drop a diagnostic
   * and try to turn the IRQ off.
   *
   * (The other 100-of-100,000 interrupts may have been a correctly
   *  functioning device sharing an IRQ with the failing one)

   */

  static void

  __report_bad_irq(unsigned int irq, struct irq_desc *desc,
  		 irqreturn_t action_ret)

  {
  	struct irqaction *action;

  	unsigned long flags;

  	if (bad_action_ret(action_ret)) {

  		printk(KERN_ERR "irq event %d: bogus return value %x
  ",
  				irq, action_ret);
  	} else {

  		printk(KERN_ERR "irq %d: nobody cared (try booting with "
  				"the \"irqpoll\" option)
  ", irq);

  	}
  	dump_stack();
  	printk(KERN_ERR "handlers:
  ");

  	/*
  	 * We need to take desc->lock here. note_interrupt() is called
  	 * w/o desc->lock held, but IRQ_PROGRESS set. We might race
  	 * with something else removing an action. It's ok to take
  	 * desc->lock here. See synchronize_irq().
  	 */
  	raw_spin_lock_irqsave(&desc->lock, flags);

  	action = desc->action;
  	while (action) {

  		printk(KERN_ERR "[<%p>] %pf", action->handler, action->handler);
  		if (action->thread_fn)
  			printk(KERN_CONT " threaded [<%p>] %pf",
  					action->thread_fn, action->thread_fn);
  		printk(KERN_CONT "
  ");

  		action = action->next;
  	}

  	raw_spin_unlock_irqrestore(&desc->lock, flags);

  }

  static void

  report_bad_irq(unsigned int irq, struct irq_desc *desc, irqreturn_t action_ret)

  {
  	static int count = 100;
  
  	if (count > 0) {
  		count--;
  		__report_bad_irq(irq, desc, action_ret);
  	}
  }

  static inline int
  try_misrouted_irq(unsigned int irq, struct irq_desc *desc,
  		  irqreturn_t action_ret)

  {
  	struct irqaction *action;
  
  	if (!irqfixup)
  		return 0;
  
  	/* We didn't actually handle the IRQ - see if it was misrouted? */
  	if (action_ret == IRQ_NONE)
  		return 1;
  
  	/*
  	 * But for 'irqfixup == 2' we also do it for handled interrupts if
  	 * they are marked as IRQF_IRQPOLL (or for irq zero, which is the
  	 * traditional PC timer interrupt.. Legacy)
  	 */
  	if (irqfixup < 2)
  		return 0;
  
  	if (!irq)
  		return 1;
  
  	/*
  	 * Since we don't get the descriptor lock, "action" can
  	 * change under us.  We don't really care, but we don't
  	 * want to follow a NULL pointer. So tell the compiler to
  	 * just load it once by using a barrier.
  	 */
  	action = desc->action;
  	barrier();
  	return action && (action->flags & IRQF_IRQPOLL);
  }

  void note_interrupt(unsigned int irq, struct irq_desc *desc,

  		    irqreturn_t action_ret)

  {

  	if (desc->istate & IRQS_POLL_INPROGRESS)

  		return;

  	/* we get here again via the threaded handler */
  	if (action_ret == IRQ_WAKE_THREAD)
  		return;
  
  	if (bad_action_ret(action_ret)) {
  		report_bad_irq(irq, desc, action_ret);
  		return;
  	}
  
  	if (unlikely(action_ret == IRQ_NONE)) {

  		/*
  		 * If we are seeing only the odd spurious IRQ caused by
  		 * bus asynchronicity then don't eventually trigger an error,

  		 * otherwise the counter becomes a doomsday timer for otherwise

  		 * working systems
  		 */

  		if (time_after(jiffies, desc->last_unhandled + HZ/10))

  			desc->irqs_unhandled = 1;
  		else
  			desc->irqs_unhandled++;
  		desc->last_unhandled = jiffies;

  	}

  	if (unlikely(try_misrouted_irq(irq, desc, action_ret))) {
  		int ok = misrouted_irq(irq);
  		if (action_ret == IRQ_NONE)
  			desc->irqs_unhandled -= ok;

  	}

  	desc->irq_count++;

  	if (likely(desc->irq_count < 100000))

  		return;
  
  	desc->irq_count = 0;

  	if (unlikely(desc->irqs_unhandled > 99900)) {

  		/*
  		 * The interrupt is stuck
  		 */
  		__report_bad_irq(irq, desc, action_ret);
  		/*
  		 * Now kill the IRQ
  		 */
  		printk(KERN_EMERG "Disabling IRQ #%d
  ", irq);

  		desc->istate |= IRQS_SPURIOUS_DISABLED;

  		desc->depth++;

  		irq_disable(desc);

  		mod_timer(&poll_spurious_irq_timer,
  			  jiffies + POLL_SPURIOUS_IRQ_INTERVAL);

  	}
  	desc->irqs_unhandled = 0;
  }

  bool noirqdebug __read_mostly;

  int noirqdebug_setup(char *str)

  {
  	noirqdebug = 1;
  	printk(KERN_INFO "IRQ lockup detection disabled
  ");

  	return 1;
  }
  
  __setup("noirqdebug", noirqdebug_setup);

  module_param(noirqdebug, bool, 0644);
  MODULE_PARM_DESC(noirqdebug, "Disable irq lockup detection when true");

  static int __init irqfixup_setup(char *str)
  {
  	irqfixup = 1;
  	printk(KERN_WARNING "Misrouted IRQ fixup support enabled.
  ");
  	printk(KERN_WARNING "This may impact system performance.
  ");

  	return 1;
  }
  
  __setup("irqfixup", irqfixup_setup);

  module_param(irqfixup, int, 0644);

  
  static int __init irqpoll_setup(char *str)
  {
  	irqfixup = 2;
  	printk(KERN_WARNING "Misrouted IRQ fixup and polling support "
  				"enabled
  ");
  	printk(KERN_WARNING "This may significantly impact system "
  				"performance
  ");
  	return 1;
  }
  
  __setup("irqpoll", irqpoll_setup);