/*
   * linux/kernel/time/clockevents.c
   *
   * This file contains functions which manage clock event devices.
   *
   * Copyright(C) 2005-2006, Thomas Gleixner <tglx@linutronix.de>
   * Copyright(C) 2005-2007, Red Hat, Inc., Ingo Molnar
   * Copyright(C) 2006-2007, Timesys Corp., Thomas Gleixner
   *
   * This code is licenced under the GPL version 2. For details see
   * kernel-base/COPYING.
   */
  
  #include <linux/clockchips.h>
  #include <linux/hrtimer.h>
  #include <linux/init.h>
  #include <linux/module.h>

  #include <linux/smp.h>

  #include <linux/device.h>

  #include "tick-internal.h"

  /* The registered clock event devices */
  static LIST_HEAD(clockevent_devices);
  static LIST_HEAD(clockevents_released);

  /* Protection for the above */

  static DEFINE_RAW_SPINLOCK(clockevents_lock);

  /* Protection for unbind operations */
  static DEFINE_MUTEX(clockevents_mutex);
  
  struct ce_unbind {
  	struct clock_event_device *ce;
  	int res;
  };

  static u64 cev_delta2ns(unsigned long latch, struct clock_event_device *evt,
  			bool ismax)

  {

  	u64 clc = (u64) latch << evt->shift;

  	u64 rnd;

  	if (unlikely(!evt->mult)) {
  		evt->mult = 1;
  		WARN_ON(1);
  	}

  	rnd = (u64) evt->mult - 1;
  
  	/*
  	 * Upper bound sanity check. If the backwards conversion is
  	 * not equal latch, we know that the above shift overflowed.
  	 */
  	if ((clc >> evt->shift) != (u64)latch)
  		clc = ~0ULL;
  
  	/*
  	 * Scaled math oddities:
  	 *
  	 * For mult <= (1 << shift) we can safely add mult - 1 to
  	 * prevent integer rounding loss. So the backwards conversion
  	 * from nsec to device ticks will be correct.
  	 *
  	 * For mult > (1 << shift), i.e. device frequency is > 1GHz we
  	 * need to be careful. Adding mult - 1 will result in a value
  	 * which when converted back to device ticks can be larger
  	 * than latch by up to (mult - 1) >> shift. For the min_delta
  	 * calculation we still want to apply this in order to stay
  	 * above the minimum device ticks limit. For the upper limit
  	 * we would end up with a latch value larger than the upper
  	 * limit of the device, so we omit the add to stay below the
  	 * device upper boundary.
  	 *
  	 * Also omit the add if it would overflow the u64 boundary.
  	 */
  	if ((~0ULL - clc > rnd) &&

  	    (!ismax || evt->mult <= (1ULL << evt->shift)))

  		clc += rnd;

  	do_div(clc, evt->mult);

  	/* Deltas less than 1usec are pointless noise */
  	return clc > 1000 ? clc : 1000;
  }
  
  /**
   * clockevents_delta2ns - Convert a latch value (device ticks) to nanoseconds
   * @latch:	value to convert
   * @evt:	pointer to clock event device descriptor
   *
   * Math helper, returns latch value converted to nanoseconds (bound checked)
   */
  u64 clockevent_delta2ns(unsigned long latch, struct clock_event_device *evt)
  {
  	return cev_delta2ns(latch, evt, false);

  }

  EXPORT_SYMBOL_GPL(clockevent_delta2ns);

  static int __clockevents_switch_state(struct clock_event_device *dev,
  				      enum clock_event_state state)

  {

  	if (dev->features & CLOCK_EVT_FEAT_DUMMY)
  		return 0;

  	/* Transition with new state-specific callbacks */
  	switch (state) {
  	case CLOCK_EVT_STATE_DETACHED:

  		/* The clockevent device is getting replaced. Shut it down. */

  	case CLOCK_EVT_STATE_SHUTDOWN:

  		if (dev->set_state_shutdown)
  			return dev->set_state_shutdown(dev);
  		return 0;

  	case CLOCK_EVT_STATE_PERIODIC:

  		/* Core internal bug */
  		if (!(dev->features & CLOCK_EVT_FEAT_PERIODIC))
  			return -ENOSYS;

  		if (dev->set_state_periodic)
  			return dev->set_state_periodic(dev);
  		return 0;

  	case CLOCK_EVT_STATE_ONESHOT:

  		/* Core internal bug */
  		if (!(dev->features & CLOCK_EVT_FEAT_ONESHOT))
  			return -ENOSYS;

  		if (dev->set_state_oneshot)
  			return dev->set_state_oneshot(dev);
  		return 0;

  	case CLOCK_EVT_STATE_ONESHOT_STOPPED:
  		/* Core internal bug */

  		if (WARN_ONCE(!clockevent_state_oneshot(dev),

  			      "Current state: %d
  ",
  			      clockevent_get_state(dev)))

  			return -EINVAL;
  
  		if (dev->set_state_oneshot_stopped)
  			return dev->set_state_oneshot_stopped(dev);
  		else
  			return -ENOSYS;

  	default:
  		return -ENOSYS;
  	}
  }

  /**

   * clockevents_switch_state - set the operating state of a clock event device

   * @dev:	device to modify

   * @state:	new state

   *
   * Must be called with interrupts disabled !
   */

  void clockevents_switch_state(struct clock_event_device *dev,
  			      enum clock_event_state state)

  {

  	if (clockevent_get_state(dev) != state) {

  		if (__clockevents_switch_state(dev, state))

  			return;

  		clockevent_set_state(dev, state);

  
  		/*
  		 * A nsec2cyc multiplicator of 0 is invalid and we'd crash
  		 * on it, so fix it up and emit a warning:
  		 */

  		if (clockevent_state_oneshot(dev)) {

  			if (unlikely(!dev->mult)) {
  				dev->mult = 1;
  				WARN_ON(1);
  			}
  		}

  	}
  }
  
  /**

   * clockevents_shutdown - shutdown the device and clear next_event
   * @dev:	device to shutdown
   */
  void clockevents_shutdown(struct clock_event_device *dev)
  {

  	clockevents_switch_state(dev, CLOCK_EVT_STATE_SHUTDOWN);

  	dev->next_event = KTIME_MAX;

  }

  /**
   * clockevents_tick_resume -	Resume the tick device before using it again
   * @dev:			device to resume
   */
  int clockevents_tick_resume(struct clock_event_device *dev)
  {
  	int ret = 0;

  	if (dev->tick_resume)

  		ret = dev->tick_resume(dev);

  
  	return ret;
  }

  #ifdef CONFIG_GENERIC_CLOCKEVENTS_MIN_ADJUST
  
  /* Limit min_delta to a jiffie */
  #define MIN_DELTA_LIMIT		(NSEC_PER_SEC / HZ)
  
  /**
   * clockevents_increase_min_delta - raise minimum delta of a clock event device
   * @dev:       device to increase the minimum delta
   *
   * Returns 0 on success, -ETIME when the minimum delta reached the limit.
   */
  static int clockevents_increase_min_delta(struct clock_event_device *dev)
  {
  	/* Nothing to do if we already reached the limit */
  	if (dev->min_delta_ns >= MIN_DELTA_LIMIT) {

  		printk_deferred(KERN_WARNING
  				"CE: Reprogramming failure. Giving up
  ");

  		dev->next_event = KTIME_MAX;

  		return -ETIME;
  	}
  
  	if (dev->min_delta_ns < 5000)
  		dev->min_delta_ns = 5000;
  	else
  		dev->min_delta_ns += dev->min_delta_ns >> 1;
  
  	if (dev->min_delta_ns > MIN_DELTA_LIMIT)
  		dev->min_delta_ns = MIN_DELTA_LIMIT;

  	printk_deferred(KERN_WARNING
  			"CE: %s increased min_delta_ns to %llu nsec
  ",
  			dev->name ? dev->name : "?",
  			(unsigned long long) dev->min_delta_ns);

  	return 0;
  }
  
  /**
   * clockevents_program_min_delta - Set clock event device to the minimum delay.
   * @dev:	device to program
   *
   * Returns 0 on success, -ETIME when the retry loop failed.
   */
  static int clockevents_program_min_delta(struct clock_event_device *dev)
  {
  	unsigned long long clc;
  	int64_t delta;
  	int i;
  
  	for (i = 0;;) {
  		delta = dev->min_delta_ns;
  		dev->next_event = ktime_add_ns(ktime_get(), delta);

  		if (clockevent_state_shutdown(dev))

  			return 0;
  
  		dev->retries++;
  		clc = ((unsigned long long) delta * dev->mult) >> dev->shift;
  		if (dev->set_next_event((unsigned long) clc, dev) == 0)
  			return 0;
  
  		if (++i > 2) {
  			/*
  			 * We tried 3 times to program the device with the
  			 * given min_delta_ns. Try to increase the minimum
  			 * delta, if that fails as well get out of here.
  			 */
  			if (clockevents_increase_min_delta(dev))
  				return -ETIME;
  			i = 0;
  		}
  	}
  }
  
  #else  /* CONFIG_GENERIC_CLOCKEVENTS_MIN_ADJUST */
  
  /**
   * clockevents_program_min_delta - Set clock event device to the minimum delay.
   * @dev:	device to program
   *
   * Returns 0 on success, -ETIME when the retry loop failed.
   */
  static int clockevents_program_min_delta(struct clock_event_device *dev)
  {
  	unsigned long long clc;

  	int64_t delta = 0;
  	int i;

  	for (i = 0; i < 10; i++) {
  		delta += dev->min_delta_ns;
  		dev->next_event = ktime_add_ns(ktime_get(), delta);

  		if (clockevent_state_shutdown(dev))
  			return 0;

  		dev->retries++;
  		clc = ((unsigned long long) delta * dev->mult) >> dev->shift;
  		if (dev->set_next_event((unsigned long) clc, dev) == 0)
  			return 0;
  	}
  	return -ETIME;

  }
  
  #endif /* CONFIG_GENERIC_CLOCKEVENTS_MIN_ADJUST */

  /**

   * clockevents_program_event - Reprogram the clock event device.

   * @dev:	device to program

   * @expires:	absolute expiry time (monotonic clock)

   * @force:	program minimum delay if expires can not be set

   *
   * Returns 0 on success, -ETIME when the event is in the past.
   */
  int clockevents_program_event(struct clock_event_device *dev, ktime_t expires,

  			      bool force)

  {
  	unsigned long long clc;
  	int64_t delta;

  	int rc;

  	if (unlikely(expires < 0)) {

  		WARN_ON_ONCE(1);
  		return -ETIME;
  	}

  	dev->next_event = expires;

  	if (clockevent_state_shutdown(dev))

  		return 0;

  	/* We must be in ONESHOT state here */

  	WARN_ONCE(!clockevent_state_oneshot(dev), "Current state: %d
  ",

  		  clockevent_get_state(dev));

  	/* Shortcut for clockevent devices that can deal with ktime. */
  	if (dev->features & CLOCK_EVT_FEAT_KTIME)
  		return dev->set_next_ktime(expires, dev);

  	delta = ktime_to_ns(ktime_sub(expires, ktime_get()));
  	if (delta <= 0)
  		return force ? clockevents_program_min_delta(dev) : -ETIME;

  	delta = min(delta, (int64_t) dev->max_delta_ns);
  	delta = max(delta, (int64_t) dev->min_delta_ns);

  	clc = ((unsigned long long) delta * dev->mult) >> dev->shift;
  	rc = dev->set_next_event((unsigned long) clc, dev);
  
  	return (rc && force) ? clockevents_program_min_delta(dev) : rc;

  }

  /*

   * Called after a notify add to make devices available which were

   * released from the notifier call.
   */
  static void clockevents_notify_released(void)
  {
  	struct clock_event_device *dev;
  
  	while (!list_empty(&clockevents_released)) {
  		dev = list_entry(clockevents_released.next,
  				 struct clock_event_device, list);
  		list_del(&dev->list);
  		list_add(&dev->list, &clockevent_devices);

  		tick_check_new_device(dev);

  	}
  }

  /*
   * Try to install a replacement clock event device
   */
  static int clockevents_replace(struct clock_event_device *ced)
  {
  	struct clock_event_device *dev, *newdev = NULL;
  
  	list_for_each_entry(dev, &clockevent_devices, list) {

  		if (dev == ced || !clockevent_state_detached(dev))

  			continue;
  
  		if (!tick_check_replacement(newdev, dev))
  			continue;
  
  		if (!try_module_get(dev->owner))
  			continue;
  
  		if (newdev)
  			module_put(newdev->owner);
  		newdev = dev;
  	}
  	if (newdev) {
  		tick_install_replacement(newdev);
  		list_del_init(&ced->list);
  	}
  	return newdev ? 0 : -EBUSY;
  }
  
  /*
   * Called with clockevents_mutex and clockevents_lock held
   */
  static int __clockevents_try_unbind(struct clock_event_device *ced, int cpu)
  {
  	/* Fast track. Device is unused */

  	if (clockevent_state_detached(ced)) {

  		list_del_init(&ced->list);
  		return 0;
  	}
  
  	return ced == per_cpu(tick_cpu_device, cpu).evtdev ? -EAGAIN : -EBUSY;
  }
  
  /*
   * SMP function call to unbind a device
   */
  static void __clockevents_unbind(void *arg)
  {
  	struct ce_unbind *cu = arg;
  	int res;
  
  	raw_spin_lock(&clockevents_lock);
  	res = __clockevents_try_unbind(cu->ce, smp_processor_id());
  	if (res == -EAGAIN)
  		res = clockevents_replace(cu->ce);
  	cu->res = res;
  	raw_spin_unlock(&clockevents_lock);
  }
  
  /*
   * Issues smp function call to unbind a per cpu device. Called with
   * clockevents_mutex held.
   */
  static int clockevents_unbind(struct clock_event_device *ced, int cpu)
  {
  	struct ce_unbind cu = { .ce = ced, .res = -ENODEV };
  
  	smp_call_function_single(cpu, __clockevents_unbind, &cu, 1);
  	return cu.res;
  }
  
  /*
   * Unbind a clockevents device.
   */
  int clockevents_unbind_device(struct clock_event_device *ced, int cpu)
  {
  	int ret;
  
  	mutex_lock(&clockevents_mutex);
  	ret = clockevents_unbind(ced, cpu);
  	mutex_unlock(&clockevents_mutex);
  	return ret;
  }

  EXPORT_SYMBOL_GPL(clockevents_unbind_device);

  /**
   * clockevents_register_device - register a clock event device
   * @dev:	device to register
   */
  void clockevents_register_device(struct clock_event_device *dev)
  {

  	unsigned long flags;

  	/* Initialize state to DETACHED */

  	clockevent_set_state(dev, CLOCK_EVT_STATE_DETACHED);

  	if (!dev->cpumask) {
  		WARN_ON(num_possible_cpus() > 1);
  		dev->cpumask = cpumask_of(smp_processor_id());
  	}

  	raw_spin_lock_irqsave(&clockevents_lock, flags);

  
  	list_add(&dev->list, &clockevent_devices);

  	tick_check_new_device(dev);

  	clockevents_notify_released();

  	raw_spin_unlock_irqrestore(&clockevents_lock, flags);

  }

  EXPORT_SYMBOL_GPL(clockevents_register_device);

  static void clockevents_config(struct clock_event_device *dev, u32 freq)

  {

  	u64 sec;

  
  	if (!(dev->features & CLOCK_EVT_FEAT_ONESHOT))
  		return;
  
  	/*
  	 * Calculate the maximum number of seconds we can sleep. Limit
  	 * to 10 minutes for hardware which can program more than
  	 * 32bit ticks so we still get reasonable conversion values.
  	 */
  	sec = dev->max_delta_ticks;
  	do_div(sec, freq);
  	if (!sec)
  		sec = 1;
  	else if (sec > 600 && dev->max_delta_ticks > UINT_MAX)
  		sec = 600;
  
  	clockevents_calc_mult_shift(dev, freq, sec);

  	dev->min_delta_ns = cev_delta2ns(dev->min_delta_ticks, dev, false);
  	dev->max_delta_ns = cev_delta2ns(dev->max_delta_ticks, dev, true);

  }
  
  /**
   * clockevents_config_and_register - Configure and register a clock event device
   * @dev:	device to register
   * @freq:	The clock frequency
   * @min_delta:	The minimum clock ticks to program in oneshot mode
   * @max_delta:	The maximum clock ticks to program in oneshot mode
   *
   * min/max_delta can be 0 for devices which do not support oneshot mode.
   */
  void clockevents_config_and_register(struct clock_event_device *dev,
  				     u32 freq, unsigned long min_delta,
  				     unsigned long max_delta)
  {
  	dev->min_delta_ticks = min_delta;
  	dev->max_delta_ticks = max_delta;
  	clockevents_config(dev, freq);
  	clockevents_register_device(dev);
  }

  EXPORT_SYMBOL_GPL(clockevents_config_and_register);

  int __clockevents_update_freq(struct clock_event_device *dev, u32 freq)
  {
  	clockevents_config(dev, freq);

  	if (clockevent_state_oneshot(dev))

  		return clockevents_program_event(dev, dev->next_event, false);

  	if (clockevent_state_periodic(dev))

  		return __clockevents_switch_state(dev, CLOCK_EVT_STATE_PERIODIC);

  	return 0;

  }

  /**
   * clockevents_update_freq - Update frequency and reprogram a clock event device.
   * @dev:	device to modify
   * @freq:	new device frequency
   *
   * Reconfigure and reprogram a clock event device in oneshot
   * mode. Must be called on the cpu for which the device delivers per

   * cpu timer events. If called for the broadcast device the core takes
   * care of serialization.
   *
   * Returns 0 on success, -ETIME when the event is in the past.

   */
  int clockevents_update_freq(struct clock_event_device *dev, u32 freq)
  {

  	unsigned long flags;
  	int ret;

  	local_irq_save(flags);
  	ret = tick_broadcast_update_freq(dev, freq);
  	if (ret == -ENODEV)
  		ret = __clockevents_update_freq(dev, freq);
  	local_irq_restore(flags);
  	return ret;

  }

  /*
   * Noop handler when we shut down an event device
   */

  void clockevents_handle_noop(struct clock_event_device *dev)

  {
  }
  
  /**
   * clockevents_exchange_device - release and request clock devices
   * @old:	device to release (can be NULL)
   * @new:	device to request (can be NULL)
   *

   * Called from various tick functions with clockevents_lock held and
   * interrupts disabled.

   */
  void clockevents_exchange_device(struct clock_event_device *old,
  				 struct clock_event_device *new)
  {

  	/*
  	 * Caller releases a clock event device. We queue it into the
  	 * released list and do a notify add later.
  	 */
  	if (old) {

  		module_put(old->owner);

  		clockevents_switch_state(old, CLOCK_EVT_STATE_DETACHED);

  		list_del(&old->list);
  		list_add(&old->list, &clockevents_released);
  	}
  
  	if (new) {

  		BUG_ON(!clockevent_state_detached(new));

  		clockevents_shutdown(new);

  	}

  }

  /**
   * clockevents_suspend - suspend clock devices
   */
  void clockevents_suspend(void)
  {
  	struct clock_event_device *dev;
  
  	list_for_each_entry_reverse(dev, &clockevent_devices, list)

  		if (dev->suspend && !clockevent_state_detached(dev))

  			dev->suspend(dev);
  }
  
  /**
   * clockevents_resume - resume clock devices
   */
  void clockevents_resume(void)
  {
  	struct clock_event_device *dev;
  
  	list_for_each_entry(dev, &clockevent_devices, list)

  		if (dev->resume && !clockevent_state_detached(dev))

  			dev->resume(dev);
  }

  #ifdef CONFIG_HOTPLUG_CPU

  /**

   * tick_cleanup_dead_cpu - Cleanup the tick and clockevents of a dead cpu

   */

  void tick_cleanup_dead_cpu(int cpu)

  {

  	struct clock_event_device *dev, *tmp;

  	unsigned long flags;

  	raw_spin_lock_irqsave(&clockevents_lock, flags);

  	tick_shutdown_broadcast_oneshot(cpu);
  	tick_shutdown_broadcast(cpu);
  	tick_shutdown(cpu);
  	/*
  	 * Unregister the clock event devices which were
  	 * released from the users in the notify chain.
  	 */
  	list_for_each_entry_safe(dev, tmp, &clockevents_released, list)
  		list_del(&dev->list);
  	/*
  	 * Now check whether the CPU has left unused per cpu devices
  	 */
  	list_for_each_entry_safe(dev, tmp, &clockevent_devices, list) {
  		if (cpumask_test_cpu(cpu, dev->cpumask) &&
  		    cpumask_weight(dev->cpumask) == 1 &&
  		    !tick_is_broadcast_device(dev)) {

  			BUG_ON(!clockevent_state_detached(dev));

  			list_del(&dev->list);

  		}

  	}

  	raw_spin_unlock_irqrestore(&clockevents_lock, flags);

  }

  #endif

  
  #ifdef CONFIG_SYSFS

  static struct bus_type clockevents_subsys = {

  	.name		= "clockevents",
  	.dev_name       = "clockevent",
  };
  
  static DEFINE_PER_CPU(struct device, tick_percpu_dev);
  static struct tick_device *tick_get_tick_dev(struct device *dev);
  
  static ssize_t sysfs_show_current_tick_dev(struct device *dev,
  					   struct device_attribute *attr,
  					   char *buf)
  {
  	struct tick_device *td;
  	ssize_t count = 0;
  
  	raw_spin_lock_irq(&clockevents_lock);
  	td = tick_get_tick_dev(dev);
  	if (td && td->evtdev)
  		count = snprintf(buf, PAGE_SIZE, "%s
  ", td->evtdev->name);
  	raw_spin_unlock_irq(&clockevents_lock);
  	return count;
  }
  static DEVICE_ATTR(current_device, 0444, sysfs_show_current_tick_dev, NULL);

  /* We don't support the abomination of removable broadcast devices */
  static ssize_t sysfs_unbind_tick_dev(struct device *dev,
  				     struct device_attribute *attr,
  				     const char *buf, size_t count)
  {
  	char name[CS_NAME_LEN];

  	ssize_t ret = sysfs_get_uname(buf, name, count);

  	struct clock_event_device *ce;
  
  	if (ret < 0)
  		return ret;
  
  	ret = -ENODEV;
  	mutex_lock(&clockevents_mutex);
  	raw_spin_lock_irq(&clockevents_lock);
  	list_for_each_entry(ce, &clockevent_devices, list) {
  		if (!strcmp(ce->name, name)) {
  			ret = __clockevents_try_unbind(ce, dev->id);
  			break;
  		}
  	}
  	raw_spin_unlock_irq(&clockevents_lock);
  	/*
  	 * We hold clockevents_mutex, so ce can't go away
  	 */
  	if (ret == -EAGAIN)
  		ret = clockevents_unbind(ce, dev->id);
  	mutex_unlock(&clockevents_mutex);
  	return ret ? ret : count;
  }
  static DEVICE_ATTR(unbind_device, 0200, NULL, sysfs_unbind_tick_dev);

  #ifdef CONFIG_GENERIC_CLOCKEVENTS_BROADCAST
  static struct device tick_bc_dev = {
  	.init_name	= "broadcast",
  	.id		= 0,
  	.bus		= &clockevents_subsys,
  };
  
  static struct tick_device *tick_get_tick_dev(struct device *dev)
  {
  	return dev == &tick_bc_dev ? tick_get_broadcast_device() :
  		&per_cpu(tick_cpu_device, dev->id);
  }
  
  static __init int tick_broadcast_init_sysfs(void)
  {
  	int err = device_register(&tick_bc_dev);
  
  	if (!err)
  		err = device_create_file(&tick_bc_dev, &dev_attr_current_device);
  	return err;
  }
  #else
  static struct tick_device *tick_get_tick_dev(struct device *dev)
  {
  	return &per_cpu(tick_cpu_device, dev->id);
  }
  static inline int tick_broadcast_init_sysfs(void) { return 0; }

  #endif

  
  static int __init tick_init_sysfs(void)
  {
  	int cpu;
  
  	for_each_possible_cpu(cpu) {
  		struct device *dev = &per_cpu(tick_percpu_dev, cpu);
  		int err;
  
  		dev->id = cpu;
  		dev->bus = &clockevents_subsys;
  		err = device_register(dev);
  		if (!err)
  			err = device_create_file(dev, &dev_attr_current_device);

  		if (!err)
  			err = device_create_file(dev, &dev_attr_unbind_device);

  		if (err)
  			return err;
  	}
  	return tick_broadcast_init_sysfs();
  }
  
  static int __init clockevents_init_sysfs(void)
  {
  	int err = subsys_system_register(&clockevents_subsys, NULL);
  
  	if (!err)
  		err = tick_init_sysfs();
  	return err;
  }
  device_initcall(clockevents_init_sysfs);
  #endif /* SYSFS */