/*
* 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/notifier.h>
#include <linux/smp.h>
#include <linux/sysdev.h>
/* The registered clock event devices */
static LIST_HEAD(clockevent_devices);
static LIST_HEAD(clockevents_released);
/* Notification for clock events */
static RAW_NOTIFIER_HEAD(clockevents_chain);
/* Protection for the above */
static DEFINE_SPINLOCK(clockevents_lock);
/**
* 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)
*/
unsigned long clockevent_delta2ns(unsigned long latch,
struct clock_event_device *evt)
{
u64 clc = ((u64) latch << evt->shift);
do_div(clc, evt->mult);
if (clc < 1000)
clc = 1000;
if (clc > LONG_MAX)
clc = LONG_MAX;
return (unsigned long) clc;
}
/**
* clockevents_set_mode - set the operating mode of a clock event device
* @dev: device to modify
* @mode: new mode
*
* Must be called with interrupts disabled !
*/
void clockevents_set_mode(struct clock_event_device *dev,
enum clock_event_mode mode)
{
if (dev->mode != mode) {
dev->set_mode(mode, dev);
dev->mode = mode;
}
}
/**
* clockevents_program_event - Reprogram the clock event device.
* @expires: absolute expiry time (monotonic clock)
*
* Returns 0 on success, -ETIME when the event is in the past.
*/
int clockevents_program_event(struct clock_event_device *dev, ktime_t expires,
ktime_t now)
{
unsigned long long clc;
int64_t delta;
delta = ktime_to_ns(ktime_sub(expires, now));
if (delta <= 0)
return -ETIME;
dev->next_event = expires;
if (dev->mode == CLOCK_EVT_MODE_SHUTDOWN)
return 0;
if (delta > dev->max_delta_ns)
delta = dev->max_delta_ns;
if (delta < dev->min_delta_ns)
delta = dev->min_delta_ns;
clc = delta * dev->mult;
clc >>= dev->shift;
return dev->set_next_event((unsigned long) clc, dev);
}
/**
* clockevents_register_notifier - register a clock events change listener
*/
int clockevents_register_notifier(struct notifier_block *nb)
{
int ret;
spin_lock(&clockevents_lock);
ret = raw_notifier_chain_register(&clockevents_chain, nb);
spin_unlock(&clockevents_lock);
return ret;
}
/**
* clockevents_unregister_notifier - unregister a clock events change listener
*/
void clockevents_unregister_notifier(struct notifier_block *nb)
{
spin_lock(&clockevents_lock);
raw_notifier_chain_unregister(&clockevents_chain, nb);
spin_unlock(&clockevents_lock);
}
/*
* Notify about a clock event change. Called with clockevents_lock
* held.
*/
static void clockevents_do_notify(unsigned long reason, void *dev)
{
raw_notifier_call_chain(&clockevents_chain, reason, dev);
}
/*
* Called after a notify add to make devices availble 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);
clockevents_do_notify(CLOCK_EVT_NOTIFY_ADD, dev);
}
}
/**
* clockevents_register_device - register a clock event device
* @dev: device to register
*/
void clockevents_register_device(struct clock_event_device *dev)
{
BUG_ON(dev->mode != CLOCK_EVT_MODE_UNUSED);
spin_lock(&clockevents_lock);
list_add(&dev->list, &clockevent_devices);
clockevents_do_notify(CLOCK_EVT_NOTIFY_ADD, dev);
clockevents_notify_released();
spin_unlock(&clockevents_lock);
}
/*
* Noop handler when we shut down an event device
*/
static 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 the notifier chain. clockevents_lock is held already
*/
void clockevents_exchange_device(struct clock_event_device *old,
struct clock_event_device *new)
{
unsigned long flags;
local_irq_save(flags);
/*
* Caller releases a clock event device. We queue it into the
* released list and do a notify add later.
*/
if (old) {
old->event_handler = clockevents_handle_noop;
clockevents_set_mode(old, CLOCK_EVT_MODE_UNUSED);
list_del(&old->list);
list_add(&old->list, &clockevents_released);
}
if (new) {
BUG_ON(new->mode != CLOCK_EVT_MODE_UNUSED);
clockevents_set_mode(new, CLOCK_EVT_MODE_SHUTDOWN);
}
local_irq_restore(flags);
}
/**
* clockevents_request_device
*/
struct clock_event_device *clockevents_request_device(unsigned int features,
cpumask_t cpumask)
{
struct clock_event_device *cur, *dev = NULL;
struct list_head *tmp;
spin_lock(&clockevents_lock);
list_for_each(tmp, &clockevent_devices) {
cur = list_entry(tmp, struct clock_event_device, list);
if ((cur->features & features) == features &&
cpus_equal(cpumask, cur->cpumask)) {
if (!dev || dev->rating < cur->rating)
dev = cur;
}
}
clockevents_exchange_device(NULL, dev);
spin_unlock(&clockevents_lock);
return dev;
}
/**
* clockevents_release_device
*/
void clockevents_release_device(struct clock_event_device *dev)
{
spin_lock(&clockevents_lock);
clockevents_exchange_device(dev, NULL);
clockevents_notify_released();
spin_unlock(&clockevents_lock);
}
/**
* clockevents_notify - notification about relevant events
*/
void clockevents_notify(unsigned long reason, void *arg)
{
spin_lock(&clockevents_lock);
clockevents_do_notify(reason, arg);
switch (reason) {
case CLOCK_EVT_NOTIFY_CPU_DEAD:
/*
* Unregister the clock event devices which were
* released from the users in the notify chain.
*/
while (!list_empty(&clockevents_released)) {
struct clock_event_device *dev;
dev = list_entry(clockevents_released.next,
struct clock_event_device, list);
list_del(&dev->list);
}
break;
default:
break;
}
spin_unlock(&clockevents_lock);
}
EXPORT_SYMBOL_GPL(clockevents_notify);
