linux/kernel/time/clockevents.c
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   1/*
   2 * linux/kernel/time/clockevents.c
   3 *
   4 * This file contains functions which manage clock event devices.
   5 *
   6 * Copyright(C) 2005-2006, Thomas Gleixner <tglx@linutronix.de>
   7 * Copyright(C) 2005-2007, Red Hat, Inc., Ingo Molnar
   8 * Copyright(C) 2006-2007, Timesys Corp., Thomas Gleixner
   9 *
  10 * This code is licenced under the GPL version 2. For details see
  11 * kernel-base/COPYING.
  12 */
  13
  14#include <linux/clockchips.h>
  15#include <linux/hrtimer.h>
  16#include <linux/init.h>
  17#include <linux/module.h>
  18#include <linux/notifier.h>
  19#include <linux/smp.h>
  20#include <linux/sysdev.h>
  21
  22/* The registered clock event devices */
  23static LIST_HEAD(clockevent_devices);
  24static LIST_HEAD(clockevents_released);
  25
  26/* Notification for clock events */
  27static RAW_NOTIFIER_HEAD(clockevents_chain);
  28
  29/* Protection for the above */
  30static DEFINE_SPINLOCK(clockevents_lock);
  31
  32/**
  33 * clockevents_delta2ns - Convert a latch value (device ticks) to nanoseconds
  34 * @latch:      value to convert
  35 * @evt:        pointer to clock event device descriptor
  36 *
  37 * Math helper, returns latch value converted to nanoseconds (bound checked)
  38 */
  39unsigned long clockevent_delta2ns(unsigned long latch,
  40                                  struct clock_event_device *evt)
  41{
  42        u64 clc = ((u64) latch << evt->shift);
  43
  44        if (unlikely(!evt->mult)) {
  45                evt->mult = 1;
  46                WARN_ON(1);
  47        }
  48
  49        do_div(clc, evt->mult);
  50        if (clc < 1000)
  51                clc = 1000;
  52        if (clc > LONG_MAX)
  53                clc = LONG_MAX;
  54
  55        return (unsigned long) clc;
  56}
  57
  58/**
  59 * clockevents_set_mode - set the operating mode of a clock event device
  60 * @dev:        device to modify
  61 * @mode:       new mode
  62 *
  63 * Must be called with interrupts disabled !
  64 */
  65void clockevents_set_mode(struct clock_event_device *dev,
  66                                 enum clock_event_mode mode)
  67{
  68        if (dev->mode != mode) {
  69                dev->set_mode(mode, dev);
  70                dev->mode = mode;
  71        }
  72}
  73
  74/**
  75 * clockevents_shutdown - shutdown the device and clear next_event
  76 * @dev:        device to shutdown
  77 */
  78void clockevents_shutdown(struct clock_event_device *dev)
  79{
  80        clockevents_set_mode(dev, CLOCK_EVT_MODE_SHUTDOWN);
  81        dev->next_event.tv64 = KTIME_MAX;
  82}
  83
  84/**
  85 * clockevents_program_event - Reprogram the clock event device.
  86 * @expires:    absolute expiry time (monotonic clock)
  87 *
  88 * Returns 0 on success, -ETIME when the event is in the past.
  89 */
  90int clockevents_program_event(struct clock_event_device *dev, ktime_t expires,
  91                              ktime_t now)
  92{
  93        unsigned long long clc;
  94        int64_t delta;
  95
  96        if (unlikely(expires.tv64 < 0)) {
  97                WARN_ON_ONCE(1);
  98                return -ETIME;
  99        }
 100
 101        delta = ktime_to_ns(ktime_sub(expires, now));
 102
 103        if (delta <= 0)
 104                return -ETIME;
 105
 106        dev->next_event = expires;
 107
 108        if (dev->mode == CLOCK_EVT_MODE_SHUTDOWN)
 109                return 0;
 110
 111        if (delta > dev->max_delta_ns)
 112                delta = dev->max_delta_ns;
 113        if (delta < dev->min_delta_ns)
 114                delta = dev->min_delta_ns;
 115
 116        clc = delta * dev->mult;
 117        clc >>= dev->shift;
 118
 119        return dev->set_next_event((unsigned long) clc, dev);
 120}
 121
 122/**
 123 * clockevents_register_notifier - register a clock events change listener
 124 */
 125int clockevents_register_notifier(struct notifier_block *nb)
 126{
 127        int ret;
 128
 129        spin_lock(&clockevents_lock);
 130        ret = raw_notifier_chain_register(&clockevents_chain, nb);
 131        spin_unlock(&clockevents_lock);
 132
 133        return ret;
 134}
 135
 136/*
 137 * Notify about a clock event change. Called with clockevents_lock
 138 * held.
 139 */
 140static void clockevents_do_notify(unsigned long reason, void *dev)
 141{
 142        raw_notifier_call_chain(&clockevents_chain, reason, dev);
 143}
 144
 145/*
 146 * Called after a notify add to make devices available which were
 147 * released from the notifier call.
 148 */
 149static void clockevents_notify_released(void)
 150{
 151        struct clock_event_device *dev;
 152
 153        while (!list_empty(&clockevents_released)) {
 154                dev = list_entry(clockevents_released.next,
 155                                 struct clock_event_device, list);
 156                list_del(&dev->list);
 157                list_add(&dev->list, &clockevent_devices);
 158                clockevents_do_notify(CLOCK_EVT_NOTIFY_ADD, dev);
 159        }
 160}
 161
 162/**
 163 * clockevents_register_device - register a clock event device
 164 * @dev:        device to register
 165 */
 166void clockevents_register_device(struct clock_event_device *dev)
 167{
 168        BUG_ON(dev->mode != CLOCK_EVT_MODE_UNUSED);
 169        /*
 170         * A nsec2cyc multiplicator of 0 is invalid and we'd crash
 171         * on it, so fix it up and emit a warning:
 172         */
 173        if (unlikely(!dev->mult)) {
 174                dev->mult = 1;
 175                WARN_ON(1);
 176        }
 177
 178        spin_lock(&clockevents_lock);
 179
 180        list_add(&dev->list, &clockevent_devices);
 181        clockevents_do_notify(CLOCK_EVT_NOTIFY_ADD, dev);
 182        clockevents_notify_released();
 183
 184        spin_unlock(&clockevents_lock);
 185}
 186
 187/*
 188 * Noop handler when we shut down an event device
 189 */
 190void clockevents_handle_noop(struct clock_event_device *dev)
 191{
 192}
 193
 194/**
 195 * clockevents_exchange_device - release and request clock devices
 196 * @old:        device to release (can be NULL)
 197 * @new:        device to request (can be NULL)
 198 *
 199 * Called from the notifier chain. clockevents_lock is held already
 200 */
 201void clockevents_exchange_device(struct clock_event_device *old,
 202                                 struct clock_event_device *new)
 203{
 204        unsigned long flags;
 205
 206        local_irq_save(flags);
 207        /*
 208         * Caller releases a clock event device. We queue it into the
 209         * released list and do a notify add later.
 210         */
 211        if (old) {
 212                clockevents_set_mode(old, CLOCK_EVT_MODE_UNUSED);
 213                list_del(&old->list);
 214                list_add(&old->list, &clockevents_released);
 215        }
 216
 217        if (new) {
 218                BUG_ON(new->mode != CLOCK_EVT_MODE_UNUSED);
 219                clockevents_shutdown(new);
 220        }
 221        local_irq_restore(flags);
 222}
 223
 224#ifdef CONFIG_GENERIC_CLOCKEVENTS
 225/**
 226 * clockevents_notify - notification about relevant events
 227 */
 228void clockevents_notify(unsigned long reason, void *arg)
 229{
 230        struct list_head *node, *tmp;
 231
 232        spin_lock(&clockevents_lock);
 233        clockevents_do_notify(reason, arg);
 234
 235        switch (reason) {
 236        case CLOCK_EVT_NOTIFY_CPU_DEAD:
 237                /*
 238                 * Unregister the clock event devices which were
 239                 * released from the users in the notify chain.
 240                 */
 241                list_for_each_safe(node, tmp, &clockevents_released)
 242                        list_del(node);
 243                break;
 244        default:
 245                break;
 246        }
 247        spin_unlock(&clockevents_lock);
 248}
 249EXPORT_SYMBOL_GPL(clockevents_notify);
 250#endif
 251