kernel/time/clockevents.c

   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 */
  23 static LIST_HEAD(clockevent_devices);
  24 static LIST_HEAD(clockevents_released);
  25
  26 /* Notification for clock events */
  27 static RAW_NOTIFIER_HEAD(clockevents_chain);
  28
  29 /* Protection for the above */
  30 static 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  */
  39 unsigned 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  */
  65 void 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_program_event - Reprogram the clock event device.
  76  * @expires:    absolute expiry time (monotonic clock)
  77  *
  78  * Returns 0 on success, -ETIME when the event is in the past.
  79  */
  80 int clockevents_program_event(struct clock_event_device *dev, ktime_t expires,
  81                               ktime_t now)
  82 {
  83         unsigned long long clc;
  84         int64_t delta;
  85
  86         if (unlikely(expires.tv64 < 0)) {
  87                 WARN_ON_ONCE(1);
  88                 return -ETIME;
  89         }
  90
  91         delta = ktime_to_ns(ktime_sub(expires, now));
  92
  93         if (delta <= 0)
  94                 return -ETIME;
  95
  96         dev->next_event = expires;
  97
  98         if (dev->mode == CLOCK_EVT_MODE_SHUTDOWN)
  99                 return 0;
 100
 101         if (delta > dev->max_delta_ns)
 102                 delta = dev->max_delta_ns;
 103         if (delta < dev->min_delta_ns)
 104                 delta = dev->min_delta_ns;
 105
 106         clc = delta * dev->mult;
 107         clc >>= dev->shift;
 108
 109         return dev->set_next_event((unsigned long) clc, dev);
 110 }
 111
 112 /**
 113  * clockevents_register_notifier - register a clock events change listener
 114  */
 115 int clockevents_register_notifier(struct notifier_block *nb)
 116 {
 117         int ret;
 118
 119         spin_lock(&clockevents_lock);
 120         ret = raw_notifier_chain_register(&clockevents_chain, nb);
 121         spin_unlock(&clockevents_lock);
 122
 123         return ret;
 124 }
 125
 126 /*
 127  * Notify about a clock event change. Called with clockevents_lock
 128  * held.
 129  */
 130 static void clockevents_do_notify(unsigned long reason, void *dev)
 131 {
 132         raw_notifier_call_chain(&clockevents_chain, reason, dev);
 133 }
 134
 135 /*
 136  * Called after a notify add to make devices available which were
 137  * released from the notifier call.
 138  */
 139 static void clockevents_notify_released(void)
 140 {
 141         struct clock_event_device *dev;
 142
 143         while (!list_empty(&clockevents_released)) {
 144                 dev = list_entry(clockevents_released.next,
 145                                  struct clock_event_device, list);
 146                 list_del(&dev->list);
 147                 list_add(&dev->list, &clockevent_devices);
 148                 clockevents_do_notify(CLOCK_EVT_NOTIFY_ADD, dev);
 149         }
 150 }
 151
 152 /**
 153  * clockevents_register_device - register a clock event device
 154  * @dev:        device to register
 155  */
 156 void clockevents_register_device(struct clock_event_device *dev)
 157 {
 158         BUG_ON(dev->mode != CLOCK_EVT_MODE_UNUSED);
 159         /*
 160          * A nsec2cyc multiplicator of 0 is invalid and we'd crash
 161          * on it, so fix it up and emit a warning:
 162          */
 163         if (unlikely(!dev->mult)) {
 164                 dev->mult = 1;
 165                 WARN_ON(1);
 166         }
 167
 168         spin_lock(&clockevents_lock);
 169
 170         list_add(&dev->list, &clockevent_devices);
 171         clockevents_do_notify(CLOCK_EVT_NOTIFY_ADD, dev);
 172         clockevents_notify_released();
 173
 174         spin_unlock(&clockevents_lock);
 175 }
 176
 177 /*
 178  * Noop handler when we shut down an event device
 179  */
 180 static void clockevents_handle_noop(struct clock_event_device *dev)
 181 {
 182 }
 183
 184 /**
 185  * clockevents_exchange_device - release and request clock devices
 186  * @old:        device to release (can be NULL)
 187  * @new:        device to request (can be NULL)
 188  *
 189  * Called from the notifier chain. clockevents_lock is held already
 190  */
 191 void clockevents_exchange_device(struct clock_event_device *old,
 192                                  struct clock_event_device *new)
 193 {
 194         unsigned long flags;
 195
 196         local_irq_save(flags);
 197         /*
 198          * Caller releases a clock event device. We queue it into the
 199          * released list and do a notify add later.
 200          */
 201         if (old) {
 202                 old->event_handler = clockevents_handle_noop;
 203                 clockevents_set_mode(old, CLOCK_EVT_MODE_UNUSED);
 204                 list_del(&old->list);
 205                 list_add(&old->list, &clockevents_released);
 206         }
 207
 208         if (new) {
 209                 BUG_ON(new->mode != CLOCK_EVT_MODE_UNUSED);
 210                 clockevents_set_mode(new, CLOCK_EVT_MODE_SHUTDOWN);
 211         }
 212         local_irq_restore(flags);
 213 }
 214
 215 #ifdef CONFIG_GENERIC_CLOCKEVENTS
 216 /**
 217  * clockevents_notify - notification about relevant events
 218  */
 219 void clockevents_notify(unsigned long reason, void *arg)
 220 {
 221         struct list_head *node, *tmp;
 222
 223         spin_lock(&clockevents_lock);
 224         clockevents_do_notify(reason, arg);
 225
 226         switch (reason) {
 227         case CLOCK_EVT_NOTIFY_CPU_DEAD:
 228                 /*
 229                  * Unregister the clock event devices which were
 230                  * released from the users in the notify chain.
 231                  */
 232                 list_for_each_safe(node, tmp, &clockevents_released)
 233                         list_del(node);
 234                 break;
 235         default:
 236                 break;
 237         }
 238         spin_unlock(&clockevents_lock);
 239 }
 240 EXPORT_SYMBOL_GPL(clockevents_notify);
 241 #endif