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         do_div(clc, evt->mult);
  45         if (clc < 1000)
  46                 clc = 1000;
  47         if (clc > LONG_MAX)
  48                 clc = LONG_MAX;
  49
  50         return (unsigned long) clc;
  51 }
  52
  53 /**
  54  * clockevents_set_mode - set the operating mode of a clock event device
  55  * @dev:        device to modify
  56  * @mode:       new mode
  57  *
  58  * Must be called with interrupts disabled !
  59  */
  60 void clockevents_set_mode(struct clock_event_device *dev,
  61                                  enum clock_event_mode mode)
  62 {
  63         if (dev->mode != mode) {
  64                 dev->set_mode(mode, dev);
  65                 dev->mode = mode;
  66         }
  67 }
  68
  69 /**
  70  * clockevents_program_event - Reprogram the clock event device.
  71  * @expires:    absolute expiry time (monotonic clock)
  72  *
  73  * Returns 0 on success, -ETIME when the event is in the past.
  74  */
  75 int clockevents_program_event(struct clock_event_device *dev, ktime_t expires,
  76                               ktime_t now)
  77 {
  78         unsigned long long clc;
  79         int64_t delta;
  80
  81         delta = ktime_to_ns(ktime_sub(expires, now));
  82
  83         if (delta <= 0)
  84                 return -ETIME;
  85
  86         dev->next_event = expires;
  87
  88         if (dev->mode == CLOCK_EVT_MODE_SHUTDOWN)
  89                 return 0;
  90
  91         if (delta > dev->max_delta_ns)
  92                 delta = dev->max_delta_ns;
  93         if (delta < dev->min_delta_ns)
  94                 delta = dev->min_delta_ns;
  95
  96         clc = delta * dev->mult;
  97         clc >>= dev->shift;
  98
  99         return dev->set_next_event((unsigned long) clc, dev);
 100 }
 101
 102 /**
 103  * clockevents_register_notifier - register a clock events change listener
 104  */
 105 int clockevents_register_notifier(struct notifier_block *nb)
 106 {
 107         int ret;
 108
 109         spin_lock(&clockevents_lock);
 110         ret = raw_notifier_chain_register(&clockevents_chain, nb);
 111         spin_unlock(&clockevents_lock);
 112
 113         return ret;
 114 }
 115
 116 /**
 117  * clockevents_unregister_notifier - unregister a clock events change listener
 118  */
 119 void clockevents_unregister_notifier(struct notifier_block *nb)
 120 {
 121         spin_lock(&clockevents_lock);
 122         raw_notifier_chain_unregister(&clockevents_chain, nb);
 123         spin_unlock(&clockevents_lock);
 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 availble 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         spin_lock(&clockevents_lock);
 161
 162         list_add(&dev->list, &clockevent_devices);
 163         clockevents_do_notify(CLOCK_EVT_NOTIFY_ADD, dev);
 164         clockevents_notify_released();
 165
 166         spin_unlock(&clockevents_lock);
 167 }
 168
 169 /*
 170  * Noop handler when we shut down an event device
 171  */
 172 static void clockevents_handle_noop(struct clock_event_device *dev)
 173 {
 174 }
 175
 176 /**
 177  * clockevents_exchange_device - release and request clock devices
 178  * @old:        device to release (can be NULL)
 179  * @new:        device to request (can be NULL)
 180  *
 181  * Called from the notifier chain. clockevents_lock is held already
 182  */
 183 void clockevents_exchange_device(struct clock_event_device *old,
 184                                  struct clock_event_device *new)
 185 {
 186         unsigned long flags;
 187
 188         local_irq_save(flags);
 189         /*
 190          * Caller releases a clock event device. We queue it into the
 191          * released list and do a notify add later.
 192          */
 193         if (old) {
 194                 old->event_handler = clockevents_handle_noop;
 195                 clockevents_set_mode(old, CLOCK_EVT_MODE_UNUSED);
 196                 list_del(&old->list);
 197                 list_add(&old->list, &clockevents_released);
 198         }
 199
 200         if (new) {
 201                 BUG_ON(new->mode != CLOCK_EVT_MODE_UNUSED);
 202                 clockevents_set_mode(new, CLOCK_EVT_MODE_SHUTDOWN);
 203         }
 204         local_irq_restore(flags);
 205 }
 206
 207 /**
 208  * clockevents_request_device
 209  */
 210 struct clock_event_device *clockevents_request_device(unsigned int features,
 211                                                       cpumask_t cpumask)
 212 {
 213         struct clock_event_device *cur, *dev = NULL;
 214         struct list_head *tmp;
 215
 216         spin_lock(&clockevents_lock);
 217
 218         list_for_each(tmp, &clockevent_devices) {
 219                 cur = list_entry(tmp, struct clock_event_device, list);
 220
 221                 if ((cur->features & features) == features &&
 222                     cpus_equal(cpumask, cur->cpumask)) {
 223                         if (!dev || dev->rating < cur->rating)
 224                                 dev = cur;
 225                 }
 226         }
 227
 228         clockevents_exchange_device(NULL, dev);
 229
 230         spin_unlock(&clockevents_lock);
 231
 232         return dev;
 233 }
 234
 235 /**
 236  * clockevents_release_device
 237  */
 238 void clockevents_release_device(struct clock_event_device *dev)
 239 {
 240         spin_lock(&clockevents_lock);
 241
 242         clockevents_exchange_device(dev, NULL);
 243         clockevents_notify_released();
 244
 245         spin_unlock(&clockevents_lock);
 246 }
 247
 248 /**
 249  * clockevents_notify - notification about relevant events
 250  */
 251 void clockevents_notify(unsigned long reason, void *arg)
 252 {
 253         spin_lock(&clockevents_lock);
 254         clockevents_do_notify(reason, arg);
 255
 256         switch (reason) {
 257         case CLOCK_EVT_NOTIFY_CPU_DEAD:
 258                 /*
 259                  * Unregister the clock event devices which were
 260                  * released from the users in the notify chain.
 261                  */
 262                 while (!list_empty(&clockevents_released)) {
 263                         struct clock_event_device *dev;
 264
 265                         dev = list_entry(clockevents_released.next,
 266                                          struct clock_event_device, list);
 267                         list_del(&dev->list);
 268                 }
 269                 break;
 270         default:
 271                 break;
 272         }
 273         spin_unlock(&clockevents_lock);
 274 }
 275 EXPORT_SYMBOL_GPL(clockevents_notify);
 276