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 #include <linux/tick.h>
  22
  23 #include "tick-internal.h"
  24
  25 /* The registered clock event devices */
  26 static LIST_HEAD(clockevent_devices);
  27 static LIST_HEAD(clockevents_released);
  28
  29 /* Notification for clock events */
  30 static RAW_NOTIFIER_HEAD(clockevents_chain);
  31
  32 /* Protection for the above */
  33 static DEFINE_RAW_SPINLOCK(clockevents_lock);
  34
  35 /**
  36  * clockevents_delta2ns - Convert a latch value (device ticks) to nanoseconds
  37  * @latch:      value to convert
  38  * @evt:        pointer to clock event device descriptor
  39  *
  40  * Math helper, returns latch value converted to nanoseconds (bound checked)
  41  */
  42 u64 clockevent_delta2ns(unsigned long latch, struct clock_event_device *evt)
  43 {
  44         u64 clc = (u64) latch << evt->shift;
  45
  46         if (unlikely(!evt->mult)) {
  47                 evt->mult = 1;
  48                 WARN_ON(1);
  49         }
  50
  51         do_div(clc, evt->mult);
  52         if (clc < 1000)
  53                 clc = 1000;
  54         if (clc > KTIME_MAX)
  55                 clc = KTIME_MAX;
  56
  57         return clc;
  58 }
  59 EXPORT_SYMBOL_GPL(clockevent_delta2ns);
  60
  61 /**
  62  * clockevents_set_mode - set the operating mode of a clock event device
  63  * @dev:        device to modify
  64  * @mode:       new mode
  65  *
  66  * Must be called with interrupts disabled !
  67  */
  68 void clockevents_set_mode(struct clock_event_device *dev,
  69                                  enum clock_event_mode mode)
  70 {
  71         if (dev->mode != mode) {
  72                 dev->set_mode(mode, dev);
  73                 dev->mode = mode;
  74
  75                 /*
  76                  * A nsec2cyc multiplicator of 0 is invalid and we'd crash
  77                  * on it, so fix it up and emit a warning:
  78                  */
  79                 if (mode == CLOCK_EVT_MODE_ONESHOT) {
  80                         if (unlikely(!dev->mult)) {
  81                                 dev->mult = 1;
  82                                 WARN_ON(1);
  83                         }
  84                 }
  85         }
  86 }
  87
  88 /**
  89  * clockevents_shutdown - shutdown the device and clear next_event
  90  * @dev:        device to shutdown
  91  */
  92 void clockevents_shutdown(struct clock_event_device *dev)
  93 {
  94         clockevents_set_mode(dev, CLOCK_EVT_MODE_SHUTDOWN);
  95         dev->next_event.tv64 = KTIME_MAX;
  96 }
  97
  98 /**
  99  * clockevents_program_event - Reprogram the clock event device.
 100  * @expires:    absolute expiry time (monotonic clock)
 101  *
 102  * Returns 0 on success, -ETIME when the event is in the past.
 103  */
 104 int clockevents_program_event(struct clock_event_device *dev, ktime_t expires,
 105                               ktime_t now)
 106 {
 107         unsigned long long clc;
 108         int64_t delta;
 109
 110         if (unlikely(expires.tv64 < 0)) {
 111                 WARN_ON_ONCE(1);
 112                 return -ETIME;
 113         }
 114
 115         delta = ktime_to_ns(ktime_sub(expires, now));
 116
 117         if (delta <= 0)
 118                 return -ETIME;
 119
 120         dev->next_event = expires;
 121
 122         if (dev->mode == CLOCK_EVT_MODE_SHUTDOWN)
 123                 return 0;
 124
 125         if (delta > dev->max_delta_ns)
 126                 delta = dev->max_delta_ns;
 127         if (delta < dev->min_delta_ns)
 128                 delta = dev->min_delta_ns;
 129
 130         clc = delta * dev->mult;
 131         clc >>= dev->shift;
 132
 133         return dev->set_next_event((unsigned long) clc, dev);
 134 }
 135
 136 /**
 137  * clockevents_register_notifier - register a clock events change listener
 138  */
 139 int clockevents_register_notifier(struct notifier_block *nb)
 140 {
 141         unsigned long flags;
 142         int ret;
 143
 144         raw_spin_lock_irqsave(&clockevents_lock, flags);
 145         ret = raw_notifier_chain_register(&clockevents_chain, nb);
 146         raw_spin_unlock_irqrestore(&clockevents_lock, flags);
 147
 148         return ret;
 149 }
 150
 151 /*
 152  * Notify about a clock event change. Called with clockevents_lock
 153  * held.
 154  */
 155 static void clockevents_do_notify(unsigned long reason, void *dev)
 156 {
 157         raw_notifier_call_chain(&clockevents_chain, reason, dev);
 158 }
 159
 160 /*
 161  * Called after a notify add to make devices available which were
 162  * released from the notifier call.
 163  */
 164 static void clockevents_notify_released(void)
 165 {
 166         struct clock_event_device *dev;
 167
 168         while (!list_empty(&clockevents_released)) {
 169                 dev = list_entry(clockevents_released.next,
 170                                  struct clock_event_device, list);
 171                 list_del(&dev->list);
 172                 list_add(&dev->list, &clockevent_devices);
 173                 clockevents_do_notify(CLOCK_EVT_NOTIFY_ADD, dev);
 174         }
 175 }
 176
 177 /**
 178  * clockevents_register_device - register a clock event device
 179  * @dev:        device to register
 180  */
 181 void clockevents_register_device(struct clock_event_device *dev)
 182 {
 183         unsigned long flags;
 184
 185         BUG_ON(dev->mode != CLOCK_EVT_MODE_UNUSED);
 186         BUG_ON(!dev->cpumask);
 187
 188         raw_spin_lock_irqsave(&clockevents_lock, flags);
 189
 190         list_add(&dev->list, &clockevent_devices);
 191         clockevents_do_notify(CLOCK_EVT_NOTIFY_ADD, dev);
 192         clockevents_notify_released();
 193
 194         raw_spin_unlock_irqrestore(&clockevents_lock, flags);
 195 }
 196 EXPORT_SYMBOL_GPL(clockevents_register_device);
 197
 198 /*
 199  * Noop handler when we shut down an event device
 200  */
 201 void clockevents_handle_noop(struct clock_event_device *dev)
 202 {
 203 }
 204
 205 /**
 206  * clockevents_exchange_device - release and request clock devices
 207  * @old:        device to release (can be NULL)
 208  * @new:        device to request (can be NULL)
 209  *
 210  * Called from the notifier chain. clockevents_lock is held already
 211  */
 212 void clockevents_exchange_device(struct clock_event_device *old,
 213                                  struct clock_event_device *new)
 214 {
 215         unsigned long flags;
 216
 217         local_irq_save(flags);
 218         /*
 219          * Caller releases a clock event device. We queue it into the
 220          * released list and do a notify add later.
 221          */
 222         if (old) {
 223                 clockevents_set_mode(old, CLOCK_EVT_MODE_UNUSED);
 224                 list_del(&old->list);
 225                 list_add(&old->list, &clockevents_released);
 226         }
 227
 228         if (new) {
 229                 BUG_ON(new->mode != CLOCK_EVT_MODE_UNUSED);
 230                 clockevents_shutdown(new);
 231         }
 232         local_irq_restore(flags);
 233 }
 234
 235 #ifdef CONFIG_GENERIC_CLOCKEVENTS
 236 /**
 237  * clockevents_notify - notification about relevant events
 238  */
 239 void clockevents_notify(unsigned long reason, void *arg)
 240 {
 241         struct clock_event_device *dev, *tmp;
 242         unsigned long flags;
 243         int cpu;
 244
 245         raw_spin_lock_irqsave(&clockevents_lock, flags);
 246         clockevents_do_notify(reason, arg);
 247
 248         switch (reason) {
 249         case CLOCK_EVT_NOTIFY_CPU_DEAD:
 250                 /*
 251                  * Unregister the clock event devices which were
 252                  * released from the users in the notify chain.
 253                  */
 254                 list_for_each_entry_safe(dev, tmp, &clockevents_released, list)
 255                         list_del(&dev->list);
 256                 /*
 257                  * Now check whether the CPU has left unused per cpu devices
 258                  */
 259                 cpu = *((int *)arg);
 260                 list_for_each_entry_safe(dev, tmp, &clockevent_devices, list) {
 261                         if (cpumask_test_cpu(cpu, dev->cpumask) &&
 262                             cpumask_weight(dev->cpumask) == 1 &&
 263                             !tick_is_broadcast_device(dev)) {
 264                                 BUG_ON(dev->mode != CLOCK_EVT_MODE_UNUSED);
 265                                 list_del(&dev->list);
 266                         }
 267                 }
 268                 break;
 269         default:
 270                 break;
 271         }
 272         raw_spin_unlock_irqrestore(&clockevents_lock, flags);
 273 }
 274 EXPORT_SYMBOL_GPL(clockevents_notify);
 275 #endif