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