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  * Notify about a clock event change. Called with clockevents_lock
 118  * held.
 119  */
 120 static void clockevents_do_notify(unsigned long reason, void *dev)
 121 {
 122         raw_notifier_call_chain(&clockevents_chain, reason, dev);
 123 }
 124
 125 /*
 126  * Called after a notify add to make devices availble which were
 127  * released from the notifier call.
 128  */
 129 static void clockevents_notify_released(void)
 130 {
 131         struct clock_event_device *dev;
 132
 133         while (!list_empty(&clockevents_released)) {
 134                 dev = list_entry(clockevents_released.next,
 135                                  struct clock_event_device, list);
 136                 list_del(&dev->list);
 137                 list_add(&dev->list, &clockevent_devices);
 138                 clockevents_do_notify(CLOCK_EVT_NOTIFY_ADD, dev);
 139         }
 140 }
 141
 142 /**
 143  * clockevents_register_device - register a clock event device
 144  * @dev:        device to register
 145  */
 146 void clockevents_register_device(struct clock_event_device *dev)
 147 {
 148         BUG_ON(dev->mode != CLOCK_EVT_MODE_UNUSED);
 149
 150         spin_lock(&clockevents_lock);
 151
 152         list_add(&dev->list, &clockevent_devices);
 153         clockevents_do_notify(CLOCK_EVT_NOTIFY_ADD, dev);
 154         clockevents_notify_released();
 155
 156         spin_unlock(&clockevents_lock);
 157 }
 158
 159 /*
 160  * Noop handler when we shut down an event device
 161  */
 162 static void clockevents_handle_noop(struct clock_event_device *dev)
 163 {
 164 }
 165
 166 /**
 167  * clockevents_exchange_device - release and request clock devices
 168  * @old:        device to release (can be NULL)
 169  * @new:        device to request (can be NULL)
 170  *
 171  * Called from the notifier chain. clockevents_lock is held already
 172  */
 173 void clockevents_exchange_device(struct clock_event_device *old,
 174                                  struct clock_event_device *new)
 175 {
 176         unsigned long flags;
 177
 178         local_irq_save(flags);
 179         /*
 180          * Caller releases a clock event device. We queue it into the
 181          * released list and do a notify add later.
 182          */
 183         if (old) {
 184                 old->event_handler = clockevents_handle_noop;
 185                 clockevents_set_mode(old, CLOCK_EVT_MODE_UNUSED);
 186                 list_del(&old->list);
 187                 list_add(&old->list, &clockevents_released);
 188         }
 189
 190         if (new) {
 191                 BUG_ON(new->mode != CLOCK_EVT_MODE_UNUSED);
 192                 clockevents_set_mode(new, CLOCK_EVT_MODE_SHUTDOWN);
 193         }
 194         local_irq_restore(flags);
 195 }
 196
 197 /**
 198  * clockevents_notify - notification about relevant events
 199  */
 200 void clockevents_notify(unsigned long reason, void *arg)
 201 {
 202         spin_lock(&clockevents_lock);
 203         clockevents_do_notify(reason, arg);
 204
 205         switch (reason) {
 206         case CLOCK_EVT_NOTIFY_CPU_DEAD:
 207                 /*
 208                  * Unregister the clock event devices which were
 209                  * released from the users in the notify chain.
 210                  */
 211                 while (!list_empty(&clockevents_released)) {
 212                         struct clock_event_device *dev;
 213
 214                         dev = list_entry(clockevents_released.next,
 215                                          struct clock_event_device, list);
 216                         list_del(&dev->list);
 217                 }
 218                 break;
 219         default:
 220                 break;
 221         }
 222         spin_unlock(&clockevents_lock);
 223 }
 224 EXPORT_SYMBOL_GPL(clockevents_notify);
 225