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