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