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