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
  21 #include "tick-internal.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_RAW_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 u64 clockevent_delta2ns(unsigned long latch, 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 > KTIME_MAX)
  53                 clc = KTIME_MAX;
  54
  55         return clc;
  56 }
  57 EXPORT_SYMBOL_GPL(clockevent_delta2ns);
  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 #ifdef CONFIG_GENERIC_CLOCKEVENTS_MIN_ADJUST
  97
  98 /* Limit min_delta to a jiffie */
  99 #define MIN_DELTA_LIMIT         (NSEC_PER_SEC / HZ)
 100
 101 /**
 102  * clockevents_increase_min_delta - raise minimum delta of a clock event device
 103  * @dev:       device to increase the minimum delta
 104  *
 105  * Returns 0 on success, -ETIME when the minimum delta reached the limit.
 106  */
 107 static int clockevents_increase_min_delta(struct clock_event_device *dev)
 108 {
 109         /* Nothing to do if we already reached the limit */
 110         if (dev->min_delta_ns >= MIN_DELTA_LIMIT) {
 111                 printk(KERN_WARNING "CE: Reprogramming failure. Giving up\n");
 112                 dev->next_event.tv64 = KTIME_MAX;
 113                 return -ETIME;
 114         }
 115
 116         if (dev->min_delta_ns < 5000)
 117                 dev->min_delta_ns = 5000;
 118         else
 119                 dev->min_delta_ns += dev->min_delta_ns >> 1;
 120
 121         if (dev->min_delta_ns > MIN_DELTA_LIMIT)
 122                 dev->min_delta_ns = MIN_DELTA_LIMIT;
 123
 124         printk(KERN_WARNING "CE: %s increased min_delta_ns to %llu nsec\n",
 125                dev->name ? dev->name : "?",
 126                (unsigned long long) dev->min_delta_ns);
 127         return 0;
 128 }
 129
 130 /**
 131  * clockevents_program_min_delta - Set clock event device to the minimum delay.
 132  * @dev:        device to program
 133  *
 134  * Returns 0 on success, -ETIME when the retry loop failed.
 135  */
 136 static int clockevents_program_min_delta(struct clock_event_device *dev)
 137 {
 138         unsigned long long clc;
 139         int64_t delta;
 140         int i;
 141
 142         for (i = 0;;) {
 143                 delta = dev->min_delta_ns;
 144                 dev->next_event = ktime_add_ns(ktime_get(), delta);
 145
 146                 if (dev->mode == CLOCK_EVT_MODE_SHUTDOWN)
 147                         return 0;
 148
 149                 dev->retries++;
 150                 clc = ((unsigned long long) delta * dev->mult) >> dev->shift;
 151                 if (dev->set_next_event((unsigned long) clc, dev) == 0)
 152                         return 0;
 153
 154                 if (++i > 2) {
 155                         /*
 156                          * We tried 3 times to program the device with the
 157                          * given min_delta_ns. Try to increase the minimum
 158                          * delta, if that fails as well get out of here.
 159                          */
 160                         if (clockevents_increase_min_delta(dev))
 161                                 return -ETIME;
 162                         i = 0;
 163                 }
 164         }
 165 }
 166
 167 #else  /* CONFIG_GENERIC_CLOCKEVENTS_MIN_ADJUST */
 168
 169 /**
 170  * clockevents_program_min_delta - Set clock event device to the minimum delay.
 171  * @dev:        device to program
 172  *
 173  * Returns 0 on success, -ETIME when the retry loop failed.
 174  */
 175 static int clockevents_program_min_delta(struct clock_event_device *dev)
 176 {
 177         unsigned long long clc;
 178         int64_t delta;
 179
 180         delta = dev->min_delta_ns;
 181         dev->next_event = ktime_add_ns(ktime_get(), delta);
 182
 183         if (dev->mode == CLOCK_EVT_MODE_SHUTDOWN)
 184                 return 0;
 185
 186         dev->retries++;
 187         clc = ((unsigned long long) delta * dev->mult) >> dev->shift;
 188         return dev->set_next_event((unsigned long) clc, dev);
 189 }
 190
 191 #endif /* CONFIG_GENERIC_CLOCKEVENTS_MIN_ADJUST */
 192
 193 /**
 194  * clockevents_program_event - Reprogram the clock event device.
 195  * @dev:        device to program
 196  * @expires:    absolute expiry time (monotonic clock)
 197  * @force:      program minimum delay if expires can not be set
 198  *
 199  * Returns 0 on success, -ETIME when the event is in the past.
 200  */
 201 int clockevents_program_event(struct clock_event_device *dev, ktime_t expires,
 202                               bool force)
 203 {
 204         unsigned long long clc;
 205         int64_t delta;
 206         int rc;
 207
 208         if (unlikely(expires.tv64 < 0)) {
 209                 WARN_ON_ONCE(1);
 210                 return -ETIME;
 211         }
 212
 213         dev->next_event = expires;
 214
 215         if (dev->mode == CLOCK_EVT_MODE_SHUTDOWN)
 216                 return 0;
 217
 218         /* Shortcut for clockevent devices that can deal with ktime. */
 219         if (dev->features & CLOCK_EVT_FEAT_KTIME)
 220                 return dev->set_next_ktime(expires, dev);
 221
 222         delta = ktime_to_ns(ktime_sub(expires, ktime_get()));
 223         if (delta <= 0)
 224                 return force ? clockevents_program_min_delta(dev) : -ETIME;
 225
 226         delta = min(delta, (int64_t) dev->max_delta_ns);
 227         delta = max(delta, (int64_t) dev->min_delta_ns);
 228
 229         clc = ((unsigned long long) delta * dev->mult) >> dev->shift;
 230         rc = dev->set_next_event((unsigned long) clc, dev);
 231
 232         return (rc && force) ? clockevents_program_min_delta(dev) : rc;
 233 }
 234
 235 /**
 236  * clockevents_register_notifier - register a clock events change listener
 237  */
 238 int clockevents_register_notifier(struct notifier_block *nb)
 239 {
 240         unsigned long flags;
 241         int ret;
 242
 243         raw_spin_lock_irqsave(&clockevents_lock, flags);
 244         ret = raw_notifier_chain_register(&clockevents_chain, nb);
 245         raw_spin_unlock_irqrestore(&clockevents_lock, flags);
 246
 247         return ret;
 248 }
 249
 250 /*
 251  * Notify about a clock event change. Called with clockevents_lock
 252  * held.
 253  */
 254 static void clockevents_do_notify(unsigned long reason, void *dev)
 255 {
 256         raw_notifier_call_chain(&clockevents_chain, reason, dev);
 257 }
 258
 259 /*
 260  * Called after a notify add to make devices available which were
 261  * released from the notifier call.
 262  */
 263 static void clockevents_notify_released(void)
 264 {
 265         struct clock_event_device *dev;
 266
 267         while (!list_empty(&clockevents_released)) {
 268                 dev = list_entry(clockevents_released.next,
 269                                  struct clock_event_device, list);
 270                 list_del(&dev->list);
 271                 list_add(&dev->list, &clockevent_devices);
 272                 clockevents_do_notify(CLOCK_EVT_NOTIFY_ADD, dev);
 273         }
 274 }
 275
 276 /**
 277  * clockevents_register_device - register a clock event device
 278  * @dev:        device to register
 279  */
 280 void clockevents_register_device(struct clock_event_device *dev)
 281 {
 282         unsigned long flags;
 283
 284         BUG_ON(dev->mode != CLOCK_EVT_MODE_UNUSED);
 285         if (!dev->cpumask) {
 286                 WARN_ON(num_possible_cpus() > 1);
 287                 dev->cpumask = cpumask_of(smp_processor_id());
 288         }
 289
 290         raw_spin_lock_irqsave(&clockevents_lock, flags);
 291
 292         list_add(&dev->list, &clockevent_devices);
 293         clockevents_do_notify(CLOCK_EVT_NOTIFY_ADD, dev);
 294         clockevents_notify_released();
 295
 296         raw_spin_unlock_irqrestore(&clockevents_lock, flags);
 297 }
 298 EXPORT_SYMBOL_GPL(clockevents_register_device);
 299
 300 static void clockevents_config(struct clock_event_device *dev,
 301                                u32 freq)
 302 {
 303         u64 sec;
 304
 305         if (!(dev->features & CLOCK_EVT_FEAT_ONESHOT))
 306                 return;
 307
 308         /*
 309          * Calculate the maximum number of seconds we can sleep. Limit
 310          * to 10 minutes for hardware which can program more than
 311          * 32bit ticks so we still get reasonable conversion values.
 312          */
 313         sec = dev->max_delta_ticks;
 314         do_div(sec, freq);
 315         if (!sec)
 316                 sec = 1;
 317         else if (sec > 600 && dev->max_delta_ticks > UINT_MAX)
 318                 sec = 600;
 319
 320         clockevents_calc_mult_shift(dev, freq, sec);
 321         dev->min_delta_ns = clockevent_delta2ns(dev->min_delta_ticks, dev);
 322         dev->max_delta_ns = clockevent_delta2ns(dev->max_delta_ticks, dev);
 323 }
 324
 325 /**
 326  * clockevents_config_and_register - Configure and register a clock event device
 327  * @dev:        device to register
 328  * @freq:       The clock frequency
 329  * @min_delta:  The minimum clock ticks to program in oneshot mode
 330  * @max_delta:  The maximum clock ticks to program in oneshot mode
 331  *
 332  * min/max_delta can be 0 for devices which do not support oneshot mode.
 333  */
 334 void clockevents_config_and_register(struct clock_event_device *dev,
 335                                      u32 freq, unsigned long min_delta,
 336                                      unsigned long max_delta)
 337 {
 338         dev->min_delta_ticks = min_delta;
 339         dev->max_delta_ticks = max_delta;
 340         clockevents_config(dev, freq);
 341         clockevents_register_device(dev);
 342 }
 343
 344 /**
 345  * clockevents_update_freq - Update frequency and reprogram a clock event device.
 346  * @dev:        device to modify
 347  * @freq:       new device frequency
 348  *
 349  * Reconfigure and reprogram a clock event device in oneshot
 350  * mode. Must be called on the cpu for which the device delivers per
 351  * cpu timer events with interrupts disabled!  Returns 0 on success,
 352  * -ETIME when the event is in the past.
 353  */
 354 int clockevents_update_freq(struct clock_event_device *dev, u32 freq)
 355 {
 356         clockevents_config(dev, freq);
 357
 358         if (dev->mode != CLOCK_EVT_MODE_ONESHOT)
 359                 return 0;
 360
 361         return clockevents_program_event(dev, dev->next_event, false);
 362 }
 363
 364 /*
 365  * Noop handler when we shut down an event device
 366  */
 367 void clockevents_handle_noop(struct clock_event_device *dev)
 368 {
 369 }
 370
 371 /**
 372  * clockevents_exchange_device - release and request clock devices
 373  * @old:        device to release (can be NULL)
 374  * @new:        device to request (can be NULL)
 375  *
 376  * Called from the notifier chain. clockevents_lock is held already
 377  */
 378 void clockevents_exchange_device(struct clock_event_device *old,
 379                                  struct clock_event_device *new)
 380 {
 381         unsigned long flags;
 382
 383         local_irq_save(flags);
 384         /*
 385          * Caller releases a clock event device. We queue it into the
 386          * released list and do a notify add later.
 387          */
 388         if (old) {
 389                 clockevents_set_mode(old, CLOCK_EVT_MODE_UNUSED);
 390                 list_del(&old->list);
 391                 list_add(&old->list, &clockevents_released);
 392         }
 393
 394         if (new) {
 395                 BUG_ON(new->mode != CLOCK_EVT_MODE_UNUSED);
 396                 clockevents_shutdown(new);
 397         }
 398         local_irq_restore(flags);
 399 }
 400
 401 #ifdef CONFIG_GENERIC_CLOCKEVENTS
 402 /**
 403  * clockevents_notify - notification about relevant events
 404  */
 405 void clockevents_notify(unsigned long reason, void *arg)
 406 {
 407         struct clock_event_device *dev, *tmp;
 408         unsigned long flags;
 409         int cpu;
 410
 411         raw_spin_lock_irqsave(&clockevents_lock, flags);
 412         clockevents_do_notify(reason, arg);
 413
 414         switch (reason) {
 415         case CLOCK_EVT_NOTIFY_CPU_DEAD:
 416                 /*
 417                  * Unregister the clock event devices which were
 418                  * released from the users in the notify chain.
 419                  */
 420                 list_for_each_entry_safe(dev, tmp, &clockevents_released, list)
 421                         list_del(&dev->list);
 422                 /*
 423                  * Now check whether the CPU has left unused per cpu devices
 424                  */
 425                 cpu = *((int *)arg);
 426                 list_for_each_entry_safe(dev, tmp, &clockevent_devices, list) {
 427                         if (cpumask_test_cpu(cpu, dev->cpumask) &&
 428                             cpumask_weight(dev->cpumask) == 1 &&
 429                             !tick_is_broadcast_device(dev)) {
 430                                 BUG_ON(dev->mode != CLOCK_EVT_MODE_UNUSED);
 431                                 list_del(&dev->list);
 432                         }
 433                 }
 434                 break;
 435         default:
 436                 break;
 437         }
 438         raw_spin_unlock_irqrestore(&clockevents_lock, flags);
 439 }
 440 EXPORT_SYMBOL_GPL(clockevents_notify);
 441 #endif