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/smp.h>
  19 #include <linux/device.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 /* Protection for the above */
  27 static DEFINE_RAW_SPINLOCK(clockevents_lock);
  28 /* Protection for unbind operations */
  29 static DEFINE_MUTEX(clockevents_mutex);
  30
  31 struct ce_unbind {
  32         struct clock_event_device *ce;
  33         int res;
  34 };
  35
  36 static u64 cev_delta2ns(unsigned long latch, struct clock_event_device *evt,
  37                         bool ismax)
  38 {
  39         u64 clc = (u64) latch << evt->shift;
  40         u64 rnd;
  41
  42         if (unlikely(!evt->mult)) {
  43                 evt->mult = 1;
  44                 WARN_ON(1);
  45         }
  46         rnd = (u64) evt->mult - 1;
  47
  48         /*
  49          * Upper bound sanity check. If the backwards conversion is
  50          * not equal latch, we know that the above shift overflowed.
  51          */
  52         if ((clc >> evt->shift) != (u64)latch)
  53                 clc = ~0ULL;
  54
  55         /*
  56          * Scaled math oddities:
  57          *
  58          * For mult <= (1 << shift) we can safely add mult - 1 to
  59          * prevent integer rounding loss. So the backwards conversion
  60          * from nsec to device ticks will be correct.
  61          *
  62          * For mult > (1 << shift), i.e. device frequency is > 1GHz we
  63          * need to be careful. Adding mult - 1 will result in a value
  64          * which when converted back to device ticks can be larger
  65          * than latch by up to (mult - 1) >> shift. For the min_delta
  66          * calculation we still want to apply this in order to stay
  67          * above the minimum device ticks limit. For the upper limit
  68          * we would end up with a latch value larger than the upper
  69          * limit of the device, so we omit the add to stay below the
  70          * device upper boundary.
  71          *
  72          * Also omit the add if it would overflow the u64 boundary.
  73          */
  74         if ((~0ULL - clc > rnd) &&
  75             (!ismax || evt->mult <= (1ULL << evt->shift)))
  76                 clc += rnd;
  77
  78         do_div(clc, evt->mult);
  79
  80         /* Deltas less than 1usec are pointless noise */
  81         return clc > 1000 ? clc : 1000;
  82 }
  83
  84 /**
  85  * clockevents_delta2ns - Convert a latch value (device ticks) to nanoseconds
  86  * @latch:      value to convert
  87  * @evt:        pointer to clock event device descriptor
  88  *
  89  * Math helper, returns latch value converted to nanoseconds (bound checked)
  90  */
  91 u64 clockevent_delta2ns(unsigned long latch, struct clock_event_device *evt)
  92 {
  93         return cev_delta2ns(latch, evt, false);
  94 }
  95 EXPORT_SYMBOL_GPL(clockevent_delta2ns);
  96
  97 static int __clockevents_set_state(struct clock_event_device *dev,
  98                                    enum clock_event_state state)
  99 {
 100         /* Transition with legacy set_mode() callback */
 101         if (dev->set_mode) {
 102                 /* Legacy callback doesn't support new modes */
 103                 if (state > CLOCK_EVT_STATE_ONESHOT)
 104                         return -ENOSYS;
 105                 /*
 106                  * 'clock_event_state' and 'clock_event_mode' have 1-to-1
 107                  * mapping until *_ONESHOT, and so a simple cast will work.
 108                  */
 109                 dev->set_mode((enum clock_event_mode)state, dev);
 110                 dev->mode = (enum clock_event_mode)state;
 111                 return 0;
 112         }
 113
 114         if (dev->features & CLOCK_EVT_FEAT_DUMMY)
 115                 return 0;
 116
 117         /* Transition with new state-specific callbacks */
 118         switch (state) {
 119         case CLOCK_EVT_STATE_DETACHED:
 120                 /*
 121                  * This is an internal state, which is guaranteed to go from
 122                  * SHUTDOWN to DETACHED. No driver interaction required.
 123                  */
 124                 return 0;
 125
 126         case CLOCK_EVT_STATE_SHUTDOWN:
 127                 return dev->set_state_shutdown(dev);
 128
 129         case CLOCK_EVT_STATE_PERIODIC:
 130                 /* Core internal bug */
 131                 if (!(dev->features & CLOCK_EVT_FEAT_PERIODIC))
 132                         return -ENOSYS;
 133                 return dev->set_state_periodic(dev);
 134
 135         case CLOCK_EVT_STATE_ONESHOT:
 136                 /* Core internal bug */
 137                 if (!(dev->features & CLOCK_EVT_FEAT_ONESHOT))
 138                         return -ENOSYS;
 139                 return dev->set_state_oneshot(dev);
 140
 141         default:
 142                 return -ENOSYS;
 143         }
 144 }
 145
 146 /**
 147  * clockevents_set_state - set the operating state of a clock event device
 148  * @dev:        device to modify
 149  * @state:      new state
 150  *
 151  * Must be called with interrupts disabled !
 152  */
 153 void clockevents_set_state(struct clock_event_device *dev,
 154                            enum clock_event_state state)
 155 {
 156         if (dev->state != state) {
 157                 if (__clockevents_set_state(dev, state))
 158                         return;
 159
 160                 dev->state = state;
 161
 162                 /*
 163                  * A nsec2cyc multiplicator of 0 is invalid and we'd crash
 164                  * on it, so fix it up and emit a warning:
 165                  */
 166                 if (state == CLOCK_EVT_STATE_ONESHOT) {
 167                         if (unlikely(!dev->mult)) {
 168                                 dev->mult = 1;
 169                                 WARN_ON(1);
 170                         }
 171                 }
 172         }
 173 }
 174
 175 /**
 176  * clockevents_shutdown - shutdown the device and clear next_event
 177  * @dev:        device to shutdown
 178  */
 179 void clockevents_shutdown(struct clock_event_device *dev)
 180 {
 181         clockevents_set_state(dev, CLOCK_EVT_STATE_SHUTDOWN);
 182         dev->next_event.tv64 = KTIME_MAX;
 183 }
 184
 185 /**
 186  * clockevents_tick_resume -    Resume the tick device before using it again
 187  * @dev:                        device to resume
 188  */
 189 int clockevents_tick_resume(struct clock_event_device *dev)
 190 {
 191         int ret = 0;
 192
 193         if (dev->set_mode) {
 194                 dev->set_mode(CLOCK_EVT_MODE_RESUME, dev);
 195                 dev->mode = CLOCK_EVT_MODE_RESUME;
 196         } else if (dev->tick_resume) {
 197                 ret = dev->tick_resume(dev);
 198         }
 199
 200         return ret;
 201 }
 202
 203 #ifdef CONFIG_GENERIC_CLOCKEVENTS_MIN_ADJUST
 204
 205 /* Limit min_delta to a jiffie */
 206 #define MIN_DELTA_LIMIT         (NSEC_PER_SEC / HZ)
 207
 208 /**
 209  * clockevents_increase_min_delta - raise minimum delta of a clock event device
 210  * @dev:       device to increase the minimum delta
 211  *
 212  * Returns 0 on success, -ETIME when the minimum delta reached the limit.
 213  */
 214 static int clockevents_increase_min_delta(struct clock_event_device *dev)
 215 {
 216         /* Nothing to do if we already reached the limit */
 217         if (dev->min_delta_ns >= MIN_DELTA_LIMIT) {
 218                 printk_deferred(KERN_WARNING
 219                                 "CE: Reprogramming failure. Giving up\n");
 220                 dev->next_event.tv64 = KTIME_MAX;
 221                 return -ETIME;
 222         }
 223
 224         if (dev->min_delta_ns < 5000)
 225                 dev->min_delta_ns = 5000;
 226         else
 227                 dev->min_delta_ns += dev->min_delta_ns >> 1;
 228
 229         if (dev->min_delta_ns > MIN_DELTA_LIMIT)
 230                 dev->min_delta_ns = MIN_DELTA_LIMIT;
 231
 232         printk_deferred(KERN_WARNING
 233                         "CE: %s increased min_delta_ns to %llu nsec\n",
 234                         dev->name ? dev->name : "?",
 235                         (unsigned long long) dev->min_delta_ns);
 236         return 0;
 237 }
 238
 239 /**
 240  * clockevents_program_min_delta - Set clock event device to the minimum delay.
 241  * @dev:        device to program
 242  *
 243  * Returns 0 on success, -ETIME when the retry loop failed.
 244  */
 245 static int clockevents_program_min_delta(struct clock_event_device *dev)
 246 {
 247         unsigned long long clc;
 248         int64_t delta;
 249         int i;
 250
 251         for (i = 0;;) {
 252                 delta = dev->min_delta_ns;
 253                 dev->next_event = ktime_add_ns(ktime_get(), delta);
 254
 255                 if (dev->state == CLOCK_EVT_STATE_SHUTDOWN)
 256                         return 0;
 257
 258                 dev->retries++;
 259                 clc = ((unsigned long long) delta * dev->mult) >> dev->shift;
 260                 if (dev->set_next_event((unsigned long) clc, dev) == 0)
 261                         return 0;
 262
 263                 if (++i > 2) {
 264                         /*
 265                          * We tried 3 times to program the device with the
 266                          * given min_delta_ns. Try to increase the minimum
 267                          * delta, if that fails as well get out of here.
 268                          */
 269                         if (clockevents_increase_min_delta(dev))
 270                                 return -ETIME;
 271                         i = 0;
 272                 }
 273         }
 274 }
 275
 276 #else  /* CONFIG_GENERIC_CLOCKEVENTS_MIN_ADJUST */
 277
 278 /**
 279  * clockevents_program_min_delta - Set clock event device to the minimum delay.
 280  * @dev:        device to program
 281  *
 282  * Returns 0 on success, -ETIME when the retry loop failed.
 283  */
 284 static int clockevents_program_min_delta(struct clock_event_device *dev)
 285 {
 286         unsigned long long clc;
 287         int64_t delta;
 288
 289         delta = dev->min_delta_ns;
 290         dev->next_event = ktime_add_ns(ktime_get(), delta);
 291
 292         if (dev->state == CLOCK_EVT_STATE_SHUTDOWN)
 293                 return 0;
 294
 295         dev->retries++;
 296         clc = ((unsigned long long) delta * dev->mult) >> dev->shift;
 297         return dev->set_next_event((unsigned long) clc, dev);
 298 }
 299
 300 #endif /* CONFIG_GENERIC_CLOCKEVENTS_MIN_ADJUST */
 301
 302 /**
 303  * clockevents_program_event - Reprogram the clock event device.
 304  * @dev:        device to program
 305  * @expires:    absolute expiry time (monotonic clock)
 306  * @force:      program minimum delay if expires can not be set
 307  *
 308  * Returns 0 on success, -ETIME when the event is in the past.
 309  */
 310 int clockevents_program_event(struct clock_event_device *dev, ktime_t expires,
 311                               bool force)
 312 {
 313         unsigned long long clc;
 314         int64_t delta;
 315         int rc;
 316
 317         if (unlikely(expires.tv64 < 0)) {
 318                 WARN_ON_ONCE(1);
 319                 return -ETIME;
 320         }
 321
 322         dev->next_event = expires;
 323
 324         if (dev->state == CLOCK_EVT_STATE_SHUTDOWN)
 325                 return 0;
 326
 327         /* Shortcut for clockevent devices that can deal with ktime. */
 328         if (dev->features & CLOCK_EVT_FEAT_KTIME)
 329                 return dev->set_next_ktime(expires, dev);
 330
 331         delta = ktime_to_ns(ktime_sub(expires, ktime_get()));
 332         if (delta <= 0)
 333                 return force ? clockevents_program_min_delta(dev) : -ETIME;
 334
 335         delta = min(delta, (int64_t) dev->max_delta_ns);
 336         delta = max(delta, (int64_t) dev->min_delta_ns);
 337
 338         clc = ((unsigned long long) delta * dev->mult) >> dev->shift;
 339         rc = dev->set_next_event((unsigned long) clc, dev);
 340
 341         return (rc && force) ? clockevents_program_min_delta(dev) : rc;
 342 }
 343
 344 /*
 345  * Called after a notify add to make devices available which were
 346  * released from the notifier call.
 347  */
 348 static void clockevents_notify_released(void)
 349 {
 350         struct clock_event_device *dev;
 351
 352         while (!list_empty(&clockevents_released)) {
 353                 dev = list_entry(clockevents_released.next,
 354                                  struct clock_event_device, list);
 355                 list_del(&dev->list);
 356                 list_add(&dev->list, &clockevent_devices);
 357                 tick_check_new_device(dev);
 358         }
 359 }
 360
 361 /*
 362  * Try to install a replacement clock event device
 363  */
 364 static int clockevents_replace(struct clock_event_device *ced)
 365 {
 366         struct clock_event_device *dev, *newdev = NULL;
 367
 368         list_for_each_entry(dev, &clockevent_devices, list) {
 369                 if (dev == ced || dev->state != CLOCK_EVT_STATE_DETACHED)
 370                         continue;
 371
 372                 if (!tick_check_replacement(newdev, dev))
 373                         continue;
 374
 375                 if (!try_module_get(dev->owner))
 376                         continue;
 377
 378                 if (newdev)
 379                         module_put(newdev->owner);
 380                 newdev = dev;
 381         }
 382         if (newdev) {
 383                 tick_install_replacement(newdev);
 384                 list_del_init(&ced->list);
 385         }
 386         return newdev ? 0 : -EBUSY;
 387 }
 388
 389 /*
 390  * Called with clockevents_mutex and clockevents_lock held
 391  */
 392 static int __clockevents_try_unbind(struct clock_event_device *ced, int cpu)
 393 {
 394         /* Fast track. Device is unused */
 395         if (ced->state == CLOCK_EVT_STATE_DETACHED) {
 396                 list_del_init(&ced->list);
 397                 return 0;
 398         }
 399
 400         return ced == per_cpu(tick_cpu_device, cpu).evtdev ? -EAGAIN : -EBUSY;
 401 }
 402
 403 /*
 404  * SMP function call to unbind a device
 405  */
 406 static void __clockevents_unbind(void *arg)
 407 {
 408         struct ce_unbind *cu = arg;
 409         int res;
 410
 411         raw_spin_lock(&clockevents_lock);
 412         res = __clockevents_try_unbind(cu->ce, smp_processor_id());
 413         if (res == -EAGAIN)
 414                 res = clockevents_replace(cu->ce);
 415         cu->res = res;
 416         raw_spin_unlock(&clockevents_lock);
 417 }
 418
 419 /*
 420  * Issues smp function call to unbind a per cpu device. Called with
 421  * clockevents_mutex held.
 422  */
 423 static int clockevents_unbind(struct clock_event_device *ced, int cpu)
 424 {
 425         struct ce_unbind cu = { .ce = ced, .res = -ENODEV };
 426
 427         smp_call_function_single(cpu, __clockevents_unbind, &cu, 1);
 428         return cu.res;
 429 }
 430
 431 /*
 432  * Unbind a clockevents device.
 433  */
 434 int clockevents_unbind_device(struct clock_event_device *ced, int cpu)
 435 {
 436         int ret;
 437
 438         mutex_lock(&clockevents_mutex);
 439         ret = clockevents_unbind(ced, cpu);
 440         mutex_unlock(&clockevents_mutex);
 441         return ret;
 442 }
 443 EXPORT_SYMBOL_GPL(clockevents_unbind);
 444
 445 /* Sanity check of state transition callbacks */
 446 static int clockevents_sanity_check(struct clock_event_device *dev)
 447 {
 448         /* Legacy set_mode() callback */
 449         if (dev->set_mode) {
 450                 /* We shouldn't be supporting new modes now */
 451                 WARN_ON(dev->set_state_periodic || dev->set_state_oneshot ||
 452                         dev->set_state_shutdown || dev->tick_resume);
 453
 454                 BUG_ON(dev->mode != CLOCK_EVT_MODE_UNUSED);
 455                 return 0;
 456         }
 457
 458         if (dev->features & CLOCK_EVT_FEAT_DUMMY)
 459                 return 0;
 460
 461         /* New state-specific callbacks */
 462         if (!dev->set_state_shutdown)
 463                 return -EINVAL;
 464
 465         if ((dev->features & CLOCK_EVT_FEAT_PERIODIC) &&
 466             !dev->set_state_periodic)
 467                 return -EINVAL;
 468
 469         if ((dev->features & CLOCK_EVT_FEAT_ONESHOT) &&
 470             !dev->set_state_oneshot)
 471                 return -EINVAL;
 472
 473         return 0;
 474 }
 475
 476 /**
 477  * clockevents_register_device - register a clock event device
 478  * @dev:        device to register
 479  */
 480 void clockevents_register_device(struct clock_event_device *dev)
 481 {
 482         unsigned long flags;
 483
 484         BUG_ON(clockevents_sanity_check(dev));
 485
 486         /* Initialize state to DETACHED */
 487         dev->state = CLOCK_EVT_STATE_DETACHED;
 488
 489         if (!dev->cpumask) {
 490                 WARN_ON(num_possible_cpus() > 1);
 491                 dev->cpumask = cpumask_of(smp_processor_id());
 492         }
 493
 494         raw_spin_lock_irqsave(&clockevents_lock, flags);
 495
 496         list_add(&dev->list, &clockevent_devices);
 497         tick_check_new_device(dev);
 498         clockevents_notify_released();
 499
 500         raw_spin_unlock_irqrestore(&clockevents_lock, flags);
 501 }
 502 EXPORT_SYMBOL_GPL(clockevents_register_device);
 503
 504 void clockevents_config(struct clock_event_device *dev, u32 freq)
 505 {
 506         u64 sec;
 507
 508         if (!(dev->features & CLOCK_EVT_FEAT_ONESHOT))
 509                 return;
 510
 511         /*
 512          * Calculate the maximum number of seconds we can sleep. Limit
 513          * to 10 minutes for hardware which can program more than
 514          * 32bit ticks so we still get reasonable conversion values.
 515          */
 516         sec = dev->max_delta_ticks;
 517         do_div(sec, freq);
 518         if (!sec)
 519                 sec = 1;
 520         else if (sec > 600 && dev->max_delta_ticks > UINT_MAX)
 521                 sec = 600;
 522
 523         clockevents_calc_mult_shift(dev, freq, sec);
 524         dev->min_delta_ns = cev_delta2ns(dev->min_delta_ticks, dev, false);
 525         dev->max_delta_ns = cev_delta2ns(dev->max_delta_ticks, dev, true);
 526 }
 527
 528 /**
 529  * clockevents_config_and_register - Configure and register a clock event device
 530  * @dev:        device to register
 531  * @freq:       The clock frequency
 532  * @min_delta:  The minimum clock ticks to program in oneshot mode
 533  * @max_delta:  The maximum clock ticks to program in oneshot mode
 534  *
 535  * min/max_delta can be 0 for devices which do not support oneshot mode.
 536  */
 537 void clockevents_config_and_register(struct clock_event_device *dev,
 538                                      u32 freq, unsigned long min_delta,
 539                                      unsigned long max_delta)
 540 {
 541         dev->min_delta_ticks = min_delta;
 542         dev->max_delta_ticks = max_delta;
 543         clockevents_config(dev, freq);
 544         clockevents_register_device(dev);
 545 }
 546 EXPORT_SYMBOL_GPL(clockevents_config_and_register);
 547
 548 int __clockevents_update_freq(struct clock_event_device *dev, u32 freq)
 549 {
 550         clockevents_config(dev, freq);
 551
 552         if (dev->state == CLOCK_EVT_STATE_ONESHOT)
 553                 return clockevents_program_event(dev, dev->next_event, false);
 554
 555         if (dev->state == CLOCK_EVT_STATE_PERIODIC)
 556                 return __clockevents_set_state(dev, CLOCK_EVT_STATE_PERIODIC);
 557
 558         return 0;
 559 }
 560
 561 /**
 562  * clockevents_update_freq - Update frequency and reprogram a clock event device.
 563  * @dev:        device to modify
 564  * @freq:       new device frequency
 565  *
 566  * Reconfigure and reprogram a clock event device in oneshot
 567  * mode. Must be called on the cpu for which the device delivers per
 568  * cpu timer events. If called for the broadcast device the core takes
 569  * care of serialization.
 570  *
 571  * Returns 0 on success, -ETIME when the event is in the past.
 572  */
 573 int clockevents_update_freq(struct clock_event_device *dev, u32 freq)
 574 {
 575         unsigned long flags;
 576         int ret;
 577
 578         local_irq_save(flags);
 579         ret = tick_broadcast_update_freq(dev, freq);
 580         if (ret == -ENODEV)
 581                 ret = __clockevents_update_freq(dev, freq);
 582         local_irq_restore(flags);
 583         return ret;
 584 }
 585
 586 /*
 587  * Noop handler when we shut down an event device
 588  */
 589 void clockevents_handle_noop(struct clock_event_device *dev)
 590 {
 591 }
 592
 593 /**
 594  * clockevents_exchange_device - release and request clock devices
 595  * @old:        device to release (can be NULL)
 596  * @new:        device to request (can be NULL)
 597  *
 598  * Called from various tick functions with clockevents_lock held and
 599  * interrupts disabled.
 600  */
 601 void clockevents_exchange_device(struct clock_event_device *old,
 602                                  struct clock_event_device *new)
 603 {
 604         /*
 605          * Caller releases a clock event device. We queue it into the
 606          * released list and do a notify add later.
 607          */
 608         if (old) {
 609                 module_put(old->owner);
 610                 clockevents_set_state(old, CLOCK_EVT_STATE_DETACHED);
 611                 list_del(&old->list);
 612                 list_add(&old->list, &clockevents_released);
 613         }
 614
 615         if (new) {
 616                 BUG_ON(new->state != CLOCK_EVT_STATE_DETACHED);
 617                 clockevents_shutdown(new);
 618         }
 619 }
 620
 621 /**
 622  * clockevents_suspend - suspend clock devices
 623  */
 624 void clockevents_suspend(void)
 625 {
 626         struct clock_event_device *dev;
 627
 628         list_for_each_entry_reverse(dev, &clockevent_devices, list)
 629                 if (dev->suspend)
 630                         dev->suspend(dev);
 631 }
 632
 633 /**
 634  * clockevents_resume - resume clock devices
 635  */
 636 void clockevents_resume(void)
 637 {
 638         struct clock_event_device *dev;
 639
 640         list_for_each_entry(dev, &clockevent_devices, list)
 641                 if (dev->resume)
 642                         dev->resume(dev);
 643 }
 644
 645 /**
 646  * clockevents_notify - notification about relevant events
 647  * Returns 0 on success, any other value on error
 648  */
 649 int clockevents_notify(unsigned long reason, void *arg)
 650 {
 651         struct clock_event_device *dev, *tmp;
 652         unsigned long flags;
 653         int cpu, ret = 0;
 654
 655         raw_spin_lock_irqsave(&clockevents_lock, flags);
 656
 657         switch (reason) {
 658         case CLOCK_EVT_NOTIFY_CPU_DEAD:
 659                 tick_shutdown_broadcast_oneshot(arg);
 660                 tick_shutdown_broadcast(arg);
 661                 tick_shutdown(arg);
 662                 /*
 663                  * Unregister the clock event devices which were
 664                  * released from the users in the notify chain.
 665                  */
 666                 list_for_each_entry_safe(dev, tmp, &clockevents_released, list)
 667                         list_del(&dev->list);
 668                 /*
 669                  * Now check whether the CPU has left unused per cpu devices
 670                  */
 671                 cpu = *((int *)arg);
 672                 list_for_each_entry_safe(dev, tmp, &clockevent_devices, list) {
 673                         if (cpumask_test_cpu(cpu, dev->cpumask) &&
 674                             cpumask_weight(dev->cpumask) == 1 &&
 675                             !tick_is_broadcast_device(dev)) {
 676                                 BUG_ON(dev->state != CLOCK_EVT_STATE_DETACHED);
 677                                 list_del(&dev->list);
 678                         }
 679                 }
 680                 break;
 681         default:
 682                 break;
 683         }
 684         raw_spin_unlock_irqrestore(&clockevents_lock, flags);
 685         return ret;
 686 }
 687 EXPORT_SYMBOL_GPL(clockevents_notify);
 688
 689 #ifdef CONFIG_SYSFS
 690 struct bus_type clockevents_subsys = {
 691         .name           = "clockevents",
 692         .dev_name       = "clockevent",
 693 };
 694
 695 static DEFINE_PER_CPU(struct device, tick_percpu_dev);
 696 static struct tick_device *tick_get_tick_dev(struct device *dev);
 697
 698 static ssize_t sysfs_show_current_tick_dev(struct device *dev,
 699                                            struct device_attribute *attr,
 700                                            char *buf)
 701 {
 702         struct tick_device *td;
 703         ssize_t count = 0;
 704
 705         raw_spin_lock_irq(&clockevents_lock);
 706         td = tick_get_tick_dev(dev);
 707         if (td && td->evtdev)
 708                 count = snprintf(buf, PAGE_SIZE, "%s\n", td->evtdev->name);
 709         raw_spin_unlock_irq(&clockevents_lock);
 710         return count;
 711 }
 712 static DEVICE_ATTR(current_device, 0444, sysfs_show_current_tick_dev, NULL);
 713
 714 /* We don't support the abomination of removable broadcast devices */
 715 static ssize_t sysfs_unbind_tick_dev(struct device *dev,
 716                                      struct device_attribute *attr,
 717                                      const char *buf, size_t count)
 718 {
 719         char name[CS_NAME_LEN];
 720         ssize_t ret = sysfs_get_uname(buf, name, count);
 721         struct clock_event_device *ce;
 722
 723         if (ret < 0)
 724                 return ret;
 725
 726         ret = -ENODEV;
 727         mutex_lock(&clockevents_mutex);
 728         raw_spin_lock_irq(&clockevents_lock);
 729         list_for_each_entry(ce, &clockevent_devices, list) {
 730                 if (!strcmp(ce->name, name)) {
 731                         ret = __clockevents_try_unbind(ce, dev->id);
 732                         break;
 733                 }
 734         }
 735         raw_spin_unlock_irq(&clockevents_lock);
 736         /*
 737          * We hold clockevents_mutex, so ce can't go away
 738          */
 739         if (ret == -EAGAIN)
 740                 ret = clockevents_unbind(ce, dev->id);
 741         mutex_unlock(&clockevents_mutex);
 742         return ret ? ret : count;
 743 }
 744 static DEVICE_ATTR(unbind_device, 0200, NULL, sysfs_unbind_tick_dev);
 745
 746 #ifdef CONFIG_GENERIC_CLOCKEVENTS_BROADCAST
 747 static struct device tick_bc_dev = {
 748         .init_name      = "broadcast",
 749         .id             = 0,
 750         .bus            = &clockevents_subsys,
 751 };
 752
 753 static struct tick_device *tick_get_tick_dev(struct device *dev)
 754 {
 755         return dev == &tick_bc_dev ? tick_get_broadcast_device() :
 756                 &per_cpu(tick_cpu_device, dev->id);
 757 }
 758
 759 static __init int tick_broadcast_init_sysfs(void)
 760 {
 761         int err = device_register(&tick_bc_dev);
 762
 763         if (!err)
 764                 err = device_create_file(&tick_bc_dev, &dev_attr_current_device);
 765         return err;
 766 }
 767 #else
 768 static struct tick_device *tick_get_tick_dev(struct device *dev)
 769 {
 770         return &per_cpu(tick_cpu_device, dev->id);
 771 }
 772 static inline int tick_broadcast_init_sysfs(void) { return 0; }
 773 #endif
 774
 775 static int __init tick_init_sysfs(void)
 776 {
 777         int cpu;
 778
 779         for_each_possible_cpu(cpu) {
 780                 struct device *dev = &per_cpu(tick_percpu_dev, cpu);
 781                 int err;
 782
 783                 dev->id = cpu;
 784                 dev->bus = &clockevents_subsys;
 785                 err = device_register(dev);
 786                 if (!err)
 787                         err = device_create_file(dev, &dev_attr_current_device);
 788                 if (!err)
 789                         err = device_create_file(dev, &dev_attr_unbind_device);
 790                 if (err)
 791                         return err;
 792         }
 793         return tick_broadcast_init_sysfs();
 794 }
 795
 796 static int __init clockevents_init_sysfs(void)
 797 {
 798         int err = subsys_system_register(&clockevents_subsys, NULL);
 799
 800         if (!err)
 801                 err = tick_init_sysfs();
 802         return err;
 803 }
 804 device_initcall(clockevents_init_sysfs);
 805 #endif /* SYSFS */