root/kernel/time/clockevents.c

DEFINITIONS

1. cev_delta2ns
2. clockevent_delta2ns
3. __clockevents_switch_state
4. clockevents_switch_state
5. clockevents_shutdown
6. clockevents_tick_resume
7. clockevents_increase_min_delta
8. clockevents_program_min_delta
9. clockevents_program_min_delta
10. clockevents_program_event
11. clockevents_notify_released
12. clockevents_replace
13. __clockevents_try_unbind
14. __clockevents_unbind
15. clockevents_unbind
16. clockevents_unbind_device
17. clockevents_register_device
18. clockevents_config
19. clockevents_config_and_register
20. __clockevents_update_freq
21. clockevents_update_freq
22. clockevents_handle_noop
23. clockevents_exchange_device
24. clockevents_suspend
25. clockevents_resume
26. tick_offline_cpu
27. tick_cleanup_dead_cpu
28. sysfs_show_current_tick_dev
29. sysfs_unbind_tick_dev
30. tick_get_tick_dev
31. tick_broadcast_init_sysfs
32. tick_get_tick_dev
33. tick_broadcast_init_sysfs
34. tick_init_sysfs
35. clockevents_init_sysfs

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * This file contains functions which manage clock event devices.
   4  *
   5  * Copyright(C) 2005-2006, Thomas Gleixner <tglx@linutronix.de>
   6  * Copyright(C) 2005-2007, Red Hat, Inc., Ingo Molnar
   7  * Copyright(C) 2006-2007, Timesys Corp., Thomas Gleixner
   8  */
   9 
  10 #include <linux/clockchips.h>
  11 #include <linux/hrtimer.h>
  12 #include <linux/init.h>
  13 #include <linux/module.h>
  14 #include <linux/smp.h>
  15 #include <linux/device.h>
  16 
  17 #include "tick-internal.h"
  18 
  19 /* The registered clock event devices */
  20 static LIST_HEAD(clockevent_devices);
  21 static LIST_HEAD(clockevents_released);
  22 /* Protection for the above */
  23 static DEFINE_RAW_SPINLOCK(clockevents_lock);
  24 /* Protection for unbind operations */
  25 static DEFINE_MUTEX(clockevents_mutex);
  26 
  27 struct ce_unbind {
  28         struct clock_event_device *ce;
  29         int res;
  30 };
  31 
  32 static u64 cev_delta2ns(unsigned long latch, struct clock_event_device *evt,
  33                         bool ismax)
  34 {
  35         u64 clc = (u64) latch << evt->shift;
  36         u64 rnd;
  37 
  38         if (WARN_ON(!evt->mult))
  39                 evt->mult = 1;
  40         rnd = (u64) evt->mult - 1;
  41 
  42         /*
  43          * Upper bound sanity check. If the backwards conversion is
  44          * not equal latch, we know that the above shift overflowed.
  45          */
  46         if ((clc >> evt->shift) != (u64)latch)
  47                 clc = ~0ULL;
  48 
  49         /*
  50          * Scaled math oddities:
  51          *
  52          * For mult <= (1 << shift) we can safely add mult - 1 to
  53          * prevent integer rounding loss. So the backwards conversion
  54          * from nsec to device ticks will be correct.
  55          *
  56          * For mult > (1 << shift), i.e. device frequency is > 1GHz we
  57          * need to be careful. Adding mult - 1 will result in a value
  58          * which when converted back to device ticks can be larger
  59          * than latch by up to (mult - 1) >> shift. For the min_delta
  60          * calculation we still want to apply this in order to stay
  61          * above the minimum device ticks limit. For the upper limit
  62          * we would end up with a latch value larger than the upper
  63          * limit of the device, so we omit the add to stay below the
  64          * device upper boundary.
  65          *
  66          * Also omit the add if it would overflow the u64 boundary.
  67          */
  68         if ((~0ULL - clc > rnd) &&
  69             (!ismax || evt->mult <= (1ULL << evt->shift)))
  70                 clc += rnd;
  71 
  72         do_div(clc, evt->mult);
  73 
  74         /* Deltas less than 1usec are pointless noise */
  75         return clc > 1000 ? clc : 1000;
  76 }
  77 
  78 /**
  79  * clockevents_delta2ns - Convert a latch value (device ticks) to nanoseconds
  80  * @latch:      value to convert
  81  * @evt:        pointer to clock event device descriptor
  82  *
  83  * Math helper, returns latch value converted to nanoseconds (bound checked)
  84  */
  85 u64 clockevent_delta2ns(unsigned long latch, struct clock_event_device *evt)
  86 {
  87         return cev_delta2ns(latch, evt, false);
  88 }
  89 EXPORT_SYMBOL_GPL(clockevent_delta2ns);
  90 
  91 static int __clockevents_switch_state(struct clock_event_device *dev,
  92                                       enum clock_event_state state)
  93 {
  94         if (dev->features & CLOCK_EVT_FEAT_DUMMY)
  95                 return 0;
  96 
  97         /* Transition with new state-specific callbacks */
  98         switch (state) {
  99         case CLOCK_EVT_STATE_DETACHED:
 100                 /* The clockevent device is getting replaced. Shut it down. */
 101 
 102         case CLOCK_EVT_STATE_SHUTDOWN:
 103                 if (dev->set_state_shutdown)
 104                         return dev->set_state_shutdown(dev);
 105                 return 0;
 106 
 107         case CLOCK_EVT_STATE_PERIODIC:
 108                 /* Core internal bug */
 109                 if (!(dev->features & CLOCK_EVT_FEAT_PERIODIC))
 110                         return -ENOSYS;
 111                 if (dev->set_state_periodic)
 112                         return dev->set_state_periodic(dev);
 113                 return 0;
 114 
 115         case CLOCK_EVT_STATE_ONESHOT:
 116                 /* Core internal bug */
 117                 if (!(dev->features & CLOCK_EVT_FEAT_ONESHOT))
 118                         return -ENOSYS;
 119                 if (dev->set_state_oneshot)
 120                         return dev->set_state_oneshot(dev);
 121                 return 0;
 122 
 123         case CLOCK_EVT_STATE_ONESHOT_STOPPED:
 124                 /* Core internal bug */
 125                 if (WARN_ONCE(!clockevent_state_oneshot(dev),
 126                               "Current state: %d\n",
 127                               clockevent_get_state(dev)))
 128                         return -EINVAL;
 129 
 130                 if (dev->set_state_oneshot_stopped)
 131                         return dev->set_state_oneshot_stopped(dev);
 132                 else
 133                         return -ENOSYS;
 134 
 135         default:
 136                 return -ENOSYS;
 137         }
 138 }
 139 
 140 /**
 141  * clockevents_switch_state - set the operating state of a clock event device
 142  * @dev:        device to modify
 143  * @state:      new state
 144  *
 145  * Must be called with interrupts disabled !
 146  */
 147 void clockevents_switch_state(struct clock_event_device *dev,
 148                               enum clock_event_state state)
 149 {
 150         if (clockevent_get_state(dev) != state) {
 151                 if (__clockevents_switch_state(dev, state))
 152                         return;
 153 
 154                 clockevent_set_state(dev, state);
 155 
 156                 /*
 157                  * A nsec2cyc multiplicator of 0 is invalid and we'd crash
 158                  * on it, so fix it up and emit a warning:
 159                  */
 160                 if (clockevent_state_oneshot(dev)) {
 161                         if (WARN_ON(!dev->mult))
 162                                 dev->mult = 1;
 163                 }
 164         }
 165 }
 166 
 167 /**
 168  * clockevents_shutdown - shutdown the device and clear next_event
 169  * @dev:        device to shutdown
 170  */
 171 void clockevents_shutdown(struct clock_event_device *dev)
 172 {
 173         clockevents_switch_state(dev, CLOCK_EVT_STATE_SHUTDOWN);
 174         dev->next_event = KTIME_MAX;
 175 }
 176 
 177 /**
 178  * clockevents_tick_resume -    Resume the tick device before using it again
 179  * @dev:                        device to resume
 180  */
 181 int clockevents_tick_resume(struct clock_event_device *dev)
 182 {
 183         int ret = 0;
 184 
 185         if (dev->tick_resume)
 186                 ret = dev->tick_resume(dev);
 187 
 188         return ret;
 189 }
 190 
 191 #ifdef CONFIG_GENERIC_CLOCKEVENTS_MIN_ADJUST
 192 
 193 /* Limit min_delta to a jiffie */
 194 #define MIN_DELTA_LIMIT         (NSEC_PER_SEC / HZ)
 195 
 196 /**
 197  * clockevents_increase_min_delta - raise minimum delta of a clock event device
 198  * @dev:       device to increase the minimum delta
 199  *
 200  * Returns 0 on success, -ETIME when the minimum delta reached the limit.
 201  */
 202 static int clockevents_increase_min_delta(struct clock_event_device *dev)
 203 {
 204         /* Nothing to do if we already reached the limit */
 205         if (dev->min_delta_ns >= MIN_DELTA_LIMIT) {
 206                 printk_deferred(KERN_WARNING
 207                                 "CE: Reprogramming failure. Giving up\n");
 208                 dev->next_event = KTIME_MAX;
 209                 return -ETIME;
 210         }
 211 
 212         if (dev->min_delta_ns < 5000)
 213                 dev->min_delta_ns = 5000;
 214         else
 215                 dev->min_delta_ns += dev->min_delta_ns >> 1;
 216 
 217         if (dev->min_delta_ns > MIN_DELTA_LIMIT)
 218                 dev->min_delta_ns = MIN_DELTA_LIMIT;
 219 
 220         printk_deferred(KERN_WARNING
 221                         "CE: %s increased min_delta_ns to %llu nsec\n",
 222                         dev->name ? dev->name : "?",
 223                         (unsigned long long) dev->min_delta_ns);
 224         return 0;
 225 }
 226 
 227 /**
 228  * clockevents_program_min_delta - Set clock event device to the minimum delay.
 229  * @dev:        device to program
 230  *
 231  * Returns 0 on success, -ETIME when the retry loop failed.
 232  */
 233 static int clockevents_program_min_delta(struct clock_event_device *dev)
 234 {
 235         unsigned long long clc;
 236         int64_t delta;
 237         int i;
 238 
 239         for (i = 0;;) {
 240                 delta = dev->min_delta_ns;
 241                 dev->next_event = ktime_add_ns(ktime_get(), delta);
 242 
 243                 if (clockevent_state_shutdown(dev))
 244                         return 0;
 245 
 246                 dev->retries++;
 247                 clc = ((unsigned long long) delta * dev->mult) >> dev->shift;
 248                 if (dev->set_next_event((unsigned long) clc, dev) == 0)
 249                         return 0;
 250 
 251                 if (++i > 2) {
 252                         /*
 253                          * We tried 3 times to program the device with the
 254                          * given min_delta_ns. Try to increase the minimum
 255                          * delta, if that fails as well get out of here.
 256                          */
 257                         if (clockevents_increase_min_delta(dev))
 258                                 return -ETIME;
 259                         i = 0;
 260                 }
 261         }
 262 }
 263 
 264 #else  /* CONFIG_GENERIC_CLOCKEVENTS_MIN_ADJUST */
 265 
 266 /**
 267  * clockevents_program_min_delta - Set clock event device to the minimum delay.
 268  * @dev:        device to program
 269  *
 270  * Returns 0 on success, -ETIME when the retry loop failed.
 271  */
 272 static int clockevents_program_min_delta(struct clock_event_device *dev)
 273 {
 274         unsigned long long clc;
 275         int64_t delta = 0;
 276         int i;
 277 
 278         for (i = 0; i < 10; i++) {
 279                 delta += dev->min_delta_ns;
 280                 dev->next_event = ktime_add_ns(ktime_get(), delta);
 281 
 282                 if (clockevent_state_shutdown(dev))
 283                         return 0;
 284 
 285                 dev->retries++;
 286                 clc = ((unsigned long long) delta * dev->mult) >> dev->shift;
 287                 if (dev->set_next_event((unsigned long) clc, dev) == 0)
 288                         return 0;
 289         }
 290         return -ETIME;
 291 }
 292 
 293 #endif /* CONFIG_GENERIC_CLOCKEVENTS_MIN_ADJUST */
 294 
 295 /**
 296  * clockevents_program_event - Reprogram the clock event device.
 297  * @dev:        device to program
 298  * @expires:    absolute expiry time (monotonic clock)
 299  * @force:      program minimum delay if expires can not be set
 300  *
 301  * Returns 0 on success, -ETIME when the event is in the past.
 302  */
 303 int clockevents_program_event(struct clock_event_device *dev, ktime_t expires,
 304                               bool force)
 305 {
 306         unsigned long long clc;
 307         int64_t delta;
 308         int rc;
 309 
 310         if (WARN_ON_ONCE(expires < 0))
 311                 return -ETIME;
 312 
 313         dev->next_event = expires;
 314 
 315         if (clockevent_state_shutdown(dev))
 316                 return 0;
 317 
 318         /* We must be in ONESHOT state here */
 319         WARN_ONCE(!clockevent_state_oneshot(dev), "Current state: %d\n",
 320                   clockevent_get_state(dev));
 321 
 322         /* Shortcut for clockevent devices that can deal with ktime. */
 323         if (dev->features & CLOCK_EVT_FEAT_KTIME)
 324                 return dev->set_next_ktime(expires, dev);
 325 
 326         delta = ktime_to_ns(ktime_sub(expires, ktime_get()));
 327         if (delta <= 0)
 328                 return force ? clockevents_program_min_delta(dev) : -ETIME;
 329 
 330         delta = min(delta, (int64_t) dev->max_delta_ns);
 331         delta = max(delta, (int64_t) dev->min_delta_ns);
 332 
 333         clc = ((unsigned long long) delta * dev->mult) >> dev->shift;
 334         rc = dev->set_next_event((unsigned long) clc, dev);
 335 
 336         return (rc && force) ? clockevents_program_min_delta(dev) : rc;
 337 }
 338 
 339 /*
 340  * Called after a notify add to make devices available which were
 341  * released from the notifier call.
 342  */
 343 static void clockevents_notify_released(void)
 344 {
 345         struct clock_event_device *dev;
 346 
 347         while (!list_empty(&clockevents_released)) {
 348                 dev = list_entry(clockevents_released.next,
 349                                  struct clock_event_device, list);
 350                 list_del(&dev->list);
 351                 list_add(&dev->list, &clockevent_devices);
 352                 tick_check_new_device(dev);
 353         }
 354 }
 355 
 356 /*
 357  * Try to install a replacement clock event device
 358  */
 359 static int clockevents_replace(struct clock_event_device *ced)
 360 {
 361         struct clock_event_device *dev, *newdev = NULL;
 362 
 363         list_for_each_entry(dev, &clockevent_devices, list) {
 364                 if (dev == ced || !clockevent_state_detached(dev))
 365                         continue;
 366 
 367                 if (!tick_check_replacement(newdev, dev))
 368                         continue;
 369 
 370                 if (!try_module_get(dev->owner))
 371                         continue;
 372 
 373                 if (newdev)
 374                         module_put(newdev->owner);
 375                 newdev = dev;
 376         }
 377         if (newdev) {
 378                 tick_install_replacement(newdev);
 379                 list_del_init(&ced->list);
 380         }
 381         return newdev ? 0 : -EBUSY;
 382 }
 383 
 384 /*
 385  * Called with clockevents_mutex and clockevents_lock held
 386  */
 387 static int __clockevents_try_unbind(struct clock_event_device *ced, int cpu)
 388 {
 389         /* Fast track. Device is unused */
 390         if (clockevent_state_detached(ced)) {
 391                 list_del_init(&ced->list);
 392                 return 0;
 393         }
 394 
 395         return ced == per_cpu(tick_cpu_device, cpu).evtdev ? -EAGAIN : -EBUSY;
 396 }
 397 
 398 /*
 399  * SMP function call to unbind a device
 400  */
 401 static void __clockevents_unbind(void *arg)
 402 {
 403         struct ce_unbind *cu = arg;
 404         int res;
 405 
 406         raw_spin_lock(&clockevents_lock);
 407         res = __clockevents_try_unbind(cu->ce, smp_processor_id());
 408         if (res == -EAGAIN)
 409                 res = clockevents_replace(cu->ce);
 410         cu->res = res;
 411         raw_spin_unlock(&clockevents_lock);
 412 }
 413 
 414 /*
 415  * Issues smp function call to unbind a per cpu device. Called with
 416  * clockevents_mutex held.
 417  */
 418 static int clockevents_unbind(struct clock_event_device *ced, int cpu)
 419 {
 420         struct ce_unbind cu = { .ce = ced, .res = -ENODEV };
 421 
 422         smp_call_function_single(cpu, __clockevents_unbind, &cu, 1);
 423         return cu.res;
 424 }
 425 
 426 /*
 427  * Unbind a clockevents device.
 428  */
 429 int clockevents_unbind_device(struct clock_event_device *ced, int cpu)
 430 {
 431         int ret;
 432 
 433         mutex_lock(&clockevents_mutex);
 434         ret = clockevents_unbind(ced, cpu);
 435         mutex_unlock(&clockevents_mutex);
 436         return ret;
 437 }
 438 EXPORT_SYMBOL_GPL(clockevents_unbind_device);
 439 
 440 /**
 441  * clockevents_register_device - register a clock event device
 442  * @dev:        device to register
 443  */
 444 void clockevents_register_device(struct clock_event_device *dev)
 445 {
 446         unsigned long flags;
 447 
 448         /* Initialize state to DETACHED */
 449         clockevent_set_state(dev, CLOCK_EVT_STATE_DETACHED);
 450 
 451         if (!dev->cpumask) {
 452                 WARN_ON(num_possible_cpus() > 1);
 453                 dev->cpumask = cpumask_of(smp_processor_id());
 454         }
 455 
 456         if (dev->cpumask == cpu_all_mask) {
 457                 WARN(1, "%s cpumask == cpu_all_mask, using cpu_possible_mask instead\n",
 458                      dev->name);
 459                 dev->cpumask = cpu_possible_mask;
 460         }
 461 
 462         raw_spin_lock_irqsave(&clockevents_lock, flags);
 463 
 464         list_add(&dev->list, &clockevent_devices);
 465         tick_check_new_device(dev);
 466         clockevents_notify_released();
 467 
 468         raw_spin_unlock_irqrestore(&clockevents_lock, flags);
 469 }
 470 EXPORT_SYMBOL_GPL(clockevents_register_device);
 471 
 472 static void clockevents_config(struct clock_event_device *dev, u32 freq)
 473 {
 474         u64 sec;
 475 
 476         if (!(dev->features & CLOCK_EVT_FEAT_ONESHOT))
 477                 return;
 478 
 479         /*
 480          * Calculate the maximum number of seconds we can sleep. Limit
 481          * to 10 minutes for hardware which can program more than
 482          * 32bit ticks so we still get reasonable conversion values.
 483          */
 484         sec = dev->max_delta_ticks;
 485         do_div(sec, freq);
 486         if (!sec)
 487                 sec = 1;
 488         else if (sec > 600 && dev->max_delta_ticks > UINT_MAX)
 489                 sec = 600;
 490 
 491         clockevents_calc_mult_shift(dev, freq, sec);
 492         dev->min_delta_ns = cev_delta2ns(dev->min_delta_ticks, dev, false);
 493         dev->max_delta_ns = cev_delta2ns(dev->max_delta_ticks, dev, true);
 494 }
 495 
 496 /**
 497  * clockevents_config_and_register - Configure and register a clock event device
 498  * @dev:        device to register
 499  * @freq:       The clock frequency
 500  * @min_delta:  The minimum clock ticks to program in oneshot mode
 501  * @max_delta:  The maximum clock ticks to program in oneshot mode
 502  *
 503  * min/max_delta can be 0 for devices which do not support oneshot mode.
 504  */
 505 void clockevents_config_and_register(struct clock_event_device *dev,
 506                                      u32 freq, unsigned long min_delta,
 507                                      unsigned long max_delta)
 508 {
 509         dev->min_delta_ticks = min_delta;
 510         dev->max_delta_ticks = max_delta;
 511         clockevents_config(dev, freq);
 512         clockevents_register_device(dev);
 513 }
 514 EXPORT_SYMBOL_GPL(clockevents_config_and_register);
 515 
 516 int __clockevents_update_freq(struct clock_event_device *dev, u32 freq)
 517 {
 518         clockevents_config(dev, freq);
 519 
 520         if (clockevent_state_oneshot(dev))
 521                 return clockevents_program_event(dev, dev->next_event, false);
 522 
 523         if (clockevent_state_periodic(dev))
 524                 return __clockevents_switch_state(dev, CLOCK_EVT_STATE_PERIODIC);
 525 
 526         return 0;
 527 }
 528 
 529 /**
 530  * clockevents_update_freq - Update frequency and reprogram a clock event device.
 531  * @dev:        device to modify
 532  * @freq:       new device frequency
 533  *
 534  * Reconfigure and reprogram a clock event device in oneshot
 535  * mode. Must be called on the cpu for which the device delivers per
 536  * cpu timer events. If called for the broadcast device the core takes
 537  * care of serialization.
 538  *
 539  * Returns 0 on success, -ETIME when the event is in the past.
 540  */
 541 int clockevents_update_freq(struct clock_event_device *dev, u32 freq)
 542 {
 543         unsigned long flags;
 544         int ret;
 545 
 546         local_irq_save(flags);
 547         ret = tick_broadcast_update_freq(dev, freq);
 548         if (ret == -ENODEV)
 549                 ret = __clockevents_update_freq(dev, freq);
 550         local_irq_restore(flags);
 551         return ret;
 552 }
 553 
 554 /*
 555  * Noop handler when we shut down an event device
 556  */
 557 void clockevents_handle_noop(struct clock_event_device *dev)
 558 {
 559 }
 560 
 561 /**
 562  * clockevents_exchange_device - release and request clock devices
 563  * @old:        device to release (can be NULL)
 564  * @new:        device to request (can be NULL)
 565  *
 566  * Called from various tick functions with clockevents_lock held and
 567  * interrupts disabled.
 568  */
 569 void clockevents_exchange_device(struct clock_event_device *old,
 570                                  struct clock_event_device *new)
 571 {
 572         /*
 573          * Caller releases a clock event device. We queue it into the
 574          * released list and do a notify add later.
 575          */
 576         if (old) {
 577                 module_put(old->owner);
 578                 clockevents_switch_state(old, CLOCK_EVT_STATE_DETACHED);
 579                 list_del(&old->list);
 580                 list_add(&old->list, &clockevents_released);
 581         }
 582 
 583         if (new) {
 584                 BUG_ON(!clockevent_state_detached(new));
 585                 clockevents_shutdown(new);
 586         }
 587 }
 588 
 589 /**
 590  * clockevents_suspend - suspend clock devices
 591  */
 592 void clockevents_suspend(void)
 593 {
 594         struct clock_event_device *dev;
 595 
 596         list_for_each_entry_reverse(dev, &clockevent_devices, list)
 597                 if (dev->suspend && !clockevent_state_detached(dev))
 598                         dev->suspend(dev);
 599 }
 600 
 601 /**
 602  * clockevents_resume - resume clock devices
 603  */
 604 void clockevents_resume(void)
 605 {
 606         struct clock_event_device *dev;
 607 
 608         list_for_each_entry(dev, &clockevent_devices, list)
 609                 if (dev->resume && !clockevent_state_detached(dev))
 610                         dev->resume(dev);
 611 }
 612 
 613 #ifdef CONFIG_HOTPLUG_CPU
 614 
 615 # ifdef CONFIG_GENERIC_CLOCKEVENTS_BROADCAST
 616 /**
 617  * tick_offline_cpu - Take CPU out of the broadcast mechanism
 618  * @cpu:        The outgoing CPU
 619  *
 620  * Called on the outgoing CPU after it took itself offline.
 621  */
 622 void tick_offline_cpu(unsigned int cpu)
 623 {
 624         raw_spin_lock(&clockevents_lock);
 625         tick_broadcast_offline(cpu);
 626         raw_spin_unlock(&clockevents_lock);
 627 }
 628 # endif
 629 
 630 /**
 631  * tick_cleanup_dead_cpu - Cleanup the tick and clockevents of a dead cpu
 632  */
 633 void tick_cleanup_dead_cpu(int cpu)
 634 {
 635         struct clock_event_device *dev, *tmp;
 636         unsigned long flags;
 637 
 638         raw_spin_lock_irqsave(&clockevents_lock, flags);
 639 
 640         tick_shutdown(cpu);
 641         /*
 642          * Unregister the clock event devices which were
 643          * released from the users in the notify chain.
 644          */
 645         list_for_each_entry_safe(dev, tmp, &clockevents_released, list)
 646                 list_del(&dev->list);
 647         /*
 648          * Now check whether the CPU has left unused per cpu devices
 649          */
 650         list_for_each_entry_safe(dev, tmp, &clockevent_devices, list) {
 651                 if (cpumask_test_cpu(cpu, dev->cpumask) &&
 652                     cpumask_weight(dev->cpumask) == 1 &&
 653                     !tick_is_broadcast_device(dev)) {
 654                         BUG_ON(!clockevent_state_detached(dev));
 655                         list_del(&dev->list);
 656                 }
 657         }
 658         raw_spin_unlock_irqrestore(&clockevents_lock, flags);
 659 }
 660 #endif
 661 
 662 #ifdef CONFIG_SYSFS
 663 static struct bus_type clockevents_subsys = {
 664         .name           = "clockevents",
 665         .dev_name       = "clockevent",
 666 };
 667 
 668 static DEFINE_PER_CPU(struct device, tick_percpu_dev);
 669 static struct tick_device *tick_get_tick_dev(struct device *dev);
 670 
 671 static ssize_t sysfs_show_current_tick_dev(struct device *dev,
 672                                            struct device_attribute *attr,
 673                                            char *buf)
 674 {
 675         struct tick_device *td;
 676         ssize_t count = 0;
 677 
 678         raw_spin_lock_irq(&clockevents_lock);
 679         td = tick_get_tick_dev(dev);
 680         if (td && td->evtdev)
 681                 count = snprintf(buf, PAGE_SIZE, "%s\n", td->evtdev->name);
 682         raw_spin_unlock_irq(&clockevents_lock);
 683         return count;
 684 }
 685 static DEVICE_ATTR(current_device, 0444, sysfs_show_current_tick_dev, NULL);
 686 
 687 /* We don't support the abomination of removable broadcast devices */
 688 static ssize_t sysfs_unbind_tick_dev(struct device *dev,
 689                                      struct device_attribute *attr,
 690                                      const char *buf, size_t count)
 691 {
 692         char name[CS_NAME_LEN];
 693         ssize_t ret = sysfs_get_uname(buf, name, count);
 694         struct clock_event_device *ce;
 695 
 696         if (ret < 0)
 697                 return ret;
 698 
 699         ret = -ENODEV;
 700         mutex_lock(&clockevents_mutex);
 701         raw_spin_lock_irq(&clockevents_lock);
 702         list_for_each_entry(ce, &clockevent_devices, list) {
 703                 if (!strcmp(ce->name, name)) {
 704                         ret = __clockevents_try_unbind(ce, dev->id);
 705                         break;
 706                 }
 707         }
 708         raw_spin_unlock_irq(&clockevents_lock);
 709         /*
 710          * We hold clockevents_mutex, so ce can't go away
 711          */
 712         if (ret == -EAGAIN)
 713                 ret = clockevents_unbind(ce, dev->id);
 714         mutex_unlock(&clockevents_mutex);
 715         return ret ? ret : count;
 716 }
 717 static DEVICE_ATTR(unbind_device, 0200, NULL, sysfs_unbind_tick_dev);
 718 
 719 #ifdef CONFIG_GENERIC_CLOCKEVENTS_BROADCAST
 720 static struct device tick_bc_dev = {
 721         .init_name      = "broadcast",
 722         .id             = 0,
 723         .bus            = &clockevents_subsys,
 724 };
 725 
 726 static struct tick_device *tick_get_tick_dev(struct device *dev)
 727 {
 728         return dev == &tick_bc_dev ? tick_get_broadcast_device() :
 729                 &per_cpu(tick_cpu_device, dev->id);
 730 }
 731 
 732 static __init int tick_broadcast_init_sysfs(void)
 733 {
 734         int err = device_register(&tick_bc_dev);
 735 
 736         if (!err)
 737                 err = device_create_file(&tick_bc_dev, &dev_attr_current_device);
 738         return err;
 739 }
 740 #else
 741 static struct tick_device *tick_get_tick_dev(struct device *dev)
 742 {
 743         return &per_cpu(tick_cpu_device, dev->id);
 744 }
 745 static inline int tick_broadcast_init_sysfs(void) { return 0; }
 746 #endif
 747 
 748 static int __init tick_init_sysfs(void)
 749 {
 750         int cpu;
 751 
 752         for_each_possible_cpu(cpu) {
 753                 struct device *dev = &per_cpu(tick_percpu_dev, cpu);
 754                 int err;
 755 
 756                 dev->id = cpu;
 757                 dev->bus = &clockevents_subsys;
 758                 err = device_register(dev);
 759                 if (!err)
 760                         err = device_create_file(dev, &dev_attr_current_device);
 761                 if (!err)
 762                         err = device_create_file(dev, &dev_attr_unbind_device);
 763                 if (err)
 764                         return err;
 765         }
 766         return tick_broadcast_init_sysfs();
 767 }
 768 
 769 static int __init clockevents_init_sysfs(void)
 770 {
 771         int err = subsys_system_register(&clockevents_subsys, NULL);
 772 
 773         if (!err)
 774                 err = tick_init_sysfs();
 775         return err;
 776 }
 777 device_initcall(clockevents_init_sysfs);
 778 #endif /* SYSFS */