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_switch_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                 /* The clockevent device is getting replaced. Shut it down. */
 121
 122         case CLOCK_EVT_STATE_SHUTDOWN:
 123                 return dev->set_state_shutdown(dev);
 124
 125         case CLOCK_EVT_STATE_PERIODIC:
 126                 /* Core internal bug */
 127                 if (!(dev->features & CLOCK_EVT_FEAT_PERIODIC))
 128                         return -ENOSYS;
 129                 return dev->set_state_periodic(dev);
 130
 131         case CLOCK_EVT_STATE_ONESHOT:
 132                 /* Core internal bug */
 133                 if (!(dev->features & CLOCK_EVT_FEAT_ONESHOT))
 134                         return -ENOSYS;
 135                 return dev->set_state_oneshot(dev);
 136
 137         case CLOCK_EVT_STATE_ONESHOT_STOPPED:
 138                 /* Core internal bug */
 139                 if (WARN_ONCE(!clockevent_state_oneshot(dev),
 140                               "Current state: %d\n",
 141                               clockevent_get_state(dev)))
 142                         return -EINVAL;
 143
 144                 if (dev->set_state_oneshot_stopped)
 145                         return dev->set_state_oneshot_stopped(dev);
 146                 else
 147                         return -ENOSYS;
 148
 149         default:
 150                 return -ENOSYS;
 151         }
 152 }
 153
 154 /**
 155  * clockevents_switch_state - set the operating state of a clock event device
 156  * @dev:        device to modify
 157  * @state:      new state
 158  *
 159  * Must be called with interrupts disabled !
 160  */
 161 void clockevents_switch_state(struct clock_event_device *dev,
 162                               enum clock_event_state state)
 163 {
 164         if (clockevent_get_state(dev) != state) {
 165                 if (__clockevents_switch_state(dev, state))
 166                         return;
 167
 168                 clockevent_set_state(dev, state);
 169
 170                 /*
 171                  * A nsec2cyc multiplicator of 0 is invalid and we'd crash
 172                  * on it, so fix it up and emit a warning:
 173                  */
 174                 if (clockevent_state_oneshot(dev)) {
 175                         if (unlikely(!dev->mult)) {
 176                                 dev->mult = 1;
 177                                 WARN_ON(1);
 178                         }
 179                 }
 180         }
 181 }
 182
 183 /**
 184  * clockevents_shutdown - shutdown the device and clear next_event
 185  * @dev:        device to shutdown
 186  */
 187 void clockevents_shutdown(struct clock_event_device *dev)
 188 {
 189         clockevents_switch_state(dev, CLOCK_EVT_STATE_SHUTDOWN);
 190         dev->next_event.tv64 = KTIME_MAX;
 191 }
 192
 193 /**
 194  * clockevents_tick_resume -    Resume the tick device before using it again
 195  * @dev:                        device to resume
 196  */
 197 int clockevents_tick_resume(struct clock_event_device *dev)
 198 {
 199         int ret = 0;
 200
 201         if (dev->set_mode) {
 202                 dev->set_mode(CLOCK_EVT_MODE_RESUME, dev);
 203                 dev->mode = CLOCK_EVT_MODE_RESUME;
 204         } else if (dev->tick_resume) {
 205                 ret = dev->tick_resume(dev);
 206         }
 207
 208         return ret;
 209 }
 210
 211 #ifdef CONFIG_GENERIC_CLOCKEVENTS_MIN_ADJUST
 212
 213 /* Limit min_delta to a jiffie */
 214 #define MIN_DELTA_LIMIT         (NSEC_PER_SEC / HZ)
 215
 216 /**
 217  * clockevents_increase_min_delta - raise minimum delta of a clock event device
 218  * @dev:       device to increase the minimum delta
 219  *
 220  * Returns 0 on success, -ETIME when the minimum delta reached the limit.
 221  */
 222 static int clockevents_increase_min_delta(struct clock_event_device *dev)
 223 {
 224         /* Nothing to do if we already reached the limit */
 225         if (dev->min_delta_ns >= MIN_DELTA_LIMIT) {
 226                 printk_deferred(KERN_WARNING
 227                                 "CE: Reprogramming failure. Giving up\n");
 228                 dev->next_event.tv64 = KTIME_MAX;
 229                 return -ETIME;
 230         }
 231
 232         if (dev->min_delta_ns < 5000)
 233                 dev->min_delta_ns = 5000;
 234         else
 235                 dev->min_delta_ns += dev->min_delta_ns >> 1;
 236
 237         if (dev->min_delta_ns > MIN_DELTA_LIMIT)
 238                 dev->min_delta_ns = MIN_DELTA_LIMIT;
 239
 240         printk_deferred(KERN_WARNING
 241                         "CE: %s increased min_delta_ns to %llu nsec\n",
 242                         dev->name ? dev->name : "?",
 243                         (unsigned long long) dev->min_delta_ns);
 244         return 0;
 245 }
 246
 247 /**
 248  * clockevents_program_min_delta - Set clock event device to the minimum delay.
 249  * @dev:        device to program
 250  *
 251  * Returns 0 on success, -ETIME when the retry loop failed.
 252  */
 253 static int clockevents_program_min_delta(struct clock_event_device *dev)
 254 {
 255         unsigned long long clc;
 256         int64_t delta;
 257         int i;
 258
 259         for (i = 0;;) {
 260                 delta = dev->min_delta_ns;
 261                 dev->next_event = ktime_add_ns(ktime_get(), delta);
 262
 263                 if (clockevent_state_shutdown(dev))
 264                         return 0;
 265
 266                 dev->retries++;
 267                 clc = ((unsigned long long) delta * dev->mult) >> dev->shift;
 268                 if (dev->set_next_event((unsigned long) clc, dev) == 0)
 269                         return 0;
 270
 271                 if (++i > 2) {
 272                         /*
 273                          * We tried 3 times to program the device with the
 274                          * given min_delta_ns. Try to increase the minimum
 275                          * delta, if that fails as well get out of here.
 276                          */
 277                         if (clockevents_increase_min_delta(dev))
 278                                 return -ETIME;
 279                         i = 0;
 280                 }
 281         }
 282 }
 283
 284 #else  /* CONFIG_GENERIC_CLOCKEVENTS_MIN_ADJUST */
 285
 286 /**
 287  * clockevents_program_min_delta - Set clock event device to the minimum delay.
 288  * @dev:        device to program
 289  *
 290  * Returns 0 on success, -ETIME when the retry loop failed.
 291  */
 292 static int clockevents_program_min_delta(struct clock_event_device *dev)
 293 {
 294         unsigned long long clc;
 295         int64_t delta;
 296
 297         delta = dev->min_delta_ns;
 298         dev->next_event = ktime_add_ns(ktime_get(), delta);
 299
 300         if (clockevent_state_shutdown(dev))
 301                 return 0;
 302
 303         dev->retries++;
 304         clc = ((unsigned long long) delta * dev->mult) >> dev->shift;
 305         return dev->set_next_event((unsigned long) clc, dev);
 306 }
 307
 308 #endif /* CONFIG_GENERIC_CLOCKEVENTS_MIN_ADJUST */
 309
 310 /**
 311  * clockevents_program_event - Reprogram the clock event device.
 312  * @dev:        device to program
 313  * @expires:    absolute expiry time (monotonic clock)
 314  * @force:      program minimum delay if expires can not be set
 315  *
 316  * Returns 0 on success, -ETIME when the event is in the past.
 317  */
 318 int clockevents_program_event(struct clock_event_device *dev, ktime_t expires,
 319                               bool force)
 320 {
 321         unsigned long long clc;
 322         int64_t delta;
 323         int rc;
 324
 325         if (unlikely(expires.tv64 < 0)) {
 326                 WARN_ON_ONCE(1);
 327                 return -ETIME;
 328         }
 329
 330         dev->next_event = expires;
 331
 332         if (clockevent_state_shutdown(dev))
 333                 return 0;
 334
 335         /* We must be in ONESHOT state here */
 336         WARN_ONCE(!clockevent_state_oneshot(dev), "Current state: %d\n",
 337                   clockevent_get_state(dev));
 338
 339         /* Shortcut for clockevent devices that can deal with ktime. */
 340         if (dev->features & CLOCK_EVT_FEAT_KTIME)
 341                 return dev->set_next_ktime(expires, dev);
 342
 343         delta = ktime_to_ns(ktime_sub(expires, ktime_get()));
 344         if (delta <= 0)
 345                 return force ? clockevents_program_min_delta(dev) : -ETIME;
 346
 347         delta = min(delta, (int64_t) dev->max_delta_ns);
 348         delta = max(delta, (int64_t) dev->min_delta_ns);
 349
 350         clc = ((unsigned long long) delta * dev->mult) >> dev->shift;
 351         rc = dev->set_next_event((unsigned long) clc, dev);
 352
 353         return (rc && force) ? clockevents_program_min_delta(dev) : rc;
 354 }
 355
 356 /*
 357  * Called after a notify add to make devices available which were
 358  * released from the notifier call.
 359  */
 360 static void clockevents_notify_released(void)
 361 {
 362         struct clock_event_device *dev;
 363
 364         while (!list_empty(&clockevents_released)) {
 365                 dev = list_entry(clockevents_released.next,
 366                                  struct clock_event_device, list);
 367                 list_del(&dev->list);
 368                 list_add(&dev->list, &clockevent_devices);
 369                 tick_check_new_device(dev);
 370         }
 371 }
 372
 373 /*
 374  * Try to install a replacement clock event device
 375  */
 376 static int clockevents_replace(struct clock_event_device *ced)
 377 {
 378         struct clock_event_device *dev, *newdev = NULL;
 379
 380         list_for_each_entry(dev, &clockevent_devices, list) {
 381                 if (dev == ced || !clockevent_state_detached(dev))
 382                         continue;
 383
 384                 if (!tick_check_replacement(newdev, dev))
 385                         continue;
 386
 387                 if (!try_module_get(dev->owner))
 388                         continue;
 389
 390                 if (newdev)
 391                         module_put(newdev->owner);
 392                 newdev = dev;
 393         }
 394         if (newdev) {
 395                 tick_install_replacement(newdev);
 396                 list_del_init(&ced->list);
 397         }
 398         return newdev ? 0 : -EBUSY;
 399 }
 400
 401 /*
 402  * Called with clockevents_mutex and clockevents_lock held
 403  */
 404 static int __clockevents_try_unbind(struct clock_event_device *ced, int cpu)
 405 {
 406         /* Fast track. Device is unused */
 407         if (clockevent_state_detached(ced)) {
 408                 list_del_init(&ced->list);
 409                 return 0;
 410         }
 411
 412         return ced == per_cpu(tick_cpu_device, cpu).evtdev ? -EAGAIN : -EBUSY;
 413 }
 414
 415 /*
 416  * SMP function call to unbind a device
 417  */
 418 static void __clockevents_unbind(void *arg)
 419 {
 420         struct ce_unbind *cu = arg;
 421         int res;
 422
 423         raw_spin_lock(&clockevents_lock);
 424         res = __clockevents_try_unbind(cu->ce, smp_processor_id());
 425         if (res == -EAGAIN)
 426                 res = clockevents_replace(cu->ce);
 427         cu->res = res;
 428         raw_spin_unlock(&clockevents_lock);
 429 }
 430
 431 /*
 432  * Issues smp function call to unbind a per cpu device. Called with
 433  * clockevents_mutex held.
 434  */
 435 static int clockevents_unbind(struct clock_event_device *ced, int cpu)
 436 {
 437         struct ce_unbind cu = { .ce = ced, .res = -ENODEV };
 438
 439         smp_call_function_single(cpu, __clockevents_unbind, &cu, 1);
 440         return cu.res;
 441 }
 442
 443 /*
 444  * Unbind a clockevents device.
 445  */
 446 int clockevents_unbind_device(struct clock_event_device *ced, int cpu)
 447 {
 448         int ret;
 449
 450         mutex_lock(&clockevents_mutex);
 451         ret = clockevents_unbind(ced, cpu);
 452         mutex_unlock(&clockevents_mutex);
 453         return ret;
 454 }
 455 EXPORT_SYMBOL_GPL(clockevents_unbind_device);
 456
 457 /* Sanity check of state transition callbacks */
 458 static int clockevents_sanity_check(struct clock_event_device *dev)
 459 {
 460         /* Legacy set_mode() callback */
 461         if (dev->set_mode) {
 462                 /* We shouldn't be supporting new modes now */
 463                 WARN_ON(dev->set_state_periodic || dev->set_state_oneshot ||
 464                         dev->set_state_shutdown || dev->tick_resume ||
 465                         dev->set_state_oneshot_stopped);
 466
 467                 BUG_ON(dev->mode != CLOCK_EVT_MODE_UNUSED);
 468                 return 0;
 469         }
 470
 471         if (dev->features & CLOCK_EVT_FEAT_DUMMY)
 472                 return 0;
 473
 474         /* New state-specific callbacks */
 475         if (!dev->set_state_shutdown)
 476                 return -EINVAL;
 477
 478         if ((dev->features & CLOCK_EVT_FEAT_PERIODIC) &&
 479             !dev->set_state_periodic)
 480                 return -EINVAL;
 481
 482         if ((dev->features & CLOCK_EVT_FEAT_ONESHOT) &&
 483             !dev->set_state_oneshot)
 484                 return -EINVAL;
 485
 486         return 0;
 487 }
 488
 489 /**
 490  * clockevents_register_device - register a clock event device
 491  * @dev:        device to register
 492  */
 493 void clockevents_register_device(struct clock_event_device *dev)
 494 {
 495         unsigned long flags;
 496
 497         BUG_ON(clockevents_sanity_check(dev));
 498
 499         /* Initialize state to DETACHED */
 500         clockevent_set_state(dev, CLOCK_EVT_STATE_DETACHED);
 501
 502         if (!dev->cpumask) {
 503                 WARN_ON(num_possible_cpus() > 1);
 504                 dev->cpumask = cpumask_of(smp_processor_id());
 505         }
 506
 507         raw_spin_lock_irqsave(&clockevents_lock, flags);
 508
 509         list_add(&dev->list, &clockevent_devices);
 510         tick_check_new_device(dev);
 511         clockevents_notify_released();
 512
 513         raw_spin_unlock_irqrestore(&clockevents_lock, flags);
 514 }
 515 EXPORT_SYMBOL_GPL(clockevents_register_device);
 516
 517 void clockevents_config(struct clock_event_device *dev, u32 freq)
 518 {
 519         u64 sec;
 520
 521         if (!(dev->features & CLOCK_EVT_FEAT_ONESHOT))
 522                 return;
 523
 524         /*
 525          * Calculate the maximum number of seconds we can sleep. Limit
 526          * to 10 minutes for hardware which can program more than
 527          * 32bit ticks so we still get reasonable conversion values.
 528          */
 529         sec = dev->max_delta_ticks;
 530         do_div(sec, freq);
 531         if (!sec)
 532                 sec = 1;
 533         else if (sec > 600 && dev->max_delta_ticks > UINT_MAX)
 534                 sec = 600;
 535
 536         clockevents_calc_mult_shift(dev, freq, sec);
 537         dev->min_delta_ns = cev_delta2ns(dev->min_delta_ticks, dev, false);
 538         dev->max_delta_ns = cev_delta2ns(dev->max_delta_ticks, dev, true);
 539 }
 540
 541 /**
 542  * clockevents_config_and_register - Configure and register a clock event device
 543  * @dev:        device to register
 544  * @freq:       The clock frequency
 545  * @min_delta:  The minimum clock ticks to program in oneshot mode
 546  * @max_delta:  The maximum clock ticks to program in oneshot mode
 547  *
 548  * min/max_delta can be 0 for devices which do not support oneshot mode.
 549  */
 550 void clockevents_config_and_register(struct clock_event_device *dev,
 551                                      u32 freq, unsigned long min_delta,
 552                                      unsigned long max_delta)
 553 {
 554         dev->min_delta_ticks = min_delta;
 555         dev->max_delta_ticks = max_delta;
 556         clockevents_config(dev, freq);
 557         clockevents_register_device(dev);
 558 }
 559 EXPORT_SYMBOL_GPL(clockevents_config_and_register);
 560
 561 int __clockevents_update_freq(struct clock_event_device *dev, u32 freq)
 562 {
 563         clockevents_config(dev, freq);
 564
 565         if (clockevent_state_oneshot(dev))
 566                 return clockevents_program_event(dev, dev->next_event, false);
 567
 568         if (clockevent_state_periodic(dev))
 569                 return __clockevents_switch_state(dev, CLOCK_EVT_STATE_PERIODIC);
 570
 571         return 0;
 572 }
 573
 574 /**
 575  * clockevents_update_freq - Update frequency and reprogram a clock event device.
 576  * @dev:        device to modify
 577  * @freq:       new device frequency
 578  *
 579  * Reconfigure and reprogram a clock event device in oneshot
 580  * mode. Must be called on the cpu for which the device delivers per
 581  * cpu timer events. If called for the broadcast device the core takes
 582  * care of serialization.
 583  *
 584  * Returns 0 on success, -ETIME when the event is in the past.
 585  */
 586 int clockevents_update_freq(struct clock_event_device *dev, u32 freq)
 587 {
 588         unsigned long flags;
 589         int ret;
 590
 591         local_irq_save(flags);
 592         ret = tick_broadcast_update_freq(dev, freq);
 593         if (ret == -ENODEV)
 594                 ret = __clockevents_update_freq(dev, freq);
 595         local_irq_restore(flags);
 596         return ret;
 597 }
 598
 599 /*
 600  * Noop handler when we shut down an event device
 601  */
 602 void clockevents_handle_noop(struct clock_event_device *dev)
 603 {
 604 }
 605
 606 /**
 607  * clockevents_exchange_device - release and request clock devices
 608  * @old:        device to release (can be NULL)
 609  * @new:        device to request (can be NULL)
 610  *
 611  * Called from various tick functions with clockevents_lock held and
 612  * interrupts disabled.
 613  */
 614 void clockevents_exchange_device(struct clock_event_device *old,
 615                                  struct clock_event_device *new)
 616 {
 617         /*
 618          * Caller releases a clock event device. We queue it into the
 619          * released list and do a notify add later.
 620          */
 621         if (old) {
 622                 module_put(old->owner);
 623                 clockevents_switch_state(old, CLOCK_EVT_STATE_DETACHED);
 624                 list_del(&old->list);
 625                 list_add(&old->list, &clockevents_released);
 626         }
 627
 628         if (new) {
 629                 BUG_ON(!clockevent_state_detached(new));
 630                 clockevents_shutdown(new);
 631         }
 632 }
 633
 634 /**
 635  * clockevents_suspend - suspend clock devices
 636  */
 637 void clockevents_suspend(void)
 638 {
 639         struct clock_event_device *dev;
 640
 641         list_for_each_entry_reverse(dev, &clockevent_devices, list)
 642                 if (dev->suspend && !clockevent_state_detached(dev))
 643                         dev->suspend(dev);
 644 }
 645
 646 /**
 647  * clockevents_resume - resume clock devices
 648  */
 649 void clockevents_resume(void)
 650 {
 651         struct clock_event_device *dev;
 652
 653         list_for_each_entry(dev, &clockevent_devices, list)
 654                 if (dev->resume && !clockevent_state_detached(dev))
 655                         dev->resume(dev);
 656 }
 657
 658 #ifdef CONFIG_HOTPLUG_CPU
 659 /**
 660  * tick_cleanup_dead_cpu - Cleanup the tick and clockevents of a dead cpu
 661  */
 662 void tick_cleanup_dead_cpu(int cpu)
 663 {
 664         struct clock_event_device *dev, *tmp;
 665         unsigned long flags;
 666
 667         raw_spin_lock_irqsave(&clockevents_lock, flags);
 668
 669         tick_shutdown_broadcast_oneshot(cpu);
 670         tick_shutdown_broadcast(cpu);
 671         tick_shutdown(cpu);
 672         /*
 673          * Unregister the clock event devices which were
 674          * released from the users in the notify chain.
 675          */
 676         list_for_each_entry_safe(dev, tmp, &clockevents_released, list)
 677                 list_del(&dev->list);
 678         /*
 679          * Now check whether the CPU has left unused per cpu devices
 680          */
 681         list_for_each_entry_safe(dev, tmp, &clockevent_devices, list) {
 682                 if (cpumask_test_cpu(cpu, dev->cpumask) &&
 683                     cpumask_weight(dev->cpumask) == 1 &&
 684                     !tick_is_broadcast_device(dev)) {
 685                         BUG_ON(!clockevent_state_detached(dev));
 686                         list_del(&dev->list);
 687                 }
 688         }
 689         raw_spin_unlock_irqrestore(&clockevents_lock, flags);
 690 }
 691 #endif
 692
 693 #ifdef CONFIG_SYSFS
 694 struct bus_type clockevents_subsys = {
 695         .name           = "clockevents",
 696         .dev_name       = "clockevent",
 697 };
 698
 699 static DEFINE_PER_CPU(struct device, tick_percpu_dev);
 700 static struct tick_device *tick_get_tick_dev(struct device *dev);
 701
 702 static ssize_t sysfs_show_current_tick_dev(struct device *dev,
 703                                            struct device_attribute *attr,
 704                                            char *buf)
 705 {
 706         struct tick_device *td;
 707         ssize_t count = 0;
 708
 709         raw_spin_lock_irq(&clockevents_lock);
 710         td = tick_get_tick_dev(dev);
 711         if (td && td->evtdev)
 712                 count = snprintf(buf, PAGE_SIZE, "%s\n", td->evtdev->name);
 713         raw_spin_unlock_irq(&clockevents_lock);
 714         return count;
 715 }
 716 static DEVICE_ATTR(current_device, 0444, sysfs_show_current_tick_dev, NULL);
 717
 718 /* We don't support the abomination of removable broadcast devices */
 719 static ssize_t sysfs_unbind_tick_dev(struct device *dev,
 720                                      struct device_attribute *attr,
 721                                      const char *buf, size_t count)
 722 {
 723         char name[CS_NAME_LEN];
 724         ssize_t ret = sysfs_get_uname(buf, name, count);
 725         struct clock_event_device *ce;
 726
 727         if (ret < 0)
 728                 return ret;
 729
 730         ret = -ENODEV;
 731         mutex_lock(&clockevents_mutex);
 732         raw_spin_lock_irq(&clockevents_lock);
 733         list_for_each_entry(ce, &clockevent_devices, list) {
 734                 if (!strcmp(ce->name, name)) {
 735                         ret = __clockevents_try_unbind(ce, dev->id);
 736                         break;
 737                 }
 738         }
 739         raw_spin_unlock_irq(&clockevents_lock);
 740         /*
 741          * We hold clockevents_mutex, so ce can't go away
 742          */
 743         if (ret == -EAGAIN)
 744                 ret = clockevents_unbind(ce, dev->id);
 745         mutex_unlock(&clockevents_mutex);
 746         return ret ? ret : count;
 747 }
 748 static DEVICE_ATTR(unbind_device, 0200, NULL, sysfs_unbind_tick_dev);
 749
 750 #ifdef CONFIG_GENERIC_CLOCKEVENTS_BROADCAST
 751 static struct device tick_bc_dev = {
 752         .init_name      = "broadcast",
 753         .id             = 0,
 754         .bus            = &clockevents_subsys,
 755 };
 756
 757 static struct tick_device *tick_get_tick_dev(struct device *dev)
 758 {
 759         return dev == &tick_bc_dev ? tick_get_broadcast_device() :
 760                 &per_cpu(tick_cpu_device, dev->id);
 761 }
 762
 763 static __init int tick_broadcast_init_sysfs(void)
 764 {
 765         int err = device_register(&tick_bc_dev);
 766
 767         if (!err)
 768                 err = device_create_file(&tick_bc_dev, &dev_attr_current_device);
 769         return err;
 770 }
 771 #else
 772 static struct tick_device *tick_get_tick_dev(struct device *dev)
 773 {
 774         return &per_cpu(tick_cpu_device, dev->id);
 775 }
 776 static inline int tick_broadcast_init_sysfs(void) { return 0; }
 777 #endif
 778
 779 static int __init tick_init_sysfs(void)
 780 {
 781         int cpu;
 782
 783         for_each_possible_cpu(cpu) {
 784                 struct device *dev = &per_cpu(tick_percpu_dev, cpu);
 785                 int err;
 786
 787                 dev->id = cpu;
 788                 dev->bus = &clockevents_subsys;
 789                 err = device_register(dev);
 790                 if (!err)
 791                         err = device_create_file(dev, &dev_attr_current_device);
 792                 if (!err)
 793                         err = device_create_file(dev, &dev_attr_unbind_device);
 794                 if (err)
 795                         return err;
 796         }
 797         return tick_broadcast_init_sysfs();
 798 }
 799
 800 static int __init clockevents_init_sysfs(void)
 801 {
 802         int err = subsys_system_register(&clockevents_subsys, NULL);
 803
 804         if (!err)
 805                 err = tick_init_sysfs();
 806         return err;
 807 }
 808 device_initcall(clockevents_init_sysfs);
 809 #endif /* SYSFS */