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