linux/kernel/time/clockevents.c
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   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 */
  20static LIST_HEAD(clockevent_devices);
  21static LIST_HEAD(clockevents_released);
  22/* Protection for the above */
  23static DEFINE_RAW_SPINLOCK(clockevents_lock);
  24/* Protection for unbind operations */
  25static DEFINE_MUTEX(clockevents_mutex);
  26
  27struct ce_unbind {
  28        struct clock_event_device *ce;
  29        int res;
  30};
  31
  32static 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 */
  85u64 clockevent_delta2ns(unsigned long latch, struct clock_event_device *evt)
  86{
  87        return cev_delta2ns(latch, evt, false);
  88}
  89EXPORT_SYMBOL_GPL(clockevent_delta2ns);
  90
  91static 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 */
 147void 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 */
 171void 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 */
 181int 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 */
 202static 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 */
 233static 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 */
 272static 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 */
 303int 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 */
 343static 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_move(&dev->list, &clockevent_devices);
 351                tick_check_new_device(dev);
 352        }
 353}
 354
 355/*
 356 * Try to install a replacement clock event device
 357 */
 358static int clockevents_replace(struct clock_event_device *ced)
 359{
 360        struct clock_event_device *dev, *newdev = NULL;
 361
 362        list_for_each_entry(dev, &clockevent_devices, list) {
 363                if (dev == ced || !clockevent_state_detached(dev))
 364                        continue;
 365
 366                if (!tick_check_replacement(newdev, dev))
 367                        continue;
 368
 369                if (!try_module_get(dev->owner))
 370                        continue;
 371
 372                if (newdev)
 373                        module_put(newdev->owner);
 374                newdev = dev;
 375        }
 376        if (newdev) {
 377                tick_install_replacement(newdev);
 378                list_del_init(&ced->list);
 379        }
 380        return newdev ? 0 : -EBUSY;
 381}
 382
 383/*
 384 * Called with clockevents_mutex and clockevents_lock held
 385 */
 386static int __clockevents_try_unbind(struct clock_event_device *ced, int cpu)
 387{
 388        /* Fast track. Device is unused */
 389        if (clockevent_state_detached(ced)) {
 390                list_del_init(&ced->list);
 391                return 0;
 392        }
 393
 394        return ced == per_cpu(tick_cpu_device, cpu).evtdev ? -EAGAIN : -EBUSY;
 395}
 396
 397/*
 398 * SMP function call to unbind a device
 399 */
 400static void __clockevents_unbind(void *arg)
 401{
 402        struct ce_unbind *cu = arg;
 403        int res;
 404
 405        raw_spin_lock(&clockevents_lock);
 406        res = __clockevents_try_unbind(cu->ce, smp_processor_id());
 407        if (res == -EAGAIN)
 408                res = clockevents_replace(cu->ce);
 409        cu->res = res;
 410        raw_spin_unlock(&clockevents_lock);
 411}
 412
 413/*
 414 * Issues smp function call to unbind a per cpu device. Called with
 415 * clockevents_mutex held.
 416 */
 417static int clockevents_unbind(struct clock_event_device *ced, int cpu)
 418{
 419        struct ce_unbind cu = { .ce = ced, .res = -ENODEV };
 420
 421        smp_call_function_single(cpu, __clockevents_unbind, &cu, 1);
 422        return cu.res;
 423}
 424
 425/*
 426 * Unbind a clockevents device.
 427 */
 428int clockevents_unbind_device(struct clock_event_device *ced, int cpu)
 429{
 430        int ret;
 431
 432        mutex_lock(&clockevents_mutex);
 433        ret = clockevents_unbind(ced, cpu);
 434        mutex_unlock(&clockevents_mutex);
 435        return ret;
 436}
 437EXPORT_SYMBOL_GPL(clockevents_unbind_device);
 438
 439/**
 440 * clockevents_register_device - register a clock event device
 441 * @dev:        device to register
 442 */
 443void clockevents_register_device(struct clock_event_device *dev)
 444{
 445        unsigned long flags;
 446
 447        /* Initialize state to DETACHED */
 448        clockevent_set_state(dev, CLOCK_EVT_STATE_DETACHED);
 449
 450        if (!dev->cpumask) {
 451                WARN_ON(num_possible_cpus() > 1);
 452                dev->cpumask = cpumask_of(smp_processor_id());
 453        }
 454
 455        if (dev->cpumask == cpu_all_mask) {
 456                WARN(1, "%s cpumask == cpu_all_mask, using cpu_possible_mask instead\n",
 457                     dev->name);
 458                dev->cpumask = cpu_possible_mask;
 459        }
 460
 461        raw_spin_lock_irqsave(&clockevents_lock, flags);
 462
 463        list_add(&dev->list, &clockevent_devices);
 464        tick_check_new_device(dev);
 465        clockevents_notify_released();
 466
 467        raw_spin_unlock_irqrestore(&clockevents_lock, flags);
 468}
 469EXPORT_SYMBOL_GPL(clockevents_register_device);
 470
 471static void clockevents_config(struct clock_event_device *dev, u32 freq)
 472{
 473        u64 sec;
 474
 475        if (!(dev->features & CLOCK_EVT_FEAT_ONESHOT))
 476                return;
 477
 478        /*
 479         * Calculate the maximum number of seconds we can sleep. Limit
 480         * to 10 minutes for hardware which can program more than
 481         * 32bit ticks so we still get reasonable conversion values.
 482         */
 483        sec = dev->max_delta_ticks;
 484        do_div(sec, freq);
 485        if (!sec)
 486                sec = 1;
 487        else if (sec > 600 && dev->max_delta_ticks > UINT_MAX)
 488                sec = 600;
 489
 490        clockevents_calc_mult_shift(dev, freq, sec);
 491        dev->min_delta_ns = cev_delta2ns(dev->min_delta_ticks, dev, false);
 492        dev->max_delta_ns = cev_delta2ns(dev->max_delta_ticks, dev, true);
 493}
 494
 495/**
 496 * clockevents_config_and_register - Configure and register a clock event device
 497 * @dev:        device to register
 498 * @freq:       The clock frequency
 499 * @min_delta:  The minimum clock ticks to program in oneshot mode
 500 * @max_delta:  The maximum clock ticks to program in oneshot mode
 501 *
 502 * min/max_delta can be 0 for devices which do not support oneshot mode.
 503 */
 504void clockevents_config_and_register(struct clock_event_device *dev,
 505                                     u32 freq, unsigned long min_delta,
 506                                     unsigned long max_delta)
 507{
 508        dev->min_delta_ticks = min_delta;
 509        dev->max_delta_ticks = max_delta;
 510        clockevents_config(dev, freq);
 511        clockevents_register_device(dev);
 512}
 513EXPORT_SYMBOL_GPL(clockevents_config_and_register);
 514
 515int __clockevents_update_freq(struct clock_event_device *dev, u32 freq)
 516{
 517        clockevents_config(dev, freq);
 518
 519        if (clockevent_state_oneshot(dev))
 520                return clockevents_program_event(dev, dev->next_event, false);
 521
 522        if (clockevent_state_periodic(dev))
 523                return __clockevents_switch_state(dev, CLOCK_EVT_STATE_PERIODIC);
 524
 525        return 0;
 526}
 527
 528/**
 529 * clockevents_update_freq - Update frequency and reprogram a clock event device.
 530 * @dev:        device to modify
 531 * @freq:       new device frequency
 532 *
 533 * Reconfigure and reprogram a clock event device in oneshot
 534 * mode. Must be called on the cpu for which the device delivers per
 535 * cpu timer events. If called for the broadcast device the core takes
 536 * care of serialization.
 537 *
 538 * Returns 0 on success, -ETIME when the event is in the past.
 539 */
 540int clockevents_update_freq(struct clock_event_device *dev, u32 freq)
 541{
 542        unsigned long flags;
 543        int ret;
 544
 545        local_irq_save(flags);
 546        ret = tick_broadcast_update_freq(dev, freq);
 547        if (ret == -ENODEV)
 548                ret = __clockevents_update_freq(dev, freq);
 549        local_irq_restore(flags);
 550        return ret;
 551}
 552
 553/*
 554 * Noop handler when we shut down an event device
 555 */
 556void clockevents_handle_noop(struct clock_event_device *dev)
 557{
 558}
 559
 560/**
 561 * clockevents_exchange_device - release and request clock devices
 562 * @old:        device to release (can be NULL)
 563 * @new:        device to request (can be NULL)
 564 *
 565 * Called from various tick functions with clockevents_lock held and
 566 * interrupts disabled.
 567 */
 568void clockevents_exchange_device(struct clock_event_device *old,
 569                                 struct clock_event_device *new)
 570{
 571        /*
 572         * Caller releases a clock event device. We queue it into the
 573         * released list and do a notify add later.
 574         */
 575        if (old) {
 576                module_put(old->owner);
 577                clockevents_switch_state(old, CLOCK_EVT_STATE_DETACHED);
 578                list_move(&old->list, &clockevents_released);
 579        }
 580
 581        if (new) {
 582                BUG_ON(!clockevent_state_detached(new));
 583                clockevents_shutdown(new);
 584        }
 585}
 586
 587/**
 588 * clockevents_suspend - suspend clock devices
 589 */
 590void clockevents_suspend(void)
 591{
 592        struct clock_event_device *dev;
 593
 594        list_for_each_entry_reverse(dev, &clockevent_devices, list)
 595                if (dev->suspend && !clockevent_state_detached(dev))
 596                        dev->suspend(dev);
 597}
 598
 599/**
 600 * clockevents_resume - resume clock devices
 601 */
 602void clockevents_resume(void)
 603{
 604        struct clock_event_device *dev;
 605
 606        list_for_each_entry(dev, &clockevent_devices, list)
 607                if (dev->resume && !clockevent_state_detached(dev))
 608                        dev->resume(dev);
 609}
 610
 611#ifdef CONFIG_HOTPLUG_CPU
 612
 613# ifdef CONFIG_GENERIC_CLOCKEVENTS_BROADCAST
 614/**
 615 * tick_offline_cpu - Take CPU out of the broadcast mechanism
 616 * @cpu:        The outgoing CPU
 617 *
 618 * Called on the outgoing CPU after it took itself offline.
 619 */
 620void tick_offline_cpu(unsigned int cpu)
 621{
 622        raw_spin_lock(&clockevents_lock);
 623        tick_broadcast_offline(cpu);
 624        raw_spin_unlock(&clockevents_lock);
 625}
 626# endif
 627
 628/**
 629 * tick_cleanup_dead_cpu - Cleanup the tick and clockevents of a dead cpu
 630 * @cpu:        The dead CPU
 631 */
 632void tick_cleanup_dead_cpu(int cpu)
 633{
 634        struct clock_event_device *dev, *tmp;
 635        unsigned long flags;
 636
 637        raw_spin_lock_irqsave(&clockevents_lock, flags);
 638
 639        tick_shutdown(cpu);
 640        /*
 641         * Unregister the clock event devices which were
 642         * released from the users in the notify chain.
 643         */
 644        list_for_each_entry_safe(dev, tmp, &clockevents_released, list)
 645                list_del(&dev->list);
 646        /*
 647         * Now check whether the CPU has left unused per cpu devices
 648         */
 649        list_for_each_entry_safe(dev, tmp, &clockevent_devices, list) {
 650                if (cpumask_test_cpu(cpu, dev->cpumask) &&
 651                    cpumask_weight(dev->cpumask) == 1 &&
 652                    !tick_is_broadcast_device(dev)) {
 653                        BUG_ON(!clockevent_state_detached(dev));
 654                        list_del(&dev->list);
 655                }
 656        }
 657        raw_spin_unlock_irqrestore(&clockevents_lock, flags);
 658}
 659#endif
 660
 661#ifdef CONFIG_SYSFS
 662static struct bus_type clockevents_subsys = {
 663        .name           = "clockevents",
 664        .dev_name       = "clockevent",
 665};
 666
 667static DEFINE_PER_CPU(struct device, tick_percpu_dev);
 668static struct tick_device *tick_get_tick_dev(struct device *dev);
 669
 670static ssize_t current_device_show(struct device *dev,
 671                                   struct device_attribute *attr,
 672                                   char *buf)
 673{
 674        struct tick_device *td;
 675        ssize_t count = 0;
 676
 677        raw_spin_lock_irq(&clockevents_lock);
 678        td = tick_get_tick_dev(dev);
 679        if (td && td->evtdev)
 680                count = snprintf(buf, PAGE_SIZE, "%s\n", td->evtdev->name);
 681        raw_spin_unlock_irq(&clockevents_lock);
 682        return count;
 683}
 684static DEVICE_ATTR_RO(current_device);
 685
 686/* We don't support the abomination of removable broadcast devices */
 687static ssize_t unbind_device_store(struct device *dev,
 688                                   struct device_attribute *attr,
 689                                   const char *buf, size_t count)
 690{
 691        char name[CS_NAME_LEN];
 692        ssize_t ret = sysfs_get_uname(buf, name, count);
 693        struct clock_event_device *ce;
 694
 695        if (ret < 0)
 696                return ret;
 697
 698        ret = -ENODEV;
 699        mutex_lock(&clockevents_mutex);
 700        raw_spin_lock_irq(&clockevents_lock);
 701        list_for_each_entry(ce, &clockevent_devices, list) {
 702                if (!strcmp(ce->name, name)) {
 703                        ret = __clockevents_try_unbind(ce, dev->id);
 704                        break;
 705                }
 706        }
 707        raw_spin_unlock_irq(&clockevents_lock);
 708        /*
 709         * We hold clockevents_mutex, so ce can't go away
 710         */
 711        if (ret == -EAGAIN)
 712                ret = clockevents_unbind(ce, dev->id);
 713        mutex_unlock(&clockevents_mutex);
 714        return ret ? ret : count;
 715}
 716static DEVICE_ATTR_WO(unbind_device);
 717
 718#ifdef CONFIG_GENERIC_CLOCKEVENTS_BROADCAST
 719static struct device tick_bc_dev = {
 720        .init_name      = "broadcast",
 721        .id             = 0,
 722        .bus            = &clockevents_subsys,
 723};
 724
 725static struct tick_device *tick_get_tick_dev(struct device *dev)
 726{
 727        return dev == &tick_bc_dev ? tick_get_broadcast_device() :
 728                &per_cpu(tick_cpu_device, dev->id);
 729}
 730
 731static __init int tick_broadcast_init_sysfs(void)
 732{
 733        int err = device_register(&tick_bc_dev);
 734
 735        if (!err)
 736                err = device_create_file(&tick_bc_dev, &dev_attr_current_device);
 737        return err;
 738}
 739#else
 740static struct tick_device *tick_get_tick_dev(struct device *dev)
 741{
 742        return &per_cpu(tick_cpu_device, dev->id);
 743}
 744static inline int tick_broadcast_init_sysfs(void) { return 0; }
 745#endif
 746
 747static int __init tick_init_sysfs(void)
 748{
 749        int cpu;
 750
 751        for_each_possible_cpu(cpu) {
 752                struct device *dev = &per_cpu(tick_percpu_dev, cpu);
 753                int err;
 754
 755                dev->id = cpu;
 756                dev->bus = &clockevents_subsys;
 757                err = device_register(dev);
 758                if (!err)
 759                        err = device_create_file(dev, &dev_attr_current_device);
 760                if (!err)
 761                        err = device_create_file(dev, &dev_attr_unbind_device);
 762                if (err)
 763                        return err;
 764        }
 765        return tick_broadcast_init_sysfs();
 766}
 767
 768static int __init clockevents_init_sysfs(void)
 769{
 770        int err = subsys_system_register(&clockevents_subsys, NULL);
 771
 772        if (!err)
 773                err = tick_init_sysfs();
 774        return err;
 775}
 776device_initcall(clockevents_init_sysfs);
 777#endif /* SYSFS */
 778