drivers/cpuidle/cpuidle.c

   1 /*
   2  * cpuidle.c - core cpuidle infrastructure
   3  *
   4  * (C) 2006-2007 Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>
   5  *               Shaohua Li <shaohua.li@intel.com>
   6  *               Adam Belay <abelay@novell.com>
   7  *
   8  * This code is licenced under the GPL.
   9  */
  10
  11 #include <linux/clockchips.h>
  12 #include <linux/kernel.h>
  13 #include <linux/mutex.h>
  14 #include <linux/sched.h>
  15 #include <linux/sched/clock.h>
  16 #include <linux/notifier.h>
  17 #include <linux/pm_qos.h>
  18 #include <linux/cpu.h>
  19 #include <linux/cpuidle.h>
  20 #include <linux/ktime.h>
  21 #include <linux/hrtimer.h>
  22 #include <linux/module.h>
  23 #include <linux/suspend.h>
  24 #include <linux/tick.h>
  25 #include <linux/mmu_context.h>
  26 #include <trace/events/power.h>
  27
  28 #include "cpuidle.h"
  29
  30 DEFINE_PER_CPU(struct cpuidle_device *, cpuidle_devices);
  31 DEFINE_PER_CPU(struct cpuidle_device, cpuidle_dev);
  32
  33 DEFINE_MUTEX(cpuidle_lock);
  34 LIST_HEAD(cpuidle_detected_devices);
  35
  36 static int enabled_devices;
  37 static int off __read_mostly;
  38 static int initialized __read_mostly;
  39
  40 int cpuidle_disabled(void)
  41 {
  42         return off;
  43 }
  44 void disable_cpuidle(void)
  45 {
  46         off = 1;
  47 }
  48
  49 bool cpuidle_not_available(struct cpuidle_driver *drv,
  50                            struct cpuidle_device *dev)
  51 {
  52         return off || !initialized || !drv || !dev || !dev->enabled;
  53 }
  54
  55 /**
  56  * cpuidle_play_dead - cpu off-lining
  57  *
  58  * Returns in case of an error or no driver
  59  */
  60 int cpuidle_play_dead(void)
  61 {
  62         struct cpuidle_device *dev = __this_cpu_read(cpuidle_devices);
  63         struct cpuidle_driver *drv = cpuidle_get_cpu_driver(dev);
  64         int i;
  65
  66         if (!drv)
  67                 return -ENODEV;
  68
  69         /* Find lowest-power state that supports long-term idle */
  70         for (i = drv->state_count - 1; i >= 0; i--)
  71                 if (drv->states[i].enter_dead)
  72                         return drv->states[i].enter_dead(dev, i);
  73
  74         return -ENODEV;
  75 }
  76
  77 static int find_deepest_state(struct cpuidle_driver *drv,
  78                               struct cpuidle_device *dev,
  79                               u64 max_latency_ns,
  80                               unsigned int forbidden_flags,
  81                               bool s2idle)
  82 {
  83         u64 latency_req = 0;
  84         int i, ret = 0;
  85
  86         for (i = 1; i < drv->state_count; i++) {
  87                 struct cpuidle_state *s = &drv->states[i];
  88
  89                 if (dev->states_usage[i].disable ||
  90                     s->exit_latency_ns <= latency_req ||
  91                     s->exit_latency_ns > max_latency_ns ||
  92                     (s->flags & forbidden_flags) ||
  93                     (s2idle && !s->enter_s2idle))
  94                         continue;
  95
  96                 latency_req = s->exit_latency_ns;
  97                 ret = i;
  98         }
  99         return ret;
 100 }
 101
 102 /**
 103  * cpuidle_use_deepest_state - Set/unset governor override mode.
 104  * @latency_limit_ns: Idle state exit latency limit (or no override if 0).
 105  *
 106  * If @latency_limit_ns is nonzero, set the current CPU to use the deepest idle
 107  * state with exit latency within @latency_limit_ns (override governors going
 108  * forward), or do not override governors if it is zero.
 109  */
 110 void cpuidle_use_deepest_state(u64 latency_limit_ns)
 111 {
 112         struct cpuidle_device *dev;
 113
 114         preempt_disable();
 115         dev = cpuidle_get_device();
 116         if (dev)
 117                 dev->forced_idle_latency_limit_ns = latency_limit_ns;
 118         preempt_enable();
 119 }
 120
 121 /**
 122  * cpuidle_find_deepest_state - Find the deepest available idle state.
 123  * @drv: cpuidle driver for the given CPU.
 124  * @dev: cpuidle device for the given CPU.
 125  * @latency_limit_ns: Idle state exit latency limit
 126  *
 127  * Return: the index of the deepest available idle state.
 128  */
 129 int cpuidle_find_deepest_state(struct cpuidle_driver *drv,
 130                                struct cpuidle_device *dev,
 131                                u64 latency_limit_ns)
 132 {
 133         return find_deepest_state(drv, dev, latency_limit_ns, 0, false);
 134 }
 135
 136 #ifdef CONFIG_SUSPEND
 137 static void enter_s2idle_proper(struct cpuidle_driver *drv,
 138                                 struct cpuidle_device *dev, int index)
 139 {
 140         ktime_t time_start, time_end;
 141         struct cpuidle_state *target_state = &drv->states[index];
 142
 143         time_start = ns_to_ktime(local_clock());
 144
 145         tick_freeze();
 146         /*
 147          * The state used here cannot be a "coupled" one, because the "coupled"
 148          * cpuidle mechanism enables interrupts and doing that with timekeeping
 149          * suspended is generally unsafe.
 150          */
 151         stop_critical_timings();
 152         if (!(target_state->flags & CPUIDLE_FLAG_RCU_IDLE))
 153                 rcu_idle_enter();
 154         target_state->enter_s2idle(dev, drv, index);
 155         if (WARN_ON_ONCE(!irqs_disabled()))
 156                 local_irq_disable();
 157         if (!(target_state->flags & CPUIDLE_FLAG_RCU_IDLE))
 158                 rcu_idle_exit();
 159         tick_unfreeze();
 160         start_critical_timings();
 161
 162         time_end = ns_to_ktime(local_clock());
 163
 164         dev->states_usage[index].s2idle_time += ktime_us_delta(time_end, time_start);
 165         dev->states_usage[index].s2idle_usage++;
 166 }
 167
 168 /**
 169  * cpuidle_enter_s2idle - Enter an idle state suitable for suspend-to-idle.
 170  * @drv: cpuidle driver for the given CPU.
 171  * @dev: cpuidle device for the given CPU.
 172  *
 173  * If there are states with the ->enter_s2idle callback, find the deepest of
 174  * them and enter it with frozen tick.
 175  */
 176 int cpuidle_enter_s2idle(struct cpuidle_driver *drv, struct cpuidle_device *dev)
 177 {
 178         int index;
 179
 180         /*
 181          * Find the deepest state with ->enter_s2idle present, which guarantees
 182          * that interrupts won't be enabled when it exits and allows the tick to
 183          * be frozen safely.
 184          */
 185         index = find_deepest_state(drv, dev, U64_MAX, 0, true);
 186         if (index > 0) {
 187                 enter_s2idle_proper(drv, dev, index);
 188                 local_irq_enable();
 189         }
 190         return index;
 191 }
 192 #endif /* CONFIG_SUSPEND */
 193
 194 /**
 195  * cpuidle_enter_state - enter the state and update stats
 196  * @dev: cpuidle device for this cpu
 197  * @drv: cpuidle driver for this cpu
 198  * @index: index into the states table in @drv of the state to enter
 199  */
 200 int cpuidle_enter_state(struct cpuidle_device *dev, struct cpuidle_driver *drv,
 201                         int index)
 202 {
 203         int entered_state;
 204
 205         struct cpuidle_state *target_state = &drv->states[index];
 206         bool broadcast = !!(target_state->flags & CPUIDLE_FLAG_TIMER_STOP);
 207         ktime_t time_start, time_end;
 208
 209         /*
 210          * Tell the time framework to switch to a broadcast timer because our
 211          * local timer will be shut down.  If a local timer is used from another
 212          * CPU as a broadcast timer, this call may fail if it is not available.
 213          */
 214         if (broadcast && tick_broadcast_enter()) {
 215                 index = find_deepest_state(drv, dev, target_state->exit_latency_ns,
 216                                            CPUIDLE_FLAG_TIMER_STOP, false);
 217                 if (index < 0) {
 218                         default_idle_call();
 219                         return -EBUSY;
 220                 }
 221                 target_state = &drv->states[index];
 222                 broadcast = false;
 223         }
 224
 225         if (target_state->flags & CPUIDLE_FLAG_TLB_FLUSHED)
 226                 leave_mm(dev->cpu);
 227
 228         /* Take note of the planned idle state. */
 229         sched_idle_set_state(target_state);
 230
 231         trace_cpu_idle(index, dev->cpu);
 232         time_start = ns_to_ktime(local_clock());
 233
 234         stop_critical_timings();
 235         if (!(target_state->flags & CPUIDLE_FLAG_RCU_IDLE))
 236                 rcu_idle_enter();
 237         entered_state = target_state->enter(dev, drv, index);
 238         if (!(target_state->flags & CPUIDLE_FLAG_RCU_IDLE))
 239                 rcu_idle_exit();
 240         start_critical_timings();
 241
 242         sched_clock_idle_wakeup_event();
 243         time_end = ns_to_ktime(local_clock());
 244         trace_cpu_idle(PWR_EVENT_EXIT, dev->cpu);
 245
 246         /* The cpu is no longer idle or about to enter idle. */
 247         sched_idle_set_state(NULL);
 248
 249         if (broadcast) {
 250                 if (WARN_ON_ONCE(!irqs_disabled()))
 251                         local_irq_disable();
 252
 253                 tick_broadcast_exit();
 254         }
 255
 256         if (!cpuidle_state_is_coupled(drv, index))
 257                 local_irq_enable();
 258
 259         if (entered_state >= 0) {
 260                 s64 diff, delay = drv->states[entered_state].exit_latency_ns;
 261                 int i;
 262
 263                 /*
 264                  * Update cpuidle counters
 265                  * This can be moved to within driver enter routine,
 266                  * but that results in multiple copies of same code.
 267                  */
 268                 diff = ktime_sub(time_end, time_start);
 269
 270                 dev->last_residency_ns = diff;
 271                 dev->states_usage[entered_state].time_ns += diff;
 272                 dev->states_usage[entered_state].usage++;
 273
 274                 if (diff < drv->states[entered_state].target_residency_ns) {
 275                         for (i = entered_state - 1; i >= 0; i--) {
 276                                 if (dev->states_usage[i].disable)
 277                                         continue;
 278
 279                                 /* Shallower states are enabled, so update. */
 280                                 dev->states_usage[entered_state].above++;
 281                                 break;
 282                         }
 283                 } else if (diff > delay) {
 284                         for (i = entered_state + 1; i < drv->state_count; i++) {
 285                                 if (dev->states_usage[i].disable)
 286                                         continue;
 287
 288                                 /*
 289                                  * Update if a deeper state would have been a
 290                                  * better match for the observed idle duration.
 291                                  */
 292                                 if (diff - delay >= drv->states[i].target_residency_ns)
 293                                         dev->states_usage[entered_state].below++;
 294
 295                                 break;
 296                         }
 297                 }
 298         } else {
 299                 dev->last_residency_ns = 0;
 300                 dev->states_usage[index].rejected++;
 301         }
 302
 303         return entered_state;
 304 }
 305
 306 /**
 307  * cpuidle_select - ask the cpuidle framework to choose an idle state
 308  *
 309  * @drv: the cpuidle driver
 310  * @dev: the cpuidle device
 311  * @stop_tick: indication on whether or not to stop the tick
 312  *
 313  * Returns the index of the idle state.  The return value must not be negative.
 314  *
 315  * The memory location pointed to by @stop_tick is expected to be written the
 316  * 'false' boolean value if the scheduler tick should not be stopped before
 317  * entering the returned state.
 318  */
 319 int cpuidle_select(struct cpuidle_driver *drv, struct cpuidle_device *dev,
 320                    bool *stop_tick)
 321 {
 322         return cpuidle_curr_governor->select(drv, dev, stop_tick);
 323 }
 324
 325 /**
 326  * cpuidle_enter - enter into the specified idle state
 327  *
 328  * @drv:   the cpuidle driver tied with the cpu
 329  * @dev:   the cpuidle device
 330  * @index: the index in the idle state table
 331  *
 332  * Returns the index in the idle state, < 0 in case of error.
 333  * The error code depends on the backend driver
 334  */
 335 int cpuidle_enter(struct cpuidle_driver *drv, struct cpuidle_device *dev,
 336                   int index)
 337 {
 338         int ret = 0;
 339
 340         /*
 341          * Store the next hrtimer, which becomes either next tick or the next
 342          * timer event, whatever expires first. Additionally, to make this data
 343          * useful for consumers outside cpuidle, we rely on that the governor's
 344          * ->select() callback have decided, whether to stop the tick or not.
 345          */
 346         WRITE_ONCE(dev->next_hrtimer, tick_nohz_get_next_hrtimer());
 347
 348         if (cpuidle_state_is_coupled(drv, index))
 349                 ret = cpuidle_enter_state_coupled(dev, drv, index);
 350         else
 351                 ret = cpuidle_enter_state(dev, drv, index);
 352
 353         WRITE_ONCE(dev->next_hrtimer, 0);
 354         return ret;
 355 }
 356
 357 /**
 358  * cpuidle_reflect - tell the underlying governor what was the state
 359  * we were in
 360  *
 361  * @dev  : the cpuidle device
 362  * @index: the index in the idle state table
 363  *
 364  */
 365 void cpuidle_reflect(struct cpuidle_device *dev, int index)
 366 {
 367         if (cpuidle_curr_governor->reflect && index >= 0)
 368                 cpuidle_curr_governor->reflect(dev, index);
 369 }
 370
 371 /*
 372  * Min polling interval of 10usec is a guess. It is assuming that
 373  * for most users, the time for a single ping-pong workload like
 374  * perf bench pipe would generally complete within 10usec but
 375  * this is hardware dependant. Actual time can be estimated with
 376  *
 377  * perf bench sched pipe -l 10000
 378  *
 379  * Run multiple times to avoid cpufreq effects.
 380  */
 381 #define CPUIDLE_POLL_MIN 10000
 382 #define CPUIDLE_POLL_MAX (TICK_NSEC / 16)
 383
 384 /**
 385  * cpuidle_poll_time - return amount of time to poll for,
 386  * governors can override dev->poll_limit_ns if necessary
 387  *
 388  * @drv:   the cpuidle driver tied with the cpu
 389  * @dev:   the cpuidle device
 390  *
 391  */
 392 u64 cpuidle_poll_time(struct cpuidle_driver *drv,
 393                       struct cpuidle_device *dev)
 394 {
 395         int i;
 396         u64 limit_ns;
 397
 398         BUILD_BUG_ON(CPUIDLE_POLL_MIN > CPUIDLE_POLL_MAX);
 399
 400         if (dev->poll_limit_ns)
 401                 return dev->poll_limit_ns;
 402
 403         limit_ns = CPUIDLE_POLL_MAX;
 404         for (i = 1; i < drv->state_count; i++) {
 405                 u64 state_limit;
 406
 407                 if (dev->states_usage[i].disable)
 408                         continue;
 409
 410                 state_limit = drv->states[i].target_residency_ns;
 411                 if (state_limit < CPUIDLE_POLL_MIN)
 412                         continue;
 413
 414                 limit_ns = min_t(u64, state_limit, CPUIDLE_POLL_MAX);
 415                 break;
 416         }
 417
 418         dev->poll_limit_ns = limit_ns;
 419
 420         return dev->poll_limit_ns;
 421 }
 422
 423 /**
 424  * cpuidle_install_idle_handler - installs the cpuidle idle loop handler
 425  */
 426 void cpuidle_install_idle_handler(void)
 427 {
 428         if (enabled_devices) {
 429                 /* Make sure all changes finished before we switch to new idle */
 430                 smp_wmb();
 431                 initialized = 1;
 432         }
 433 }
 434
 435 /**
 436  * cpuidle_uninstall_idle_handler - uninstalls the cpuidle idle loop handler
 437  */
 438 void cpuidle_uninstall_idle_handler(void)
 439 {
 440         if (enabled_devices) {
 441                 initialized = 0;
 442                 wake_up_all_idle_cpus();
 443         }
 444
 445         /*
 446          * Make sure external observers (such as the scheduler)
 447          * are done looking at pointed idle states.
 448          */
 449         synchronize_rcu();
 450 }
 451
 452 /**
 453  * cpuidle_pause_and_lock - temporarily disables CPUIDLE
 454  */
 455 void cpuidle_pause_and_lock(void)
 456 {
 457         mutex_lock(&cpuidle_lock);
 458         cpuidle_uninstall_idle_handler();
 459 }
 460
 461 EXPORT_SYMBOL_GPL(cpuidle_pause_and_lock);
 462
 463 /**
 464  * cpuidle_resume_and_unlock - resumes CPUIDLE operation
 465  */
 466 void cpuidle_resume_and_unlock(void)
 467 {
 468         cpuidle_install_idle_handler();
 469         mutex_unlock(&cpuidle_lock);
 470 }
 471
 472 EXPORT_SYMBOL_GPL(cpuidle_resume_and_unlock);
 473
 474 /* Currently used in suspend/resume path to suspend cpuidle */
 475 void cpuidle_pause(void)
 476 {
 477         mutex_lock(&cpuidle_lock);
 478         cpuidle_uninstall_idle_handler();
 479         mutex_unlock(&cpuidle_lock);
 480 }
 481
 482 /* Currently used in suspend/resume path to resume cpuidle */
 483 void cpuidle_resume(void)
 484 {
 485         mutex_lock(&cpuidle_lock);
 486         cpuidle_install_idle_handler();
 487         mutex_unlock(&cpuidle_lock);
 488 }
 489
 490 /**
 491  * cpuidle_enable_device - enables idle PM for a CPU
 492  * @dev: the CPU
 493  *
 494  * This function must be called between cpuidle_pause_and_lock and
 495  * cpuidle_resume_and_unlock when used externally.
 496  */
 497 int cpuidle_enable_device(struct cpuidle_device *dev)
 498 {
 499         int ret;
 500         struct cpuidle_driver *drv;
 501
 502         if (!dev)
 503                 return -EINVAL;
 504
 505         if (dev->enabled)
 506                 return 0;
 507
 508         if (!cpuidle_curr_governor)
 509                 return -EIO;
 510
 511         drv = cpuidle_get_cpu_driver(dev);
 512
 513         if (!drv)
 514                 return -EIO;
 515
 516         if (!dev->registered)
 517                 return -EINVAL;
 518
 519         ret = cpuidle_add_device_sysfs(dev);
 520         if (ret)
 521                 return ret;
 522
 523         if (cpuidle_curr_governor->enable) {
 524                 ret = cpuidle_curr_governor->enable(drv, dev);
 525                 if (ret)
 526                         goto fail_sysfs;
 527         }
 528
 529         smp_wmb();
 530
 531         dev->enabled = 1;
 532
 533         enabled_devices++;
 534         return 0;
 535
 536 fail_sysfs:
 537         cpuidle_remove_device_sysfs(dev);
 538
 539         return ret;
 540 }
 541
 542 EXPORT_SYMBOL_GPL(cpuidle_enable_device);
 543
 544 /**
 545  * cpuidle_disable_device - disables idle PM for a CPU
 546  * @dev: the CPU
 547  *
 548  * This function must be called between cpuidle_pause_and_lock and
 549  * cpuidle_resume_and_unlock when used externally.
 550  */
 551 void cpuidle_disable_device(struct cpuidle_device *dev)
 552 {
 553         struct cpuidle_driver *drv = cpuidle_get_cpu_driver(dev);
 554
 555         if (!dev || !dev->enabled)
 556                 return;
 557
 558         if (!drv || !cpuidle_curr_governor)
 559                 return;
 560
 561         dev->enabled = 0;
 562
 563         if (cpuidle_curr_governor->disable)
 564                 cpuidle_curr_governor->disable(drv, dev);
 565
 566         cpuidle_remove_device_sysfs(dev);
 567         enabled_devices--;
 568 }
 569
 570 EXPORT_SYMBOL_GPL(cpuidle_disable_device);
 571
 572 static void __cpuidle_unregister_device(struct cpuidle_device *dev)
 573 {
 574         struct cpuidle_driver *drv = cpuidle_get_cpu_driver(dev);
 575
 576         list_del(&dev->device_list);
 577         per_cpu(cpuidle_devices, dev->cpu) = NULL;
 578         module_put(drv->owner);
 579
 580         dev->registered = 0;
 581 }
 582
 583 static void __cpuidle_device_init(struct cpuidle_device *dev)
 584 {
 585         memset(dev->states_usage, 0, sizeof(dev->states_usage));
 586         dev->last_residency_ns = 0;
 587         dev->next_hrtimer = 0;
 588 }
 589
 590 /**
 591  * __cpuidle_register_device - internal register function called before register
 592  * and enable routines
 593  * @dev: the cpu
 594  *
 595  * cpuidle_lock mutex must be held before this is called
 596  */
 597 static int __cpuidle_register_device(struct cpuidle_device *dev)
 598 {
 599         struct cpuidle_driver *drv = cpuidle_get_cpu_driver(dev);
 600         int i, ret;
 601
 602         if (!try_module_get(drv->owner))
 603                 return -EINVAL;
 604
 605         for (i = 0; i < drv->state_count; i++) {
 606                 if (drv->states[i].flags & CPUIDLE_FLAG_UNUSABLE)
 607                         dev->states_usage[i].disable |= CPUIDLE_STATE_DISABLED_BY_DRIVER;
 608
 609                 if (drv->states[i].flags & CPUIDLE_FLAG_OFF)
 610                         dev->states_usage[i].disable |= CPUIDLE_STATE_DISABLED_BY_USER;
 611         }
 612
 613         per_cpu(cpuidle_devices, dev->cpu) = dev;
 614         list_add(&dev->device_list, &cpuidle_detected_devices);
 615
 616         ret = cpuidle_coupled_register_device(dev);
 617         if (ret)
 618                 __cpuidle_unregister_device(dev);
 619         else
 620                 dev->registered = 1;
 621
 622         return ret;
 623 }
 624
 625 /**
 626  * cpuidle_register_device - registers a CPU's idle PM feature
 627  * @dev: the cpu
 628  */
 629 int cpuidle_register_device(struct cpuidle_device *dev)
 630 {
 631         int ret = -EBUSY;
 632
 633         if (!dev)
 634                 return -EINVAL;
 635
 636         mutex_lock(&cpuidle_lock);
 637
 638         if (dev->registered)
 639                 goto out_unlock;
 640
 641         __cpuidle_device_init(dev);
 642
 643         ret = __cpuidle_register_device(dev);
 644         if (ret)
 645                 goto out_unlock;
 646
 647         ret = cpuidle_add_sysfs(dev);
 648         if (ret)
 649                 goto out_unregister;
 650
 651         ret = cpuidle_enable_device(dev);
 652         if (ret)
 653                 goto out_sysfs;
 654
 655         cpuidle_install_idle_handler();
 656
 657 out_unlock:
 658         mutex_unlock(&cpuidle_lock);
 659
 660         return ret;
 661
 662 out_sysfs:
 663         cpuidle_remove_sysfs(dev);
 664 out_unregister:
 665         __cpuidle_unregister_device(dev);
 666         goto out_unlock;
 667 }
 668
 669 EXPORT_SYMBOL_GPL(cpuidle_register_device);
 670
 671 /**
 672  * cpuidle_unregister_device - unregisters a CPU's idle PM feature
 673  * @dev: the cpu
 674  */
 675 void cpuidle_unregister_device(struct cpuidle_device *dev)
 676 {
 677         if (!dev || dev->registered == 0)
 678                 return;
 679
 680         cpuidle_pause_and_lock();
 681
 682         cpuidle_disable_device(dev);
 683
 684         cpuidle_remove_sysfs(dev);
 685
 686         __cpuidle_unregister_device(dev);
 687
 688         cpuidle_coupled_unregister_device(dev);
 689
 690         cpuidle_resume_and_unlock();
 691 }
 692
 693 EXPORT_SYMBOL_GPL(cpuidle_unregister_device);
 694
 695 /**
 696  * cpuidle_unregister: unregister a driver and the devices. This function
 697  * can be used only if the driver has been previously registered through
 698  * the cpuidle_register function.
 699  *
 700  * @drv: a valid pointer to a struct cpuidle_driver
 701  */
 702 void cpuidle_unregister(struct cpuidle_driver *drv)
 703 {
 704         int cpu;
 705         struct cpuidle_device *device;
 706
 707         for_each_cpu(cpu, drv->cpumask) {
 708                 device = &per_cpu(cpuidle_dev, cpu);
 709                 cpuidle_unregister_device(device);
 710         }
 711
 712         cpuidle_unregister_driver(drv);
 713 }
 714 EXPORT_SYMBOL_GPL(cpuidle_unregister);
 715
 716 /**
 717  * cpuidle_register: registers the driver and the cpu devices with the
 718  * coupled_cpus passed as parameter. This function is used for all common
 719  * initialization pattern there are in the arch specific drivers. The
 720  * devices is globally defined in this file.
 721  *
 722  * @drv         : a valid pointer to a struct cpuidle_driver
 723  * @coupled_cpus: a cpumask for the coupled states
 724  *
 725  * Returns 0 on success, < 0 otherwise
 726  */
 727 int cpuidle_register(struct cpuidle_driver *drv,
 728                      const struct cpumask *const coupled_cpus)
 729 {
 730         int ret, cpu;
 731         struct cpuidle_device *device;
 732
 733         ret = cpuidle_register_driver(drv);
 734         if (ret) {
 735                 pr_err("failed to register cpuidle driver\n");
 736                 return ret;
 737         }
 738
 739         for_each_cpu(cpu, drv->cpumask) {
 740                 device = &per_cpu(cpuidle_dev, cpu);
 741                 device->cpu = cpu;
 742
 743 #ifdef CONFIG_ARCH_NEEDS_CPU_IDLE_COUPLED
 744                 /*
 745                  * On multiplatform for ARM, the coupled idle states could be
 746                  * enabled in the kernel even if the cpuidle driver does not
 747                  * use it. Note, coupled_cpus is a struct copy.
 748                  */
 749                 if (coupled_cpus)
 750                         device->coupled_cpus = *coupled_cpus;
 751 #endif
 752                 ret = cpuidle_register_device(device);
 753                 if (!ret)
 754                         continue;
 755
 756                 pr_err("Failed to register cpuidle device for cpu%d\n", cpu);
 757
 758                 cpuidle_unregister(drv);
 759                 break;
 760         }
 761
 762         return ret;
 763 }
 764 EXPORT_SYMBOL_GPL(cpuidle_register);
 765
 766 /**
 767  * cpuidle_init - core initializer
 768  */
 769 static int __init cpuidle_init(void)
 770 {
 771         if (cpuidle_disabled())
 772                 return -ENODEV;
 773
 774         return cpuidle_add_interface(cpu_subsys.dev_root);
 775 }
 776
 777 module_param(off, int, 0444);
 778 module_param_string(governor, param_governor, CPUIDLE_NAME_LEN, 0444);
 779 core_initcall(cpuidle_init);