root/drivers/cpuidle/cpuidle.c

DEFINITIONS

1. cpuidle_disabled
2. disable_cpuidle
3. cpuidle_not_available
4. cpuidle_play_dead
5. find_deepest_state
6. cpuidle_use_deepest_state
7. cpuidle_find_deepest_state
8. enter_s2idle_proper
9. cpuidle_enter_s2idle
10. cpuidle_enter_state
11. cpuidle_select
12. cpuidle_enter
13. cpuidle_reflect
14. cpuidle_poll_time
15. cpuidle_install_idle_handler
16. cpuidle_uninstall_idle_handler
17. cpuidle_pause_and_lock
18. cpuidle_resume_and_unlock
19. cpuidle_pause
20. cpuidle_resume
21. cpuidle_enable_device
22. cpuidle_disable_device
23. __cpuidle_unregister_device
24. __cpuidle_device_init
25. __cpuidle_register_device
26. cpuidle_register_device
27. cpuidle_unregister_device
28. cpuidle_unregister
29. cpuidle_register
30. cpuidle_latency_notify
31. latency_notifier_init
32. cpuidle_init

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