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/notifier.h>
  16 #include <linux/pm_qos.h>
  17 #include <linux/cpu.h>
  18 #include <linux/cpuidle.h>
  19 #include <linux/ktime.h>
  20 #include <linux/hrtimer.h>
  21 #include <linux/module.h>
  22 #include <linux/suspend.h>
  23 #include <linux/tick.h>
  24 #include <trace/events/power.h>
  25
  26 #include "cpuidle.h"
  27
  28 DEFINE_PER_CPU(struct cpuidle_device *, cpuidle_devices);
  29 DEFINE_PER_CPU(struct cpuidle_device, cpuidle_dev);
  30
  31 DEFINE_MUTEX(cpuidle_lock);
  32 LIST_HEAD(cpuidle_detected_devices);
  33
  34 static int enabled_devices;
  35 static int off __read_mostly;
  36 static int initialized __read_mostly;
  37
  38 int cpuidle_disabled(void)
  39 {
  40         return off;
  41 }
  42 void disable_cpuidle(void)
  43 {
  44         off = 1;
  45 }
  46
  47 bool cpuidle_not_available(struct cpuidle_driver *drv,
  48                            struct cpuidle_device *dev)
  49 {
  50         return off || !initialized || !drv || !dev || !dev->enabled;
  51 }
  52
  53 /**
  54  * cpuidle_play_dead - cpu off-lining
  55  *
  56  * Returns in case of an error or no driver
  57  */
  58 int cpuidle_play_dead(void)
  59 {
  60         struct cpuidle_device *dev = __this_cpu_read(cpuidle_devices);
  61         struct cpuidle_driver *drv = cpuidle_get_cpu_driver(dev);
  62         int i;
  63
  64         if (!drv)
  65                 return -ENODEV;
  66
  67         /* Find lowest-power state that supports long-term idle */
  68         for (i = drv->state_count - 1; i >= CPUIDLE_DRIVER_STATE_START; i--)
  69                 if (drv->states[i].enter_dead)
  70                         return drv->states[i].enter_dead(dev, i);
  71
  72         return -ENODEV;
  73 }
  74
  75 static int find_deepest_state(struct cpuidle_driver *drv,
  76                               struct cpuidle_device *dev, bool freeze)
  77 {
  78         unsigned int latency_req = 0;
  79         int i, ret = freeze ? -1 : CPUIDLE_DRIVER_STATE_START - 1;
  80
  81         for (i = CPUIDLE_DRIVER_STATE_START; i < drv->state_count; i++) {
  82                 struct cpuidle_state *s = &drv->states[i];
  83                 struct cpuidle_state_usage *su = &dev->states_usage[i];
  84
  85                 if (s->disabled || su->disable || s->exit_latency <= latency_req
  86                     || (freeze && !s->enter_freeze))
  87                         continue;
  88
  89                 latency_req = s->exit_latency;
  90                 ret = i;
  91         }
  92         return ret;
  93 }
  94
  95 /**
  96  * cpuidle_find_deepest_state - Find the deepest available idle state.
  97  * @drv: cpuidle driver for the given CPU.
  98  * @dev: cpuidle device for the given CPU.
  99  */
 100 int cpuidle_find_deepest_state(struct cpuidle_driver *drv,
 101                                struct cpuidle_device *dev)
 102 {
 103         return find_deepest_state(drv, dev, false);
 104 }
 105
 106 static void enter_freeze_proper(struct cpuidle_driver *drv,
 107                                 struct cpuidle_device *dev, int index)
 108 {
 109         tick_freeze();
 110         /*
 111          * The state used here cannot be a "coupled" one, because the "coupled"
 112          * cpuidle mechanism enables interrupts and doing that with timekeeping
 113          * suspended is generally unsafe.
 114          */
 115         drv->states[index].enter_freeze(dev, drv, index);
 116         WARN_ON(!irqs_disabled());
 117         /*
 118          * timekeeping_resume() that will be called by tick_unfreeze() for the
 119          * last CPU executing it calls functions containing RCU read-side
 120          * critical sections, so tell RCU about that.
 121          */
 122         RCU_NONIDLE(tick_unfreeze());
 123 }
 124
 125 /**
 126  * cpuidle_enter_freeze - Enter an idle state suitable for suspend-to-idle.
 127  * @drv: cpuidle driver for the given CPU.
 128  * @dev: cpuidle device for the given CPU.
 129  *
 130  * If there are states with the ->enter_freeze callback, find the deepest of
 131  * them and enter it with frozen tick.
 132  */
 133 int cpuidle_enter_freeze(struct cpuidle_driver *drv, struct cpuidle_device *dev)
 134 {
 135         int index;
 136
 137         /*
 138          * Find the deepest state with ->enter_freeze present, which guarantees
 139          * that interrupts won't be enabled when it exits and allows the tick to
 140          * be frozen safely.
 141          */
 142         index = find_deepest_state(drv, dev, true);
 143         if (index >= 0)
 144                 enter_freeze_proper(drv, dev, index);
 145
 146         return index;
 147 }
 148
 149 /**
 150  * cpuidle_enter_state - enter the state and update stats
 151  * @dev: cpuidle device for this cpu
 152  * @drv: cpuidle driver for this cpu
 153  * @next_state: index into drv->states of the state to enter
 154  */
 155 int cpuidle_enter_state(struct cpuidle_device *dev, struct cpuidle_driver *drv,
 156                         int index)
 157 {
 158         int entered_state;
 159
 160         struct cpuidle_state *target_state = &drv->states[index];
 161         bool broadcast = !!(target_state->flags & CPUIDLE_FLAG_TIMER_STOP);
 162         ktime_t time_start, time_end;
 163         s64 diff;
 164
 165         /*
 166          * Tell the time framework to switch to a broadcast timer because our
 167          * local timer will be shut down.  If a local timer is used from another
 168          * CPU as a broadcast timer, this call may fail if it is not available.
 169          */
 170         if (broadcast && tick_broadcast_enter())
 171                 return -EBUSY;
 172
 173         trace_cpu_idle_rcuidle(index, dev->cpu);
 174         time_start = ktime_get();
 175
 176         entered_state = target_state->enter(dev, drv, index);
 177
 178         time_end = ktime_get();
 179         trace_cpu_idle_rcuidle(PWR_EVENT_EXIT, dev->cpu);
 180
 181         if (broadcast) {
 182                 if (WARN_ON_ONCE(!irqs_disabled()))
 183                         local_irq_disable();
 184
 185                 tick_broadcast_exit();
 186         }
 187
 188         if (!cpuidle_state_is_coupled(dev, drv, entered_state))
 189                 local_irq_enable();
 190
 191         diff = ktime_to_us(ktime_sub(time_end, time_start));
 192         if (diff > INT_MAX)
 193                 diff = INT_MAX;
 194
 195         dev->last_residency = (int) diff;
 196
 197         if (entered_state >= 0) {
 198                 /* Update cpuidle counters */
 199                 /* This can be moved to within driver enter routine
 200                  * but that results in multiple copies of same code.
 201                  */
 202                 dev->states_usage[entered_state].time += dev->last_residency;
 203                 dev->states_usage[entered_state].usage++;
 204         } else {
 205                 dev->last_residency = 0;
 206         }
 207
 208         return entered_state;
 209 }
 210
 211 /**
 212  * cpuidle_select - ask the cpuidle framework to choose an idle state
 213  *
 214  * @drv: the cpuidle driver
 215  * @dev: the cpuidle device
 216  *
 217  * Returns the index of the idle state.
 218  */
 219 int cpuidle_select(struct cpuidle_driver *drv, struct cpuidle_device *dev)
 220 {
 221         return cpuidle_curr_governor->select(drv, dev);
 222 }
 223
 224 /**
 225  * cpuidle_enter - enter into the specified idle state
 226  *
 227  * @drv:   the cpuidle driver tied with the cpu
 228  * @dev:   the cpuidle device
 229  * @index: the index in the idle state table
 230  *
 231  * Returns the index in the idle state, < 0 in case of error.
 232  * The error code depends on the backend driver
 233  */
 234 int cpuidle_enter(struct cpuidle_driver *drv, struct cpuidle_device *dev,
 235                   int index)
 236 {
 237         if (cpuidle_state_is_coupled(dev, drv, index))
 238                 return cpuidle_enter_state_coupled(dev, drv, index);
 239         return cpuidle_enter_state(dev, drv, index);
 240 }
 241
 242 /**
 243  * cpuidle_reflect - tell the underlying governor what was the state
 244  * we were in
 245  *
 246  * @dev  : the cpuidle device
 247  * @index: the index in the idle state table
 248  *
 249  */
 250 void cpuidle_reflect(struct cpuidle_device *dev, int index)
 251 {
 252         if (cpuidle_curr_governor->reflect)
 253                 cpuidle_curr_governor->reflect(dev, index);
 254 }
 255
 256 /**
 257  * cpuidle_install_idle_handler - installs the cpuidle idle loop handler
 258  */
 259 void cpuidle_install_idle_handler(void)
 260 {
 261         if (enabled_devices) {
 262                 /* Make sure all changes finished before we switch to new idle */
 263                 smp_wmb();
 264                 initialized = 1;
 265         }
 266 }
 267
 268 /**
 269  * cpuidle_uninstall_idle_handler - uninstalls the cpuidle idle loop handler
 270  */
 271 void cpuidle_uninstall_idle_handler(void)
 272 {
 273         if (enabled_devices) {
 274                 initialized = 0;
 275                 wake_up_all_idle_cpus();
 276         }
 277
 278         /*
 279          * Make sure external observers (such as the scheduler)
 280          * are done looking at pointed idle states.
 281          */
 282         synchronize_rcu();
 283 }
 284
 285 /**
 286  * cpuidle_pause_and_lock - temporarily disables CPUIDLE
 287  */
 288 void cpuidle_pause_and_lock(void)
 289 {
 290         mutex_lock(&cpuidle_lock);
 291         cpuidle_uninstall_idle_handler();
 292 }
 293
 294 EXPORT_SYMBOL_GPL(cpuidle_pause_and_lock);
 295
 296 /**
 297  * cpuidle_resume_and_unlock - resumes CPUIDLE operation
 298  */
 299 void cpuidle_resume_and_unlock(void)
 300 {
 301         cpuidle_install_idle_handler();
 302         mutex_unlock(&cpuidle_lock);
 303 }
 304
 305 EXPORT_SYMBOL_GPL(cpuidle_resume_and_unlock);
 306
 307 /* Currently used in suspend/resume path to suspend cpuidle */
 308 void cpuidle_pause(void)
 309 {
 310         mutex_lock(&cpuidle_lock);
 311         cpuidle_uninstall_idle_handler();
 312         mutex_unlock(&cpuidle_lock);
 313 }
 314
 315 /* Currently used in suspend/resume path to resume cpuidle */
 316 void cpuidle_resume(void)
 317 {
 318         mutex_lock(&cpuidle_lock);
 319         cpuidle_install_idle_handler();
 320         mutex_unlock(&cpuidle_lock);
 321 }
 322
 323 /**
 324  * cpuidle_enable_device - enables idle PM for a CPU
 325  * @dev: the CPU
 326  *
 327  * This function must be called between cpuidle_pause_and_lock and
 328  * cpuidle_resume_and_unlock when used externally.
 329  */
 330 int cpuidle_enable_device(struct cpuidle_device *dev)
 331 {
 332         int ret;
 333         struct cpuidle_driver *drv;
 334
 335         if (!dev)
 336                 return -EINVAL;
 337
 338         if (dev->enabled)
 339                 return 0;
 340
 341         drv = cpuidle_get_cpu_driver(dev);
 342
 343         if (!drv || !cpuidle_curr_governor)
 344                 return -EIO;
 345
 346         if (!dev->registered)
 347                 return -EINVAL;
 348
 349         ret = cpuidle_add_device_sysfs(dev);
 350         if (ret)
 351                 return ret;
 352
 353         if (cpuidle_curr_governor->enable &&
 354             (ret = cpuidle_curr_governor->enable(drv, dev)))
 355                 goto fail_sysfs;
 356
 357         smp_wmb();
 358
 359         dev->enabled = 1;
 360
 361         enabled_devices++;
 362         return 0;
 363
 364 fail_sysfs:
 365         cpuidle_remove_device_sysfs(dev);
 366
 367         return ret;
 368 }
 369
 370 EXPORT_SYMBOL_GPL(cpuidle_enable_device);
 371
 372 /**
 373  * cpuidle_disable_device - disables idle PM for a CPU
 374  * @dev: the CPU
 375  *
 376  * This function must be called between cpuidle_pause_and_lock and
 377  * cpuidle_resume_and_unlock when used externally.
 378  */
 379 void cpuidle_disable_device(struct cpuidle_device *dev)
 380 {
 381         struct cpuidle_driver *drv = cpuidle_get_cpu_driver(dev);
 382
 383         if (!dev || !dev->enabled)
 384                 return;
 385
 386         if (!drv || !cpuidle_curr_governor)
 387                 return;
 388
 389         dev->enabled = 0;
 390
 391         if (cpuidle_curr_governor->disable)
 392                 cpuidle_curr_governor->disable(drv, dev);
 393
 394         cpuidle_remove_device_sysfs(dev);
 395         enabled_devices--;
 396 }
 397
 398 EXPORT_SYMBOL_GPL(cpuidle_disable_device);
 399
 400 static void __cpuidle_unregister_device(struct cpuidle_device *dev)
 401 {
 402         struct cpuidle_driver *drv = cpuidle_get_cpu_driver(dev);
 403
 404         list_del(&dev->device_list);
 405         per_cpu(cpuidle_devices, dev->cpu) = NULL;
 406         module_put(drv->owner);
 407 }
 408
 409 static void __cpuidle_device_init(struct cpuidle_device *dev)
 410 {
 411         memset(dev->states_usage, 0, sizeof(dev->states_usage));
 412         dev->last_residency = 0;
 413 }
 414
 415 /**
 416  * __cpuidle_register_device - internal register function called before register
 417  * and enable routines
 418  * @dev: the cpu
 419  *
 420  * cpuidle_lock mutex must be held before this is called
 421  */
 422 static int __cpuidle_register_device(struct cpuidle_device *dev)
 423 {
 424         int ret;
 425         struct cpuidle_driver *drv = cpuidle_get_cpu_driver(dev);
 426
 427         if (!try_module_get(drv->owner))
 428                 return -EINVAL;
 429
 430         per_cpu(cpuidle_devices, dev->cpu) = dev;
 431         list_add(&dev->device_list, &cpuidle_detected_devices);
 432
 433         ret = cpuidle_coupled_register_device(dev);
 434         if (ret)
 435                 __cpuidle_unregister_device(dev);
 436         else
 437                 dev->registered = 1;
 438
 439         return ret;
 440 }
 441
 442 /**
 443  * cpuidle_register_device - registers a CPU's idle PM feature
 444  * @dev: the cpu
 445  */
 446 int cpuidle_register_device(struct cpuidle_device *dev)
 447 {
 448         int ret = -EBUSY;
 449
 450         if (!dev)
 451                 return -EINVAL;
 452
 453         mutex_lock(&cpuidle_lock);
 454
 455         if (dev->registered)
 456                 goto out_unlock;
 457
 458         __cpuidle_device_init(dev);
 459
 460         ret = __cpuidle_register_device(dev);
 461         if (ret)
 462                 goto out_unlock;
 463
 464         ret = cpuidle_add_sysfs(dev);
 465         if (ret)
 466                 goto out_unregister;
 467
 468         ret = cpuidle_enable_device(dev);
 469         if (ret)
 470                 goto out_sysfs;
 471
 472         cpuidle_install_idle_handler();
 473
 474 out_unlock:
 475         mutex_unlock(&cpuidle_lock);
 476
 477         return ret;
 478
 479 out_sysfs:
 480         cpuidle_remove_sysfs(dev);
 481 out_unregister:
 482         __cpuidle_unregister_device(dev);
 483         goto out_unlock;
 484 }
 485
 486 EXPORT_SYMBOL_GPL(cpuidle_register_device);
 487
 488 /**
 489  * cpuidle_unregister_device - unregisters a CPU's idle PM feature
 490  * @dev: the cpu
 491  */
 492 void cpuidle_unregister_device(struct cpuidle_device *dev)
 493 {
 494         if (!dev || dev->registered == 0)
 495                 return;
 496
 497         cpuidle_pause_and_lock();
 498
 499         cpuidle_disable_device(dev);
 500
 501         cpuidle_remove_sysfs(dev);
 502
 503         __cpuidle_unregister_device(dev);
 504
 505         cpuidle_coupled_unregister_device(dev);
 506
 507         cpuidle_resume_and_unlock();
 508 }
 509
 510 EXPORT_SYMBOL_GPL(cpuidle_unregister_device);
 511
 512 /**
 513  * cpuidle_unregister: unregister a driver and the devices. This function
 514  * can be used only if the driver has been previously registered through
 515  * the cpuidle_register function.
 516  *
 517  * @drv: a valid pointer to a struct cpuidle_driver
 518  */
 519 void cpuidle_unregister(struct cpuidle_driver *drv)
 520 {
 521         int cpu;
 522         struct cpuidle_device *device;
 523
 524         for_each_cpu(cpu, drv->cpumask) {
 525                 device = &per_cpu(cpuidle_dev, cpu);
 526                 cpuidle_unregister_device(device);
 527         }
 528
 529         cpuidle_unregister_driver(drv);
 530 }
 531 EXPORT_SYMBOL_GPL(cpuidle_unregister);
 532
 533 /**
 534  * cpuidle_register: registers the driver and the cpu devices with the
 535  * coupled_cpus passed as parameter. This function is used for all common
 536  * initialization pattern there are in the arch specific drivers. The
 537  * devices is globally defined in this file.
 538  *
 539  * @drv         : a valid pointer to a struct cpuidle_driver
 540  * @coupled_cpus: a cpumask for the coupled states
 541  *
 542  * Returns 0 on success, < 0 otherwise
 543  */
 544 int cpuidle_register(struct cpuidle_driver *drv,
 545                      const struct cpumask *const coupled_cpus)
 546 {
 547         int ret, cpu;
 548         struct cpuidle_device *device;
 549
 550         ret = cpuidle_register_driver(drv);
 551         if (ret) {
 552                 pr_err("failed to register cpuidle driver\n");
 553                 return ret;
 554         }
 555
 556         for_each_cpu(cpu, drv->cpumask) {
 557                 device = &per_cpu(cpuidle_dev, cpu);
 558                 device->cpu = cpu;
 559
 560 #ifdef CONFIG_ARCH_NEEDS_CPU_IDLE_COUPLED
 561                 /*
 562                  * On multiplatform for ARM, the coupled idle states could be
 563                  * enabled in the kernel even if the cpuidle driver does not
 564                  * use it. Note, coupled_cpus is a struct copy.
 565                  */
 566                 if (coupled_cpus)
 567                         device->coupled_cpus = *coupled_cpus;
 568 #endif
 569                 ret = cpuidle_register_device(device);
 570                 if (!ret)
 571                         continue;
 572
 573                 pr_err("Failed to register cpuidle device for cpu%d\n", cpu);
 574
 575                 cpuidle_unregister(drv);
 576                 break;
 577         }
 578
 579         return ret;
 580 }
 581 EXPORT_SYMBOL_GPL(cpuidle_register);
 582
 583 #ifdef CONFIG_SMP
 584
 585 /*
 586  * This function gets called when a part of the kernel has a new latency
 587  * requirement.  This means we need to get all processors out of their C-state,
 588  * and then recalculate a new suitable C-state. Just do a cross-cpu IPI; that
 589  * wakes them all right up.
 590  */
 591 static int cpuidle_latency_notify(struct notifier_block *b,
 592                 unsigned long l, void *v)
 593 {
 594         wake_up_all_idle_cpus();
 595         return NOTIFY_OK;
 596 }
 597
 598 static struct notifier_block cpuidle_latency_notifier = {
 599         .notifier_call = cpuidle_latency_notify,
 600 };
 601
 602 static inline void latency_notifier_init(struct notifier_block *n)
 603 {
 604         pm_qos_add_notifier(PM_QOS_CPU_DMA_LATENCY, n);
 605 }
 606
 607 #else /* CONFIG_SMP */
 608
 609 #define latency_notifier_init(x) do { } while (0)
 610
 611 #endif /* CONFIG_SMP */
 612
 613 /**
 614  * cpuidle_init - core initializer
 615  */
 616 static int __init cpuidle_init(void)
 617 {
 618         int ret;
 619
 620         if (cpuidle_disabled())
 621                 return -ENODEV;
 622
 623         ret = cpuidle_add_interface(cpu_subsys.dev_root);
 624         if (ret)
 625                 return ret;
 626
 627         latency_notifier_init(&cpuidle_latency_notifier);
 628
 629         return 0;
 630 }
 631
 632 module_param(off, int, 0444);
 633 core_initcall(cpuidle_init);