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