linux/drivers/cpuidle/cpuidle.c
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   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/kernel.h>
  12#include <linux/mutex.h>
  13#include <linux/sched.h>
  14#include <linux/notifier.h>
  15#include <linux/pm_qos.h>
  16#include <linux/cpu.h>
  17#include <linux/cpuidle.h>
  18#include <linux/ktime.h>
  19#include <linux/hrtimer.h>
  20#include <linux/module.h>
  21#include <trace/events/power.h>
  22
  23#include "cpuidle.h"
  24
  25DEFINE_PER_CPU(struct cpuidle_device *, cpuidle_devices);
  26
  27DEFINE_MUTEX(cpuidle_lock);
  28LIST_HEAD(cpuidle_detected_devices);
  29
  30static int enabled_devices;
  31static int off __read_mostly;
  32static int initialized __read_mostly;
  33
  34int cpuidle_disabled(void)
  35{
  36        return off;
  37}
  38void disable_cpuidle(void)
  39{
  40        off = 1;
  41}
  42
  43static int __cpuidle_register_device(struct cpuidle_device *dev);
  44
  45static inline int cpuidle_enter(struct cpuidle_device *dev,
  46                                struct cpuidle_driver *drv, int index)
  47{
  48        struct cpuidle_state *target_state = &drv->states[index];
  49        return target_state->enter(dev, drv, index);
  50}
  51
  52static inline int cpuidle_enter_tk(struct cpuidle_device *dev,
  53                               struct cpuidle_driver *drv, int index)
  54{
  55        return cpuidle_wrap_enter(dev, drv, index, cpuidle_enter);
  56}
  57
  58typedef int (*cpuidle_enter_t)(struct cpuidle_device *dev,
  59                               struct cpuidle_driver *drv, int index);
  60
  61static cpuidle_enter_t cpuidle_enter_ops;
  62
  63/**
  64 * cpuidle_play_dead - cpu off-lining
  65 *
  66 * Returns in case of an error or no driver
  67 */
  68int cpuidle_play_dead(void)
  69{
  70        struct cpuidle_device *dev = __this_cpu_read(cpuidle_devices);
  71        struct cpuidle_driver *drv = cpuidle_get_cpu_driver(dev);
  72        int i;
  73
  74        if (!drv)
  75                return -ENODEV;
  76
  77        /* Find lowest-power state that supports long-term idle */
  78        for (i = drv->state_count - 1; i >= CPUIDLE_DRIVER_STATE_START; i--)
  79                if (drv->states[i].enter_dead)
  80                        return drv->states[i].enter_dead(dev, i);
  81
  82        return -ENODEV;
  83}
  84
  85/**
  86 * cpuidle_enter_state - enter the state and update stats
  87 * @dev: cpuidle device for this cpu
  88 * @drv: cpuidle driver for this cpu
  89 * @next_state: index into drv->states of the state to enter
  90 */
  91int cpuidle_enter_state(struct cpuidle_device *dev, struct cpuidle_driver *drv,
  92                int next_state)
  93{
  94        int entered_state;
  95
  96        entered_state = cpuidle_enter_ops(dev, drv, next_state);
  97
  98        if (entered_state >= 0) {
  99                /* Update cpuidle counters */
 100                /* This can be moved to within driver enter routine
 101                 * but that results in multiple copies of same code.
 102                 */
 103                dev->states_usage[entered_state].time += dev->last_residency;
 104                dev->states_usage[entered_state].usage++;
 105        } else {
 106                dev->last_residency = 0;
 107        }
 108
 109        return entered_state;
 110}
 111
 112/**
 113 * cpuidle_idle_call - the main idle loop
 114 *
 115 * NOTE: no locks or semaphores should be used here
 116 * return non-zero on failure
 117 */
 118int cpuidle_idle_call(void)
 119{
 120        struct cpuidle_device *dev = __this_cpu_read(cpuidle_devices);
 121        struct cpuidle_driver *drv;
 122        int next_state, entered_state;
 123
 124        if (off)
 125                return -ENODEV;
 126
 127        if (!initialized)
 128                return -ENODEV;
 129
 130        /* check if the device is ready */
 131        if (!dev || !dev->enabled)
 132                return -EBUSY;
 133
 134        drv = cpuidle_get_cpu_driver(dev);
 135
 136        /* ask the governor for the next state */
 137        next_state = cpuidle_curr_governor->select(drv, dev);
 138        if (need_resched()) {
 139                dev->last_residency = 0;
 140                /* give the governor an opportunity to reflect on the outcome */
 141                if (cpuidle_curr_governor->reflect)
 142                        cpuidle_curr_governor->reflect(dev, next_state);
 143                local_irq_enable();
 144                return 0;
 145        }
 146
 147        trace_power_start_rcuidle(POWER_CSTATE, next_state, dev->cpu);
 148        trace_cpu_idle_rcuidle(next_state, dev->cpu);
 149
 150        if (cpuidle_state_is_coupled(dev, drv, next_state))
 151                entered_state = cpuidle_enter_state_coupled(dev, drv,
 152                                                            next_state);
 153        else
 154                entered_state = cpuidle_enter_state(dev, drv, next_state);
 155
 156        trace_power_end_rcuidle(dev->cpu);
 157        trace_cpu_idle_rcuidle(PWR_EVENT_EXIT, dev->cpu);
 158
 159        /* give the governor an opportunity to reflect on the outcome */
 160        if (cpuidle_curr_governor->reflect)
 161                cpuidle_curr_governor->reflect(dev, entered_state);
 162
 163        return 0;
 164}
 165
 166/**
 167 * cpuidle_install_idle_handler - installs the cpuidle idle loop handler
 168 */
 169void cpuidle_install_idle_handler(void)
 170{
 171        if (enabled_devices) {
 172                /* Make sure all changes finished before we switch to new idle */
 173                smp_wmb();
 174                initialized = 1;
 175        }
 176}
 177
 178/**
 179 * cpuidle_uninstall_idle_handler - uninstalls the cpuidle idle loop handler
 180 */
 181void cpuidle_uninstall_idle_handler(void)
 182{
 183        if (enabled_devices) {
 184                initialized = 0;
 185                kick_all_cpus_sync();
 186        }
 187}
 188
 189/**
 190 * cpuidle_pause_and_lock - temporarily disables CPUIDLE
 191 */
 192void cpuidle_pause_and_lock(void)
 193{
 194        mutex_lock(&cpuidle_lock);
 195        cpuidle_uninstall_idle_handler();
 196}
 197
 198EXPORT_SYMBOL_GPL(cpuidle_pause_and_lock);
 199
 200/**
 201 * cpuidle_resume_and_unlock - resumes CPUIDLE operation
 202 */
 203void cpuidle_resume_and_unlock(void)
 204{
 205        cpuidle_install_idle_handler();
 206        mutex_unlock(&cpuidle_lock);
 207}
 208
 209EXPORT_SYMBOL_GPL(cpuidle_resume_and_unlock);
 210
 211/* Currently used in suspend/resume path to suspend cpuidle */
 212void cpuidle_pause(void)
 213{
 214        mutex_lock(&cpuidle_lock);
 215        cpuidle_uninstall_idle_handler();
 216        mutex_unlock(&cpuidle_lock);
 217}
 218
 219/* Currently used in suspend/resume path to resume cpuidle */
 220void cpuidle_resume(void)
 221{
 222        mutex_lock(&cpuidle_lock);
 223        cpuidle_install_idle_handler();
 224        mutex_unlock(&cpuidle_lock);
 225}
 226
 227/**
 228 * cpuidle_wrap_enter - performs timekeeping and irqen around enter function
 229 * @dev: pointer to a valid cpuidle_device object
 230 * @drv: pointer to a valid cpuidle_driver object
 231 * @index: index of the target cpuidle state.
 232 */
 233int cpuidle_wrap_enter(struct cpuidle_device *dev,
 234                                struct cpuidle_driver *drv, int index,
 235                                int (*enter)(struct cpuidle_device *dev,
 236                                        struct cpuidle_driver *drv, int index))
 237{
 238        ktime_t time_start, time_end;
 239        s64 diff;
 240
 241        time_start = ktime_get();
 242
 243        index = enter(dev, drv, index);
 244
 245        time_end = ktime_get();
 246
 247        local_irq_enable();
 248
 249        diff = ktime_to_us(ktime_sub(time_end, time_start));
 250        if (diff > INT_MAX)
 251                diff = INT_MAX;
 252
 253        dev->last_residency = (int) diff;
 254
 255        return index;
 256}
 257
 258#ifdef CONFIG_ARCH_HAS_CPU_RELAX
 259static int poll_idle(struct cpuidle_device *dev,
 260                struct cpuidle_driver *drv, int index)
 261{
 262        ktime_t t1, t2;
 263        s64 diff;
 264
 265        t1 = ktime_get();
 266        local_irq_enable();
 267        while (!need_resched())
 268                cpu_relax();
 269
 270        t2 = ktime_get();
 271        diff = ktime_to_us(ktime_sub(t2, t1));
 272        if (diff > INT_MAX)
 273                diff = INT_MAX;
 274
 275        dev->last_residency = (int) diff;
 276
 277        return index;
 278}
 279
 280static void poll_idle_init(struct cpuidle_driver *drv)
 281{
 282        struct cpuidle_state *state = &drv->states[0];
 283
 284        snprintf(state->name, CPUIDLE_NAME_LEN, "POLL");
 285        snprintf(state->desc, CPUIDLE_DESC_LEN, "CPUIDLE CORE POLL IDLE");
 286        state->exit_latency = 0;
 287        state->target_residency = 0;
 288        state->power_usage = -1;
 289        state->flags = 0;
 290        state->enter = poll_idle;
 291        state->disabled = false;
 292}
 293#else
 294static void poll_idle_init(struct cpuidle_driver *drv) {}
 295#endif /* CONFIG_ARCH_HAS_CPU_RELAX */
 296
 297/**
 298 * cpuidle_enable_device - enables idle PM for a CPU
 299 * @dev: the CPU
 300 *
 301 * This function must be called between cpuidle_pause_and_lock and
 302 * cpuidle_resume_and_unlock when used externally.
 303 */
 304int cpuidle_enable_device(struct cpuidle_device *dev)
 305{
 306        int ret, i;
 307        struct cpuidle_driver *drv;
 308
 309        if (!dev)
 310                return -EINVAL;
 311
 312        if (dev->enabled)
 313                return 0;
 314
 315        drv = cpuidle_get_cpu_driver(dev);
 316
 317        if (!drv || !cpuidle_curr_governor)
 318                return -EIO;
 319
 320        if (!dev->state_count)
 321                dev->state_count = drv->state_count;
 322
 323        if (dev->registered == 0) {
 324                ret = __cpuidle_register_device(dev);
 325                if (ret)
 326                        return ret;
 327        }
 328
 329        cpuidle_enter_ops = drv->en_core_tk_irqen ?
 330                cpuidle_enter_tk : cpuidle_enter;
 331
 332        poll_idle_init(drv);
 333
 334        ret = cpuidle_add_device_sysfs(dev);
 335        if (ret)
 336                return ret;
 337
 338        if (cpuidle_curr_governor->enable &&
 339            (ret = cpuidle_curr_governor->enable(drv, dev)))
 340                goto fail_sysfs;
 341
 342        for (i = 0; i < dev->state_count; i++) {
 343                dev->states_usage[i].usage = 0;
 344                dev->states_usage[i].time = 0;
 345        }
 346        dev->last_residency = 0;
 347
 348        smp_wmb();
 349
 350        dev->enabled = 1;
 351
 352        enabled_devices++;
 353        return 0;
 354
 355fail_sysfs:
 356        cpuidle_remove_device_sysfs(dev);
 357
 358        return ret;
 359}
 360
 361EXPORT_SYMBOL_GPL(cpuidle_enable_device);
 362
 363/**
 364 * cpuidle_disable_device - disables idle PM for a CPU
 365 * @dev: the CPU
 366 *
 367 * This function must be called between cpuidle_pause_and_lock and
 368 * cpuidle_resume_and_unlock when used externally.
 369 */
 370void cpuidle_disable_device(struct cpuidle_device *dev)
 371{
 372        struct cpuidle_driver *drv = cpuidle_get_cpu_driver(dev);
 373
 374        if (!dev || !dev->enabled)
 375                return;
 376
 377        if (!drv || !cpuidle_curr_governor)
 378                return;
 379
 380        dev->enabled = 0;
 381
 382        if (cpuidle_curr_governor->disable)
 383                cpuidle_curr_governor->disable(drv, dev);
 384
 385        cpuidle_remove_device_sysfs(dev);
 386        enabled_devices--;
 387}
 388
 389EXPORT_SYMBOL_GPL(cpuidle_disable_device);
 390
 391/**
 392 * __cpuidle_register_device - internal register function called before register
 393 * and enable routines
 394 * @dev: the cpu
 395 *
 396 * cpuidle_lock mutex must be held before this is called
 397 */
 398static int __cpuidle_register_device(struct cpuidle_device *dev)
 399{
 400        int ret;
 401        struct cpuidle_driver *drv = cpuidle_get_cpu_driver(dev);
 402
 403        if (!try_module_get(drv->owner))
 404                return -EINVAL;
 405
 406        per_cpu(cpuidle_devices, dev->cpu) = dev;
 407        list_add(&dev->device_list, &cpuidle_detected_devices);
 408        ret = cpuidle_add_sysfs(dev);
 409        if (ret)
 410                goto err_sysfs;
 411
 412        ret = cpuidle_coupled_register_device(dev);
 413        if (ret)
 414                goto err_coupled;
 415
 416        dev->registered = 1;
 417        return 0;
 418
 419err_coupled:
 420        cpuidle_remove_sysfs(dev);
 421err_sysfs:
 422        list_del(&dev->device_list);
 423        per_cpu(cpuidle_devices, dev->cpu) = NULL;
 424        module_put(drv->owner);
 425        return ret;
 426}
 427
 428/**
 429 * cpuidle_register_device - registers a CPU's idle PM feature
 430 * @dev: the cpu
 431 */
 432int cpuidle_register_device(struct cpuidle_device *dev)
 433{
 434        int ret;
 435
 436        if (!dev)
 437                return -EINVAL;
 438
 439        mutex_lock(&cpuidle_lock);
 440
 441        if ((ret = __cpuidle_register_device(dev))) {
 442                mutex_unlock(&cpuidle_lock);
 443                return ret;
 444        }
 445
 446        cpuidle_enable_device(dev);
 447        cpuidle_install_idle_handler();
 448
 449        mutex_unlock(&cpuidle_lock);
 450
 451        return 0;
 452
 453}
 454
 455EXPORT_SYMBOL_GPL(cpuidle_register_device);
 456
 457/**
 458 * cpuidle_unregister_device - unregisters a CPU's idle PM feature
 459 * @dev: the cpu
 460 */
 461void cpuidle_unregister_device(struct cpuidle_device *dev)
 462{
 463        struct cpuidle_driver *drv = cpuidle_get_cpu_driver(dev);
 464
 465        if (dev->registered == 0)
 466                return;
 467
 468        cpuidle_pause_and_lock();
 469
 470        cpuidle_disable_device(dev);
 471
 472        cpuidle_remove_sysfs(dev);
 473        list_del(&dev->device_list);
 474        per_cpu(cpuidle_devices, dev->cpu) = NULL;
 475
 476        cpuidle_coupled_unregister_device(dev);
 477
 478        cpuidle_resume_and_unlock();
 479
 480        module_put(drv->owner);
 481}
 482
 483EXPORT_SYMBOL_GPL(cpuidle_unregister_device);
 484
 485#ifdef CONFIG_SMP
 486
 487static void smp_callback(void *v)
 488{
 489        /* we already woke the CPU up, nothing more to do */
 490}
 491
 492/*
 493 * This function gets called when a part of the kernel has a new latency
 494 * requirement.  This means we need to get all processors out of their C-state,
 495 * and then recalculate a new suitable C-state. Just do a cross-cpu IPI; that
 496 * wakes them all right up.
 497 */
 498static int cpuidle_latency_notify(struct notifier_block *b,
 499                unsigned long l, void *v)
 500{
 501        smp_call_function(smp_callback, NULL, 1);
 502        return NOTIFY_OK;
 503}
 504
 505static struct notifier_block cpuidle_latency_notifier = {
 506        .notifier_call = cpuidle_latency_notify,
 507};
 508
 509static inline void latency_notifier_init(struct notifier_block *n)
 510{
 511        pm_qos_add_notifier(PM_QOS_CPU_DMA_LATENCY, n);
 512}
 513
 514#else /* CONFIG_SMP */
 515
 516#define latency_notifier_init(x) do { } while (0)
 517
 518#endif /* CONFIG_SMP */
 519
 520/**
 521 * cpuidle_init - core initializer
 522 */
 523static int __init cpuidle_init(void)
 524{
 525        int ret;
 526
 527        if (cpuidle_disabled())
 528                return -ENODEV;
 529
 530        ret = cpuidle_add_interface(cpu_subsys.dev_root);
 531        if (ret)
 532                return ret;
 533
 534        latency_notifier_init(&cpuidle_latency_notifier);
 535
 536        return 0;
 537}
 538
 539module_param(off, int, 0444);
 540core_initcall(cpuidle_init);
 541
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