linux/drivers/cpuidle/cpuidle.c
<<
>>
Prefs
   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_driver();
  72        int i, dead_state = -1;
  73        int power_usage = -1;
  74
  75        if (!drv)
  76                return -ENODEV;
  77
  78        /* Find lowest-power state that supports long-term idle */
  79        for (i = CPUIDLE_DRIVER_STATE_START; i < drv->state_count; i++) {
  80                struct cpuidle_state *s = &drv->states[i];
  81
  82                if (s->power_usage < power_usage && s->enter_dead) {
  83                        power_usage = s->power_usage;
  84                        dead_state = i;
  85                }
  86        }
  87
  88        if (dead_state != -1)
  89                return drv->states[dead_state].enter_dead(dev, dead_state);
  90
  91        return -ENODEV;
  92}
  93
  94/**
  95 * cpuidle_enter_state - enter the state and update stats
  96 * @dev: cpuidle device for this cpu
  97 * @drv: cpuidle driver for this cpu
  98 * @next_state: index into drv->states of the state to enter
  99 */
 100int cpuidle_enter_state(struct cpuidle_device *dev, struct cpuidle_driver *drv,
 101                int next_state)
 102{
 103        int entered_state;
 104
 105        entered_state = cpuidle_enter_ops(dev, drv, next_state);
 106
 107        if (entered_state >= 0) {
 108                /* Update cpuidle counters */
 109                /* This can be moved to within driver enter routine
 110                 * but that results in multiple copies of same code.
 111                 */
 112                dev->states_usage[entered_state].time +=
 113                                (unsigned long long)dev->last_residency;
 114                dev->states_usage[entered_state].usage++;
 115        } else {
 116                dev->last_residency = 0;
 117        }
 118
 119        return entered_state;
 120}
 121
 122/**
 123 * cpuidle_idle_call - the main idle loop
 124 *
 125 * NOTE: no locks or semaphores should be used here
 126 * return non-zero on failure
 127 */
 128int cpuidle_idle_call(void)
 129{
 130        struct cpuidle_device *dev = __this_cpu_read(cpuidle_devices);
 131        struct cpuidle_driver *drv = cpuidle_get_driver();
 132        int next_state, entered_state;
 133
 134        if (off)
 135                return -ENODEV;
 136
 137        if (!initialized)
 138                return -ENODEV;
 139
 140        /* check if the device is ready */
 141        if (!dev || !dev->enabled)
 142                return -EBUSY;
 143
 144        /* ask the governor for the next state */
 145        next_state = cpuidle_curr_governor->select(drv, dev);
 146        if (need_resched()) {
 147                local_irq_enable();
 148                return 0;
 149        }
 150
 151        trace_power_start_rcuidle(POWER_CSTATE, next_state, dev->cpu);
 152        trace_cpu_idle_rcuidle(next_state, dev->cpu);
 153
 154        if (cpuidle_state_is_coupled(dev, drv, next_state))
 155                entered_state = cpuidle_enter_state_coupled(dev, drv,
 156                                                            next_state);
 157        else
 158                entered_state = cpuidle_enter_state(dev, drv, next_state);
 159
 160        trace_power_end_rcuidle(dev->cpu);
 161        trace_cpu_idle_rcuidle(PWR_EVENT_EXIT, dev->cpu);
 162
 163        /* give the governor an opportunity to reflect on the outcome */
 164        if (cpuidle_curr_governor->reflect)
 165                cpuidle_curr_governor->reflect(dev, entered_state);
 166
 167        return 0;
 168}
 169
 170/**
 171 * cpuidle_install_idle_handler - installs the cpuidle idle loop handler
 172 */
 173void cpuidle_install_idle_handler(void)
 174{
 175        if (enabled_devices) {
 176                /* Make sure all changes finished before we switch to new idle */
 177                smp_wmb();
 178                initialized = 1;
 179        }
 180}
 181
 182/**
 183 * cpuidle_uninstall_idle_handler - uninstalls the cpuidle idle loop handler
 184 */
 185void cpuidle_uninstall_idle_handler(void)
 186{
 187        if (enabled_devices) {
 188                initialized = 0;
 189                kick_all_cpus_sync();
 190        }
 191}
 192
 193/**
 194 * cpuidle_pause_and_lock - temporarily disables CPUIDLE
 195 */
 196void cpuidle_pause_and_lock(void)
 197{
 198        mutex_lock(&cpuidle_lock);
 199        cpuidle_uninstall_idle_handler();
 200}
 201
 202EXPORT_SYMBOL_GPL(cpuidle_pause_and_lock);
 203
 204/**
 205 * cpuidle_resume_and_unlock - resumes CPUIDLE operation
 206 */
 207void cpuidle_resume_and_unlock(void)
 208{
 209        cpuidle_install_idle_handler();
 210        mutex_unlock(&cpuidle_lock);
 211}
 212
 213EXPORT_SYMBOL_GPL(cpuidle_resume_and_unlock);
 214
 215/* Currently used in suspend/resume path to suspend cpuidle */
 216void cpuidle_pause(void)
 217{
 218        mutex_lock(&cpuidle_lock);
 219        cpuidle_uninstall_idle_handler();
 220        mutex_unlock(&cpuidle_lock);
 221}
 222
 223/* Currently used in suspend/resume path to resume cpuidle */
 224void cpuidle_resume(void)
 225{
 226        mutex_lock(&cpuidle_lock);
 227        cpuidle_install_idle_handler();
 228        mutex_unlock(&cpuidle_lock);
 229}
 230
 231/**
 232 * cpuidle_wrap_enter - performs timekeeping and irqen around enter function
 233 * @dev: pointer to a valid cpuidle_device object
 234 * @drv: pointer to a valid cpuidle_driver object
 235 * @index: index of the target cpuidle state.
 236 */
 237int cpuidle_wrap_enter(struct cpuidle_device *dev,
 238                                struct cpuidle_driver *drv, int index,
 239                                int (*enter)(struct cpuidle_device *dev,
 240                                        struct cpuidle_driver *drv, int index))
 241{
 242        ktime_t time_start, time_end;
 243        s64 diff;
 244
 245        time_start = ktime_get();
 246
 247        index = enter(dev, drv, index);
 248
 249        time_end = ktime_get();
 250
 251        local_irq_enable();
 252
 253        diff = ktime_to_us(ktime_sub(time_end, time_start));
 254        if (diff > INT_MAX)
 255                diff = INT_MAX;
 256
 257        dev->last_residency = (int) diff;
 258
 259        return index;
 260}
 261
 262#ifdef CONFIG_ARCH_HAS_CPU_RELAX
 263static int poll_idle(struct cpuidle_device *dev,
 264                struct cpuidle_driver *drv, int index)
 265{
 266        ktime_t t1, t2;
 267        s64 diff;
 268
 269        t1 = ktime_get();
 270        local_irq_enable();
 271        while (!need_resched())
 272                cpu_relax();
 273
 274        t2 = ktime_get();
 275        diff = ktime_to_us(ktime_sub(t2, t1));
 276        if (diff > INT_MAX)
 277                diff = INT_MAX;
 278
 279        dev->last_residency = (int) diff;
 280
 281        return index;
 282}
 283
 284static void poll_idle_init(struct cpuidle_driver *drv)
 285{
 286        struct cpuidle_state *state = &drv->states[0];
 287
 288        snprintf(state->name, CPUIDLE_NAME_LEN, "POLL");
 289        snprintf(state->desc, CPUIDLE_DESC_LEN, "CPUIDLE CORE POLL IDLE");
 290        state->exit_latency = 0;
 291        state->target_residency = 0;
 292        state->power_usage = -1;
 293        state->flags = 0;
 294        state->enter = poll_idle;
 295        state->disabled = false;
 296}
 297#else
 298static void poll_idle_init(struct cpuidle_driver *drv) {}
 299#endif /* CONFIG_ARCH_HAS_CPU_RELAX */
 300
 301/**
 302 * cpuidle_enable_device - enables idle PM for a CPU
 303 * @dev: the CPU
 304 *
 305 * This function must be called between cpuidle_pause_and_lock and
 306 * cpuidle_resume_and_unlock when used externally.
 307 */
 308int cpuidle_enable_device(struct cpuidle_device *dev)
 309{
 310        int ret, i;
 311        struct cpuidle_driver *drv = cpuidle_get_driver();
 312
 313        if (!dev)
 314                return -EINVAL;
 315
 316        if (dev->enabled)
 317                return 0;
 318        if (!drv || !cpuidle_curr_governor)
 319                return -EIO;
 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        if ((ret = cpuidle_add_state_sysfs(dev)))
 335                return ret;
 336
 337        if (cpuidle_curr_governor->enable &&
 338            (ret = cpuidle_curr_governor->enable(drv, dev)))
 339                goto fail_sysfs;
 340
 341        for (i = 0; i < dev->state_count; i++) {
 342                dev->states_usage[i].usage = 0;
 343                dev->states_usage[i].time = 0;
 344        }
 345        dev->last_residency = 0;
 346
 347        smp_wmb();
 348
 349        dev->enabled = 1;
 350
 351        enabled_devices++;
 352        return 0;
 353
 354fail_sysfs:
 355        cpuidle_remove_state_sysfs(dev);
 356
 357        return ret;
 358}
 359
 360EXPORT_SYMBOL_GPL(cpuidle_enable_device);
 361
 362/**
 363 * cpuidle_disable_device - disables idle PM for a CPU
 364 * @dev: the CPU
 365 *
 366 * This function must be called between cpuidle_pause_and_lock and
 367 * cpuidle_resume_and_unlock when used externally.
 368 */
 369void cpuidle_disable_device(struct cpuidle_device *dev)
 370{
 371        if (!dev->enabled)
 372                return;
 373        if (!cpuidle_get_driver() || !cpuidle_curr_governor)
 374                return;
 375
 376        dev->enabled = 0;
 377
 378        if (cpuidle_curr_governor->disable)
 379                cpuidle_curr_governor->disable(cpuidle_get_driver(), dev);
 380
 381        cpuidle_remove_state_sysfs(dev);
 382        enabled_devices--;
 383}
 384
 385EXPORT_SYMBOL_GPL(cpuidle_disable_device);
 386
 387/**
 388 * __cpuidle_register_device - internal register function called before register
 389 * and enable routines
 390 * @dev: the cpu
 391 *
 392 * cpuidle_lock mutex must be held before this is called
 393 */
 394static int __cpuidle_register_device(struct cpuidle_device *dev)
 395{
 396        int ret;
 397        struct device *cpu_dev = get_cpu_device((unsigned long)dev->cpu);
 398        struct cpuidle_driver *cpuidle_driver = cpuidle_get_driver();
 399
 400        if (!try_module_get(cpuidle_driver->owner))
 401                return -EINVAL;
 402
 403        init_completion(&dev->kobj_unregister);
 404
 405        per_cpu(cpuidle_devices, dev->cpu) = dev;
 406        list_add(&dev->device_list, &cpuidle_detected_devices);
 407        ret = cpuidle_add_sysfs(cpu_dev);
 408        if (ret)
 409                goto err_sysfs;
 410
 411        ret = cpuidle_coupled_register_device(dev);
 412        if (ret)
 413                goto err_coupled;
 414
 415        dev->registered = 1;
 416        return 0;
 417
 418err_coupled:
 419        cpuidle_remove_sysfs(cpu_dev);
 420        wait_for_completion(&dev->kobj_unregister);
 421err_sysfs:
 422        list_del(&dev->device_list);
 423        per_cpu(cpuidle_devices, dev->cpu) = NULL;
 424        module_put(cpuidle_driver->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 device *cpu_dev = get_cpu_device((unsigned long)dev->cpu);
 464        struct cpuidle_driver *cpuidle_driver = cpuidle_get_driver();
 465
 466        if (dev->registered == 0)
 467                return;
 468
 469        cpuidle_pause_and_lock();
 470
 471        cpuidle_disable_device(dev);
 472
 473        cpuidle_remove_sysfs(cpu_dev);
 474        list_del(&dev->device_list);
 475        wait_for_completion(&dev->kobj_unregister);
 476        per_cpu(cpuidle_devices, dev->cpu) = NULL;
 477
 478        cpuidle_coupled_unregister_device(dev);
 479
 480        cpuidle_resume_and_unlock();
 481
 482        module_put(cpuidle_driver->owner);
 483}
 484
 485EXPORT_SYMBOL_GPL(cpuidle_unregister_device);
 486
 487#ifdef CONFIG_SMP
 488
 489static void smp_callback(void *v)
 490{
 491        /* we already woke the CPU up, nothing more to do */
 492}
 493
 494/*
 495 * This function gets called when a part of the kernel has a new latency
 496 * requirement.  This means we need to get all processors out of their C-state,
 497 * and then recalculate a new suitable C-state. Just do a cross-cpu IPI; that
 498 * wakes them all right up.
 499 */
 500static int cpuidle_latency_notify(struct notifier_block *b,
 501                unsigned long l, void *v)
 502{
 503        smp_call_function(smp_callback, NULL, 1);
 504        return NOTIFY_OK;
 505}
 506
 507static struct notifier_block cpuidle_latency_notifier = {
 508        .notifier_call = cpuidle_latency_notify,
 509};
 510
 511static inline void latency_notifier_init(struct notifier_block *n)
 512{
 513        pm_qos_add_notifier(PM_QOS_CPU_DMA_LATENCY, n);
 514}
 515
 516#else /* CONFIG_SMP */
 517
 518#define latency_notifier_init(x) do { } while (0)
 519
 520#endif /* CONFIG_SMP */
 521
 522/**
 523 * cpuidle_init - core initializer
 524 */
 525static int __init cpuidle_init(void)
 526{
 527        int ret;
 528
 529        if (cpuidle_disabled())
 530                return -ENODEV;
 531
 532        ret = cpuidle_add_interface(cpu_subsys.dev_root);
 533        if (ret)
 534                return ret;
 535
 536        latency_notifier_init(&cpuidle_latency_notifier);
 537
 538        return 0;
 539}
 540
 541module_param(off, int, 0444);
 542core_initcall(cpuidle_init);
 543
lxr.linux.no kindly hosted by Redpill Linpro AS, provider of Linux consulting and operations services since 1995.