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/kernel.h>
  12 #include <linux/mutex.h>
  13 #include <linux/sched.h>
  14 #include <linux/notifier.h>
  15 #include <linux/pm_qos_params.h>
  16 #include <linux/cpu.h>
  17 #include <linux/cpuidle.h>
  18 #include <linux/ktime.h>
  19 #include <linux/hrtimer.h>
  20 #include <trace/events/power.h>
  21
  22 #include "cpuidle.h"
  23
  24 DEFINE_PER_CPU(struct cpuidle_device *, cpuidle_devices);
  25
  26 DEFINE_MUTEX(cpuidle_lock);
  27 LIST_HEAD(cpuidle_detected_devices);
  28
  29 static int enabled_devices;
  30 static int off __read_mostly;
  31 static int initialized __read_mostly;
  32
  33 int cpuidle_disabled(void)
  34 {
  35         return off;
  36 }
  37 void disable_cpuidle(void)
  38 {
  39         off = 1;
  40 }
  41
  42 #if defined(CONFIG_ARCH_HAS_CPU_IDLE_WAIT)
  43 static void cpuidle_kick_cpus(void)
  44 {
  45         cpu_idle_wait();
  46 }
  47 #elif defined(CONFIG_SMP)
  48 # error "Arch needs cpu_idle_wait() equivalent here"
  49 #else /* !CONFIG_ARCH_HAS_CPU_IDLE_WAIT && !CONFIG_SMP */
  50 static void cpuidle_kick_cpus(void) {}
  51 #endif
  52
  53 static int __cpuidle_register_device(struct cpuidle_device *dev);
  54
  55 /**
  56  * cpuidle_idle_call - the main idle loop
  57  *
  58  * NOTE: no locks or semaphores should be used here
  59  * return non-zero on failure
  60  */
  61 int cpuidle_idle_call(void)
  62 {
  63         struct cpuidle_device *dev = __this_cpu_read(cpuidle_devices);
  64         struct cpuidle_state *target_state;
  65         int next_state;
  66
  67         if (off)
  68                 return -ENODEV;
  69
  70         if (!initialized)
  71                 return -ENODEV;
  72
  73         /* check if the device is ready */
  74         if (!dev || !dev->enabled)
  75                 return -EBUSY;
  76
  77 #if 0
  78         /* shows regressions, re-enable for 2.6.29 */
  79         /*
  80          * run any timers that can be run now, at this point
  81          * before calculating the idle duration etc.
  82          */
  83         hrtimer_peek_ahead_timers();
  84 #endif
  85
  86         /*
  87          * Call the device's prepare function before calling the
  88          * governor's select function.  ->prepare gives the device's
  89          * cpuidle driver a chance to update any dynamic information
  90          * of its cpuidle states for the current idle period, e.g.
  91          * state availability, latencies, residencies, etc.
  92          */
  93         if (dev->prepare)
  94                 dev->prepare(dev);
  95
  96         /* ask the governor for the next state */
  97         next_state = cpuidle_curr_governor->select(dev);
  98         if (need_resched()) {
  99                 local_irq_enable();
 100                 return 0;
 101         }
 102
 103         target_state = &dev->states[next_state];
 104
 105         /* enter the state and update stats */
 106         dev->last_state = target_state;
 107
 108         trace_power_start(POWER_CSTATE, next_state, dev->cpu);
 109         trace_cpu_idle(next_state, dev->cpu);
 110
 111         dev->last_residency = target_state->enter(dev, target_state);
 112
 113         trace_power_end(dev->cpu);
 114         trace_cpu_idle(PWR_EVENT_EXIT, dev->cpu);
 115
 116         if (dev->last_state)
 117                 target_state = dev->last_state;
 118
 119         target_state->time += (unsigned long long)dev->last_residency;
 120         target_state->usage++;
 121
 122         /* give the governor an opportunity to reflect on the outcome */
 123         if (cpuidle_curr_governor->reflect)
 124                 cpuidle_curr_governor->reflect(dev);
 125
 126         return 0;
 127 }
 128
 129 /**
 130  * cpuidle_install_idle_handler - installs the cpuidle idle loop handler
 131  */
 132 void cpuidle_install_idle_handler(void)
 133 {
 134         if (enabled_devices) {
 135                 /* Make sure all changes finished before we switch to new idle */
 136                 smp_wmb();
 137                 initialized = 1;
 138         }
 139 }
 140
 141 /**
 142  * cpuidle_uninstall_idle_handler - uninstalls the cpuidle idle loop handler
 143  */
 144 void cpuidle_uninstall_idle_handler(void)
 145 {
 146         if (enabled_devices) {
 147                 initialized = 0;
 148                 cpuidle_kick_cpus();
 149         }
 150 }
 151
 152 /**
 153  * cpuidle_pause_and_lock - temporarily disables CPUIDLE
 154  */
 155 void cpuidle_pause_and_lock(void)
 156 {
 157         mutex_lock(&cpuidle_lock);
 158         cpuidle_uninstall_idle_handler();
 159 }
 160
 161 EXPORT_SYMBOL_GPL(cpuidle_pause_and_lock);
 162
 163 /**
 164  * cpuidle_resume_and_unlock - resumes CPUIDLE operation
 165  */
 166 void cpuidle_resume_and_unlock(void)
 167 {
 168         cpuidle_install_idle_handler();
 169         mutex_unlock(&cpuidle_lock);
 170 }
 171
 172 EXPORT_SYMBOL_GPL(cpuidle_resume_and_unlock);
 173
 174 #ifdef CONFIG_ARCH_HAS_CPU_RELAX
 175 static int poll_idle(struct cpuidle_device *dev, struct cpuidle_state *st)
 176 {
 177         ktime_t t1, t2;
 178         s64 diff;
 179         int ret;
 180
 181         t1 = ktime_get();
 182         local_irq_enable();
 183         while (!need_resched())
 184                 cpu_relax();
 185
 186         t2 = ktime_get();
 187         diff = ktime_to_us(ktime_sub(t2, t1));
 188         if (diff > INT_MAX)
 189                 diff = INT_MAX;
 190
 191         ret = (int) diff;
 192         return ret;
 193 }
 194
 195 static void poll_idle_init(struct cpuidle_device *dev)
 196 {
 197         struct cpuidle_state *state = &dev->states[0];
 198
 199         cpuidle_set_statedata(state, NULL);
 200
 201         snprintf(state->name, CPUIDLE_NAME_LEN, "POLL");
 202         snprintf(state->desc, CPUIDLE_DESC_LEN, "CPUIDLE CORE POLL IDLE");
 203         state->exit_latency = 0;
 204         state->target_residency = 0;
 205         state->power_usage = -1;
 206         state->flags = 0;
 207         state->enter = poll_idle;
 208 }
 209 #else
 210 static void poll_idle_init(struct cpuidle_device *dev) {}
 211 #endif /* CONFIG_ARCH_HAS_CPU_RELAX */
 212
 213 /**
 214  * cpuidle_enable_device - enables idle PM for a CPU
 215  * @dev: the CPU
 216  *
 217  * This function must be called between cpuidle_pause_and_lock and
 218  * cpuidle_resume_and_unlock when used externally.
 219  */
 220 int cpuidle_enable_device(struct cpuidle_device *dev)
 221 {
 222         int ret, i;
 223
 224         if (dev->enabled)
 225                 return 0;
 226         if (!cpuidle_get_driver() || !cpuidle_curr_governor)
 227                 return -EIO;
 228         if (!dev->state_count)
 229                 return -EINVAL;
 230
 231         if (dev->registered == 0) {
 232                 ret = __cpuidle_register_device(dev);
 233                 if (ret)
 234                         return ret;
 235         }
 236
 237         poll_idle_init(dev);
 238
 239         if ((ret = cpuidle_add_state_sysfs(dev)))
 240                 return ret;
 241
 242         if (cpuidle_curr_governor->enable &&
 243             (ret = cpuidle_curr_governor->enable(dev)))
 244                 goto fail_sysfs;
 245
 246         for (i = 0; i < dev->state_count; i++) {
 247                 dev->states[i].usage = 0;
 248                 dev->states[i].time = 0;
 249         }
 250         dev->last_residency = 0;
 251         dev->last_state = NULL;
 252
 253         smp_wmb();
 254
 255         dev->enabled = 1;
 256
 257         enabled_devices++;
 258         return 0;
 259
 260 fail_sysfs:
 261         cpuidle_remove_state_sysfs(dev);
 262
 263         return ret;
 264 }
 265
 266 EXPORT_SYMBOL_GPL(cpuidle_enable_device);
 267
 268 /**
 269  * cpuidle_disable_device - disables idle PM for a CPU
 270  * @dev: the CPU
 271  *
 272  * This function must be called between cpuidle_pause_and_lock and
 273  * cpuidle_resume_and_unlock when used externally.
 274  */
 275 void cpuidle_disable_device(struct cpuidle_device *dev)
 276 {
 277         if (!dev->enabled)
 278                 return;
 279         if (!cpuidle_get_driver() || !cpuidle_curr_governor)
 280                 return;
 281
 282         dev->enabled = 0;
 283
 284         if (cpuidle_curr_governor->disable)
 285                 cpuidle_curr_governor->disable(dev);
 286
 287         cpuidle_remove_state_sysfs(dev);
 288         enabled_devices--;
 289 }
 290
 291 EXPORT_SYMBOL_GPL(cpuidle_disable_device);
 292
 293 /**
 294  * __cpuidle_register_device - internal register function called before register
 295  * and enable routines
 296  * @dev: the cpu
 297  *
 298  * cpuidle_lock mutex must be held before this is called
 299  */
 300 static int __cpuidle_register_device(struct cpuidle_device *dev)
 301 {
 302         int ret;
 303         struct sys_device *sys_dev = get_cpu_sysdev((unsigned long)dev->cpu);
 304         struct cpuidle_driver *cpuidle_driver = cpuidle_get_driver();
 305
 306         if (!sys_dev)
 307                 return -EINVAL;
 308         if (!try_module_get(cpuidle_driver->owner))
 309                 return -EINVAL;
 310
 311         init_completion(&dev->kobj_unregister);
 312
 313         /*
 314          * cpuidle driver should set the dev->power_specified bit
 315          * before registering the device if the driver provides
 316          * power_usage numbers.
 317          *
 318          * For those devices whose ->power_specified is not set,
 319          * we fill in power_usage with decreasing values as the
 320          * cpuidle code has an implicit assumption that state Cn
 321          * uses less power than C(n-1).
 322          *
 323          * With CONFIG_ARCH_HAS_CPU_RELAX, C0 is already assigned
 324          * an power value of -1.  So we use -2, -3, etc, for other
 325          * c-states.
 326          */
 327         if (!dev->power_specified) {
 328                 int i;
 329                 for (i = CPUIDLE_DRIVER_STATE_START; i < dev->state_count; i++)
 330                         dev->states[i].power_usage = -1 - i;
 331         }
 332
 333         per_cpu(cpuidle_devices, dev->cpu) = dev;
 334         list_add(&dev->device_list, &cpuidle_detected_devices);
 335         if ((ret = cpuidle_add_sysfs(sys_dev))) {
 336                 module_put(cpuidle_driver->owner);
 337                 return ret;
 338         }
 339
 340         dev->registered = 1;
 341         return 0;
 342 }
 343
 344 /**
 345  * cpuidle_register_device - registers a CPU's idle PM feature
 346  * @dev: the cpu
 347  */
 348 int cpuidle_register_device(struct cpuidle_device *dev)
 349 {
 350         int ret;
 351
 352         mutex_lock(&cpuidle_lock);
 353
 354         if ((ret = __cpuidle_register_device(dev))) {
 355                 mutex_unlock(&cpuidle_lock);
 356                 return ret;
 357         }
 358
 359         cpuidle_enable_device(dev);
 360         cpuidle_install_idle_handler();
 361
 362         mutex_unlock(&cpuidle_lock);
 363
 364         return 0;
 365
 366 }
 367
 368 EXPORT_SYMBOL_GPL(cpuidle_register_device);
 369
 370 /**
 371  * cpuidle_unregister_device - unregisters a CPU's idle PM feature
 372  * @dev: the cpu
 373  */
 374 void cpuidle_unregister_device(struct cpuidle_device *dev)
 375 {
 376         struct sys_device *sys_dev = get_cpu_sysdev((unsigned long)dev->cpu);
 377         struct cpuidle_driver *cpuidle_driver = cpuidle_get_driver();
 378
 379         if (dev->registered == 0)
 380                 return;
 381
 382         cpuidle_pause_and_lock();
 383
 384         cpuidle_disable_device(dev);
 385
 386         cpuidle_remove_sysfs(sys_dev);
 387         list_del(&dev->device_list);
 388         wait_for_completion(&dev->kobj_unregister);
 389         per_cpu(cpuidle_devices, dev->cpu) = NULL;
 390
 391         cpuidle_resume_and_unlock();
 392
 393         module_put(cpuidle_driver->owner);
 394 }
 395
 396 EXPORT_SYMBOL_GPL(cpuidle_unregister_device);
 397
 398 #ifdef CONFIG_SMP
 399
 400 static void smp_callback(void *v)
 401 {
 402         /* we already woke the CPU up, nothing more to do */
 403 }
 404
 405 /*
 406  * This function gets called when a part of the kernel has a new latency
 407  * requirement.  This means we need to get all processors out of their C-state,
 408  * and then recalculate a new suitable C-state. Just do a cross-cpu IPI; that
 409  * wakes them all right up.
 410  */
 411 static int cpuidle_latency_notify(struct notifier_block *b,
 412                 unsigned long l, void *v)
 413 {
 414         smp_call_function(smp_callback, NULL, 1);
 415         return NOTIFY_OK;
 416 }
 417
 418 static struct notifier_block cpuidle_latency_notifier = {
 419         .notifier_call = cpuidle_latency_notify,
 420 };
 421
 422 static inline void latency_notifier_init(struct notifier_block *n)
 423 {
 424         pm_qos_add_notifier(PM_QOS_CPU_DMA_LATENCY, n);
 425 }
 426
 427 #else /* CONFIG_SMP */
 428
 429 #define latency_notifier_init(x) do { } while (0)
 430
 431 #endif /* CONFIG_SMP */
 432
 433 /**
 434  * cpuidle_init - core initializer
 435  */
 436 static int __init cpuidle_init(void)
 437 {
 438         int ret;
 439
 440         if (cpuidle_disabled())
 441                 return -ENODEV;
 442
 443         ret = cpuidle_add_class_sysfs(&cpu_sysdev_class);
 444         if (ret)
 445                 return ret;
 446
 447         latency_notifier_init(&cpuidle_latency_notifier);
 448
 449         return 0;
 450 }
 451
 452 module_param(off, int, 0444);
 453 core_initcall(cpuidle_init);