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