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