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