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         /*
  69          * run any timers that can be run now, at this point
  70          * before calculating the idle duration etc.
  71          */
  72         hrtimer_peek_ahead_timers();
  73
  74         /* ask the governor for the next state */
  75         next_state = cpuidle_curr_governor->select(dev);
  76         if (need_resched())
  77                 return;
  78         target_state = &dev->states[next_state];
  79
  80         /* enter the state and update stats */
  81         dev->last_state = target_state;
  82         dev->last_residency = target_state->enter(dev, target_state);
  83         if (dev->last_state)
  84                 target_state = dev->last_state;
  85
  86         target_state->time += (unsigned long long)dev->last_residency;
  87         target_state->usage++;
  88
  89         /* give the governor an opportunity to reflect on the outcome */
  90         if (cpuidle_curr_governor->reflect)
  91                 cpuidle_curr_governor->reflect(dev);
  92 }
  93
  94 /**
  95  * cpuidle_install_idle_handler - installs the cpuidle idle loop handler
  96  */
  97 void cpuidle_install_idle_handler(void)
  98 {
  99         if (enabled_devices && (pm_idle != cpuidle_idle_call)) {
 100                 /* Make sure all changes finished before we switch to new idle */
 101                 smp_wmb();
 102                 pm_idle = cpuidle_idle_call;
 103         }
 104 }
 105
 106 /**
 107  * cpuidle_uninstall_idle_handler - uninstalls the cpuidle idle loop handler
 108  */
 109 void cpuidle_uninstall_idle_handler(void)
 110 {
 111         if (enabled_devices && pm_idle_old && (pm_idle != pm_idle_old)) {
 112                 pm_idle = pm_idle_old;
 113                 cpuidle_kick_cpus();
 114         }
 115 }
 116
 117 /**
 118  * cpuidle_pause_and_lock - temporarily disables CPUIDLE
 119  */
 120 void cpuidle_pause_and_lock(void)
 121 {
 122         mutex_lock(&cpuidle_lock);
 123         cpuidle_uninstall_idle_handler();
 124 }
 125
 126 EXPORT_SYMBOL_GPL(cpuidle_pause_and_lock);
 127
 128 /**
 129  * cpuidle_resume_and_unlock - resumes CPUIDLE operation
 130  */
 131 void cpuidle_resume_and_unlock(void)
 132 {
 133         cpuidle_install_idle_handler();
 134         mutex_unlock(&cpuidle_lock);
 135 }
 136
 137 EXPORT_SYMBOL_GPL(cpuidle_resume_and_unlock);
 138
 139 /**
 140  * cpuidle_enable_device - enables idle PM for a CPU
 141  * @dev: the CPU
 142  *
 143  * This function must be called between cpuidle_pause_and_lock and
 144  * cpuidle_resume_and_unlock when used externally.
 145  */
 146 int cpuidle_enable_device(struct cpuidle_device *dev)
 147 {
 148         int ret, i;
 149
 150         if (dev->enabled)
 151                 return 0;
 152         if (!cpuidle_curr_driver || !cpuidle_curr_governor)
 153                 return -EIO;
 154         if (!dev->state_count)
 155                 return -EINVAL;
 156
 157         if (dev->registered == 0) {
 158                 ret = __cpuidle_register_device(dev);
 159                 if (ret)
 160                         return ret;
 161         }
 162
 163         if ((ret = cpuidle_add_state_sysfs(dev)))
 164                 return ret;
 165
 166         if (cpuidle_curr_governor->enable &&
 167             (ret = cpuidle_curr_governor->enable(dev)))
 168                 goto fail_sysfs;
 169
 170         for (i = 0; i < dev->state_count; i++) {
 171                 dev->states[i].usage = 0;
 172                 dev->states[i].time = 0;
 173         }
 174         dev->last_residency = 0;
 175         dev->last_state = NULL;
 176
 177         smp_wmb();
 178
 179         dev->enabled = 1;
 180
 181         enabled_devices++;
 182         return 0;
 183
 184 fail_sysfs:
 185         cpuidle_remove_state_sysfs(dev);
 186
 187         return ret;
 188 }
 189
 190 EXPORT_SYMBOL_GPL(cpuidle_enable_device);
 191
 192 /**
 193  * cpuidle_disable_device - disables idle PM for a CPU
 194  * @dev: the CPU
 195  *
 196  * This function must be called between cpuidle_pause_and_lock and
 197  * cpuidle_resume_and_unlock when used externally.
 198  */
 199 void cpuidle_disable_device(struct cpuidle_device *dev)
 200 {
 201         if (!dev->enabled)
 202                 return;
 203         if (!cpuidle_curr_driver || !cpuidle_curr_governor)
 204                 return;
 205
 206         dev->enabled = 0;
 207
 208         if (cpuidle_curr_governor->disable)
 209                 cpuidle_curr_governor->disable(dev);
 210
 211         cpuidle_remove_state_sysfs(dev);
 212         enabled_devices--;
 213 }
 214
 215 EXPORT_SYMBOL_GPL(cpuidle_disable_device);
 216
 217 #ifdef CONFIG_ARCH_HAS_CPU_RELAX
 218 static int poll_idle(struct cpuidle_device *dev, struct cpuidle_state *st)
 219 {
 220         ktime_t t1, t2;
 221         s64 diff;
 222         int ret;
 223
 224         t1 = ktime_get();
 225         local_irq_enable();
 226         while (!need_resched())
 227                 cpu_relax();
 228
 229         t2 = ktime_get();
 230         diff = ktime_to_us(ktime_sub(t2, t1));
 231         if (diff > INT_MAX)
 232                 diff = INT_MAX;
 233
 234         ret = (int) diff;
 235         return ret;
 236 }
 237
 238 static void poll_idle_init(struct cpuidle_device *dev)
 239 {
 240         struct cpuidle_state *state = &dev->states[0];
 241
 242         cpuidle_set_statedata(state, NULL);
 243
 244         snprintf(state->name, CPUIDLE_NAME_LEN, "C0");
 245         snprintf(state->desc, CPUIDLE_DESC_LEN, "CPUIDLE CORE POLL IDLE");
 246         state->exit_latency = 0;
 247         state->target_residency = 0;
 248         state->power_usage = -1;
 249         state->flags = CPUIDLE_FLAG_POLL;
 250         state->enter = poll_idle;
 251 }
 252 #else
 253 static void poll_idle_init(struct cpuidle_device *dev) {}
 254 #endif /* CONFIG_ARCH_HAS_CPU_RELAX */
 255
 256 /**
 257  * __cpuidle_register_device - internal register function called before register
 258  * and enable routines
 259  * @dev: the cpu
 260  *
 261  * cpuidle_lock mutex must be held before this is called
 262  */
 263 static int __cpuidle_register_device(struct cpuidle_device *dev)
 264 {
 265         int ret;
 266         struct sys_device *sys_dev = get_cpu_sysdev((unsigned long)dev->cpu);
 267
 268         if (!sys_dev)
 269                 return -EINVAL;
 270         if (!try_module_get(cpuidle_curr_driver->owner))
 271                 return -EINVAL;
 272
 273         init_completion(&dev->kobj_unregister);
 274
 275         poll_idle_init(dev);
 276
 277         per_cpu(cpuidle_devices, dev->cpu) = dev;
 278         list_add(&dev->device_list, &cpuidle_detected_devices);
 279         if ((ret = cpuidle_add_sysfs(sys_dev))) {
 280                 module_put(cpuidle_curr_driver->owner);
 281                 return ret;
 282         }
 283
 284         dev->registered = 1;
 285         return 0;
 286 }
 287
 288 /**
 289  * cpuidle_register_device - registers a CPU's idle PM feature
 290  * @dev: the cpu
 291  */
 292 int cpuidle_register_device(struct cpuidle_device *dev)
 293 {
 294         int ret;
 295
 296         mutex_lock(&cpuidle_lock);
 297
 298         if ((ret = __cpuidle_register_device(dev))) {
 299                 mutex_unlock(&cpuidle_lock);
 300                 return ret;
 301         }
 302
 303         cpuidle_enable_device(dev);
 304         cpuidle_install_idle_handler();
 305
 306         mutex_unlock(&cpuidle_lock);
 307
 308         return 0;
 309
 310 }
 311
 312 EXPORT_SYMBOL_GPL(cpuidle_register_device);
 313
 314 /**
 315  * cpuidle_unregister_device - unregisters a CPU's idle PM feature
 316  * @dev: the cpu
 317  */
 318 void cpuidle_unregister_device(struct cpuidle_device *dev)
 319 {
 320         struct sys_device *sys_dev = get_cpu_sysdev((unsigned long)dev->cpu);
 321
 322         if (dev->registered == 0)
 323                 return;
 324
 325         cpuidle_pause_and_lock();
 326
 327         cpuidle_disable_device(dev);
 328
 329         cpuidle_remove_sysfs(sys_dev);
 330         list_del(&dev->device_list);
 331         wait_for_completion(&dev->kobj_unregister);
 332         per_cpu(cpuidle_devices, dev->cpu) = NULL;
 333
 334         cpuidle_resume_and_unlock();
 335
 336         module_put(cpuidle_curr_driver->owner);
 337 }
 338
 339 EXPORT_SYMBOL_GPL(cpuidle_unregister_device);
 340
 341 #ifdef CONFIG_SMP
 342
 343 static void smp_callback(void *v)
 344 {
 345         /* we already woke the CPU up, nothing more to do */
 346 }
 347
 348 /*
 349  * This function gets called when a part of the kernel has a new latency
 350  * requirement.  This means we need to get all processors out of their C-state,
 351  * and then recalculate a new suitable C-state. Just do a cross-cpu IPI; that
 352  * wakes them all right up.
 353  */
 354 static int cpuidle_latency_notify(struct notifier_block *b,
 355                 unsigned long l, void *v)
 356 {
 357         smp_call_function(smp_callback, NULL, 1);
 358         return NOTIFY_OK;
 359 }
 360
 361 static struct notifier_block cpuidle_latency_notifier = {
 362         .notifier_call = cpuidle_latency_notify,
 363 };
 364
 365 static inline void latency_notifier_init(struct notifier_block *n)
 366 {
 367         pm_qos_add_notifier(PM_QOS_CPU_DMA_LATENCY, n);
 368 }
 369
 370 #else /* CONFIG_SMP */
 371
 372 #define latency_notifier_init(x) do { } while (0)
 373
 374 #endif /* CONFIG_SMP */
 375
 376 /**
 377  * cpuidle_init - core initializer
 378  */
 379 static int __init cpuidle_init(void)
 380 {
 381         int ret;
 382
 383         pm_idle_old = pm_idle;
 384
 385         ret = cpuidle_add_class_sysfs(&cpu_sysdev_class);
 386         if (ret)
 387                 return ret;
 388
 389         latency_notifier_init(&cpuidle_latency_notifier);
 390
 391         return 0;
 392 }
 393
 394 core_initcall(cpuidle_init);