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