release/src-rt-6.x.4708/linux/linux-2.6.36/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 = __get_cpu_var(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
  70         /*
  71          * Call the device's prepare function before calling the
  72          * governor's select function.  ->prepare gives the device's
  73          * cpuidle driver a chance to update any dynamic information
  74          * of its cpuidle states for the current idle period, e.g.
  75          * state availability, latencies, residencies, etc.
  76          */
  77         if (dev->prepare)
  78                 dev->prepare(dev);
  79
  80         /* ask the governor for the next state */
  81         next_state = cpuidle_curr_governor->select(dev);
  82         if (need_resched()) {
  83                 local_irq_enable();
  84                 return;
  85         }
  86
  87         target_state = &dev->states[next_state];
  88
  89         /* enter the state and update stats */
  90         dev->last_state = target_state;
  91         dev->last_residency = target_state->enter(dev, target_state);
  92         if (dev->last_state)
  93                 target_state = dev->last_state;
  94
  95         target_state->time += (unsigned long long)dev->last_residency;
  96         target_state->usage++;
  97
  98         /* give the governor an opportunity to reflect on the outcome */
  99         if (cpuidle_curr_governor->reflect)
 100                 cpuidle_curr_governor->reflect(dev);
 101         trace_power_end(smp_processor_id());
 102 }
 103
 104 /**
 105  * cpuidle_install_idle_handler - installs the cpuidle idle loop handler
 106  */
 107 void cpuidle_install_idle_handler(void)
 108 {
 109         if (enabled_devices && (pm_idle != cpuidle_idle_call)) {
 110                 /* Make sure all changes finished before we switch to new idle */
 111                 smp_wmb();
 112                 pm_idle = cpuidle_idle_call;
 113         }
 114 }
 115
 116 /**
 117  * cpuidle_uninstall_idle_handler - uninstalls the cpuidle idle loop handler
 118  */
 119 void cpuidle_uninstall_idle_handler(void)
 120 {
 121         if (enabled_devices && pm_idle_old && (pm_idle != pm_idle_old)) {
 122                 pm_idle = pm_idle_old;
 123                 cpuidle_kick_cpus();
 124         }
 125 }
 126
 127 /**
 128  * cpuidle_pause_and_lock - temporarily disables CPUIDLE
 129  */
 130 void cpuidle_pause_and_lock(void)
 131 {
 132         mutex_lock(&cpuidle_lock);
 133         cpuidle_uninstall_idle_handler();
 134 }
 135
 136 EXPORT_SYMBOL_GPL(cpuidle_pause_and_lock);
 137
 138 /**
 139  * cpuidle_resume_and_unlock - resumes CPUIDLE operation
 140  */
 141 void cpuidle_resume_and_unlock(void)
 142 {
 143         cpuidle_install_idle_handler();
 144         mutex_unlock(&cpuidle_lock);
 145 }
 146
 147 EXPORT_SYMBOL_GPL(cpuidle_resume_and_unlock);
 148
 149 #ifdef CONFIG_ARCH_HAS_CPU_RELAX
 150 static int poll_idle(struct cpuidle_device *dev, struct cpuidle_state *st)
 151 {
 152         ktime_t t1, t2;
 153         s64 diff;
 154         int ret;
 155
 156         t1 = ktime_get();
 157         local_irq_enable();
 158         while (!need_resched())
 159                 cpu_relax();
 160
 161         t2 = ktime_get();
 162         diff = ktime_to_us(ktime_sub(t2, t1));
 163         if (diff > INT_MAX)
 164                 diff = INT_MAX;
 165
 166         ret = (int) diff;
 167         return ret;
 168 }
 169
 170 static void poll_idle_init(struct cpuidle_device *dev)
 171 {
 172         struct cpuidle_state *state = &dev->states[0];
 173
 174         cpuidle_set_statedata(state, NULL);
 175
 176         snprintf(state->name, CPUIDLE_NAME_LEN, "C0");
 177         snprintf(state->desc, CPUIDLE_DESC_LEN, "CPUIDLE CORE POLL IDLE");
 178         state->exit_latency = 0;
 179         state->target_residency = 0;
 180         state->power_usage = -1;
 181         state->flags = CPUIDLE_FLAG_POLL;
 182         state->enter = poll_idle;
 183 }
 184 #else
 185 static void poll_idle_init(struct cpuidle_device *dev) {}
 186 #endif /* CONFIG_ARCH_HAS_CPU_RELAX */
 187
 188 /**
 189  * cpuidle_enable_device - enables idle PM for a CPU
 190  * @dev: the CPU
 191  *
 192  * This function must be called between cpuidle_pause_and_lock and
 193  * cpuidle_resume_and_unlock when used externally.
 194  */
 195 int cpuidle_enable_device(struct cpuidle_device *dev)
 196 {
 197         int ret, i;
 198
 199         if (dev->enabled)
 200                 return 0;
 201         if (!cpuidle_get_driver() || !cpuidle_curr_governor)
 202                 return -EIO;
 203         if (!dev->state_count)
 204                 return -EINVAL;
 205
 206         if (dev->registered == 0) {
 207                 ret = __cpuidle_register_device(dev);
 208                 if (ret)
 209                         return ret;
 210         }
 211
 212         poll_idle_init(dev);
 213
 214         if ((ret = cpuidle_add_state_sysfs(dev)))
 215                 return ret;
 216
 217         if (cpuidle_curr_governor->enable &&
 218             (ret = cpuidle_curr_governor->enable(dev)))
 219                 goto fail_sysfs;
 220
 221         for (i = 0; i < dev->state_count; i++) {
 222                 dev->states[i].usage = 0;
 223                 dev->states[i].time = 0;
 224         }
 225         dev->last_residency = 0;
 226         dev->last_state = NULL;
 227
 228         smp_wmb();
 229
 230         dev->enabled = 1;
 231
 232         enabled_devices++;
 233         return 0;
 234
 235 fail_sysfs:
 236         cpuidle_remove_state_sysfs(dev);
 237
 238         return ret;
 239 }
 240
 241 EXPORT_SYMBOL_GPL(cpuidle_enable_device);
 242
 243 /**
 244  * cpuidle_disable_device - disables idle PM for a CPU
 245  * @dev: the CPU
 246  *
 247  * This function must be called between cpuidle_pause_and_lock and
 248  * cpuidle_resume_and_unlock when used externally.
 249  */
 250 void cpuidle_disable_device(struct cpuidle_device *dev)
 251 {
 252         if (!dev->enabled)
 253                 return;
 254         if (!cpuidle_get_driver() || !cpuidle_curr_governor)
 255                 return;
 256
 257         dev->enabled = 0;
 258
 259         if (cpuidle_curr_governor->disable)
 260                 cpuidle_curr_governor->disable(dev);
 261
 262         cpuidle_remove_state_sysfs(dev);
 263         enabled_devices--;
 264 }
 265
 266 EXPORT_SYMBOL_GPL(cpuidle_disable_device);
 267
 268 /**
 269  * __cpuidle_register_device - internal register function called before register
 270  * and enable routines
 271  * @dev: the cpu
 272  *
 273  * cpuidle_lock mutex must be held before this is called
 274  */
 275 static int __cpuidle_register_device(struct cpuidle_device *dev)
 276 {
 277         int ret;
 278         struct sys_device *sys_dev = get_cpu_sysdev((unsigned long)dev->cpu);
 279         struct cpuidle_driver *cpuidle_driver = cpuidle_get_driver();
 280
 281         if (!sys_dev)
 282                 return -EINVAL;
 283         if (!try_module_get(cpuidle_driver->owner))
 284                 return -EINVAL;
 285
 286         init_completion(&dev->kobj_unregister);
 287
 288         /*
 289          * cpuidle driver should set the dev->power_specified bit
 290          * before registering the device if the driver provides
 291          * power_usage numbers.
 292          *
 293          * For those devices whose ->power_specified is not set,
 294          * we fill in power_usage with decreasing values as the
 295          * cpuidle code has an implicit assumption that state Cn
 296          * uses less power than C(n-1).
 297          *
 298          * With CONFIG_ARCH_HAS_CPU_RELAX, C0 is already assigned
 299          * an power value of -1.  So we use -2, -3, etc, for other
 300          * c-states.
 301          */
 302         if (!dev->power_specified) {
 303                 int i;
 304                 for (i = CPUIDLE_DRIVER_STATE_START; i < dev->state_count; i++)
 305                         dev->states[i].power_usage = -1 - i;
 306         }
 307
 308         per_cpu(cpuidle_devices, dev->cpu) = dev;
 309         list_add(&dev->device_list, &cpuidle_detected_devices);
 310         if ((ret = cpuidle_add_sysfs(sys_dev))) {
 311                 module_put(cpuidle_driver->owner);
 312                 return ret;
 313         }
 314
 315         dev->registered = 1;
 316         return 0;
 317 }
 318
 319 /**
 320  * cpuidle_register_device - registers a CPU's idle PM feature
 321  * @dev: the cpu
 322  */
 323 int cpuidle_register_device(struct cpuidle_device *dev)
 324 {
 325         int ret;
 326
 327         mutex_lock(&cpuidle_lock);
 328
 329         if ((ret = __cpuidle_register_device(dev))) {
 330                 mutex_unlock(&cpuidle_lock);
 331                 return ret;
 332         }
 333
 334         cpuidle_enable_device(dev);
 335         cpuidle_install_idle_handler();
 336
 337         mutex_unlock(&cpuidle_lock);
 338
 339         return 0;
 340
 341 }
 342
 343 EXPORT_SYMBOL_GPL(cpuidle_register_device);
 344
 345 /**
 346  * cpuidle_unregister_device - unregisters a CPU's idle PM feature
 347  * @dev: the cpu
 348  */
 349 void cpuidle_unregister_device(struct cpuidle_device *dev)
 350 {
 351         struct sys_device *sys_dev = get_cpu_sysdev((unsigned long)dev->cpu);
 352         struct cpuidle_driver *cpuidle_driver = cpuidle_get_driver();
 353
 354         if (dev->registered == 0)
 355                 return;
 356
 357         cpuidle_pause_and_lock();
 358
 359         cpuidle_disable_device(dev);
 360
 361         cpuidle_remove_sysfs(sys_dev);
 362         list_del(&dev->device_list);
 363         wait_for_completion(&dev->kobj_unregister);
 364         per_cpu(cpuidle_devices, dev->cpu) = NULL;
 365
 366         cpuidle_resume_and_unlock();
 367
 368         module_put(cpuidle_driver->owner);
 369 }
 370
 371 EXPORT_SYMBOL_GPL(cpuidle_unregister_device);
 372
 373 #ifdef CONFIG_SMP
 374
 375 static void smp_callback(void *v)
 376 {
 377         /* we already woke the CPU up, nothing more to do */
 378 }
 379
 380 /*
 381  * This function gets called when a part of the kernel has a new latency
 382  * requirement.  This means we need to get all processors out of their C-state,
 383  * and then recalculate a new suitable C-state. Just do a cross-cpu IPI; that
 384  * wakes them all right up.
 385  */
 386 static int cpuidle_latency_notify(struct notifier_block *b,
 387                 unsigned long l, void *v)
 388 {
 389         smp_call_function(smp_callback, NULL, 1);
 390         return NOTIFY_OK;
 391 }
 392
 393 static struct notifier_block cpuidle_latency_notifier = {
 394         .notifier_call = cpuidle_latency_notify,
 395 };
 396
 397 static inline void latency_notifier_init(struct notifier_block *n)
 398 {
 399         pm_qos_add_notifier(PM_QOS_CPU_DMA_LATENCY, n);
 400 }
 401
 402 #else /* CONFIG_SMP */
 403
 404 #define latency_notifier_init(x) do { } while (0)
 405
 406 #endif /* CONFIG_SMP */
 407
 408 /**
 409  * cpuidle_init - core initializer
 410  */
 411 static int __init cpuidle_init(void)
 412 {
 413         int ret;
 414
 415         pm_idle_old = pm_idle;
 416
 417         ret = cpuidle_add_class_sysfs(&cpu_sysdev_class);
 418         if (ret)
 419                 return ret;
 420
 421         latency_notifier_init(&cpuidle_latency_notifier);
 422
 423         return 0;
 424 }
 425
 426 core_initcall(cpuidle_init);