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cpuidle.c

/*
 * cpuidle.c - core cpuidle infrastructure
 *
 * (C) 2006-2007 Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>
 *               Shaohua Li <shaohua.li@intel.com>
 *               Adam Belay <abelay@novell.com>
 *
 * This code is licenced under the GPL.
 */

#include <linux/kernel.h>
#include <linux/mutex.h>
#include <linux/sched.h>
#include <linux/notifier.h>
#include <linux/latency.h>
#include <linux/cpu.h>
#include <linux/cpuidle.h>

#include "cpuidle.h"

DEFINE_PER_CPU(struct cpuidle_device *, cpuidle_devices);

DEFINE_MUTEX(cpuidle_lock);
LIST_HEAD(cpuidle_detected_devices);
static void (*pm_idle_old)(void);

static int enabled_devices;

/**
 * cpuidle_idle_call - the main idle loop
 *
 * NOTE: no locks or semaphores should be used here
 */
static void cpuidle_idle_call(void)
{
      struct cpuidle_device *dev = __get_cpu_var(cpuidle_devices);
      struct cpuidle_state *target_state;
      int next_state;

      /* check if the device is ready */
      if (!dev || !dev->enabled) {
            if (pm_idle_old)
                  pm_idle_old();
            else
                  local_irq_enable();
            return;
      }

      /* ask the governor for the next state */
      next_state = cpuidle_curr_governor->select(dev);
      if (need_resched())
            return;
      target_state = &dev->states[next_state];

      /* enter the state and update stats */
      dev->last_residency = target_state->enter(dev, target_state);
      dev->last_state = target_state;
      target_state->time += dev->last_residency;
      target_state->usage++;

      /* give the governor an opportunity to reflect on the outcome */
      if (cpuidle_curr_governor->reflect)
            cpuidle_curr_governor->reflect(dev);
}

/**
 * cpuidle_install_idle_handler - installs the cpuidle idle loop handler
 */
void cpuidle_install_idle_handler(void)
{
      if (enabled_devices && (pm_idle != cpuidle_idle_call)) {
            /* Make sure all changes finished before we switch to new idle */
            smp_wmb();
            pm_idle = cpuidle_idle_call;
      }
}

/**
 * cpuidle_uninstall_idle_handler - uninstalls the cpuidle idle loop handler
 */
void cpuidle_uninstall_idle_handler(void)
{
      if (enabled_devices && (pm_idle != pm_idle_old)) {
            pm_idle = pm_idle_old;
            cpu_idle_wait();
      }
}

/**
 * cpuidle_pause_and_lock - temporarily disables CPUIDLE
 */
void cpuidle_pause_and_lock(void)
{
      mutex_lock(&cpuidle_lock);
      cpuidle_uninstall_idle_handler();
}

EXPORT_SYMBOL_GPL(cpuidle_pause_and_lock);

/**
 * cpuidle_resume_and_unlock - resumes CPUIDLE operation
 */
void cpuidle_resume_and_unlock(void)
{
      cpuidle_install_idle_handler();
      mutex_unlock(&cpuidle_lock);
}

EXPORT_SYMBOL_GPL(cpuidle_resume_and_unlock);

/**
 * cpuidle_enable_device - enables idle PM for a CPU
 * @dev: the CPU
 *
 * This function must be called between cpuidle_pause_and_lock and
 * cpuidle_resume_and_unlock when used externally.
 */
int cpuidle_enable_device(struct cpuidle_device *dev)
{
      int ret, i;

      if (dev->enabled)
            return 0;
      if (!cpuidle_curr_driver || !cpuidle_curr_governor)
            return -EIO;
      if (!dev->state_count)
            return -EINVAL;

      if ((ret = cpuidle_add_state_sysfs(dev)))
            return ret;

      if (cpuidle_curr_governor->enable &&
          (ret = cpuidle_curr_governor->enable(dev)))
            goto fail_sysfs;

      for (i = 0; i < dev->state_count; i++) {
            dev->states[i].usage = 0;
            dev->states[i].time = 0;
      }
      dev->last_residency = 0;
      dev->last_state = NULL;

      smp_wmb();

      dev->enabled = 1;

      enabled_devices++;
      return 0;

fail_sysfs:
      cpuidle_remove_state_sysfs(dev);

      return ret;
}

EXPORT_SYMBOL_GPL(cpuidle_enable_device);

/**
 * cpuidle_disable_device - disables idle PM for a CPU
 * @dev: the CPU
 *
 * This function must be called between cpuidle_pause_and_lock and
 * cpuidle_resume_and_unlock when used externally.
 */
void cpuidle_disable_device(struct cpuidle_device *dev)
{
      if (!dev->enabled)
            return;
      if (!cpuidle_curr_driver || !cpuidle_curr_governor)
            return;

      dev->enabled = 0;

      if (cpuidle_curr_governor->disable)
            cpuidle_curr_governor->disable(dev);

      cpuidle_remove_state_sysfs(dev);
      enabled_devices--;
}

EXPORT_SYMBOL_GPL(cpuidle_disable_device);

/**
 * cpuidle_register_device - registers a CPU's idle PM feature
 * @dev: the cpu
 */
int cpuidle_register_device(struct cpuidle_device *dev)
{
      int ret;
      struct sys_device *sys_dev = get_cpu_sysdev((unsigned long)dev->cpu);

      if (!sys_dev)
            return -EINVAL;
      if (!try_module_get(cpuidle_curr_driver->owner))
            return -EINVAL;

      init_completion(&dev->kobj_unregister);

      mutex_lock(&cpuidle_lock);

      per_cpu(cpuidle_devices, dev->cpu) = dev;
      list_add(&dev->device_list, &cpuidle_detected_devices);
      if ((ret = cpuidle_add_sysfs(sys_dev))) {
            mutex_unlock(&cpuidle_lock);
            module_put(cpuidle_curr_driver->owner);
            return ret;
      }

      cpuidle_enable_device(dev);
      cpuidle_install_idle_handler();

      mutex_unlock(&cpuidle_lock);

      return 0;

}

EXPORT_SYMBOL_GPL(cpuidle_register_device);

/**
 * cpuidle_unregister_device - unregisters a CPU's idle PM feature
 * @dev: the cpu
 */
void cpuidle_unregister_device(struct cpuidle_device *dev)
{
      struct sys_device *sys_dev = get_cpu_sysdev((unsigned long)dev->cpu);

      cpuidle_pause_and_lock();

      cpuidle_disable_device(dev);

      cpuidle_remove_sysfs(sys_dev);
      list_del(&dev->device_list);
      wait_for_completion(&dev->kobj_unregister);
      per_cpu(cpuidle_devices, dev->cpu) = NULL;

      cpuidle_resume_and_unlock();

      module_put(cpuidle_curr_driver->owner);
}

EXPORT_SYMBOL_GPL(cpuidle_unregister_device);

#ifdef CONFIG_SMP

static void smp_callback(void *v)
{
      /* we already woke the CPU up, nothing more to do */
}

/*
 * This function gets called when a part of the kernel has a new latency
 * requirement.  This means we need to get all processors out of their C-state,
 * and then recalculate a new suitable C-state. Just do a cross-cpu IPI; that
 * wakes them all right up.
 */
static int cpuidle_latency_notify(struct notifier_block *b,
            unsigned long l, void *v)
{
      smp_call_function(smp_callback, NULL, 0, 1);
      return NOTIFY_OK;
}

static struct notifier_block cpuidle_latency_notifier = {
      .notifier_call = cpuidle_latency_notify,
};

#define latency_notifier_init(x) do { register_latency_notifier(x); } while (0)

#else /* CONFIG_SMP */

#define latency_notifier_init(x) do { } while (0)

#endif /* CONFIG_SMP */

/**
 * cpuidle_init - core initializer
 */
static int __init cpuidle_init(void)
{
      int ret;

      pm_idle_old = pm_idle;

      ret = cpuidle_add_class_sysfs(&cpu_sysdev_class);
      if (ret)
            return ret;

      latency_notifier_init(&cpuidle_latency_notifier);

      return 0;
}

core_initcall(cpuidle_init);

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