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/*

 * 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);