driver.c

Go to the documentation of this file.

/*
 * driver.c - driver support
 *
 * (C) 2006-2007 Venkatesh Pallipadi <[email protected]>
 *               Shaohua Li <[email protected]>
 *               Adam Belay <[email protected]>
 *
 * This code is licenced under the GPL.
 */

#include <linux/mutex.h>
#include <linux/module.h>
#include <linux/cpuidle.h>

#include "cpuidle.h"

static struct cpuidle_driver *cpuidle_curr_driver;
DEFINE_SPINLOCK(cpuidle_driver_lock);
int cpuidle_driver_refcount;

static void set_power_states(struct cpuidle_driver *drv)
{
    int i;

    /*
     * cpuidle driver should set the drv->power_specified bit
     * before registering if the driver provides
     * power_usage numbers.
     *
     * If power_specified is not set,
     * we fill in power_usage with decreasing values as the
     * cpuidle code has an implicit assumption that state Cn
     * uses less power than C(n-1).
     *
     * With CONFIG_ARCH_HAS_CPU_RELAX, C0 is already assigned
     * an power value of -1.  So we use -2, -3, etc, for other
     * c-states.
     */
    for (i = CPUIDLE_DRIVER_STATE_START; i < drv->state_count; i++)
        drv->states[i].power_usage = -1 - i;
}

int cpuidle_register_driver(struct cpuidle_driver *drv)
{
    if (!drv || !drv->state_count)
        return -EINVAL;

    if (cpuidle_disabled())
        return -ENODEV;

    spin_lock(&cpuidle_driver_lock);
    if (cpuidle_curr_driver) {
        spin_unlock(&cpuidle_driver_lock);
        return -EBUSY;
    }

    if (!drv->power_specified)
        set_power_states(drv);

    cpuidle_curr_driver = drv;

    spin_unlock(&cpuidle_driver_lock);

    return 0;
}
EXPORT_SYMBOL_GPL(cpuidle_register_driver);

struct cpuidle_driver *cpuidle_get_driver(void)
{
    return cpuidle_curr_driver;
}
EXPORT_SYMBOL_GPL(cpuidle_get_driver);

void cpuidle_unregister_driver(struct cpuidle_driver *drv)
{
    if (drv != cpuidle_curr_driver) {
        WARN(1, "invalid cpuidle_unregister_driver(%s)\n",
            drv->name);
        return;
    }

    spin_lock(&cpuidle_driver_lock);

    if (!WARN_ON(cpuidle_driver_refcount > 0))
        cpuidle_curr_driver = NULL;

    spin_unlock(&cpuidle_driver_lock);
}
EXPORT_SYMBOL_GPL(cpuidle_unregister_driver);

struct cpuidle_driver *cpuidle_driver_ref(void)
{
    struct cpuidle_driver *drv;

    spin_lock(&cpuidle_driver_lock);

    drv = cpuidle_curr_driver;
    cpuidle_driver_refcount++;

    spin_unlock(&cpuidle_driver_lock);
    return drv;
}

void cpuidle_driver_unref(void)
{
    spin_lock(&cpuidle_driver_lock);

    if (!WARN_ON(cpuidle_driver_refcount <= 0))
        cpuidle_driver_refcount--;

    spin_unlock(&cpuidle_driver_lock);
}