cpufreq: suspend governors on system suspend/hibernate

[mirror_ubuntu-artful-kernel.git] / drivers / cpufreq / cpufreq.c

/*
 *  linux/drivers/cpufreq/cpufreq.c
 *
 *  Copyright (C) 2001 Russell King
 *            (C) 2002 - 2003 Dominik Brodowski <linux@brodo.de>
 *            (C) 2013 Viresh Kumar <viresh.kumar@linaro.org>
 *
 *  Oct 2005 - Ashok Raj <ashok.raj@intel.com>
 *      Added handling for CPU hotplug
 *  Feb 2006 - Jacob Shin <jacob.shin@amd.com>
 *      Fix handling for CPU hotplug -- affected CPUs
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/cpu.h>
#include <linux/cpufreq.h>
#include <linux/delay.h>
#include <linux/device.h>
#include <linux/init.h>
#include <linux/kernel_stat.h>
#include <linux/module.h>
#include <linux/mutex.h>
#include <linux/slab.h>
#include <linux/suspend.h>
#include <linux/tick.h>
#include <trace/events/power.h>

/**
 * The "cpufreq driver" - the arch- or hardware-dependent low
 * level driver of CPUFreq support, and its spinlock. This lock
 * also protects the cpufreq_cpu_data array.
 */
static struct cpufreq_driver *cpufreq_driver;
static DEFINE_PER_CPU(struct cpufreq_policy *, cpufreq_cpu_data);
static DEFINE_PER_CPU(struct cpufreq_policy *, cpufreq_cpu_data_fallback);
static DEFINE_RWLOCK(cpufreq_driver_lock);
DEFINE_MUTEX(cpufreq_governor_lock);
static LIST_HEAD(cpufreq_policy_list);

/* This one keeps track of the previously set governor of a removed CPU */
static DEFINE_PER_CPU(char[CPUFREQ_NAME_LEN], cpufreq_cpu_governor);

/* Flag to suspend/resume CPUFreq governors */
static bool cpufreq_suspended;

static inline bool has_target(void)
{
        return cpufreq_driver->target_index || cpufreq_driver->target;
}

/*
 * rwsem to guarantee that cpufreq driver module doesn't unload during critical
 * sections
 */
static DECLARE_RWSEM(cpufreq_rwsem);

/* internal prototypes */
static int __cpufreq_governor(struct cpufreq_policy *policy,
                unsigned int event);
static unsigned int __cpufreq_get(unsigned int cpu);
static void handle_update(struct work_struct *work);

/**
 * Two notifier lists: the "policy" list is involved in the
 * validation process for a new CPU frequency policy; the
 * "transition" list for kernel code that needs to handle
 * changes to devices when the CPU clock speed changes.
 * The mutex locks both lists.
 */
static BLOCKING_NOTIFIER_HEAD(cpufreq_policy_notifier_list);
static struct srcu_notifier_head cpufreq_transition_notifier_list;

static bool init_cpufreq_transition_notifier_list_called;
static int __init init_cpufreq_transition_notifier_list(void)
{
        srcu_init_notifier_head(&cpufreq_transition_notifier_list);
        init_cpufreq_transition_notifier_list_called = true;
        return 0;
}
pure_initcall(init_cpufreq_transition_notifier_list);

static int off __read_mostly;
static int cpufreq_disabled(void)
{
        return off;
}
void disable_cpufreq(void)
{
        off = 1;
}
static LIST_HEAD(cpufreq_governor_list);
static DEFINE_MUTEX(cpufreq_governor_mutex);

bool have_governor_per_policy(void)
{
        return !!(cpufreq_driver->flags & CPUFREQ_HAVE_GOVERNOR_PER_POLICY);
}
EXPORT_SYMBOL_GPL(have_governor_per_policy);

struct kobject *get_governor_parent_kobj(struct cpufreq_policy *policy)
{
        if (have_governor_per_policy())
                return &policy->kobj;
        else
                return cpufreq_global_kobject;
}
EXPORT_SYMBOL_GPL(get_governor_parent_kobj);

static inline u64 get_cpu_idle_time_jiffy(unsigned int cpu, u64 *wall)
{
        u64 idle_time;
        u64 cur_wall_time;
        u64 busy_time;

        cur_wall_time = jiffies64_to_cputime64(get_jiffies_64());

        busy_time = kcpustat_cpu(cpu).cpustat[CPUTIME_USER];
        busy_time += kcpustat_cpu(cpu).cpustat[CPUTIME_SYSTEM];
        busy_time += kcpustat_cpu(cpu).cpustat[CPUTIME_IRQ];
        busy_time += kcpustat_cpu(cpu).cpustat[CPUTIME_SOFTIRQ];
        busy_time += kcpustat_cpu(cpu).cpustat[CPUTIME_STEAL];
        busy_time += kcpustat_cpu(cpu).cpustat[CPUTIME_NICE];

        idle_time = cur_wall_time - busy_time;
        if (wall)
                *wall = cputime_to_usecs(cur_wall_time);

        return cputime_to_usecs(idle_time);
}

u64 get_cpu_idle_time(unsigned int cpu, u64 *wall, int io_busy)
{
        u64 idle_time = get_cpu_idle_time_us(cpu, io_busy ? wall : NULL);

        if (idle_time == -1ULL)
                return get_cpu_idle_time_jiffy(cpu, wall);
        else if (!io_busy)
                idle_time += get_cpu_iowait_time_us(cpu, wall);

        return idle_time;
}
EXPORT_SYMBOL_GPL(get_cpu_idle_time);

/*
 * This is a generic cpufreq init() routine which can be used by cpufreq
 * drivers of SMP systems. It will do following:
 * - validate & show freq table passed
 * - set policies transition latency
 * - policy->cpus with all possible CPUs
 */
int cpufreq_generic_init(struct cpufreq_policy *policy,
                struct cpufreq_frequency_table *table,
                unsigned int transition_latency)
{
        int ret;

        ret = cpufreq_table_validate_and_show(policy, table);
        if (ret) {
                pr_err("%s: invalid frequency table: %d\n", __func__, ret);
                return ret;
        }

        policy->cpuinfo.transition_latency = transition_latency;

        /*
         * The driver only supports the SMP configuartion where all processors
         * share the clock and voltage and clock.
         */
        cpumask_setall(policy->cpus);

        return 0;
}
EXPORT_SYMBOL_GPL(cpufreq_generic_init);

unsigned int cpufreq_generic_get(unsigned int cpu)
{
        struct cpufreq_policy *policy = per_cpu(cpufreq_cpu_data, cpu);

        if (!policy || IS_ERR(policy->clk)) {
                pr_err("%s: No %s associated to cpu: %d\n", __func__,
                                policy ? "clk" : "policy", cpu);
                return 0;
        }

        return clk_get_rate(policy->clk) / 1000;
}
EXPORT_SYMBOL_GPL(cpufreq_generic_get);

struct cpufreq_policy *cpufreq_cpu_get(unsigned int cpu)
{
        struct cpufreq_policy *policy = NULL;
        unsigned long flags;

        if (cpufreq_disabled() || (cpu >= nr_cpu_ids))
                return NULL;

        if (!down_read_trylock(&cpufreq_rwsem))
                return NULL;

        /* get the cpufreq driver */
        read_lock_irqsave(&cpufreq_driver_lock, flags);

        if (cpufreq_driver) {
                /* get the CPU */
                policy = per_cpu(cpufreq_cpu_data, cpu);
                if (policy)
                        kobject_get(&policy->kobj);
        }

        read_unlock_irqrestore(&cpufreq_driver_lock, flags);

        if (!policy)
                up_read(&cpufreq_rwsem);

        return policy;
}
EXPORT_SYMBOL_GPL(cpufreq_cpu_get);

void cpufreq_cpu_put(struct cpufreq_policy *policy)
{
        if (cpufreq_disabled())
                return;

        kobject_put(&policy->kobj);
        up_read(&cpufreq_rwsem);
}
EXPORT_SYMBOL_GPL(cpufreq_cpu_put);

/*********************************************************************
 *            EXTERNALLY AFFECTING FREQUENCY CHANGES                 *
 *********************************************************************/

/**
 * adjust_jiffies - adjust the system "loops_per_jiffy"
 *
 * This function alters the system "loops_per_jiffy" for the clock
 * speed change. Note that loops_per_jiffy cannot be updated on SMP
 * systems as each CPU might be scaled differently. So, use the arch
 * per-CPU loops_per_jiffy value wherever possible.
 */
#ifndef CONFIG_SMP
static unsigned long l_p_j_ref;
static unsigned int l_p_j_ref_freq;

static void adjust_jiffies(unsigned long val, struct cpufreq_freqs *ci)
{
        if (ci->flags & CPUFREQ_CONST_LOOPS)
                return;

        if (!l_p_j_ref_freq) {
                l_p_j_ref = loops_per_jiffy;
                l_p_j_ref_freq = ci->old;
                pr_debug("saving %lu as reference value for loops_per_jiffy; "
                        "freq is %u kHz\n", l_p_j_ref, l_p_j_ref_freq);
        }
        if ((val == CPUFREQ_POSTCHANGE && ci->old != ci->new) ||
            (val == CPUFREQ_RESUMECHANGE || val == CPUFREQ_SUSPENDCHANGE)) {
                loops_per_jiffy = cpufreq_scale(l_p_j_ref, l_p_j_ref_freq,
                                                                ci->new);
                pr_debug("scaling loops_per_jiffy to %lu "
                        "for frequency %u kHz\n", loops_per_jiffy, ci->new);
        }
}
#else
static inline void adjust_jiffies(unsigned long val, struct cpufreq_freqs *ci)
{
        return;
}
#endif

static void __cpufreq_notify_transition(struct cpufreq_policy *policy,
                struct cpufreq_freqs *freqs, unsigned int state)
{
        BUG_ON(irqs_disabled());

        if (cpufreq_disabled())
                return;

        freqs->flags = cpufreq_driver->flags;
        pr_debug("notification %u of frequency transition to %u kHz\n",
                state, freqs->new);

        switch (state) {

        case CPUFREQ_PRECHANGE:
                /* detect if the driver reported a value as "old frequency"
                 * which is not equal to what the cpufreq core thinks is
                 * "old frequency".
                 */
                if (!(cpufreq_driver->flags & CPUFREQ_CONST_LOOPS)) {
                        if ((policy) && (policy->cpu == freqs->cpu) &&
                            (policy->cur) && (policy->cur != freqs->old)) {
                                pr_debug("Warning: CPU frequency is"
                                        " %u, cpufreq assumed %u kHz.\n",
                                        freqs->old, policy->cur);
                                freqs->old = policy->cur;
                        }
                }
                srcu_notifier_call_chain(&cpufreq_transition_notifier_list,
                                CPUFREQ_PRECHANGE, freqs);
                adjust_jiffies(CPUFREQ_PRECHANGE, freqs);
                break;

        case CPUFREQ_POSTCHANGE:
                adjust_jiffies(CPUFREQ_POSTCHANGE, freqs);
                pr_debug("FREQ: %lu - CPU: %lu", (unsigned long)freqs->new,
                        (unsigned long)freqs->cpu);
                trace_cpu_frequency(freqs->new, freqs->cpu);
                srcu_notifier_call_chain(&cpufreq_transition_notifier_list,
                                CPUFREQ_POSTCHANGE, freqs);
                if (likely(policy) && likely(policy->cpu == freqs->cpu))
                        policy->cur = freqs->new;
                break;
        }
}

/**
 * cpufreq_notify_transition - call notifier chain and adjust_jiffies
 * on frequency transition.
 *
 * This function calls the transition notifiers and the "adjust_jiffies"
 * function. It is called twice on all CPU frequency changes that have
 * external effects.
 */
void cpufreq_notify_transition(struct cpufreq_policy *policy,
                struct cpufreq_freqs *freqs, unsigned int state)
{
        for_each_cpu(freqs->cpu, policy->cpus)
                __cpufreq_notify_transition(policy, freqs, state);
}
EXPORT_SYMBOL_GPL(cpufreq_notify_transition);

/* Do post notifications when there are chances that transition has failed */
void cpufreq_notify_post_transition(struct cpufreq_policy *policy,
                struct cpufreq_freqs *freqs, int transition_failed)
{
        cpufreq_notify_transition(policy, freqs, CPUFREQ_POSTCHANGE);
        if (!transition_failed)
                return;

        swap(freqs->old, freqs->new);
        cpufreq_notify_transition(policy, freqs, CPUFREQ_PRECHANGE);
        cpufreq_notify_transition(policy, freqs, CPUFREQ_POSTCHANGE);
}
EXPORT_SYMBOL_GPL(cpufreq_notify_post_transition);


/*********************************************************************
 *                          SYSFS INTERFACE                          *
 *********************************************************************/
static ssize_t show_boost(struct kobject *kobj,
                                 struct attribute *attr, char *buf)
{
        return sprintf(buf, "%d\n", cpufreq_driver->boost_enabled);
}

static ssize_t store_boost(struct kobject *kobj, struct attribute *attr,
                                  const char *buf, size_t count)
{
        int ret, enable;

        ret = sscanf(buf, "%d", &enable);
        if (ret != 1 || enable < 0 || enable > 1)
                return -EINVAL;

        if (cpufreq_boost_trigger_state(enable)) {
                pr_err("%s: Cannot %s BOOST!\n", __func__,
                       enable ? "enable" : "disable");
                return -EINVAL;
        }

        pr_debug("%s: cpufreq BOOST %s\n", __func__,
                 enable ? "enabled" : "disabled");

        return count;
}
define_one_global_rw(boost);

static struct cpufreq_governor *__find_governor(const char *str_governor)
{
        struct cpufreq_governor *t;

        list_for_each_entry(t, &cpufreq_governor_list, governor_list)
                if (!strnicmp(str_governor, t->name, CPUFREQ_NAME_LEN))
                        return t;

        return NULL;
}

/**
 * cpufreq_parse_governor - parse a governor string
 */
static int cpufreq_parse_governor(char *str_governor, unsigned int *policy,
                                struct cpufreq_governor **governor)
{
        int err = -EINVAL;

        if (!cpufreq_driver)
                goto out;

        if (cpufreq_driver->setpolicy) {
                if (!strnicmp(str_governor, "performance", CPUFREQ_NAME_LEN)) {
                        *policy = CPUFREQ_POLICY_PERFORMANCE;
                        err = 0;
                } else if (!strnicmp(str_governor, "powersave",
                                                CPUFREQ_NAME_LEN)) {
                        *policy = CPUFREQ_POLICY_POWERSAVE;
                        err = 0;
                }
        } else if (has_target()) {
                struct cpufreq_governor *t;

                mutex_lock(&cpufreq_governor_mutex);

                t = __find_governor(str_governor);

                if (t == NULL) {
                        int ret;

                        mutex_unlock(&cpufreq_governor_mutex);
                        ret = request_module("cpufreq_%s", str_governor);
                        mutex_lock(&cpufreq_governor_mutex);

                        if (ret == 0)
                                t = __find_governor(str_governor);
                }

                if (t != NULL) {
                        *governor = t;
                        err = 0;
                }

                mutex_unlock(&cpufreq_governor_mutex);
        }
out:
        return err;
}

/**
 * cpufreq_per_cpu_attr_read() / show_##file_name() -
 * print out cpufreq information
 *
 * Write out information from cpufreq_driver->policy[cpu]; object must be
 * "unsigned int".
 */

#define show_one(file_name, object)                     \
static ssize_t show_##file_name                         \
(struct cpufreq_policy *policy, char *buf)              \
{                                                       \
        return sprintf(buf, "%u\n", policy->object);    \
}

show_one(cpuinfo_min_freq, cpuinfo.min_freq);
show_one(cpuinfo_max_freq, cpuinfo.max_freq);
show_one(cpuinfo_transition_latency, cpuinfo.transition_latency);
show_one(scaling_min_freq, min);
show_one(scaling_max_freq, max);
show_one(scaling_cur_freq, cur);

static int cpufreq_set_policy(struct cpufreq_policy *policy,
                                struct cpufreq_policy *new_policy);

/**
 * cpufreq_per_cpu_attr_write() / store_##file_name() - sysfs write access
 */
#define store_one(file_name, object)                    \
static ssize_t store_##file_name                                        \
(struct cpufreq_policy *policy, const char *buf, size_t count)          \
{                                                                       \
        int ret;                                                        \
        struct cpufreq_policy new_policy;                               \
                                                                        \
        ret = cpufreq_get_policy(&new_policy, policy->cpu);             \
        if (ret)                                                        \
                return -EINVAL;                                         \
                                                                        \
        ret = sscanf(buf, "%u", &new_policy.object);                    \
        if (ret != 1)                                                   \
                return -EINVAL;                                         \
                                                                        \
        ret = cpufreq_set_policy(policy, &new_policy);          \
        policy->user_policy.object = policy->object;                    \
                                                                        \
        return ret ? ret : count;                                       \
}

store_one(scaling_min_freq, min);
store_one(scaling_max_freq, max);

/**
 * show_cpuinfo_cur_freq - current CPU frequency as detected by hardware
 */
static ssize_t show_cpuinfo_cur_freq(struct cpufreq_policy *policy,
                                        char *buf)
{
        unsigned int cur_freq = __cpufreq_get(policy->cpu);
        if (!cur_freq)
                return sprintf(buf, "<unknown>");
        return sprintf(buf, "%u\n", cur_freq);
}

/**
 * show_scaling_governor - show the current policy for the specified CPU
 */
static ssize_t show_scaling_governor(struct cpufreq_policy *policy, char *buf)
{
        if (policy->policy == CPUFREQ_POLICY_POWERSAVE)
                return sprintf(buf, "powersave\n");
        else if (policy->policy == CPUFREQ_POLICY_PERFORMANCE)
                return sprintf(buf, "performance\n");
        else if (policy->governor)
                return scnprintf(buf, CPUFREQ_NAME_PLEN, "%s\n",
                                policy->governor->name);
        return -EINVAL;
}

/**
 * store_scaling_governor - store policy for the specified CPU
 */
static ssize_t store_scaling_governor(struct cpufreq_policy *policy,
                                        const char *buf, size_t count)
{
        int ret;
        char    str_governor[16];
        struct cpufreq_policy new_policy;

        ret = cpufreq_get_policy(&new_policy, policy->cpu);
        if (ret)
                return ret;

        ret = sscanf(buf, "%15s", str_governor);
        if (ret != 1)
                return -EINVAL;

        if (cpufreq_parse_governor(str_governor, &new_policy.policy,
                                                &new_policy.governor))
                return -EINVAL;

        ret = cpufreq_set_policy(policy, &new_policy);

        policy->user_policy.policy = policy->policy;
        policy->user_policy.governor = policy->governor;

        if (ret)
                return ret;
        else
                return count;
}

/**
 * show_scaling_driver - show the cpufreq driver currently loaded
 */
static ssize_t show_scaling_driver(struct cpufreq_policy *policy, char *buf)
{
        return scnprintf(buf, CPUFREQ_NAME_PLEN, "%s\n", cpufreq_driver->name);
}

/**
 * show_scaling_available_governors - show the available CPUfreq governors
 */
static ssize_t show_scaling_available_governors(struct cpufreq_policy *policy,
                                                char *buf)
{
        ssize_t i = 0;
        struct cpufreq_governor *t;

        if (!has_target()) {
                i += sprintf(buf, "performance powersave");
                goto out;
        }

        list_for_each_entry(t, &cpufreq_governor_list, governor_list) {
                if (i >= (ssize_t) ((PAGE_SIZE / sizeof(char))
                    - (CPUFREQ_NAME_LEN + 2)))
                        goto out;
                i += scnprintf(&buf[i], CPUFREQ_NAME_PLEN, "%s ", t->name);
        }
out:
        i += sprintf(&buf[i], "\n");
        return i;
}

ssize_t cpufreq_show_cpus(const struct cpumask *mask, char *buf)
{
        ssize_t i = 0;
        unsigned int cpu;

        for_each_cpu(cpu, mask) {
                if (i)
                        i += scnprintf(&buf[i], (PAGE_SIZE - i - 2), " ");
                i += scnprintf(&buf[i], (PAGE_SIZE - i - 2), "%u", cpu);
                if (i >= (PAGE_SIZE - 5))
                        break;
        }
        i += sprintf(&buf[i], "\n");
        return i;
}
EXPORT_SYMBOL_GPL(cpufreq_show_cpus);

/**
 * show_related_cpus - show the CPUs affected by each transition even if
 * hw coordination is in use
 */
static ssize_t show_related_cpus(struct cpufreq_policy *policy, char *buf)
{
        return cpufreq_show_cpus(policy->related_cpus, buf);
}

/**
 * show_affected_cpus - show the CPUs affected by each transition
 */
static ssize_t show_affected_cpus(struct cpufreq_policy *policy, char *buf)
{
        return cpufreq_show_cpus(policy->cpus, buf);
}

static ssize_t store_scaling_setspeed(struct cpufreq_policy *policy,
                                        const char *buf, size_t count)
{
        unsigned int freq = 0;
        unsigned int ret;

        if (!policy->governor || !policy->governor->store_setspeed)
                return -EINVAL;

        ret = sscanf(buf, "%u", &freq);
        if (ret != 1)
                return -EINVAL;

        policy->governor->store_setspeed(policy, freq);

        return count;
}

static ssize_t show_scaling_setspeed(struct cpufreq_policy *policy, char *buf)
{
        if (!policy->governor || !policy->governor->show_setspeed)
                return sprintf(buf, "<unsupported>\n");

        return policy->governor->show_setspeed(policy, buf);
}

/**
 * show_bios_limit - show the current cpufreq HW/BIOS limitation
 */
static ssize_t show_bios_limit(struct cpufreq_policy *policy, char *buf)
{
        unsigned int limit;
        int ret;
        if (cpufreq_driver->bios_limit) {
                ret = cpufreq_driver->bios_limit(policy->cpu, &limit);
                if (!ret)
                        return sprintf(buf, "%u\n", limit);
        }
        return sprintf(buf, "%u\n", policy->cpuinfo.max_freq);
}

cpufreq_freq_attr_ro_perm(cpuinfo_cur_freq, 0400);
cpufreq_freq_attr_ro(cpuinfo_min_freq);
cpufreq_freq_attr_ro(cpuinfo_max_freq);
cpufreq_freq_attr_ro(cpuinfo_transition_latency);
cpufreq_freq_attr_ro(scaling_available_governors);
cpufreq_freq_attr_ro(scaling_driver);
cpufreq_freq_attr_ro(scaling_cur_freq);
cpufreq_freq_attr_ro(bios_limit);
cpufreq_freq_attr_ro(related_cpus);
cpufreq_freq_attr_ro(affected_cpus);
cpufreq_freq_attr_rw(scaling_min_freq);
cpufreq_freq_attr_rw(scaling_max_freq);
cpufreq_freq_attr_rw(scaling_governor);
cpufreq_freq_attr_rw(scaling_setspeed);

static struct attribute *default_attrs[] = {
        &cpuinfo_min_freq.attr,
        &cpuinfo_max_freq.attr,
        &cpuinfo_transition_latency.attr,
        &scaling_min_freq.attr,
        &scaling_max_freq.attr,
        &affected_cpus.attr,
        &related_cpus.attr,
        &scaling_governor.attr,
        &scaling_driver.attr,
        &scaling_available_governors.attr,
        &scaling_setspeed.attr,
        NULL
};

#define to_policy(k) container_of(k, struct cpufreq_policy, kobj)
#define to_attr(a) container_of(a, struct freq_attr, attr)

static ssize_t show(struct kobject *kobj, struct attribute *attr, char *buf)
{
        struct cpufreq_policy *policy = to_policy(kobj);
        struct freq_attr *fattr = to_attr(attr);
        ssize_t ret;

        if (!down_read_trylock(&cpufreq_rwsem))
                return -EINVAL;

        down_read(&policy->rwsem);

        if (fattr->show)
                ret = fattr->show(policy, buf);
        else
                ret = -EIO;

        up_read(&policy->rwsem);
        up_read(&cpufreq_rwsem);

        return ret;
}

static ssize_t store(struct kobject *kobj, struct attribute *attr,
                     const char *buf, size_t count)
{
        struct cpufreq_policy *policy = to_policy(kobj);
        struct freq_attr *fattr = to_attr(attr);
        ssize_t ret = -EINVAL;

        get_online_cpus();

        if (!cpu_online(policy->cpu))
                goto unlock;

        if (!down_read_trylock(&cpufreq_rwsem))
                goto unlock;

        down_write(&policy->rwsem);

        if (fattr->store)
                ret = fattr->store(policy, buf, count);
        else
                ret = -EIO;

        up_write(&policy->rwsem);

        up_read(&cpufreq_rwsem);
unlock:
        put_online_cpus();

        return ret;
}

static void cpufreq_sysfs_release(struct kobject *kobj)
{
        struct cpufreq_policy *policy = to_policy(kobj);
        pr_debug("last reference is dropped\n");
        complete(&policy->kobj_unregister);
}

static const struct sysfs_ops sysfs_ops = {
        .show   = show,
        .store  = store,
};

static struct kobj_type ktype_cpufreq = {
        .sysfs_ops      = &sysfs_ops,
        .default_attrs  = default_attrs,
        .release        = cpufreq_sysfs_release,
};

struct kobject *cpufreq_global_kobject;
EXPORT_SYMBOL(cpufreq_global_kobject);

static int cpufreq_global_kobject_usage;

int cpufreq_get_global_kobject(void)
{
        if (!cpufreq_global_kobject_usage++)
                return kobject_add(cpufreq_global_kobject,
                                &cpu_subsys.dev_root->kobj, "%s", "cpufreq");

        return 0;
}
EXPORT_SYMBOL(cpufreq_get_global_kobject);

void cpufreq_put_global_kobject(void)
{
        if (!--cpufreq_global_kobject_usage)
                kobject_del(cpufreq_global_kobject);
}
EXPORT_SYMBOL(cpufreq_put_global_kobject);

int cpufreq_sysfs_create_file(const struct attribute *attr)
{
        int ret = cpufreq_get_global_kobject();

        if (!ret) {
                ret = sysfs_create_file(cpufreq_global_kobject, attr);
                if (ret)
                        cpufreq_put_global_kobject();
        }

        return ret;
}
EXPORT_SYMBOL(cpufreq_sysfs_create_file);

void cpufreq_sysfs_remove_file(const struct attribute *attr)
{
        sysfs_remove_file(cpufreq_global_kobject, attr);
        cpufreq_put_global_kobject();
}
EXPORT_SYMBOL(cpufreq_sysfs_remove_file);

/* symlink affected CPUs */
static int cpufreq_add_dev_symlink(struct cpufreq_policy *policy)
{
        unsigned int j;
        int ret = 0;

        for_each_cpu(j, policy->cpus) {
                struct device *cpu_dev;

                if (j == policy->cpu)
                        continue;

                pr_debug("Adding link for CPU: %u\n", j);
                cpu_dev = get_cpu_device(j);
                ret = sysfs_create_link(&cpu_dev->kobj, &policy->kobj,
                                        "cpufreq");
                if (ret)
                        break;
        }
        return ret;
}

static int cpufreq_add_dev_interface(struct cpufreq_policy *policy,
                                     struct device *dev)
{
        struct freq_attr **drv_attr;
        int ret = 0;

        /* prepare interface data */
        ret = kobject_init_and_add(&policy->kobj, &ktype_cpufreq,
                                   &dev->kobj, "cpufreq");
        if (ret)
                return ret;

        /* set up files for this cpu device */
        drv_attr = cpufreq_driver->attr;
        while ((drv_attr) && (*drv_attr)) {
                ret = sysfs_create_file(&policy->kobj, &((*drv_attr)->attr));
                if (ret)
                        goto err_out_kobj_put;
                drv_attr++;
        }
        if (cpufreq_driver->get) {
                ret = sysfs_create_file(&policy->kobj, &cpuinfo_cur_freq.attr);
                if (ret)
                        goto err_out_kobj_put;
        }
        if (has_target()) {
                ret = sysfs_create_file(&policy->kobj, &scaling_cur_freq.attr);
                if (ret)
                        goto err_out_kobj_put;
        }
        if (cpufreq_driver->bios_limit) {
                ret = sysfs_create_file(&policy->kobj, &bios_limit.attr);
                if (ret)
                        goto err_out_kobj_put;
        }

        ret = cpufreq_add_dev_symlink(policy);
        if (ret)
                goto err_out_kobj_put;

        return ret;

err_out_kobj_put:
        kobject_put(&policy->kobj);
        wait_for_completion(&policy->kobj_unregister);
        return ret;
}

static void cpufreq_init_policy(struct cpufreq_policy *policy)
{
        struct cpufreq_governor *gov = NULL;
        struct cpufreq_policy new_policy;
        int ret = 0;

        memcpy(&new_policy, policy, sizeof(*policy));

        /* Update governor of new_policy to the governor used before hotplug */
        gov = __find_governor(per_cpu(cpufreq_cpu_governor, policy->cpu));
        if (gov)
                pr_debug("Restoring governor %s for cpu %d\n",
                                policy->governor->name, policy->cpu);
        else
                gov = CPUFREQ_DEFAULT_GOVERNOR;

        new_policy.governor = gov;

        /* Use the default policy if its valid. */
        if (cpufreq_driver->setpolicy)
                cpufreq_parse_governor(gov->name, &new_policy.policy, NULL);

        /* set default policy */
        ret = cpufreq_set_policy(policy, &new_policy);
        if (ret) {
                pr_debug("setting policy failed\n");
                if (cpufreq_driver->exit)
                        cpufreq_driver->exit(policy);
        }
}

#ifdef CONFIG_HOTPLUG_CPU
static int cpufreq_add_policy_cpu(struct cpufreq_policy *policy,
                                  unsigned int cpu, struct device *dev)
{
        int ret = 0;
        unsigned long flags;

        if (has_target()) {
                ret = __cpufreq_governor(policy, CPUFREQ_GOV_STOP);
                if (ret) {
                        pr_err("%s: Failed to stop governor\n", __func__);
                        return ret;
                }
        }

        down_write(&policy->rwsem);

        write_lock_irqsave(&cpufreq_driver_lock, flags);

        cpumask_set_cpu(cpu, policy->cpus);
        per_cpu(cpufreq_cpu_data, cpu) = policy;
        write_unlock_irqrestore(&cpufreq_driver_lock, flags);

        up_write(&policy->rwsem);

        if (has_target()) {
                if ((ret = __cpufreq_governor(policy, CPUFREQ_GOV_START)) ||
                        (ret = __cpufreq_governor(policy, CPUFREQ_GOV_LIMITS))) {
                        pr_err("%s: Failed to start governor\n", __func__);
                        return ret;
                }
        }

        return sysfs_create_link(&dev->kobj, &policy->kobj, "cpufreq");
}
#endif

static struct cpufreq_policy *cpufreq_policy_restore(unsigned int cpu)
{
        struct cpufreq_policy *policy;
        unsigned long flags;

        read_lock_irqsave(&cpufreq_driver_lock, flags);

        policy = per_cpu(cpufreq_cpu_data_fallback, cpu);

        read_unlock_irqrestore(&cpufreq_driver_lock, flags);

        policy->governor = NULL;

        return policy;
}

static struct cpufreq_policy *cpufreq_policy_alloc(void)
{
        struct cpufreq_policy *policy;

        policy = kzalloc(sizeof(*policy), GFP_KERNEL);
        if (!policy)
                return NULL;

        if (!alloc_cpumask_var(&policy->cpus, GFP_KERNEL))
                goto err_free_policy;

        if (!zalloc_cpumask_var(&policy->related_cpus, GFP_KERNEL))
                goto err_free_cpumask;

        INIT_LIST_HEAD(&policy->policy_list);
        init_rwsem(&policy->rwsem);

        return policy;

err_free_cpumask:
        free_cpumask_var(policy->cpus);
err_free_policy:
        kfree(policy);

        return NULL;
}

static void cpufreq_policy_put_kobj(struct cpufreq_policy *policy)
{
        struct kobject *kobj;
        struct completion *cmp;

        blocking_notifier_call_chain(&cpufreq_policy_notifier_list,
                        CPUFREQ_REMOVE_POLICY, policy);

        down_read(&policy->rwsem);
        kobj = &policy->kobj;
        cmp = &policy->kobj_unregister;
        up_read(&policy->rwsem);
        kobject_put(kobj);

        /*
         * We need to make sure that the underlying kobj is
         * actually not referenced anymore by anybody before we
         * proceed with unloading.
         */
        pr_debug("waiting for dropping of refcount\n");
        wait_for_completion(cmp);
        pr_debug("wait complete\n");
}

static void cpufreq_policy_free(struct cpufreq_policy *policy)
{
        free_cpumask_var(policy->related_cpus);
        free_cpumask_var(policy->cpus);
        kfree(policy);
}

static void update_policy_cpu(struct cpufreq_policy *policy, unsigned int cpu)
{
        if (WARN_ON(cpu == policy->cpu))
                return;

        down_write(&policy->rwsem);

        policy->last_cpu = policy->cpu;
        policy->cpu = cpu;

        up_write(&policy->rwsem);

        cpufreq_frequency_table_update_policy_cpu(policy);
        blocking_notifier_call_chain(&cpufreq_policy_notifier_list,
                        CPUFREQ_UPDATE_POLICY_CPU, policy);
}

static int __cpufreq_add_dev(struct device *dev, struct subsys_interface *sif,
                             bool frozen)
{
        unsigned int j, cpu = dev->id;
        int ret = -ENOMEM;
        struct cpufreq_policy *policy;
        unsigned long flags;
#ifdef CONFIG_HOTPLUG_CPU
        struct cpufreq_policy *tpolicy;
#endif

        if (cpu_is_offline(cpu))
                return 0;

        pr_debug("adding CPU %u\n", cpu);

#ifdef CONFIG_SMP
        /* check whether a different CPU already registered this
         * CPU because it is in the same boat. */
        policy = cpufreq_cpu_get(cpu);
        if (unlikely(policy)) {
                cpufreq_cpu_put(policy);
                return 0;
        }
#endif

        if (!down_read_trylock(&cpufreq_rwsem))
                return 0;

#ifdef CONFIG_HOTPLUG_CPU
        /* Check if this cpu was hot-unplugged earlier and has siblings */
        read_lock_irqsave(&cpufreq_driver_lock, flags);
        list_for_each_entry(tpolicy, &cpufreq_policy_list, policy_list) {
                if (cpumask_test_cpu(cpu, tpolicy->related_cpus)) {
                        read_unlock_irqrestore(&cpufreq_driver_lock, flags);
                        ret = cpufreq_add_policy_cpu(tpolicy, cpu, dev);
                        up_read(&cpufreq_rwsem);
                        return ret;
                }
        }
        read_unlock_irqrestore(&cpufreq_driver_lock, flags);
#endif

        /*
         * Restore the saved policy when doing light-weight init and fall back
         * to the full init if that fails.
         */
        policy = frozen ? cpufreq_policy_restore(cpu) : NULL;
        if (!policy) {
                frozen = false;
                policy = cpufreq_policy_alloc();
                if (!policy)
                        goto nomem_out;
        }

        /*
         * In the resume path, since we restore a saved policy, the assignment
         * to policy->cpu is like an update of the existing policy, rather than
         * the creation of a brand new one. So we need to perform this update
         * by invoking update_policy_cpu().
         */
        if (frozen && cpu != policy->cpu)
                update_policy_cpu(policy, cpu);
        else
                policy->cpu = cpu;

        cpumask_copy(policy->cpus, cpumask_of(cpu));

        init_completion(&policy->kobj_unregister);
        INIT_WORK(&policy->update, handle_update);

        /* call driver. From then on the cpufreq must be able
         * to accept all calls to ->verify and ->setpolicy for this CPU
         */
        ret = cpufreq_driver->init(policy);
        if (ret) {
                pr_debug("initialization failed\n");
                goto err_set_policy_cpu;
        }

        /* related cpus should atleast have policy->cpus */
        cpumask_or(policy->related_cpus, policy->related_cpus, policy->cpus);

        /*
         * affected cpus must always be the one, which are online. We aren't
         * managing offline cpus here.
         */
        cpumask_and(policy->cpus, policy->cpus, cpu_online_mask);

        if (!frozen) {
                policy->user_policy.min = policy->min;
                policy->user_policy.max = policy->max;
        }

        down_write(&policy->rwsem);
        write_lock_irqsave(&cpufreq_driver_lock, flags);
        for_each_cpu(j, policy->cpus)
                per_cpu(cpufreq_cpu_data, j) = policy;
        write_unlock_irqrestore(&cpufreq_driver_lock, flags);

        if (cpufreq_driver->get) {
                policy->cur = cpufreq_driver->get(policy->cpu);
                if (!policy->cur) {
                        pr_err("%s: ->get() failed\n", __func__);
                        goto err_get_freq;
                }
        }

        /*
         * Sometimes boot loaders set CPU frequency to a value outside of
         * frequency table present with cpufreq core. In such cases CPU might be
         * unstable if it has to run on that frequency for long duration of time
         * and so its better to set it to a frequency which is specified in
         * freq-table. This also makes cpufreq stats inconsistent as
         * cpufreq-stats would fail to register because current frequency of CPU
         * isn't found in freq-table.
         *
         * Because we don't want this change to effect boot process badly, we go
         * for the next freq which is >= policy->cur ('cur' must be set by now,
         * otherwise we will end up setting freq to lowest of the table as 'cur'
         * is initialized to zero).
         *
         * We are passing target-freq as "policy->cur - 1" otherwise
         * __cpufreq_driver_target() would simply fail, as policy->cur will be
         * equal to target-freq.
         */
        if ((cpufreq_driver->flags & CPUFREQ_NEED_INITIAL_FREQ_CHECK)
            && has_target()) {
                /* Are we running at unknown frequency ? */
                ret = cpufreq_frequency_table_get_index(policy, policy->cur);
                if (ret == -EINVAL) {
                        /* Warn user and fix it */
                        pr_warn("%s: CPU%d: Running at unlisted freq: %u KHz\n",
                                __func__, policy->cpu, policy->cur);
                        ret = __cpufreq_driver_target(policy, policy->cur - 1,
                                CPUFREQ_RELATION_L);

                        /*
                         * Reaching here after boot in a few seconds may not
                         * mean that system will remain stable at "unknown"
                         * frequency for longer duration. Hence, a BUG_ON().
                         */
                        BUG_ON(ret);
                        pr_warn("%s: CPU%d: Unlisted initial frequency changed to: %u KHz\n",
                                __func__, policy->cpu, policy->cur);
                }
        }

        blocking_notifier_call_chain(&cpufreq_policy_notifier_list,
                                     CPUFREQ_START, policy);

        if (!frozen) {
                ret = cpufreq_add_dev_interface(policy, dev);
                if (ret)
                        goto err_out_unregister;
                blocking_notifier_call_chain(&cpufreq_policy_notifier_list,
                                CPUFREQ_CREATE_POLICY, policy);
        }

        write_lock_irqsave(&cpufreq_driver_lock, flags);
        list_add(&policy->policy_list, &cpufreq_policy_list);
        write_unlock_irqrestore(&cpufreq_driver_lock, flags);

        cpufreq_init_policy(policy);

        if (!frozen) {
                policy->user_policy.policy = policy->policy;
                policy->user_policy.governor = policy->governor;
        }
        up_write(&policy->rwsem);

        kobject_uevent(&policy->kobj, KOBJ_ADD);
        up_read(&cpufreq_rwsem);

        pr_debug("initialization complete\n");

        return 0;

err_out_unregister:
err_get_freq:
        write_lock_irqsave(&cpufreq_driver_lock, flags);
        for_each_cpu(j, policy->cpus)
                per_cpu(cpufreq_cpu_data, j) = NULL;
        write_unlock_irqrestore(&cpufreq_driver_lock, flags);

        if (cpufreq_driver->exit)
                cpufreq_driver->exit(policy);
err_set_policy_cpu:
        if (frozen) {
                /* Do not leave stale fallback data behind. */
                per_cpu(cpufreq_cpu_data_fallback, cpu) = NULL;
                cpufreq_policy_put_kobj(policy);
        }
        cpufreq_policy_free(policy);

nomem_out:
        up_read(&cpufreq_rwsem);

        return ret;
}

/**
 * cpufreq_add_dev - add a CPU device
 *
 * Adds the cpufreq interface for a CPU device.
 *
 * The Oracle says: try running cpufreq registration/unregistration concurrently
 * with with cpu hotplugging and all hell will break loose. Tried to clean this
 * mess up, but more thorough testing is needed. - Mathieu
 */
static int cpufreq_add_dev(struct device *dev, struct subsys_interface *sif)
{
        return __cpufreq_add_dev(dev, sif, false);
}

static int cpufreq_nominate_new_policy_cpu(struct cpufreq_policy *policy,
                                           unsigned int old_cpu)
{
        struct device *cpu_dev;
        int ret;

        /* first sibling now owns the new sysfs dir */
        cpu_dev = get_cpu_device(cpumask_any_but(policy->cpus, old_cpu));

        sysfs_remove_link(&cpu_dev->kobj, "cpufreq");
        ret = kobject_move(&policy->kobj, &cpu_dev->kobj);
        if (ret) {
                pr_err("%s: Failed to move kobj: %d", __func__, ret);

                down_write(&policy->rwsem);
                cpumask_set_cpu(old_cpu, policy->cpus);
                up_write(&policy->rwsem);

                ret = sysfs_create_link(&cpu_dev->kobj, &policy->kobj,
                                        "cpufreq");

                return -EINVAL;
        }

        return cpu_dev->id;
}

static int __cpufreq_remove_dev_prepare(struct device *dev,
                                        struct subsys_interface *sif,
                                        bool frozen)
{
        unsigned int cpu = dev->id, cpus;
        int new_cpu, ret;
        unsigned long flags;
        struct cpufreq_policy *policy;

        pr_debug("%s: unregistering CPU %u\n", __func__, cpu);

        write_lock_irqsave(&cpufreq_driver_lock, flags);

        policy = per_cpu(cpufreq_cpu_data, cpu);

        /* Save the policy somewhere when doing a light-weight tear-down */
        if (frozen)
                per_cpu(cpufreq_cpu_data_fallback, cpu) = policy;

        write_unlock_irqrestore(&cpufreq_driver_lock, flags);

        if (!policy) {
                pr_debug("%s: No cpu_data found\n", __func__);
                return -EINVAL;
        }

        if (has_target()) {
                ret = __cpufreq_governor(policy, CPUFREQ_GOV_STOP);
                if (ret) {
                        pr_err("%s: Failed to stop governor\n", __func__);
                        return ret;
                }
        }

        if (!cpufreq_driver->setpolicy)
                strncpy(per_cpu(cpufreq_cpu_governor, cpu),
                        policy->governor->name, CPUFREQ_NAME_LEN);

        down_read(&policy->rwsem);
        cpus = cpumask_weight(policy->cpus);
        up_read(&policy->rwsem);

        if (cpu != policy->cpu) {
                sysfs_remove_link(&dev->kobj, "cpufreq");
        } else if (cpus > 1) {
                new_cpu = cpufreq_nominate_new_policy_cpu(policy, cpu);
                if (new_cpu >= 0) {
                        update_policy_cpu(policy, new_cpu);

                        if (!frozen) {
                                pr_debug("%s: policy Kobject moved to cpu: %d from: %d\n",
                                                __func__, new_cpu, cpu);
                        }
                }
        }

        return 0;
}

static int __cpufreq_remove_dev_finish(struct device *dev,
                                       struct subsys_interface *sif,
                                       bool frozen)
{
        unsigned int cpu = dev->id, cpus;
        int ret;
        unsigned long flags;
        struct cpufreq_policy *policy;

        read_lock_irqsave(&cpufreq_driver_lock, flags);
        policy = per_cpu(cpufreq_cpu_data, cpu);
        read_unlock_irqrestore(&cpufreq_driver_lock, flags);

        if (!policy) {
                pr_debug("%s: No cpu_data found\n", __func__);
                return -EINVAL;
        }

        down_write(&policy->rwsem);
        cpus = cpumask_weight(policy->cpus);

        if (cpus > 1)
                cpumask_clear_cpu(cpu, policy->cpus);
        up_write(&policy->rwsem);

        /* If cpu is last user of policy, free policy */
        if (cpus == 1) {
                if (has_target()) {
                        ret = __cpufreq_governor(policy,
                                        CPUFREQ_GOV_POLICY_EXIT);
                        if (ret) {
                                pr_err("%s: Failed to exit governor\n",
                                                __func__);
                                return ret;
                        }
                }

                if (!frozen)
                        cpufreq_policy_put_kobj(policy);

                /*
                 * Perform the ->exit() even during light-weight tear-down,
                 * since this is a core component, and is essential for the
                 * subsequent light-weight ->init() to succeed.
                 */
                if (cpufreq_driver->exit)
                        cpufreq_driver->exit(policy);

                /* Remove policy from list of active policies */
                write_lock_irqsave(&cpufreq_driver_lock, flags);
                list_del(&policy->policy_list);
                write_unlock_irqrestore(&cpufreq_driver_lock, flags);

                if (!frozen)
                        cpufreq_policy_free(policy);
        } else {
                if (has_target()) {
                        if ((ret = __cpufreq_governor(policy, CPUFREQ_GOV_START)) ||
                                        (ret = __cpufreq_governor(policy, CPUFREQ_GOV_LIMITS))) {
                                pr_err("%s: Failed to start governor\n",
                                                __func__);
                                return ret;
                        }
                }
        }

        per_cpu(cpufreq_cpu_data, cpu) = NULL;
        return 0;
}

/**
 * cpufreq_remove_dev - remove a CPU device
 *
 * Removes the cpufreq interface for a CPU device.
 */
static int cpufreq_remove_dev(struct device *dev, struct subsys_interface *sif)
{
        unsigned int cpu = dev->id;
        int ret;

        if (cpu_is_offline(cpu))
                return 0;

        ret = __cpufreq_remove_dev_prepare(dev, sif, false);

        if (!ret)
                ret = __cpufreq_remove_dev_finish(dev, sif, false);

        return ret;
}

static void handle_update(struct work_struct *work)
{
        struct cpufreq_policy *policy =
                container_of(work, struct cpufreq_policy, update);
        unsigned int cpu = policy->cpu;
        pr_debug("handle_update for cpu %u called\n", cpu);
        cpufreq_update_policy(cpu);
}

/**
 *      cpufreq_out_of_sync - If actual and saved CPU frequency differs, we're
 *      in deep trouble.
 *      @cpu: cpu number
 *      @old_freq: CPU frequency the kernel thinks the CPU runs at
 *      @new_freq: CPU frequency the CPU actually runs at
 *
 *      We adjust to current frequency first, and need to clean up later.
 *      So either call to cpufreq_update_policy() or schedule handle_update()).
 */
static void cpufreq_out_of_sync(unsigned int cpu, unsigned int old_freq,
                                unsigned int new_freq)
{
        struct cpufreq_policy *policy;
        struct cpufreq_freqs freqs;
        unsigned long flags;

        pr_debug("Warning: CPU frequency out of sync: cpufreq and timing "
               "core thinks of %u, is %u kHz.\n", old_freq, new_freq);

        freqs.old = old_freq;
        freqs.new = new_freq;

        read_lock_irqsave(&cpufreq_driver_lock, flags);
        policy = per_cpu(cpufreq_cpu_data, cpu);
        read_unlock_irqrestore(&cpufreq_driver_lock, flags);

        cpufreq_notify_transition(policy, &freqs, CPUFREQ_PRECHANGE);
        cpufreq_notify_transition(policy, &freqs, CPUFREQ_POSTCHANGE);
}

/**
 * cpufreq_quick_get - get the CPU frequency (in kHz) from policy->cur
 * @cpu: CPU number
 *
 * This is the last known freq, without actually getting it from the driver.
 * Return value will be same as what is shown in scaling_cur_freq in sysfs.
 */
unsigned int cpufreq_quick_get(unsigned int cpu)
{
        struct cpufreq_policy *policy;
        unsigned int ret_freq = 0;

        if (cpufreq_driver && cpufreq_driver->setpolicy && cpufreq_driver->get)
                return cpufreq_driver->get(cpu);

        policy = cpufreq_cpu_get(cpu);
        if (policy) {
                ret_freq = policy->cur;
                cpufreq_cpu_put(policy);
        }

        return ret_freq;
}
EXPORT_SYMBOL(cpufreq_quick_get);

/**
 * cpufreq_quick_get_max - get the max reported CPU frequency for this CPU
 * @cpu: CPU number
 *
 * Just return the max possible frequency for a given CPU.
 */
unsigned int cpufreq_quick_get_max(unsigned int cpu)
{
        struct cpufreq_policy *policy = cpufreq_cpu_get(cpu);
        unsigned int ret_freq = 0;

        if (policy) {
                ret_freq = policy->max;
                cpufreq_cpu_put(policy);
        }

        return ret_freq;
}
EXPORT_SYMBOL(cpufreq_quick_get_max);

static unsigned int __cpufreq_get(unsigned int cpu)
{
        struct cpufreq_policy *policy = per_cpu(cpufreq_cpu_data, cpu);
        unsigned int ret_freq = 0;

        if (!cpufreq_driver->get)
                return ret_freq;

        ret_freq = cpufreq_driver->get(cpu);

        if (ret_freq && policy->cur &&
                !(cpufreq_driver->flags & CPUFREQ_CONST_LOOPS)) {
                /* verify no discrepancy between actual and
                                        saved value exists */
                if (unlikely(ret_freq != policy->cur)) {
                        cpufreq_out_of_sync(cpu, policy->cur, ret_freq);
                        schedule_work(&policy->update);
                }
        }

        return ret_freq;
}

/**
 * cpufreq_get - get the current CPU frequency (in kHz)
 * @cpu: CPU number
 *
 * Get the CPU current (static) CPU frequency
 */
unsigned int cpufreq_get(unsigned int cpu)
{
        struct cpufreq_policy *policy = cpufreq_cpu_get(cpu);
        unsigned int ret_freq = 0;

        if (policy) {
                down_read(&policy->rwsem);
                ret_freq = __cpufreq_get(cpu);
                up_read(&policy->rwsem);

                cpufreq_cpu_put(policy);
        }

        return ret_freq;
}
EXPORT_SYMBOL(cpufreq_get);

static struct subsys_interface cpufreq_interface = {
        .name           = "cpufreq",
        .subsys         = &cpu_subsys,
        .add_dev        = cpufreq_add_dev,
        .remove_dev     = cpufreq_remove_dev,
};

/**
 * cpufreq_suspend() - Suspend CPUFreq governors
 *
 * Called during system wide Suspend/Hibernate cycles for suspending governors
 * as some platforms can't change frequency after this point in suspend cycle.
 * Because some of the devices (like: i2c, regulators, etc) they use for
 * changing frequency are suspended quickly after this point.
 */
void cpufreq_suspend(void)
{
        struct cpufreq_policy *policy;

        if (!cpufreq_driver)
                return;

        if (!has_target())
                return;

        pr_debug("%s: Suspending Governors\n", __func__);

        list_for_each_entry(policy, &cpufreq_policy_list, policy_list) {
                if (__cpufreq_governor(policy, CPUFREQ_GOV_STOP))
                        pr_err("%s: Failed to stop governor for policy: %p\n",
                                __func__, policy);
                else if (cpufreq_driver->suspend
                    && cpufreq_driver->suspend(policy))
                        pr_err("%s: Failed to suspend driver: %p\n", __func__,
                                policy);
        }

        cpufreq_suspended = true;
}

/**
 * cpufreq_resume() - Resume CPUFreq governors
 *
 * Called during system wide Suspend/Hibernate cycle for resuming governors that
 * are suspended with cpufreq_suspend().
 */
void cpufreq_resume(void)
{
        struct cpufreq_policy *policy;

        if (!cpufreq_driver)
                return;

        if (!has_target())
                return;

        pr_debug("%s: Resuming Governors\n", __func__);

        cpufreq_suspended = false;

        list_for_each_entry(policy, &cpufreq_policy_list, policy_list) {
                if (__cpufreq_governor(policy, CPUFREQ_GOV_START)
                    || __cpufreq_governor(policy, CPUFREQ_GOV_LIMITS))
                        pr_err("%s: Failed to start governor for policy: %p\n",
                                __func__, policy);
                else if (cpufreq_driver->resume
                    && cpufreq_driver->resume(policy))
                        pr_err("%s: Failed to resume driver: %p\n", __func__,
                                policy);

                /*
                 * schedule call cpufreq_update_policy() for boot CPU, i.e. last
                 * policy in list. It will verify that the current freq is in
                 * sync with what we believe it to be.
                 */
                if (list_is_last(&policy->policy_list, &cpufreq_policy_list))
                        schedule_work(&policy->update);
        }
}

/**
 *      cpufreq_get_current_driver - return current driver's name
 *
 *      Return the name string of the currently loaded cpufreq driver
 *      or NULL, if none.
 */
const char *cpufreq_get_current_driver(void)
{
        if (cpufreq_driver)
                return cpufreq_driver->name;

        return NULL;
}
EXPORT_SYMBOL_GPL(cpufreq_get_current_driver);

/*********************************************************************
 *                     NOTIFIER LISTS INTERFACE                      *
 *********************************************************************/

/**
 *      cpufreq_register_notifier - register a driver with cpufreq
 *      @nb: notifier function to register
 *      @list: CPUFREQ_TRANSITION_NOTIFIER or CPUFREQ_POLICY_NOTIFIER
 *
 *      Add a driver to one of two lists: either a list of drivers that
 *      are notified about clock rate changes (once before and once after
 *      the transition), or a list of drivers that are notified about
 *      changes in cpufreq policy.
 *
 *      This function may sleep, and has the same return conditions as
 *      blocking_notifier_chain_register.
 */
int cpufreq_register_notifier(struct notifier_block *nb, unsigned int list)
{
        int ret;

        if (cpufreq_disabled())
                return -EINVAL;

        WARN_ON(!init_cpufreq_transition_notifier_list_called);

        switch (list) {
        case CPUFREQ_TRANSITION_NOTIFIER:
                ret = srcu_notifier_chain_register(
                                &cpufreq_transition_notifier_list, nb);
                break;
        case CPUFREQ_POLICY_NOTIFIER:
                ret = blocking_notifier_chain_register(
                                &cpufreq_policy_notifier_list, nb);
                break;
        default:
                ret = -EINVAL;
        }

        return ret;
}
EXPORT_SYMBOL(cpufreq_register_notifier);

/**
 *      cpufreq_unregister_notifier - unregister a driver with cpufreq
 *      @nb: notifier block to be unregistered
 *      @list: CPUFREQ_TRANSITION_NOTIFIER or CPUFREQ_POLICY_NOTIFIER
 *
 *      Remove a driver from the CPU frequency notifier list.
 *
 *      This function may sleep, and has the same return conditions as
 *      blocking_notifier_chain_unregister.
 */
int cpufreq_unregister_notifier(struct notifier_block *nb, unsigned int list)
{
        int ret;

        if (cpufreq_disabled())
                return -EINVAL;

        switch (list) {
        case CPUFREQ_TRANSITION_NOTIFIER:
                ret = srcu_notifier_chain_unregister(
                                &cpufreq_transition_notifier_list, nb);
                break;
        case CPUFREQ_POLICY_NOTIFIER:
                ret = blocking_notifier_chain_unregister(
                                &cpufreq_policy_notifier_list, nb);
                break;
        default:
                ret = -EINVAL;
        }

        return ret;
}
EXPORT_SYMBOL(cpufreq_unregister_notifier);


/*********************************************************************
 *                              GOVERNORS                            *
 *********************************************************************/

int __cpufreq_driver_target(struct cpufreq_policy *policy,
                            unsigned int target_freq,
                            unsigned int relation)
{
        int retval = -EINVAL;
        unsigned int old_target_freq = target_freq;

        if (cpufreq_disabled())
                return -ENODEV;

        /* Make sure that target_freq is within supported range */
        if (target_freq > policy->max)
                target_freq = policy->max;
        if (target_freq < policy->min)
                target_freq = policy->min;

        pr_debug("target for CPU %u: %u kHz, relation %u, requested %u kHz\n",
                        policy->cpu, target_freq, relation, old_target_freq);

        /*
         * This might look like a redundant call as we are checking it again
         * after finding index. But it is left intentionally for cases where
         * exactly same freq is called again and so we can save on few function
         * calls.
         */
        if (target_freq == policy->cur)
                return 0;

        if (cpufreq_driver->target)
                retval = cpufreq_driver->target(policy, target_freq, relation);
        else if (cpufreq_driver->target_index) {
                struct cpufreq_frequency_table *freq_table;
                struct cpufreq_freqs freqs;
                bool notify;
                int index;

                freq_table = cpufreq_frequency_get_table(policy->cpu);
                if (unlikely(!freq_table)) {
                        pr_err("%s: Unable to find freq_table\n", __func__);
                        goto out;
                }

                retval = cpufreq_frequency_table_target(policy, freq_table,
                                target_freq, relation, &index);
                if (unlikely(retval)) {
                        pr_err("%s: Unable to find matching freq\n", __func__);
                        goto out;
                }

                if (freq_table[index].frequency == policy->cur) {
                        retval = 0;
                        goto out;
                }

                notify = !(cpufreq_driver->flags & CPUFREQ_ASYNC_NOTIFICATION);

                if (notify) {
                        freqs.old = policy->cur;
                        freqs.new = freq_table[index].frequency;
                        freqs.flags = 0;

                        pr_debug("%s: cpu: %d, oldfreq: %u, new freq: %u\n",
                                        __func__, policy->cpu, freqs.old,
                                        freqs.new);

                        cpufreq_notify_transition(policy, &freqs,
                                        CPUFREQ_PRECHANGE);
                }

                retval = cpufreq_driver->target_index(policy, index);
                if (retval)
                        pr_err("%s: Failed to change cpu frequency: %d\n",
                                        __func__, retval);

                if (notify)
                        cpufreq_notify_post_transition(policy, &freqs, retval);
        }

out:
        return retval;
}
EXPORT_SYMBOL_GPL(__cpufreq_driver_target);

int cpufreq_driver_target(struct cpufreq_policy *policy,
                          unsigned int target_freq,
                          unsigned int relation)
{
        int ret = -EINVAL;

        down_write(&policy->rwsem);

        ret = __cpufreq_driver_target(policy, target_freq, relation);

        up_write(&policy->rwsem);

        return ret;
}
EXPORT_SYMBOL_GPL(cpufreq_driver_target);

/*
 * when "event" is CPUFREQ_GOV_LIMITS
 */

static int __cpufreq_governor(struct cpufreq_policy *policy,
                                        unsigned int event)
{
        int ret;

        /* Only must be defined when default governor is known to have latency
           restrictions, like e.g. conservative or ondemand.
           That this is the case is already ensured in Kconfig
        */
#ifdef CONFIG_CPU_FREQ_GOV_PERFORMANCE
        struct cpufreq_governor *gov = &cpufreq_gov_performance;
#else
        struct cpufreq_governor *gov = NULL;
#endif

        /* Don't start any governor operations if we are entering suspend */
        if (cpufreq_suspended)
                return 0;

        if (policy->governor->max_transition_latency &&
            policy->cpuinfo.transition_latency >
            policy->governor->max_transition_latency) {
                if (!gov)
                        return -EINVAL;
                else {
                        printk(KERN_WARNING "%s governor failed, too long"
                               " transition latency of HW, fallback"
                               " to %s governor\n",
                               policy->governor->name,
                               gov->name);
                        policy->governor = gov;
                }
        }

        if (event == CPUFREQ_GOV_POLICY_INIT)
                if (!try_module_get(policy->governor->owner))
                        return -EINVAL;

        pr_debug("__cpufreq_governor for CPU %u, event %u\n",
                                                policy->cpu, event);

        mutex_lock(&cpufreq_governor_lock);
        if ((policy->governor_enabled && event == CPUFREQ_GOV_START)
            || (!policy->governor_enabled
            && (event == CPUFREQ_GOV_LIMITS || event == CPUFREQ_GOV_STOP))) {
                mutex_unlock(&cpufreq_governor_lock);
                return -EBUSY;
        }

        if (event == CPUFREQ_GOV_STOP)
                policy->governor_enabled = false;
        else if (event == CPUFREQ_GOV_START)
                policy->governor_enabled = true;

        mutex_unlock(&cpufreq_governor_lock);

        ret = policy->governor->governor(policy, event);

        if (!ret) {
                if (event == CPUFREQ_GOV_POLICY_INIT)
                        policy->governor->initialized++;
                else if (event == CPUFREQ_GOV_POLICY_EXIT)
                        policy->governor->initialized--;
        } else {
                /* Restore original values */
                mutex_lock(&cpufreq_governor_lock);
                if (event == CPUFREQ_GOV_STOP)
                        policy->governor_enabled = true;
                else if (event == CPUFREQ_GOV_START)
                        policy->governor_enabled = false;
                mutex_unlock(&cpufreq_governor_lock);
        }

        if (((event == CPUFREQ_GOV_POLICY_INIT) && ret) ||
                        ((event == CPUFREQ_GOV_POLICY_EXIT) && !ret))
                module_put(policy->governor->owner);

        return ret;
}

int cpufreq_register_governor(struct cpufreq_governor *governor)
{
        int err;

        if (!governor)
                return -EINVAL;

        if (cpufreq_disabled())
                return -ENODEV;

        mutex_lock(&cpufreq_governor_mutex);

        governor->initialized = 0;
        err = -EBUSY;
        if (__find_governor(governor->name) == NULL) {
                err = 0;
                list_add(&governor->governor_list, &cpufreq_governor_list);
        }

        mutex_unlock(&cpufreq_governor_mutex);
        return err;
}
EXPORT_SYMBOL_GPL(cpufreq_register_governor);

void cpufreq_unregister_governor(struct cpufreq_governor *governor)
{
        int cpu;

        if (!governor)
                return;

        if (cpufreq_disabled())
                return;

        for_each_present_cpu(cpu) {
                if (cpu_online(cpu))
                        continue;
                if (!strcmp(per_cpu(cpufreq_cpu_governor, cpu), governor->name))
                        strcpy(per_cpu(cpufreq_cpu_governor, cpu), "\0");
        }

        mutex_lock(&cpufreq_governor_mutex);
        list_del(&governor->governor_list);
        mutex_unlock(&cpufreq_governor_mutex);
        return;
}
EXPORT_SYMBOL_GPL(cpufreq_unregister_governor);


/*********************************************************************
 *                          POLICY INTERFACE                         *
 *********************************************************************/

/**
 * cpufreq_get_policy - get the current cpufreq_policy
 * @policy: struct cpufreq_policy into which the current cpufreq_policy
 *      is written
 *
 * Reads the current cpufreq policy.
 */
int cpufreq_get_policy(struct cpufreq_policy *policy, unsigned int cpu)
{
        struct cpufreq_policy *cpu_policy;
        if (!policy)
                return -EINVAL;

        cpu_policy = cpufreq_cpu_get(cpu);
        if (!cpu_policy)
                return -EINVAL;

        memcpy(policy, cpu_policy, sizeof(*policy));

        cpufreq_cpu_put(cpu_policy);
        return 0;
}
EXPORT_SYMBOL(cpufreq_get_policy);

/*
 * policy : current policy.
 * new_policy: policy to be set.
 */
static int cpufreq_set_policy(struct cpufreq_policy *policy,
                                struct cpufreq_policy *new_policy)
{
        struct cpufreq_governor *old_gov;
        int ret;

        pr_debug("setting new policy for CPU %u: %u - %u kHz\n", new_policy->cpu,
                new_policy->min, new_policy->max);

        memcpy(&new_policy->cpuinfo, &policy->cpuinfo, sizeof(policy->cpuinfo));

        if (new_policy->min > policy->max || new_policy->max < policy->min)
                return -EINVAL;

        /* verify the cpu speed can be set within this limit */
        ret = cpufreq_driver->verify(new_policy);
        if (ret)
                return ret;

        /* adjust if necessary - all reasons */
        blocking_notifier_call_chain(&cpufreq_policy_notifier_list,
                        CPUFREQ_ADJUST, new_policy);

        /* adjust if necessary - hardware incompatibility*/
        blocking_notifier_call_chain(&cpufreq_policy_notifier_list,
                        CPUFREQ_INCOMPATIBLE, new_policy);

        /*
         * verify the cpu speed can be set within this limit, which might be
         * different to the first one
         */
        ret = cpufreq_driver->verify(new_policy);
        if (ret)
                return ret;

        /* notification of the new policy */
        blocking_notifier_call_chain(&cpufreq_policy_notifier_list,
                        CPUFREQ_NOTIFY, new_policy);

        policy->min = new_policy->min;
        policy->max = new_policy->max;

        pr_debug("new min and max freqs are %u - %u kHz\n",
                                        policy->min, policy->max);

        if (cpufreq_driver->setpolicy) {
                policy->policy = new_policy->policy;
                pr_debug("setting range\n");
                return cpufreq_driver->setpolicy(new_policy);
        }

        if (new_policy->governor == policy->governor)
                goto out;

        pr_debug("governor switch\n");

        /* save old, working values */
        old_gov = policy->governor;
        /* end old governor */
        if (old_gov) {
                __cpufreq_governor(policy, CPUFREQ_GOV_STOP);
                up_write(&policy->rwsem);
                __cpufreq_governor(policy,CPUFREQ_GOV_POLICY_EXIT);
                down_write(&policy->rwsem);
        }

        /* start new governor */
        policy->governor = new_policy->governor;
        if (!__cpufreq_governor(policy, CPUFREQ_GOV_POLICY_INIT)) {
                if (!__cpufreq_governor(policy, CPUFREQ_GOV_START))
                        goto out;

                up_write(&policy->rwsem);
                __cpufreq_governor(policy, CPUFREQ_GOV_POLICY_EXIT);
                down_write(&policy->rwsem);
        }

        /* new governor failed, so re-start old one */
        pr_debug("starting governor %s failed\n", policy->governor->name);
        if (old_gov) {
                policy->governor = old_gov;
                __cpufreq_governor(policy, CPUFREQ_GOV_POLICY_INIT);
                __cpufreq_governor(policy, CPUFREQ_GOV_START);
        }

        return -EINVAL;

 out:
        pr_debug("governor: change or update limits\n");
        return __cpufreq_governor(policy, CPUFREQ_GOV_LIMITS);
}

/**
 *      cpufreq_update_policy - re-evaluate an existing cpufreq policy
 *      @cpu: CPU which shall be re-evaluated
 *
 *      Useful for policy notifiers which have different necessities
 *      at different times.
 */
int cpufreq_update_policy(unsigned int cpu)
{
        struct cpufreq_policy *policy = cpufreq_cpu_get(cpu);
        struct cpufreq_policy new_policy;
        int ret;

        if (!policy) {
                ret = -ENODEV;
                goto no_policy;
        }

        down_write(&policy->rwsem);

        pr_debug("updating policy for CPU %u\n", cpu);
        memcpy(&new_policy, policy, sizeof(*policy));
        new_policy.min = policy->user_policy.min;
        new_policy.max = policy->user_policy.max;
        new_policy.policy = policy->user_policy.policy;
        new_policy.governor = policy->user_policy.governor;

        /*
         * BIOS might change freq behind our back
         * -> ask driver for current freq and notify governors about a change
         */
        if (cpufreq_driver->get) {
                new_policy.cur = cpufreq_driver->get(cpu);
                if (WARN_ON(!new_policy.cur)) {
                        ret = -EIO;
                        goto no_policy;
                }

                if (!policy->cur) {
                        pr_debug("Driver did not initialize current freq");
                        policy->cur = new_policy.cur;
                } else {
                        if (policy->cur != new_policy.cur && has_target())
                                cpufreq_out_of_sync(cpu, policy->cur,
                                                                new_policy.cur);
                }
        }

        ret = cpufreq_set_policy(policy, &new_policy);

        up_write(&policy->rwsem);

        cpufreq_cpu_put(policy);
no_policy:
        return ret;
}
EXPORT_SYMBOL(cpufreq_update_policy);

static int cpufreq_cpu_callback(struct notifier_block *nfb,
                                        unsigned long action, void *hcpu)
{
        unsigned int cpu = (unsigned long)hcpu;
        struct device *dev;
        bool frozen = false;

        dev = get_cpu_device(cpu);
        if (dev) {

                if (action & CPU_TASKS_FROZEN)
                        frozen = true;

                switch (action & ~CPU_TASKS_FROZEN) {
                case CPU_ONLINE:
                        __cpufreq_add_dev(dev, NULL, frozen);
                        break;

                case CPU_DOWN_PREPARE:
                        __cpufreq_remove_dev_prepare(dev, NULL, frozen);
                        break;

                case CPU_POST_DEAD:
                        __cpufreq_remove_dev_finish(dev, NULL, frozen);
                        break;

                case CPU_DOWN_FAILED:
                        __cpufreq_add_dev(dev, NULL, frozen);
                        break;
                }
        }
        return NOTIFY_OK;
}

static struct notifier_block __refdata cpufreq_cpu_notifier = {
        .notifier_call = cpufreq_cpu_callback,
};

/*********************************************************************
 *               BOOST                                               *
 *********************************************************************/
static int cpufreq_boost_set_sw(int state)
{
        struct cpufreq_frequency_table *freq_table;
        struct cpufreq_policy *policy;
        int ret = -EINVAL;

        list_for_each_entry(policy, &cpufreq_policy_list, policy_list) {
                freq_table = cpufreq_frequency_get_table(policy->cpu);
                if (freq_table) {
                        ret = cpufreq_frequency_table_cpuinfo(policy,
                                                        freq_table);
                        if (ret) {
                                pr_err("%s: Policy frequency update failed\n",
                                       __func__);
                                break;
                        }
                        policy->user_policy.max = policy->max;
                        __cpufreq_governor(policy, CPUFREQ_GOV_LIMITS);
                }
        }

        return ret;
}

int cpufreq_boost_trigger_state(int state)
{
        unsigned long flags;
        int ret = 0;

        if (cpufreq_driver->boost_enabled == state)
                return 0;

        write_lock_irqsave(&cpufreq_driver_lock, flags);
        cpufreq_driver->boost_enabled = state;
        write_unlock_irqrestore(&cpufreq_driver_lock, flags);

        ret = cpufreq_driver->set_boost(state);
        if (ret) {
                write_lock_irqsave(&cpufreq_driver_lock, flags);
                cpufreq_driver->boost_enabled = !state;
                write_unlock_irqrestore(&cpufreq_driver_lock, flags);

                pr_err("%s: Cannot %s BOOST\n", __func__,
                       state ? "enable" : "disable");
        }

        return ret;
}

int cpufreq_boost_supported(void)
{
        if (likely(cpufreq_driver))
                return cpufreq_driver->boost_supported;

        return 0;
}
EXPORT_SYMBOL_GPL(cpufreq_boost_supported);

int cpufreq_boost_enabled(void)
{
        return cpufreq_driver->boost_enabled;
}
EXPORT_SYMBOL_GPL(cpufreq_boost_enabled);

/*********************************************************************
 *               REGISTER / UNREGISTER CPUFREQ DRIVER                *
 *********************************************************************/

/**
 * cpufreq_register_driver - register a CPU Frequency driver
 * @driver_data: A struct cpufreq_driver containing the values#
 * submitted by the CPU Frequency driver.
 *
 * Registers a CPU Frequency driver to this core code. This code
 * returns zero on success, -EBUSY when another driver got here first
 * (and isn't unregistered in the meantime).
 *
 */
int cpufreq_register_driver(struct cpufreq_driver *driver_data)
{
        unsigned long flags;
        int ret;

        if (cpufreq_disabled())
                return -ENODEV;

        if (!driver_data || !driver_data->verify || !driver_data->init ||
            !(driver_data->setpolicy || driver_data->target_index ||
                    driver_data->target))
                return -EINVAL;

        pr_debug("trying to register driver %s\n", driver_data->name);

        if (driver_data->setpolicy)
                driver_data->flags |= CPUFREQ_CONST_LOOPS;

        write_lock_irqsave(&cpufreq_driver_lock, flags);
        if (cpufreq_driver) {
                write_unlock_irqrestore(&cpufreq_driver_lock, flags);
                return -EEXIST;
        }
        cpufreq_driver = driver_data;
        write_unlock_irqrestore(&cpufreq_driver_lock, flags);

        if (cpufreq_boost_supported()) {
                /*
                 * Check if driver provides function to enable boost -
                 * if not, use cpufreq_boost_set_sw as default
                 */
                if (!cpufreq_driver->set_boost)
                        cpufreq_driver->set_boost = cpufreq_boost_set_sw;

                ret = cpufreq_sysfs_create_file(&boost.attr);
                if (ret) {
                        pr_err("%s: cannot register global BOOST sysfs file\n",
                                __func__);
                        goto err_null_driver;
                }
        }

        ret = subsys_interface_register(&cpufreq_interface);
        if (ret)
                goto err_boost_unreg;

        if (!(cpufreq_driver->flags & CPUFREQ_STICKY)) {
                int i;
                ret = -ENODEV;

                /* check for at least one working CPU */
                for (i = 0; i < nr_cpu_ids; i++)
                        if (cpu_possible(i) && per_cpu(cpufreq_cpu_data, i)) {
                                ret = 0;
                                break;
                        }

                /* if all ->init() calls failed, unregister */
                if (ret) {
                        pr_debug("no CPU initialized for driver %s\n",
                                                        driver_data->name);
                        goto err_if_unreg;
                }
        }

        register_hotcpu_notifier(&cpufreq_cpu_notifier);
        pr_debug("driver %s up and running\n", driver_data->name);

        return 0;
err_if_unreg:
        subsys_interface_unregister(&cpufreq_interface);
err_boost_unreg:
        if (cpufreq_boost_supported())
                cpufreq_sysfs_remove_file(&boost.attr);
err_null_driver:
        write_lock_irqsave(&cpufreq_driver_lock, flags);
        cpufreq_driver = NULL;
        write_unlock_irqrestore(&cpufreq_driver_lock, flags);
        return ret;
}
EXPORT_SYMBOL_GPL(cpufreq_register_driver);

/**
 * cpufreq_unregister_driver - unregister the current CPUFreq driver
 *
 * Unregister the current CPUFreq driver. Only call this if you have
 * the right to do so, i.e. if you have succeeded in initialising before!
 * Returns zero if successful, and -EINVAL if the cpufreq_driver is
 * currently not initialised.
 */
int cpufreq_unregister_driver(struct cpufreq_driver *driver)
{
        unsigned long flags;

        if (!cpufreq_driver || (driver != cpufreq_driver))
                return -EINVAL;

        pr_debug("unregistering driver %s\n", driver->name);

        subsys_interface_unregister(&cpufreq_interface);
        if (cpufreq_boost_supported())
                cpufreq_sysfs_remove_file(&boost.attr);

        unregister_hotcpu_notifier(&cpufreq_cpu_notifier);

        down_write(&cpufreq_rwsem);
        write_lock_irqsave(&cpufreq_driver_lock, flags);

        cpufreq_driver = NULL;

        write_unlock_irqrestore(&cpufreq_driver_lock, flags);
        up_write(&cpufreq_rwsem);

        return 0;
}
EXPORT_SYMBOL_GPL(cpufreq_unregister_driver);

static int __init cpufreq_core_init(void)
{
        if (cpufreq_disabled())
                return -ENODEV;

        cpufreq_global_kobject = kobject_create();
        BUG_ON(!cpufreq_global_kobject);

        return 0;
}
core_initcall(cpufreq_core_init);