text: /*
   *  linux/drivers/cpufreq/cpufreq.c
   *
   *  Copyright (C) 2001 Russell King
   *            (C) 2002 - 2003 Dominik Brodowski <linux@brodo.de>
   *
   *  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/kernel.h>
  #include <linux/module.h>
  #include <linux/init.h>
  #include <linux/notifier.h>
  #include <linux/cpufreq.h>
  #include <linux/delay.h>
  #include <linux/interrupt.h>
  #include <linux/spinlock.h>
  #include <linux/device.h>
  #include <linux/slab.h>
  #include <linux/cpu.h>
  #include <linux/completion.h>
  #include <linux/mutex.h>
  #include <linux/syscore_ops.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);
  #ifdef CONFIG_HOTPLUG_CPU
  /* This one keeps track of the previously set governor of a removed CPU */
  static DEFINE_PER_CPU(char[CPUFREQ_NAME_LEN], cpufreq_cpu_governor);
  #endif
  static DEFINE_RWLOCK(cpufreq_driver_lock);
  static DEFINE_MUTEX(cpufreq_governor_lock);
  
  /*
   * cpu_policy_rwsem is a per CPU reader-writer semaphore designed to cure
   * all cpufreq/hotplug/workqueue/etc related lock issues.
   *
   * The rules for this semaphore:
   * - Any routine that wants to read from the policy structure will
   *   do a down_read on this semaphore.
   * - Any routine that will write to the policy structure and/or may take away
   *   the policy altogether (eg. CPU hotplug), will hold this lock in write
   *   mode before doing so.
   *
   * Additional rules:
   * - Governor routines that can be called in cpufreq hotplug path should not
   *   take this sem as top level hotplug notifier handler takes this.
   * - Lock should not be held across
   *     __cpufreq_governor(data, CPUFREQ_GOV_STOP);
   */
  static DEFINE_PER_CPU(int, cpufreq_policy_cpu);
  static DEFINE_PER_CPU(struct rw_semaphore, cpu_policy_rwsem);
  
  #define lock_policy_rwsem(mode, cpu)					\
  static int lock_policy_rwsem_##mode(int cpu)				\
  {									\
  	int policy_cpu = per_cpu(cpufreq_policy_cpu, cpu);		\
  	BUG_ON(policy_cpu == -1);					\
  	down_##mode(&per_cpu(cpu_policy_rwsem, policy_cpu));		\
  									\
  	return 0;							\
  }
  
  lock_policy_rwsem(read, cpu);
  lock_policy_rwsem(write, cpu);
  
  #define unlock_policy_rwsem(mode, cpu)					\
  static void unlock_policy_rwsem_##mode(int cpu)				\
  {									\
  	int policy_cpu = per_cpu(cpufreq_policy_cpu, cpu);		\
  	BUG_ON(policy_cpu == -1);					\
  	up_##mode(&per_cpu(cpu_policy_rwsem, policy_cpu));		\
  }
  
  unlock_policy_rwsem(read, cpu);
  unlock_policy_rwsem(write, cpu);
  
  /* 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->have_governor_per_policy;
  }
  
  static struct cpufreq_policy *__cpufreq_cpu_get(unsigned int cpu, bool sysfs)
  {
  	struct cpufreq_policy *data;
  	unsigned long flags;
  
  	if (cpu >= nr_cpu_ids)
  		goto err_out;
  
  	/* get the cpufreq driver */
  	read_lock_irqsave(&cpufreq_driver_lock, flags);
  
  	if (!cpufreq_driver)
  		goto err_out_unlock;
  
  	if (!try_module_get(cpufreq_driver->owner))
  		goto err_out_unlock;
  
  
  	/* get the CPU */
  	data = per_cpu(cpufreq_cpu_data, cpu);
  
  	if (!data)
  		goto err_out_put_module;
  
  	if (!sysfs && !kobject_get(&data->kobj))
  		goto err_out_put_module;
  
  	read_unlock_irqrestore(&cpufreq_driver_lock, flags);
  	return data;
  
  err_out_put_module:
  	module_put(cpufreq_driver->owner);
  err_out_unlock:
  	read_unlock_irqrestore(&cpufreq_driver_lock, flags);
  err_out:
  	return NULL;
  }
  
  struct cpufreq_policy *cpufreq_cpu_get(unsigned int cpu)
  {
  	if (cpufreq_disabled())
  		return NULL;
  
  	return __cpufreq_cpu_get(cpu, false);
  }
  EXPORT_SYMBOL_GPL(cpufreq_cpu_get);
  
  static struct cpufreq_policy *cpufreq_cpu_get_sysfs(unsigned int cpu)
  {
  	return __cpufreq_cpu_get(cpu, true);
  }
  
  static void __cpufreq_cpu_put(struct cpufreq_policy *data, bool sysfs)
  {
  	if (!sysfs)
  		kobject_put(&data->kobj);
  	module_put(cpufreq_driver->owner);
  }
  
  void cpufreq_cpu_put(struct cpufreq_policy *data)
  {
  	if (cpufreq_disabled())
  		return;
  
  	__cpufreq_cpu_put(data, false);
  }
  EXPORT_SYMBOL_GPL(cpufreq_cpu_put);
  
  static void cpufreq_cpu_put_sysfs(struct cpufreq_policy *data)
  {
  	__cpufreq_cpu_put(data, true);
  }
  
  /*********************************************************************
   *            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
  
  
  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);
  
  
  
  /*********************************************************************
   *                          SYSFS INTERFACE                          *
   *********************************************************************/
  
  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 (cpufreq_driver->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 *data,
  				struct cpufreq_policy *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)		\
  {									\
  	unsigned 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)
  {
  	unsigned 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;
  
  	/* Do not use cpufreq_set_policy here or the user_policy.max
  	   will be wrongly overridden */
  	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 (!cpufreq_driver->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;
  }
  
  static ssize_t 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;
  }
  
  /**
   * 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 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 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
  };
  
  struct kobject *cpufreq_global_kobject;
  EXPORT_SYMBOL(cpufreq_global_kobject);
  
  #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 = -EINVAL;
  	policy = cpufreq_cpu_get_sysfs(policy->cpu);
  	if (!policy)
  		goto no_policy;
  
  	if (lock_policy_rwsem_read(policy->cpu) < 0)
  		goto fail;
  
  	if (fattr->show)
  		ret = fattr->show(policy, buf);
  	else
  		ret = -EIO;
  
  	unlock_policy_rwsem_read(policy->cpu);
  fail:
  	cpufreq_cpu_put_sysfs(policy);
  no_policy:
  	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;
  	policy = cpufreq_cpu_get_sysfs(policy->cpu);
  	if (!policy)
  		goto no_policy;
  
  	if (lock_policy_rwsem_write(policy->cpu) < 0)
  		goto fail;
  
  	if (fattr->store)
  		ret = fattr->store(policy, buf, count);
  	else
  		ret = -EIO;
  
  	unlock_policy_rwsem_write(policy->cpu);
  fail:
  	cpufreq_cpu_put_sysfs(policy);
  no_policy:
  	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,
  };
  
  /* symlink affected CPUs */
  static int cpufreq_add_dev_symlink(unsigned int cpu,
  				   struct cpufreq_policy *policy)
  {
  	unsigned int j;
  	int ret = 0;
  
  	for_each_cpu(j, policy->cpus) {
  		struct cpufreq_policy *managed_policy;
  		struct device *cpu_dev;
  
  		if (j == cpu)
  			continue;
  
  		pr_debug("CPU %u already managed, adding link\n", j);
  		managed_policy = cpufreq_cpu_get(cpu);
  		cpu_dev = get_cpu_device(j);
  		ret = sysfs_create_link(&cpu_dev->kobj, &policy->kobj,
  					"cpufreq");
  		if (ret) {
  			cpufreq_cpu_put(managed_policy);
  			return ret;
  		}
  	}
  	return ret;
  }
  
  static int cpufreq_add_dev_interface(unsigned int cpu,
  				     struct cpufreq_policy *policy,
  				     struct device *dev)
  {
  	struct cpufreq_policy new_policy;
  	struct freq_attr **drv_attr;
  	unsigned long flags;
  	int ret = 0;
  	unsigned int j;
  
  	/* 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 (cpufreq_driver->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;
  	}
  
  	write_lock_irqsave(&cpufreq_driver_lock, flags);
  	for_each_cpu(j, policy->cpus) {
  		per_cpu(cpufreq_cpu_data, j) = policy;
  		per_cpu(cpufreq_policy_cpu, j) = policy->cpu;
  	}
  	write_unlock_irqrestore(&cpufreq_driver_lock, flags);
  
  	ret = cpufreq_add_dev_symlink(cpu, policy);
  	if (ret)
  		goto err_out_kobj_put;
  
  	memcpy(&new_policy, policy, sizeof(struct cpufreq_policy));
  	/* assure that the starting sequence is run in __cpufreq_set_policy */
  	policy->governor = NULL;
  
  	/* set default policy */
  	ret = __cpufreq_set_policy(policy, &new_policy);
  	policy->user_policy.policy = policy->policy;
  	policy->user_policy.governor = policy->governor;
  
  	if (ret) {
  		pr_debug("setting policy failed\n");
  		if (cpufreq_driver->exit)
  			cpufreq_driver->exit(policy);
  	}
  	return ret;
  
  err_out_kobj_put:
  	kobject_put(&policy->kobj);
  	wait_for_completion(&policy->kobj_unregister);
  	return ret;
  }
  
  #ifdef CONFIG_HOTPLUG_CPU
  static int cpufreq_add_policy_cpu(unsigned int cpu, unsigned int sibling,
  				  struct device *dev)
  {
  	struct cpufreq_policy *policy;
  	int ret = 0, has_target = !!cpufreq_driver->target;
  	unsigned long flags;
  
  	policy = cpufreq_cpu_get(sibling);
  	WARN_ON(!policy);
  
  	if (has_target)
  		__cpufreq_governor(policy, CPUFREQ_GOV_STOP);
  
  	lock_policy_rwsem_write(sibling);
  
  	write_lock_irqsave(&cpufreq_driver_lock, flags);
  
  	cpumask_set_cpu(cpu, policy->cpus);
  	per_cpu(cpufreq_policy_cpu, cpu) = policy->cpu;
  	per_cpu(cpufreq_cpu_data, cpu) = policy;
  	write_unlock_irqrestore(&cpufreq_driver_lock, flags);
  
  	unlock_policy_rwsem_write(sibling);
  
  	if (has_target) {
  		__cpufreq_governor(policy, CPUFREQ_GOV_START);
  		__cpufreq_governor(policy, CPUFREQ_GOV_LIMITS);
  	}
  
  	ret = sysfs_create_link(&dev->kobj, &policy->kobj, "cpufreq");
  	if (ret) {
  		cpufreq_cpu_put(policy);
  		return ret;
  	}
  
  	return 0;
  }
  #endif
  
  /**
   * 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)
  {
  	unsigned int j, cpu = dev->id;
  	int ret = -ENOMEM;
  	struct cpufreq_policy *policy;
  	unsigned long flags;
  #ifdef CONFIG_HOTPLUG_CPU
  	struct cpufreq_governor *gov;
  	int sibling;
  #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;
  	}
  
  #ifdef CONFIG_HOTPLUG_CPU
  	/* Check if this cpu was hot-unplugged earlier and has siblings */
  	read_lock_irqsave(&cpufreq_driver_lock, flags);
  	for_each_online_cpu(sibling) {
  		struct cpufreq_policy *cp = per_cpu(cpufreq_cpu_data, sibling);
  		if (cp && cpumask_test_cpu(cpu, cp->related_cpus)) {
  			read_unlock_irqrestore(&cpufreq_driver_lock, flags);
  			return cpufreq_add_policy_cpu(cpu, sibling, dev);
  		}
  	}
  	read_unlock_irqrestore(&cpufreq_driver_lock, flags);
  #endif
  #endif
  
  	if (!try_module_get(cpufreq_driver->owner)) {
  		ret = -EINVAL;
  		goto module_out;
  	}
  
  	policy = kzalloc(sizeof(struct cpufreq_policy), GFP_KERNEL);
  	if (!policy)
  		goto nomem_out;
  
  	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;
  
  	policy->cpu = cpu;
  	policy->governor = CPUFREQ_DEFAULT_GOVERNOR;
  	cpumask_copy(policy->cpus, cpumask_of(cpu));
  
  	/* Initially set CPU itself as the policy_cpu */
  	per_cpu(cpufreq_policy_cpu, cpu) = 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);
  
  	policy->user_policy.min = policy->min;
  	policy->user_policy.max = policy->max;
  
  	blocking_notifier_call_chain(&cpufreq_policy_notifier_list,
  				     CPUFREQ_START, policy);
  
  #ifdef CONFIG_HOTPLUG_CPU
  	gov = __find_governor(per_cpu(cpufreq_cpu_governor, cpu));
  	if (gov) {
  		policy->governor = gov;
  		pr_debug("Restoring governor %s for cpu %d\n",
  		       policy->governor->name, cpu);
  	}
  #endif
  
  	ret = cpufreq_add_dev_interface(cpu, policy, dev);
  	if (ret)
  		goto err_out_unregister;
  
  	kobject_uevent(&policy->kobj, KOBJ_ADD);
  	module_put(cpufreq_driver->owner);
  	pr_debug("initialization complete\n");
  
  	return 0;
  
  err_out_unregister:
  	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);
  
  	kobject_put(&policy->kobj);
  	wait_for_completion(&policy->kobj_unregister);
  
  err_set_policy_cpu:
  	per_cpu(cpufreq_policy_cpu, cpu) = -1;
  	free_cpumask_var(policy->related_cpus);
  err_free_cpumask:
  	free_cpumask_var(policy->cpus);
  err_free_policy:
  	kfree(policy);
  nomem_out:
  	module_put(cpufreq_driver->owner);
  module_out:
  	return ret;
  }
  
  static void update_policy_cpu(struct cpufreq_policy *policy, unsigned int cpu)
  {
  	int j;
  
  	policy->last_cpu = policy->cpu;
  	policy->cpu = cpu;
  
  	for_each_cpu(j, policy->cpus)
  		per_cpu(cpufreq_policy_cpu, j) = cpu;
  
  #ifdef CONFIG_CPU_FREQ_TABLE
  	cpufreq_frequency_table_update_policy_cpu(policy);
  #endif
  	blocking_notifier_call_chain(&cpufreq_policy_notifier_list,
  			CPUFREQ_UPDATE_POLICY_CPU, policy);
  }
  
  /**
   * __cpufreq_remove_dev - remove a CPU device
   *
   * Removes the cpufreq interface for a CPU device.
   * Caller should already have policy_rwsem in write mode for this CPU.
   * This routine frees the rwsem before returning.
   */
  static int __cpufreq_remove_dev(struct device *dev, struct subsys_interface *sif)
  {
  	unsigned int cpu = dev->id, ret, cpus;
  	unsigned long flags;
  	struct cpufreq_policy *data;
  	struct kobject *kobj;
  	struct completion *cmp;
  	struct device *cpu_dev;
  
  	pr_debug("%s: unregistering CPU %u\n", __func__, cpu);
  
  	write_lock_irqsave(&cpufreq_driver_lock, flags);
  
  	data = per_cpu(cpufreq_cpu_data, cpu);
  	per_cpu(cpufreq_cpu_data, cpu) = NULL;
  
  	write_unlock_irqrestore(&cpufreq_driver_lock, flags);
  
  	if (!data) {
  		pr_debug("%s: No cpu_data found\n", __func__);
  		return -EINVAL;
  	}
  
  	if (cpufreq_driver->target)
  		__cpufreq_governor(data, CPUFREQ_GOV_STOP);
  
  #ifdef CONFIG_HOTPLUG_CPU
  	if (!cpufreq_driver->setpolicy)
  		strncpy(per_cpu(cpufreq_cpu_governor, cpu),
  			data->governor->name, CPUFREQ_NAME_LEN);
  #endif
  
  	WARN_ON(lock_policy_rwsem_write(cpu));
  	cpus = cpumask_weight(data->cpus);
  
  	if (cpus > 1)
  		cpumask_clear_cpu(cpu, data->cpus);
  	unlock_policy_rwsem_write(cpu);
  
  	if (cpu != data->cpu) {
  		sysfs_remove_link(&dev->kobj, "cpufreq");
  	} else if (cpus > 1) {
  		/* first sibling now owns the new sysfs dir */
  		cpu_dev = get_cpu_device(cpumask_first(data->cpus));
  		sysfs_remove_link(&cpu_dev->kobj, "cpufreq");
  		ret = kobject_move(&data->kobj, &cpu_dev->kobj);
  		if (ret) {
  			pr_err("%s: Failed to move kobj: %d", __func__, ret);
  
  			WARN_ON(lock_policy_rwsem_write(cpu));
  			cpumask_set_cpu(cpu, data->cpus);
  
  			write_lock_irqsave(&cpufreq_driver_lock, flags);
  			per_cpu(cpufreq_cpu_data, cpu) = data;
  			write_unlock_irqrestore(&cpufreq_driver_lock, flags);
  
  			unlock_policy_rwsem_write(cpu);
  
  			ret = sysfs_create_link(&cpu_dev->kobj, &data->kobj,
  					"cpufreq");
  			return -EINVAL;
  		}
  
  		WARN_ON(lock_policy_rwsem_write(cpu));
  		update_policy_cpu(data, cpu_dev->id);
  		unlock_policy_rwsem_write(cpu);
  		pr_debug("%s: policy Kobject moved to cpu: %d from: %d\n",
  				__func__, cpu_dev->id, cpu);
  	}
  
  	/* If cpu is last user of policy, free policy */
  	if (cpus == 1) {
  		if (cpufreq_driver->target)
  			__cpufreq_governor(data, CPUFREQ_GOV_POLICY_EXIT);
  
  		lock_policy_rwsem_read(cpu);
  		kobj = &data->kobj;
  		cmp = &data->kobj_unregister;
  		unlock_policy_rwsem_read(cpu);
  		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");
  
  		if (cpufreq_driver->exit)
  			cpufreq_driver->exit(data);
  
  		free_cpumask_var(data->related_cpus);
  		free_cpumask_var(data->cpus);
  		kfree(data);
  	} else {
  		pr_debug("%s: removing link, cpu: %d\n", __func__, cpu);
  		cpufreq_cpu_put(data);
  		if (cpufreq_driver->target) {
  			__cpufreq_governor(data, CPUFREQ_GOV_START);
  			__cpufreq_governor(data, CPUFREQ_GOV_LIMITS);
  		}
  	}
  
  	per_cpu(cpufreq_policy_cpu, cpu) = -1;
  	return 0;
  }
  
  
  static int cpufreq_remove_dev(struct device *dev, struct subsys_interface *sif)
  {
  	unsigned int cpu = dev->id;
  	int retval;
  
  	if (cpu_is_offline(cpu))
  		return 0;
  
  	retval = __cpufreq_remove_dev(dev, sif);
  	return retval;
  }
  
  
  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)
  {
  	unsigned int ret_freq = 0;
  	struct cpufreq_policy *policy = cpufreq_cpu_get(cpu);
  
  	if (!policy)
  		goto out;
  
  	if (unlikely(lock_policy_rwsem_read(cpu)))
  		goto out_policy;
  
  	ret_freq = __cpufreq_get(cpu);
  
  	unlock_policy_rwsem_read(cpu);
  
  out_policy:
  	cpufreq_cpu_put(policy);
  out:
  	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_bp_suspend - Prepare the boot CPU for system suspend.
   *
   * This function is only executed for the boot processor.  The other CPUs
   * have been put offline by means of CPU hotplug.
   */
  static int cpufreq_bp_suspend(void)
  {
  	int ret = 0;
  
  	int cpu = smp_processor_id();
  	struct cpufreq_policy *cpu_policy;
  
  	pr_debug("suspending cpu %u\n", cpu);
  
  	/* If there's no policy for the boot CPU, we have nothing to do. */
  	cpu_policy = cpufreq_cpu_get(cpu);
  	if (!cpu_policy)
  		return 0;
  
  	if (cpufreq_driver->suspend) {
  		ret = cpufreq_driver->suspend(cpu_policy);
  		if (ret)
  			printk(KERN_ERR "cpufreq: suspend failed in ->suspend "
  					"step on CPU %u\n", cpu_policy->cpu);
  	}
  
  	cpufreq_cpu_put(cpu_policy);
  	return ret;
  }
  
  /**
   * cpufreq_bp_resume - Restore proper frequency handling of the boot CPU.
   *
   *	1.) resume CPUfreq hardware support (cpufreq_driver->resume())
   *	2.) schedule call cpufreq_update_policy() ASAP as interrupts are
   *	    restored. It will verify that the current freq is in sync with
   *	    what we believe it to be. This is a bit later than when it
   *	    should be, but nonethteless it's better than calling
   *	    cpufreq_driver->get() here which might re-enable interrupts...
   *
   * This function is only executed for the boot CPU.  The other CPUs have not
   * been turned on yet.
   */
  static void cpufreq_bp_resume(void)
  {
  	int ret = 0;
  
  	int cpu = smp_processor_id();
  	struct cpufreq_policy *cpu_policy;
  
  	pr_debug("resuming cpu %u\n", cpu);
  
  	/* If there's no policy for the boot CPU, we have nothing to do. */
  	cpu_policy = cpufreq_cpu_get(cpu);
  	if (!cpu_policy)
  		return;
  
  	if (cpufreq_driver->resume) {
  		ret = cpufreq_driver->resume(cpu_policy);
  		if (ret) {
  			printk(KERN_ERR "cpufreq: resume failed in ->resume "
  					"step on CPU %u\n", cpu_policy->cpu);
  			goto fail;
  		}
  	}
  
  	schedule_work(&cpu_policy->update);
  
  fail:
  	cpufreq_cpu_put(cpu_policy);
  }
  
  static struct syscore_ops cpufreq_syscore_ops = {
  	.suspend	= cpufreq_bp_suspend,
  	.resume		= cpufreq_bp_resume,
  };
  
  /**
   *	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);
  
  	if (target_freq == policy->cur)
  		return 0;
  
  	if (cpufreq_driver->target)
  		retval = cpufreq_driver->target(policy, target_freq, relation);
  
  	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;
  
  	policy = cpufreq_cpu_get(policy->cpu);
  	if (!policy)
  		goto no_policy;
  
  	if (unlikely(lock_policy_rwsem_write(policy->cpu)))
  		goto fail;
  
  	ret = __cpufreq_driver_target(policy, target_freq, relation);
  
  	unlock_policy_rwsem_write(policy->cpu);
  
  fail:
  	cpufreq_cpu_put(policy);
  no_policy:
  	return ret;
  }
  EXPORT_SYMBOL_GPL(cpufreq_driver_target);
  
  int __cpufreq_driver_getavg(struct cpufreq_policy *policy, unsigned int cpu)
  {
  	int ret = 0;
  
  	if (cpufreq_disabled())
  		return ret;
  
  	if (!cpufreq_driver->getavg)
  		return 0;
  
  	policy = cpufreq_cpu_get(policy->cpu);
  	if (!policy)
  		return -EINVAL;
  
  	ret = cpufreq_driver->getavg(policy, cpu);
  
  	cpufreq_cpu_put(policy);
  	return ret;
  }
  EXPORT_SYMBOL_GPL(__cpufreq_driver_getavg);
  
  /*
   * 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
  
  	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 (!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_STOP)) ||
  	    (policy->governor_enabled && (event == CPUFREQ_GOV_START))) {
  		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);
  	}
  
  	/* we keep one module reference alive for
  			each CPU governed by this CPU */
  	if ((event != CPUFREQ_GOV_START) || ret)
  		module_put(policy->governor->owner);
  	if ((event == CPUFREQ_GOV_STOP) && !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)
  {
  #ifdef CONFIG_HOTPLUG_CPU
  	int cpu;
  #endif
  
  	if (!governor)
  		return;
  
  	if (cpufreq_disabled())
  		return;
  
  #ifdef CONFIG_HOTPLUG_CPU
  	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");
  	}
  #endif
  
  	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(struct cpufreq_policy));
  
  	cpufreq_cpu_put(cpu_policy);
  	return 0;
  }
  EXPORT_SYMBOL(cpufreq_get_policy);
  
  
  /*
   * data   : current policy.
   * policy : policy to be set.
   */
  static int __cpufreq_set_policy(struct cpufreq_policy *data,
  				struct cpufreq_policy *policy)
  {
  	int ret = 0, failed = 1;
  
  	pr_debug("setting new policy for CPU %u: %u - %u kHz\n", policy->cpu,
  		policy->min, policy->max);
  
  	memcpy(&policy->cpuinfo, &data->cpuinfo,
  				sizeof(struct cpufreq_cpuinfo));
  
  	if (policy->min > data->max || policy->max < data->min) {
  		ret = -EINVAL;
  		goto error_out;
  	}
  
  	/* verify the cpu speed can be set within this limit */
  	ret = cpufreq_driver->verify(policy);
  	if (ret)
  		goto error_out;
  
  	/* adjust if necessary - all reasons */
  	blocking_notifier_call_chain(&cpufreq_policy_notifier_list,
  			CPUFREQ_ADJUST, policy);
  
  	/* adjust if necessary - hardware incompatibility*/
  	blocking_notifier_call_chain(&cpufreq_policy_notifier_list,
  			CPUFREQ_INCOMPATIBLE, policy);
  
  	/* verify the cpu speed can be set within this limit,
  	   which might be different to the first one */
  	ret = cpufreq_driver->verify(policy);
  	if (ret)
  		goto error_out;
  
  	/* notification of the new policy */
  	blocking_notifier_call_chain(&cpufreq_policy_notifier_list,
  			CPUFREQ_NOTIFY, policy);
  
  	data->min = policy->min;
  	data->max = policy->max;
  
  	pr_debug("new min and max freqs are %u - %u kHz\n",
  					data->min, data->max);
  
  	if (cpufreq_driver->setpolicy) {
  		data->policy = policy->policy;
  		pr_debug("setting range\n");
  		ret = cpufreq_driver->setpolicy(policy);
  	} else {
  		if (policy->governor != data->governor) {
  			/* save old, working values */
  			struct cpufreq_governor *old_gov = data->governor;
  
  			pr_debug("governor switch\n");
  
  			/* end old governor */
  			if (data->governor) {
  				__cpufreq_governor(data, CPUFREQ_GOV_STOP);
  				unlock_policy_rwsem_write(policy->cpu);
  				__cpufreq_governor(data,
  						CPUFREQ_GOV_POLICY_EXIT);
  				lock_policy_rwsem_write(policy->cpu);
  			}
  
  			/* start new governor */
  			data->governor = policy->governor;
  			if (!__cpufreq_governor(data, CPUFREQ_GOV_POLICY_INIT)) {
  				if (!__cpufreq_governor(data, CPUFREQ_GOV_START)) {
  					failed = 0;
  				} else {
  					unlock_policy_rwsem_write(policy->cpu);
  					__cpufreq_governor(data,
  							CPUFREQ_GOV_POLICY_EXIT);
  					lock_policy_rwsem_write(policy->cpu);
  				}
  			}
  
  			if (failed) {
  				/* new governor failed, so re-start old one */
  				pr_debug("starting governor %s failed\n",
  							data->governor->name);
  				if (old_gov) {
  					data->governor = old_gov;
  					__cpufreq_governor(data,
  							CPUFREQ_GOV_POLICY_INIT);
  					__cpufreq_governor(data,
  							   CPUFREQ_GOV_START);
  				}
  				ret = -EINVAL;
  				goto error_out;
  			}
  			/* might be a policy change, too, so fall through */
  		}
  		pr_debug("governor: change or update limits\n");
  		__cpufreq_governor(data, CPUFREQ_GOV_LIMITS);
  	}
  
  error_out:
  	return ret;
  }
  
  /**
   *	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 *data = cpufreq_cpu_get(cpu);
  	struct cpufreq_policy policy;
  	int ret;
  
  	if (!data) {
  		ret = -ENODEV;
  		goto no_policy;
  	}
  
  	if (unlikely(lock_policy_rwsem_write(cpu))) {
  		ret = -EINVAL;
  		goto fail;
  	}
  
  	pr_debug("updating policy for CPU %u\n", cpu);
  	memcpy(&policy, data, sizeof(struct cpufreq_policy));
  	policy.min = data->user_policy.min;
  	policy.max = data->user_policy.max;
  	policy.policy = data->user_policy.policy;
  	policy.governor = data->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) {
  		policy.cur = cpufreq_driver->get(cpu);
  		if (!data->cur) {
  			pr_debug("Driver did not initialize current freq");
  			data->cur = policy.cur;
  		} else {
  			if (data->cur != policy.cur && cpufreq_driver->target)
  				cpufreq_out_of_sync(cpu, data->cur,
  								policy.cur);
  		}
  	}
  
  	ret = __cpufreq_set_policy(data, &policy);
  
  	unlock_policy_rwsem_write(cpu);
  
  fail:
  	cpufreq_cpu_put(data);
  no_policy:
  	return ret;
  }
  EXPORT_SYMBOL(cpufreq_update_policy);
  
  static int __cpuinit cpufreq_cpu_callback(struct notifier_block *nfb,
  					unsigned long action, void *hcpu)
  {
  	unsigned int cpu = (unsigned long)hcpu;
  	struct device *dev;
  
  	dev = get_cpu_device(cpu);
  	if (dev) {
  		switch (action) {
  		case CPU_ONLINE:
  		case CPU_ONLINE_FROZEN:
  			cpufreq_add_dev(dev, NULL);
  			break;
  		case CPU_DOWN_PREPARE:
  		case CPU_DOWN_PREPARE_FROZEN:
  			__cpufreq_remove_dev(dev, NULL);
  			break;
  		case CPU_DOWN_FAILED:
  		case CPU_DOWN_FAILED_FROZEN:
  			cpufreq_add_dev(dev, NULL);
  			break;
  		}
  	}
  	return NOTIFY_OK;
  }
  
  static struct notifier_block __refdata cpufreq_cpu_notifier = {
      .notifier_call = cpufreq_cpu_callback,
  };
  
  /*********************************************************************
   *               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)))
  		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 -EBUSY;
  	}
  	cpufreq_driver = driver_data;
  	write_unlock_irqrestore(&cpufreq_driver_lock, flags);
  
  	ret = subsys_interface_register(&cpufreq_interface);
  	if (ret)
  		goto err_null_driver;
  
  	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_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);
  	unregister_hotcpu_notifier(&cpufreq_cpu_notifier);
  
  	write_lock_irqsave(&cpufreq_driver_lock, flags);
  	cpufreq_driver = NULL;
  	write_unlock_irqrestore(&cpufreq_driver_lock, flags);
  
  	return 0;
  }
  EXPORT_SYMBOL_GPL(cpufreq_unregister_driver);
  
  static int __init cpufreq_core_init(void)
  {
  	int cpu;
  
  	if (cpufreq_disabled())
  		return -ENODEV;
  
  	for_each_possible_cpu(cpu) {
  		per_cpu(cpufreq_policy_cpu, cpu) = -1;
  		init_rwsem(&per_cpu(cpu_policy_rwsem, cpu));
  	}
  
  	cpufreq_global_kobject = kobject_create_and_add("cpufreq", &cpu_subsys.dev_root->kobj);
  	BUG_ON(!cpufreq_global_kobject);
  	register_syscore_ops(&cpufreq_syscore_ops);
  
  	return 0;
  }
  core_initcall(cpufreq_core_init);
  