drivers/cpufreq/cpufreq_stats.c - kernel/panda - Git at Google

 /*
  *  drivers/cpufreq/cpufreq_stats.c
  *
  *  Copyright (C) 2003-2004 Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>.
  *  (C) 2004 Zou Nan hai <nanhai.zou@intel.com>.
  *
  * 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.
  */

 #include <linux/kernel.h>
 #include <linux/slab.h>
 #include <linux/sysdev.h>
 #include <linux/cpu.h>
 #include <linux/sysfs.h>
 #include <linux/cpufreq.h>
 #include <linux/module.h>
 #include <linux/jiffies.h>
 #include <linux/percpu.h>
 #include <linux/kobject.h>
 #include <linux/spinlock.h>
 #include <linux/notifier.h>
 #include <asm/cputime.h>

 static spinlock_t cpufreq_stats_lock;

 #define CPUFREQ_STATDEVICE_ATTR(_name, _mode, _show) \
 static struct freq_attr _attr_##_name = {\
 	.attr = {.name = __stringify(_name), .mode = _mode, }, \
 	.show = _show,\
 };

 struct cpufreq_stats {
 	unsigned int cpu;
 	unsigned int total_trans;
 	unsigned long long  last_time;
 	unsigned int max_state;
 	unsigned int state_num;
 	unsigned int last_index;
 	cputime64_t *time_in_state;
 	unsigned int *freq_table;
 #ifdef CONFIG_CPU_FREQ_STAT_DETAILS
 	unsigned int *trans_table;
 #endif
 };

 static DEFINE_PER_CPU(struct cpufreq_stats *, cpufreq_stats_table);

 struct cpufreq_stats_attribute {
 	struct attribute attr;
 	ssize_t(*show) (struct cpufreq_stats *, char *);
 };

 static int cpufreq_stats_update(unsigned int cpu)
 {
 	struct cpufreq_stats *stat;
 	unsigned long long cur_time;

 	cur_time = get_jiffies_64();
 	spin_lock(&cpufreq_stats_lock);
 	stat = per_cpu(cpufreq_stats_table, cpu);
 	if (stat->time_in_state)
 		stat->time_in_state[stat->last_index] =
 			cputime64_add(stat->time_in_state[stat->last_index],
 				      cputime_sub(cur_time, stat->last_time));
 	stat->last_time = cur_time;
 	spin_unlock(&cpufreq_stats_lock);
 	return 0;
 }

 static ssize_t show_total_trans(struct cpufreq_policy *policy, char *buf)
 {
 	struct cpufreq_stats *stat = per_cpu(cpufreq_stats_table, policy->cpu);
 	if (!stat)
 		return 0;
 	return sprintf(buf, "%d\n",
 			per_cpu(cpufreq_stats_table, stat->cpu)->total_trans);
 }

 static ssize_t show_time_in_state(struct cpufreq_policy *policy, char *buf)
 {
 	ssize_t len = 0;
 	int i;
 	struct cpufreq_stats *stat = per_cpu(cpufreq_stats_table, policy->cpu);
 	if (!stat)
 		return 0;
 	cpufreq_stats_update(stat->cpu);
 	for (i = 0; i < stat->state_num; i++) {
 		len += sprintf(buf + len, "%u %llu\n", stat->freq_table[i],
 			(unsigned long long)
 			cputime64_to_clock_t(stat->time_in_state[i]));
 	}
 	return len;
 }

 #ifdef CONFIG_CPU_FREQ_STAT_DETAILS
 static ssize_t show_trans_table(struct cpufreq_policy *policy, char *buf)
 {
 	ssize_t len = 0;
 	int i, j;

 	struct cpufreq_stats *stat = per_cpu(cpufreq_stats_table, policy->cpu);
 	if (!stat)
 		return 0;
 	cpufreq_stats_update(stat->cpu);
 	len += snprintf(buf + len, PAGE_SIZE - len, "   From  :    To\n");
 	len += snprintf(buf + len, PAGE_SIZE - len, "         : ");
 	for (i = 0; i < stat->state_num; i++) {
 		if (len >= PAGE_SIZE)
 			break;
 		len += snprintf(buf + len, PAGE_SIZE - len, "%9u ",
 				stat->freq_table[i]);
 	}
 	if (len >= PAGE_SIZE)
 		return PAGE_SIZE;

 	len += snprintf(buf + len, PAGE_SIZE - len, "\n");

 	for (i = 0; i < stat->state_num; i++) {
 		if (len >= PAGE_SIZE)
 			break;

 		len += snprintf(buf + len, PAGE_SIZE - len, "%9u: ",
 				stat->freq_table[i]);

 		for (j = 0; j < stat->state_num; j++)   {
 			if (len >= PAGE_SIZE)
 				break;
 			len += snprintf(buf + len, PAGE_SIZE - len, "%9u ",
 					stat->trans_table[i*stat->max_state+j]);
 		}
 		if (len >= PAGE_SIZE)
 			break;
 		len += snprintf(buf + len, PAGE_SIZE - len, "\n");
 	}
 	if (len >= PAGE_SIZE)
 		return PAGE_SIZE;
 	return len;
 }
 CPUFREQ_STATDEVICE_ATTR(trans_table, 0444, show_trans_table);
 #endif

 CPUFREQ_STATDEVICE_ATTR(total_trans, 0444, show_total_trans);
 CPUFREQ_STATDEVICE_ATTR(time_in_state, 0444, show_time_in_state);

 static struct attribute *default_attrs[] = {
 	&_attr_total_trans.attr,
 	&_attr_time_in_state.attr,
 #ifdef CONFIG_CPU_FREQ_STAT_DETAILS
 	&_attr_trans_table.attr,
 #endif
 	NULL
 };
 static struct attribute_group stats_attr_group = {
 	.attrs = default_attrs,
 	.name = "stats"
 };

 static int freq_table_get_index(struct cpufreq_stats *stat, unsigned int freq)
 {
 	int index;
 	for (index = 0; index < stat->max_state; index++)
 		if (stat->freq_table[index] == freq)
 			return index;
 	return -1;
 }

 /* should be called late in the CPU removal sequence so that the stats
  * memory is still available in case someone tries to use it.
  */
 static void cpufreq_stats_free_table(unsigned int cpu)
 {
 	struct cpufreq_stats *stat = per_cpu(cpufreq_stats_table, cpu);
 	if (stat) {
 		kfree(stat->time_in_state);
 		kfree(stat);
 	}
 	per_cpu(cpufreq_stats_table, cpu) = NULL;
 }

 /* must be called early in the CPU removal sequence (before
  * cpufreq_remove_dev) so that policy is still valid.
  */
 static void cpufreq_stats_free_sysfs(unsigned int cpu)
 {
 	struct cpufreq_policy *policy = cpufreq_cpu_get(cpu);
 	if (policy && policy->cpu == cpu)
 		sysfs_remove_group(&policy->kobj, &stats_attr_group);
 	if (policy)
 		cpufreq_cpu_put(policy);
 }

 static int cpufreq_stats_create_table(struct cpufreq_policy *policy,
 		struct cpufreq_frequency_table *table)
 {
 	unsigned int i, j, count = 0, ret = 0;
 	struct cpufreq_stats *stat;
 	struct cpufreq_policy *data;
 	unsigned int alloc_size;
 	unsigned int cpu = policy->cpu;
 	if (per_cpu(cpufreq_stats_table, cpu))
 		return -EBUSY;
 	stat = kzalloc(sizeof(struct cpufreq_stats), GFP_KERNEL);
 	if ((stat) == NULL)
 		return -ENOMEM;

 	data = cpufreq_cpu_get(cpu);
 	if (data == NULL) {
 		ret = -EINVAL;
 		goto error_get_fail;
 	}

 	ret = sysfs_create_group(&data->kobj, &stats_attr_group);
 	if (ret)
 		goto error_out;

 	stat->cpu = cpu;
 	per_cpu(cpufreq_stats_table, cpu) = stat;

 	for (i = 0; table[i].frequency != CPUFREQ_TABLE_END; i++) {
 		unsigned int freq = table[i].frequency;
 		if (freq == CPUFREQ_ENTRY_INVALID)
 			continue;
 		count++;
 	}

 	alloc_size = count * sizeof(int) + count * sizeof(cputime64_t);

 #ifdef CONFIG_CPU_FREQ_STAT_DETAILS
 	alloc_size += count * count * sizeof(int);
 #endif
 	stat->max_state = count;
 	stat->time_in_state = kzalloc(alloc_size, GFP_KERNEL);
 	if (!stat->time_in_state) {
 		ret = -ENOMEM;
 		goto error_out;
 	}
 	stat->freq_table = (unsigned int *)(stat->time_in_state + count);

 #ifdef CONFIG_CPU_FREQ_STAT_DETAILS
 	stat->trans_table = stat->freq_table + count;
 #endif
 	j = 0;
 	for (i = 0; table[i].frequency != CPUFREQ_TABLE_END; i++) {
 		unsigned int freq = table[i].frequency;
 		if (freq == CPUFREQ_ENTRY_INVALID)
 			continue;
 		if (freq_table_get_index(stat, freq) == -1)
 			stat->freq_table[j++] = freq;
 	}
 	stat->state_num = j;
 	spin_lock(&cpufreq_stats_lock);
 	stat->last_time = get_jiffies_64();
 	stat->last_index = freq_table_get_index(stat, policy->cur);
 	spin_unlock(&cpufreq_stats_lock);
 	cpufreq_cpu_put(data);
 	return 0;
 error_out:
 	cpufreq_cpu_put(data);
 error_get_fail:
 	kfree(stat);
 	per_cpu(cpufreq_stats_table, cpu) = NULL;
 	return ret;
 }

 static int cpufreq_stat_notifier_policy(struct notifier_block *nb,
 		unsigned long val, void *data)
 {
 	int ret;
 	struct cpufreq_policy *policy = data;
 	struct cpufreq_frequency_table *table;
 	unsigned int cpu = policy->cpu;
 	if (val != CPUFREQ_NOTIFY)
 		return 0;
 	table = cpufreq_frequency_get_table(cpu);
 	if (!table)
 		return 0;
 	ret = cpufreq_stats_create_table(policy, table);
 	if (ret)
 		return ret;
 	return 0;
 }

 static int cpufreq_stat_notifier_trans(struct notifier_block *nb,
 		unsigned long val, void *data)
 {
 	struct cpufreq_freqs *freq = data;
 	struct cpufreq_stats *stat;
 	int old_index, new_index;

 	if (val != CPUFREQ_POSTCHANGE)
 		return 0;

 	stat = per_cpu(cpufreq_stats_table, freq->cpu);
 	if (!stat)
 		return 0;

 	old_index = stat->last_index;
 	new_index = freq_table_get_index(stat, freq->new);

 	/* We can't do stat->time_in_state[-1]= .. */
 	if (old_index == -1 || new_index == -1)
 		return 0;

 	cpufreq_stats_update(freq->cpu);

 	if (old_index == new_index)
 		return 0;

 	spin_lock(&cpufreq_stats_lock);
 	stat->last_index = new_index;
 #ifdef CONFIG_CPU_FREQ_STAT_DETAILS
 	stat->trans_table[old_index * stat->max_state + new_index]++;
 #endif
 	stat->total_trans++;
 	spin_unlock(&cpufreq_stats_lock);
 	return 0;
 }

 static int cpufreq_stats_create_table_cpu(unsigned int cpu)
 {
 	struct cpufreq_policy *policy;
 	struct cpufreq_frequency_table *table;
 	int ret = -ENODEV;

 	policy = cpufreq_cpu_get(cpu);
 	if (!policy)
 		return -ENODEV;

 	table = cpufreq_frequency_get_table(cpu);
 	if (!table)
 		goto out;

 	ret = cpufreq_stats_create_table(policy, table);

 out:
 	cpufreq_cpu_put(policy);
 	return ret;
 }

 static int __cpuinit cpufreq_stat_cpu_callback(struct notifier_block *nfb,
 					       unsigned long action,
 					       void *hcpu)
 {
 	unsigned int cpu = (unsigned long)hcpu;

 	switch (action) {
 	case CPU_ONLINE:
 	case CPU_ONLINE_FROZEN:
 		cpufreq_update_policy(cpu);
 		break;
 	case CPU_DOWN_PREPARE:
 		cpufreq_stats_free_sysfs(cpu);
 		break;
 	case CPU_DEAD:
 	case CPU_DEAD_FROZEN:
 		cpufreq_stats_free_table(cpu);
 		break;
 	case CPU_DOWN_FAILED:
 	case CPU_DOWN_FAILED_FROZEN:
 		cpufreq_stats_create_table_cpu(cpu);
 		break;
 	}
 	return NOTIFY_OK;
 }

 /* priority=1 so this will get called before cpufreq_remove_dev */
 static struct notifier_block cpufreq_stat_cpu_notifier __refdata = {
 	.notifier_call = cpufreq_stat_cpu_callback,
 	.priority = 1,
 };

 static struct notifier_block notifier_policy_block = {
 	.notifier_call = cpufreq_stat_notifier_policy
 };

 static struct notifier_block notifier_trans_block = {
 	.notifier_call = cpufreq_stat_notifier_trans
 };

 static int __init cpufreq_stats_init(void)
 {
 	int ret;
 	unsigned int cpu;

 	spin_lock_init(&cpufreq_stats_lock);
 	ret = cpufreq_register_notifier(&notifier_policy_block,
 				CPUFREQ_POLICY_NOTIFIER);
 	if (ret)
 		return ret;

 	ret = cpufreq_register_notifier(&notifier_trans_block,
 				CPUFREQ_TRANSITION_NOTIFIER);
 	if (ret) {
 		cpufreq_unregister_notifier(&notifier_policy_block,
 				CPUFREQ_POLICY_NOTIFIER);
 		return ret;
 	}

 	register_hotcpu_notifier(&cpufreq_stat_cpu_notifier);
 	for_each_online_cpu(cpu) {
 		cpufreq_update_policy(cpu);
 	}
 	return 0;
 }
 static void __exit cpufreq_stats_exit(void)
 {
 	unsigned int cpu;

 	cpufreq_unregister_notifier(&notifier_policy_block,
 			CPUFREQ_POLICY_NOTIFIER);
 	cpufreq_unregister_notifier(&notifier_trans_block,
 			CPUFREQ_TRANSITION_NOTIFIER);
 	unregister_hotcpu_notifier(&cpufreq_stat_cpu_notifier);
 	for_each_online_cpu(cpu) {
 		cpufreq_stats_free_table(cpu);
 		cpufreq_stats_free_sysfs(cpu);
 	}
 }

 MODULE_AUTHOR("Zou Nan hai <nanhai.zou@intel.com>");
 MODULE_DESCRIPTION("'cpufreq_stats' - A driver to export cpufreq stats "
 				"through sysfs filesystem");
 MODULE_LICENSE("GPL");

 module_init(cpufreq_stats_init);
 module_exit(cpufreq_stats_exit);
	/*
	* drivers/cpufreq/cpufreq_stats.c
	*
	* Copyright (C) 2003-2004 Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>.
	* (C) 2004 Zou Nan hai <nanhai.zou@intel.com>.
	*
	* 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.
	*/

	#include <linux/kernel.h>
	#include <linux/slab.h>
	#include <linux/sysdev.h>
	#include <linux/cpu.h>
	#include <linux/sysfs.h>
	#include <linux/cpufreq.h>
	#include <linux/module.h>
	#include <linux/jiffies.h>
	#include <linux/percpu.h>
	#include <linux/kobject.h>
	#include <linux/spinlock.h>
	#include <linux/notifier.h>
	#include <asm/cputime.h>

	static spinlock_t cpufreq_stats_lock;

	#define CPUFREQ_STATDEVICE_ATTR(_name, _mode, _show) \
	static struct freq_attr _attr_##_name = {\
	.attr = {.name = __stringify(_name), .mode = _mode, }, \
	.show = _show,\
	};

	struct cpufreq_stats {
	unsigned int cpu;
	unsigned int total_trans;
	unsigned long long last_time;
	unsigned int max_state;
	unsigned int state_num;
	unsigned int last_index;
	cputime64_t *time_in_state;
	unsigned int *freq_table;
	#ifdef CONFIG_CPU_FREQ_STAT_DETAILS
	unsigned int *trans_table;
	#endif
	};

	static DEFINE_PER_CPU(struct cpufreq_stats *, cpufreq_stats_table);

	struct cpufreq_stats_attribute {
	struct attribute attr;
	ssize_t(show) (struct cpufreq_stats , char *);
	};

	static int cpufreq_stats_update(unsigned int cpu)
	{
	struct cpufreq_stats *stat;
	unsigned long long cur_time;

	cur_time = get_jiffies_64();
	spin_lock(&cpufreq_stats_lock);
	stat = per_cpu(cpufreq_stats_table, cpu);
	if (stat->time_in_state)
	stat->time_in_state[stat->last_index] =
	cputime64_add(stat->time_in_state[stat->last_index],
	cputime_sub(cur_time, stat->last_time));
	stat->last_time = cur_time;
	spin_unlock(&cpufreq_stats_lock);
	return 0;
	}

	static ssize_t show_total_trans(struct cpufreq_policy policy, char buf)
	{
	struct cpufreq_stats *stat = per_cpu(cpufreq_stats_table, policy->cpu);
	if (!stat)
	return 0;
	return sprintf(buf, "%d\n",
	per_cpu(cpufreq_stats_table, stat->cpu)->total_trans);
	}

	static ssize_t show_time_in_state(struct cpufreq_policy policy, char buf)
	{
	ssize_t len = 0;
	int i;
	struct cpufreq_stats *stat = per_cpu(cpufreq_stats_table, policy->cpu);
	if (!stat)
	return 0;
	cpufreq_stats_update(stat->cpu);
	for (i = 0; i < stat->state_num; i++) {
	len += sprintf(buf + len, "%u %llu\n", stat->freq_table[i],
	(unsigned long long)
	cputime64_to_clock_t(stat->time_in_state[i]));
	}
	return len;
	}

	#ifdef CONFIG_CPU_FREQ_STAT_DETAILS
	static ssize_t show_trans_table(struct cpufreq_policy policy, char buf)
	{
	ssize_t len = 0;
	int i, j;

	struct cpufreq_stats *stat = per_cpu(cpufreq_stats_table, policy->cpu);
	if (!stat)
	return 0;
	cpufreq_stats_update(stat->cpu);
	len += snprintf(buf + len, PAGE_SIZE - len, " From : To\n");
	len += snprintf(buf + len, PAGE_SIZE - len, " : ");
	for (i = 0; i < stat->state_num; i++) {
	if (len >= PAGE_SIZE)
	break;
	len += snprintf(buf + len, PAGE_SIZE - len, "%9u ",
	stat->freq_table[i]);
	}
	if (len >= PAGE_SIZE)
	return PAGE_SIZE;

	len += snprintf(buf + len, PAGE_SIZE - len, "\n");

	for (i = 0; i < stat->state_num; i++) {
	if (len >= PAGE_SIZE)
	break;

	len += snprintf(buf + len, PAGE_SIZE - len, "%9u: ",
	stat->freq_table[i]);

	for (j = 0; j < stat->state_num; j++) {
	if (len >= PAGE_SIZE)
	break;
	len += snprintf(buf + len, PAGE_SIZE - len, "%9u ",
	stat->trans_table[i*stat->max_state+j]);
	}
	if (len >= PAGE_SIZE)
	break;
	len += snprintf(buf + len, PAGE_SIZE - len, "\n");
	}
	if (len >= PAGE_SIZE)
	return PAGE_SIZE;
	return len;
	}
	CPUFREQ_STATDEVICE_ATTR(trans_table, 0444, show_trans_table);
	#endif

	CPUFREQ_STATDEVICE_ATTR(total_trans, 0444, show_total_trans);
	CPUFREQ_STATDEVICE_ATTR(time_in_state, 0444, show_time_in_state);

	static struct attribute *default_attrs[] = {
	&_attr_total_trans.attr,
	&_attr_time_in_state.attr,
	#ifdef CONFIG_CPU_FREQ_STAT_DETAILS
	&_attr_trans_table.attr,
	#endif
	NULL
	};
	static struct attribute_group stats_attr_group = {
	.attrs = default_attrs,
	.name = "stats"
	};

	static int freq_table_get_index(struct cpufreq_stats *stat, unsigned int freq)
	{
	int index;
	for (index = 0; index < stat->max_state; index++)
	if (stat->freq_table[index] == freq)
	return index;
	return -1;
	}

	/* should be called late in the CPU removal sequence so that the stats
	* memory is still available in case someone tries to use it.
	*/
	static void cpufreq_stats_free_table(unsigned int cpu)
	{
	struct cpufreq_stats *stat = per_cpu(cpufreq_stats_table, cpu);
	if (stat) {
	kfree(stat->time_in_state);
	kfree(stat);
	}
	per_cpu(cpufreq_stats_table, cpu) = NULL;
	}

	/* must be called early in the CPU removal sequence (before
	* cpufreq_remove_dev) so that policy is still valid.
	*/
	static void cpufreq_stats_free_sysfs(unsigned int cpu)
	{
	struct cpufreq_policy *policy = cpufreq_cpu_get(cpu);
	if (policy && policy->cpu == cpu)
	sysfs_remove_group(&policy->kobj, &stats_attr_group);
	if (policy)
	cpufreq_cpu_put(policy);
	}

	static int cpufreq_stats_create_table(struct cpufreq_policy *policy,
	struct cpufreq_frequency_table *table)
	{
	unsigned int i, j, count = 0, ret = 0;
	struct cpufreq_stats *stat;
	struct cpufreq_policy *data;
	unsigned int alloc_size;
	unsigned int cpu = policy->cpu;
	if (per_cpu(cpufreq_stats_table, cpu))
	return -EBUSY;
	stat = kzalloc(sizeof(struct cpufreq_stats), GFP_KERNEL);
	if ((stat) == NULL)
	return -ENOMEM;

	data = cpufreq_cpu_get(cpu);
	if (data == NULL) {
	ret = -EINVAL;
	goto error_get_fail;
	}

	ret = sysfs_create_group(&data->kobj, &stats_attr_group);
	if (ret)
	goto error_out;

	stat->cpu = cpu;
	per_cpu(cpufreq_stats_table, cpu) = stat;

	for (i = 0; table[i].frequency != CPUFREQ_TABLE_END; i++) {
	unsigned int freq = table[i].frequency;
	if (freq == CPUFREQ_ENTRY_INVALID)
	continue;
	count++;
	}

	alloc_size = count * sizeof(int) + count * sizeof(cputime64_t);

	#ifdef CONFIG_CPU_FREQ_STAT_DETAILS
	alloc_size += count * count * sizeof(int);
	#endif
	stat->max_state = count;
	stat->time_in_state = kzalloc(alloc_size, GFP_KERNEL);
	if (!stat->time_in_state) {
	ret = -ENOMEM;
	goto error_out;
	}
	stat->freq_table = (unsigned int *)(stat->time_in_state + count);

	#ifdef CONFIG_CPU_FREQ_STAT_DETAILS
	stat->trans_table = stat->freq_table + count;
	#endif
	j = 0;
	for (i = 0; table[i].frequency != CPUFREQ_TABLE_END; i++) {
	unsigned int freq = table[i].frequency;
	if (freq == CPUFREQ_ENTRY_INVALID)
	continue;
	if (freq_table_get_index(stat, freq) == -1)
	stat->freq_table[j++] = freq;
	}
	stat->state_num = j;
	spin_lock(&cpufreq_stats_lock);
	stat->last_time = get_jiffies_64();
	stat->last_index = freq_table_get_index(stat, policy->cur);
	spin_unlock(&cpufreq_stats_lock);
	cpufreq_cpu_put(data);
	return 0;
	error_out:
	cpufreq_cpu_put(data);
	error_get_fail:
	kfree(stat);
	per_cpu(cpufreq_stats_table, cpu) = NULL;
	return ret;
	}

	static int cpufreq_stat_notifier_policy(struct notifier_block *nb,
	unsigned long val, void *data)
	{
	int ret;
	struct cpufreq_policy *policy = data;
	struct cpufreq_frequency_table *table;
	unsigned int cpu = policy->cpu;
	if (val != CPUFREQ_NOTIFY)
	return 0;
	table = cpufreq_frequency_get_table(cpu);
	if (!table)
	return 0;
	ret = cpufreq_stats_create_table(policy, table);
	if (ret)
	return ret;
	return 0;
	}

	static int cpufreq_stat_notifier_trans(struct notifier_block *nb,
	unsigned long val, void *data)
	{
	struct cpufreq_freqs *freq = data;
	struct cpufreq_stats *stat;
	int old_index, new_index;

	if (val != CPUFREQ_POSTCHANGE)
	return 0;

	stat = per_cpu(cpufreq_stats_table, freq->cpu);
	if (!stat)
	return 0;

	old_index = stat->last_index;
	new_index = freq_table_get_index(stat, freq->new);

	/* We can't do stat->time_in_state[-1]= .. */
	if (old_index == -1 \|\| new_index == -1)
	return 0;

	cpufreq_stats_update(freq->cpu);

	if (old_index == new_index)
	return 0;

	spin_lock(&cpufreq_stats_lock);
	stat->last_index = new_index;
	#ifdef CONFIG_CPU_FREQ_STAT_DETAILS
	stat->trans_table[old_index * stat->max_state + new_index]++;
	#endif
	stat->total_trans++;
	spin_unlock(&cpufreq_stats_lock);
	return 0;
	}

	static int cpufreq_stats_create_table_cpu(unsigned int cpu)
	{
	struct cpufreq_policy *policy;
	struct cpufreq_frequency_table *table;
	int ret = -ENODEV;

	policy = cpufreq_cpu_get(cpu);
	if (!policy)
	return -ENODEV;

	table = cpufreq_frequency_get_table(cpu);
	if (!table)
	goto out;

	ret = cpufreq_stats_create_table(policy, table);

	out:
	cpufreq_cpu_put(policy);
	return ret;
	}

	static int __cpuinit cpufreq_stat_cpu_callback(struct notifier_block *nfb,
	unsigned long action,
	void *hcpu)
	{
	unsigned int cpu = (unsigned long)hcpu;

	switch (action) {
	case CPU_ONLINE:
	case CPU_ONLINE_FROZEN:
	cpufreq_update_policy(cpu);
	break;
	case CPU_DOWN_PREPARE:
	cpufreq_stats_free_sysfs(cpu);
	break;
	case CPU_DEAD:
	case CPU_DEAD_FROZEN:
	cpufreq_stats_free_table(cpu);
	break;
	case CPU_DOWN_FAILED:
	case CPU_DOWN_FAILED_FROZEN:
	cpufreq_stats_create_table_cpu(cpu);
	break;
	}
	return NOTIFY_OK;
	}

	/* priority=1 so this will get called before cpufreq_remove_dev */
	static struct notifier_block cpufreq_stat_cpu_notifier __refdata = {
	.notifier_call = cpufreq_stat_cpu_callback,
	.priority = 1,
	};

	static struct notifier_block notifier_policy_block = {
	.notifier_call = cpufreq_stat_notifier_policy
	};

	static struct notifier_block notifier_trans_block = {
	.notifier_call = cpufreq_stat_notifier_trans
	};

	static int __init cpufreq_stats_init(void)
	{
	int ret;
	unsigned int cpu;

	spin_lock_init(&cpufreq_stats_lock);
	ret = cpufreq_register_notifier(&notifier_policy_block,
	CPUFREQ_POLICY_NOTIFIER);
	if (ret)
	return ret;

	ret = cpufreq_register_notifier(&notifier_trans_block,
	CPUFREQ_TRANSITION_NOTIFIER);
	if (ret) {
	cpufreq_unregister_notifier(&notifier_policy_block,
	CPUFREQ_POLICY_NOTIFIER);
	return ret;
	}

	register_hotcpu_notifier(&cpufreq_stat_cpu_notifier);
	for_each_online_cpu(cpu) {
	cpufreq_update_policy(cpu);
	}
	return 0;
	}
	static void __exit cpufreq_stats_exit(void)
	{
	unsigned int cpu;

	cpufreq_unregister_notifier(&notifier_policy_block,
	CPUFREQ_POLICY_NOTIFIER);
	cpufreq_unregister_notifier(&notifier_trans_block,
	CPUFREQ_TRANSITION_NOTIFIER);
	unregister_hotcpu_notifier(&cpufreq_stat_cpu_notifier);
	for_each_online_cpu(cpu) {
	cpufreq_stats_free_table(cpu);
	cpufreq_stats_free_sysfs(cpu);
	}
	}

	MODULE_AUTHOR("Zou Nan hai <nanhai.zou@intel.com>");
	MODULE_DESCRIPTION("'cpufreq_stats' - A driver to export cpufreq stats "
	"through sysfs filesystem");
	MODULE_LICENSE("GPL");

	module_init(cpufreq_stats_init);
	module_exit(cpufreq_stats_exit);