arch/arm/mach-msm/cpufreq.c - kernel/msm - Gitiles

 /* arch/arm/mach-msm/cpufreq.c
  *
  * MSM architecture cpufreq driver
  *
  * Copyright (C) 2007 Google, Inc.
  * Copyright (c) 2007-2013, The Linux Foundation. All rights reserved.
  * Author: Mike A. Chan <mikechan@google.com>
  *
  * This software is licensed under the terms of the GNU General Public
  * License version 2, as published by the Free Software Foundation, and
  * may be copied, distributed, and modified under those terms.
  *
  * This program is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.	 See the
  * GNU General Public License for more details.
  *
  */

 #include <linux/earlysuspend.h>
 #include <linux/init.h>
 #include <linux/module.h>
 #include <linux/cpufreq.h>
 #include <linux/workqueue.h>
 #include <linux/completion.h>
 #include <linux/cpu.h>
 #include <linux/cpumask.h>
 #include <linux/sched.h>
 #include <linux/suspend.h>
 #include <mach/socinfo.h>
 #include <mach/cpufreq.h>

 #include "acpuclock.h"

 struct cpufreq_work_struct {
 	struct work_struct work;
 	struct cpufreq_policy *policy;
 	struct completion complete;
 	int frequency;
 	int status;
 };

 static DEFINE_PER_CPU(struct cpufreq_work_struct, cpufreq_work);
 static struct workqueue_struct *msm_cpufreq_wq;

 struct cpufreq_suspend_t {
 	struct mutex suspend_mutex;
 	int device_suspended;
 };

 static DEFINE_PER_CPU(struct cpufreq_suspend_t, cpufreq_suspend);

 struct cpu_freq {
 	uint32_t max;
 	uint32_t min;
 	uint32_t allowed_max;
 	uint32_t allowed_min;
 	uint32_t limits_init;
 };

 static DEFINE_PER_CPU(struct cpu_freq, cpu_freq_info);

 static int set_cpu_freq(struct cpufreq_policy *policy, unsigned int new_freq)
 {
 	int ret = 0;
 	int saved_sched_policy = -EINVAL;
 	int saved_sched_rt_prio = -EINVAL;
 	struct cpufreq_freqs freqs;
 	struct cpu_freq *limit = &per_cpu(cpu_freq_info, policy->cpu);
 	struct sched_param param = { .sched_priority = MAX_RT_PRIO-1 };

 	if (limit->limits_init) {
 		if (new_freq > limit->allowed_max) {
 			new_freq = limit->allowed_max;
 			pr_debug("max: limiting freq to %d\n", new_freq);
 		}

 		if (new_freq < limit->allowed_min) {
 			new_freq = limit->allowed_min;
 			pr_debug("min: limiting freq to %d\n", new_freq);
 		}
 	}

 	freqs.old = policy->cur;
 	freqs.new = new_freq;
 	freqs.cpu = policy->cpu;

 	/*
 	 * Put the caller into SCHED_FIFO priority to avoid cpu starvation
 	 * in the acpuclk_set_rate path while increasing frequencies
 	 */

 	if (freqs.new > freqs.old && current->policy != SCHED_FIFO) {
 		saved_sched_policy = current->policy;
 		saved_sched_rt_prio = current->rt_priority;
 		sched_setscheduler_nocheck(current, SCHED_FIFO, &param);
 	}

 	cpufreq_notify_transition(&freqs, CPUFREQ_PRECHANGE);

 	ret = acpuclk_set_rate(policy->cpu, new_freq, SETRATE_CPUFREQ);
 	if (!ret)
 		cpufreq_notify_transition(&freqs, CPUFREQ_POSTCHANGE);

 	/* Restore priority after clock ramp-up */
 	if (freqs.new > freqs.old && saved_sched_policy >= 0) {
 		param.sched_priority = saved_sched_rt_prio;
 		sched_setscheduler_nocheck(current, saved_sched_policy, &param);
 	}
 	return ret;
 }

 static void set_cpu_work(struct work_struct *work)
 {
 	struct cpufreq_work_struct *cpu_work =
 		container_of(work, struct cpufreq_work_struct, work);

 	cpu_work->status = set_cpu_freq(cpu_work->policy, cpu_work->frequency);
 	complete(&cpu_work->complete);
 }

 static int msm_cpufreq_target(struct cpufreq_policy *policy,
 				unsigned int target_freq,
 				unsigned int relation)
 {
 	int ret = -EFAULT;
 	int index;
 	struct cpufreq_frequency_table *table;

 	struct cpufreq_work_struct *cpu_work = NULL;

 	mutex_lock(&per_cpu(cpufreq_suspend, policy->cpu).suspend_mutex);

 	if (per_cpu(cpufreq_suspend, policy->cpu).device_suspended) {
 		pr_debug("cpufreq: cpu%d scheduling frequency change "
 				"in suspend.\n", policy->cpu);
 		ret = -EFAULT;
 		goto done;
 	}

 	table = cpufreq_frequency_get_table(policy->cpu);
 	if (cpufreq_frequency_table_target(policy, table, target_freq, relation,
 			&index)) {
 		pr_err("cpufreq: invalid target_freq: %d\n", target_freq);
 		ret = -EINVAL;
 		goto done;
 	}

 	pr_debug("CPU[%d] target %d relation %d (%d-%d) selected %d\n",
 		policy->cpu, target_freq, relation,
 		policy->min, policy->max, table[index].frequency);

 	cpu_work = &per_cpu(cpufreq_work, policy->cpu);
 	cpu_work->policy = policy;
 	cpu_work->frequency = table[index].frequency;
 	cpu_work->status = -ENODEV;

 	cancel_work_sync(&cpu_work->work);
 	INIT_COMPLETION(cpu_work->complete);
 	queue_work_on(policy->cpu, msm_cpufreq_wq, &cpu_work->work);
 	wait_for_completion(&cpu_work->complete);

 	ret = cpu_work->status;

 done:
 	mutex_unlock(&per_cpu(cpufreq_suspend, policy->cpu).suspend_mutex);
 	return ret;
 }

 static int msm_cpufreq_verify(struct cpufreq_policy *policy)
 {
 	cpufreq_verify_within_limits(policy, policy->cpuinfo.min_freq,
 			policy->cpuinfo.max_freq);
 	return 0;
 }

 static unsigned int msm_cpufreq_get_freq(unsigned int cpu)
 {
 	return acpuclk_get_rate(cpu);
 }

 static inline int msm_cpufreq_limits_init(void)
 {
 	int cpu = 0;
 	int i = 0;
 	struct cpufreq_frequency_table *table = NULL;
 	uint32_t min = (uint32_t) -1;
 	uint32_t max = 0;
 	struct cpu_freq *limit = NULL;

 	for_each_possible_cpu(cpu) {
 		limit = &per_cpu(cpu_freq_info, cpu);
 		table = cpufreq_frequency_get_table(cpu);
 		if (table == NULL) {
 			pr_err("%s: error reading cpufreq table for cpu %d\n",
 					__func__, cpu);
 			continue;
 		}
 		for (i = 0; (table[i].frequency != CPUFREQ_TABLE_END); i++) {
 			if (table[i].frequency > max)
 				max = table[i].frequency;
 			if (table[i].frequency < min)
 				min = table[i].frequency;
 		}
 		limit->allowed_min = min;
 		limit->allowed_max = max;
 		limit->min = min;
 		limit->max = max;
 		limit->limits_init = 1;
 	}

 	return 0;
 }

 int msm_cpufreq_set_freq_limits(uint32_t cpu, uint32_t min, uint32_t max)
 {
 	struct cpu_freq *limit = &per_cpu(cpu_freq_info, cpu);

 	if (!limit->limits_init)
 		msm_cpufreq_limits_init();

 	if ((min != MSM_CPUFREQ_NO_LIMIT) &&
 		min >= limit->min && min <= limit->max)
 		limit->allowed_min = min;
 	else
 		limit->allowed_min = limit->min;


 	if ((max != MSM_CPUFREQ_NO_LIMIT) &&
 		max <= limit->max && max >= limit->min)
 		limit->allowed_max = max;
 	else
 		limit->allowed_max = limit->max;

 	pr_debug("%s: Limiting cpu %d min = %d, max = %d\n",
 			__func__, cpu,
 			limit->allowed_min, limit->allowed_max);

 	return 0;
 }
 EXPORT_SYMBOL(msm_cpufreq_set_freq_limits);

 static int __cpuinit msm_cpufreq_init(struct cpufreq_policy *policy)
 {
 	int cur_freq;
 	int index;
 	int ret = 0;
 	struct cpufreq_frequency_table *table;
 	struct cpufreq_work_struct *cpu_work = NULL;

 	table = cpufreq_frequency_get_table(policy->cpu);
 	if (table == NULL)
 		return -ENODEV;
 	/*
 	 * In 8625, 8610, and 8226 both cpu core's frequency can not
 	 * be changed independently. Each cpu is bound to
 	 * same frequency. Hence set the cpumask to all cpu.
 	 */
 	if (cpu_is_msm8625() || cpu_is_msm8625q() || cpu_is_msm8226()
 		|| cpu_is_msm8610())
 		cpumask_setall(policy->cpus);

 	if (cpufreq_frequency_table_cpuinfo(policy, table)) {
 #ifdef CONFIG_MSM_CPU_FREQ_SET_MIN_MAX
 		policy->cpuinfo.min_freq = CONFIG_MSM_CPU_FREQ_MIN;
 		policy->cpuinfo.max_freq = CONFIG_MSM_CPU_FREQ_MAX;
 #endif
 	}
 #ifdef CONFIG_MSM_CPU_FREQ_SET_MIN_MAX
 	policy->min = CONFIG_MSM_CPU_FREQ_MIN;
 	policy->max = CONFIG_MSM_CPU_FREQ_MAX;
 #endif

 	cur_freq = acpuclk_get_rate(policy->cpu);
 	if (cpufreq_frequency_table_target(policy, table, cur_freq,
 	    CPUFREQ_RELATION_H, &index) &&
 	    cpufreq_frequency_table_target(policy, table, cur_freq,
 	    CPUFREQ_RELATION_L, &index)) {
 		pr_info("cpufreq: cpu%d at invalid freq: %d\n",
 				policy->cpu, cur_freq);
 		return -EINVAL;
 	}
 	/*
 	 * Call set_cpu_freq unconditionally so that when cpu is set to
 	 * online, frequency limit will always be updated.
 	 */
 	ret = set_cpu_freq(policy, table[index].frequency);
 	if (ret)
 		return ret;
 	pr_debug("cpufreq: cpu%d init at %d switching to %d\n",
 			policy->cpu, cur_freq, table[index].frequency);
 	policy->cur = table[index].frequency;

 	policy->cpuinfo.transition_latency =
 		acpuclk_get_switch_time() * NSEC_PER_USEC;

 	cpu_work = &per_cpu(cpufreq_work, policy->cpu);
 	INIT_WORK(&cpu_work->work, set_cpu_work);
 	init_completion(&cpu_work->complete);

 	return 0;
 }

 static int __cpuinit msm_cpufreq_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:
 		per_cpu(cpufreq_suspend, cpu).device_suspended = 0;
 		break;
 	case CPU_DOWN_PREPARE:
 	case CPU_DOWN_PREPARE_FROZEN:
 		mutex_lock(&per_cpu(cpufreq_suspend, cpu).suspend_mutex);
 		per_cpu(cpufreq_suspend, cpu).device_suspended = 1;
 		mutex_unlock(&per_cpu(cpufreq_suspend, cpu).suspend_mutex);
 		break;
 	case CPU_DOWN_FAILED:
 	case CPU_DOWN_FAILED_FROZEN:
 		per_cpu(cpufreq_suspend, cpu).device_suspended = 0;
 		break;
 	}

 	return NOTIFY_OK;
 }

 static struct notifier_block __refdata msm_cpufreq_cpu_notifier = {
 	.notifier_call = msm_cpufreq_cpu_callback,
 };

 /*
  * Define suspend/resume for cpufreq_driver. Kernel will call
  * these during suspend/resume with interrupts disabled. This
  * helps the suspend/resume variable get's updated before cpufreq
  * governor tries to change the frequency after coming out of suspend.
  */
 static int msm_cpufreq_suspend(struct cpufreq_policy *policy)
 {
 	int cpu;

 	for_each_possible_cpu(cpu) {
 		per_cpu(cpufreq_suspend, cpu).device_suspended = 1;
 	}

 	return 0;
 }

 static int msm_cpufreq_resume(struct cpufreq_policy *policy)
 {
 	int cpu;

 	for_each_possible_cpu(cpu) {
 		per_cpu(cpufreq_suspend, cpu).device_suspended = 0;
 	}

 	return 0;
 }

 static struct freq_attr *msm_freq_attr[] = {
 	&cpufreq_freq_attr_scaling_available_freqs,
 	NULL,
 };

 static struct cpufreq_driver msm_cpufreq_driver = {
 	/* lps calculations are handled here. */
 	.flags		= CPUFREQ_STICKY | CPUFREQ_CONST_LOOPS,
 	.init		= msm_cpufreq_init,
 	.verify		= msm_cpufreq_verify,
 	.target		= msm_cpufreq_target,
 	.get		= msm_cpufreq_get_freq,
 	.suspend	= msm_cpufreq_suspend,
 	.resume		= msm_cpufreq_resume,
 	.name		= "msm",
 	.attr		= msm_freq_attr,
 };

 static int __init msm_cpufreq_register(void)
 {
 	int cpu;

 	for_each_possible_cpu(cpu) {
 		mutex_init(&(per_cpu(cpufreq_suspend, cpu).suspend_mutex));
 		per_cpu(cpufreq_suspend, cpu).device_suspended = 0;
 	}

 	msm_cpufreq_wq = alloc_workqueue("msm-cpufreq", WQ_HIGHPRI, 0);
 	register_hotcpu_notifier(&msm_cpufreq_cpu_notifier);

 	return cpufreq_register_driver(&msm_cpufreq_driver);
 }

 device_initcall(msm_cpufreq_register);
	/* arch/arm/mach-msm/cpufreq.c
	*
	* MSM architecture cpufreq driver
	*
	* Copyright (C) 2007 Google, Inc.
	* Copyright (c) 2007-2013, The Linux Foundation. All rights reserved.
	* Author: Mike A. Chan <mikechan@google.com>
	*
	* This software is licensed under the terms of the GNU General Public
	* License version 2, as published by the Free Software Foundation, and
	* may be copied, distributed, and modified under those terms.
	*
	* This program is distributed in the hope that it will be useful,
	* but WITHOUT ANY WARRANTY; without even the implied warranty of
	* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
	* GNU General Public License for more details.
	*
	*/

	#include <linux/earlysuspend.h>
	#include <linux/init.h>
	#include <linux/module.h>
	#include <linux/cpufreq.h>
	#include <linux/workqueue.h>
	#include <linux/completion.h>
	#include <linux/cpu.h>
	#include <linux/cpumask.h>
	#include <linux/sched.h>
	#include <linux/suspend.h>
	#include <mach/socinfo.h>
	#include <mach/cpufreq.h>

	#include "acpuclock.h"

	struct cpufreq_work_struct {
	struct work_struct work;
	struct cpufreq_policy *policy;
	struct completion complete;
	int frequency;
	int status;
	};

	static DEFINE_PER_CPU(struct cpufreq_work_struct, cpufreq_work);
	static struct workqueue_struct *msm_cpufreq_wq;

	struct cpufreq_suspend_t {
	struct mutex suspend_mutex;
	int device_suspended;
	};

	static DEFINE_PER_CPU(struct cpufreq_suspend_t, cpufreq_suspend);

	struct cpu_freq {
	uint32_t max;
	uint32_t min;
	uint32_t allowed_max;
	uint32_t allowed_min;
	uint32_t limits_init;
	};

	static DEFINE_PER_CPU(struct cpu_freq, cpu_freq_info);

	static int set_cpu_freq(struct cpufreq_policy *policy, unsigned int new_freq)
	{
	int ret = 0;
	int saved_sched_policy = -EINVAL;
	int saved_sched_rt_prio = -EINVAL;
	struct cpufreq_freqs freqs;
	struct cpu_freq *limit = &per_cpu(cpu_freq_info, policy->cpu);
	struct sched_param param = { .sched_priority = MAX_RT_PRIO-1 };

	if (limit->limits_init) {
	if (new_freq > limit->allowed_max) {
	new_freq = limit->allowed_max;
	pr_debug("max: limiting freq to %d\n", new_freq);
	}

	if (new_freq < limit->allowed_min) {
	new_freq = limit->allowed_min;
	pr_debug("min: limiting freq to %d\n", new_freq);
	}
	}

	freqs.old = policy->cur;
	freqs.new = new_freq;
	freqs.cpu = policy->cpu;

	/*
	* Put the caller into SCHED_FIFO priority to avoid cpu starvation
	* in the acpuclk_set_rate path while increasing frequencies
	*/

	if (freqs.new > freqs.old && current->policy != SCHED_FIFO) {
	saved_sched_policy = current->policy;
	saved_sched_rt_prio = current->rt_priority;
	sched_setscheduler_nocheck(current, SCHED_FIFO, &param);
	}

	cpufreq_notify_transition(&freqs, CPUFREQ_PRECHANGE);

	ret = acpuclk_set_rate(policy->cpu, new_freq, SETRATE_CPUFREQ);
	if (!ret)
	cpufreq_notify_transition(&freqs, CPUFREQ_POSTCHANGE);

	/* Restore priority after clock ramp-up */
	if (freqs.new > freqs.old && saved_sched_policy >= 0) {
	param.sched_priority = saved_sched_rt_prio;
	sched_setscheduler_nocheck(current, saved_sched_policy, &param);
	}
	return ret;
	}

	static void set_cpu_work(struct work_struct *work)
	{
	struct cpufreq_work_struct *cpu_work =
	container_of(work, struct cpufreq_work_struct, work);

	cpu_work->status = set_cpu_freq(cpu_work->policy, cpu_work->frequency);
	complete(&cpu_work->complete);
	}

	static int msm_cpufreq_target(struct cpufreq_policy *policy,
	unsigned int target_freq,
	unsigned int relation)
	{
	int ret = -EFAULT;
	int index;
	struct cpufreq_frequency_table *table;

	struct cpufreq_work_struct *cpu_work = NULL;

	mutex_lock(&per_cpu(cpufreq_suspend, policy->cpu).suspend_mutex);

	if (per_cpu(cpufreq_suspend, policy->cpu).device_suspended) {
	pr_debug("cpufreq: cpu%d scheduling frequency change "
	"in suspend.\n", policy->cpu);
	ret = -EFAULT;
	goto done;
	}

	table = cpufreq_frequency_get_table(policy->cpu);
	if (cpufreq_frequency_table_target(policy, table, target_freq, relation,
	&index)) {
	pr_err("cpufreq: invalid target_freq: %d\n", target_freq);
	ret = -EINVAL;
	goto done;
	}

	pr_debug("CPU[%d] target %d relation %d (%d-%d) selected %d\n",
	policy->cpu, target_freq, relation,
	policy->min, policy->max, table[index].frequency);

	cpu_work = &per_cpu(cpufreq_work, policy->cpu);
	cpu_work->policy = policy;
	cpu_work->frequency = table[index].frequency;
	cpu_work->status = -ENODEV;

	cancel_work_sync(&cpu_work->work);
	INIT_COMPLETION(cpu_work->complete);
	queue_work_on(policy->cpu, msm_cpufreq_wq, &cpu_work->work);
	wait_for_completion(&cpu_work->complete);

	ret = cpu_work->status;

	done:
	mutex_unlock(&per_cpu(cpufreq_suspend, policy->cpu).suspend_mutex);
	return ret;
	}

	static int msm_cpufreq_verify(struct cpufreq_policy *policy)
	{
	cpufreq_verify_within_limits(policy, policy->cpuinfo.min_freq,
	policy->cpuinfo.max_freq);
	return 0;
	}

	static unsigned int msm_cpufreq_get_freq(unsigned int cpu)
	{
	return acpuclk_get_rate(cpu);
	}

	static inline int msm_cpufreq_limits_init(void)
	{
	int cpu = 0;
	int i = 0;
	struct cpufreq_frequency_table *table = NULL;
	uint32_t min = (uint32_t) -1;
	uint32_t max = 0;
	struct cpu_freq *limit = NULL;

	for_each_possible_cpu(cpu) {
	limit = &per_cpu(cpu_freq_info, cpu);
	table = cpufreq_frequency_get_table(cpu);
	if (table == NULL) {
	pr_err("%s: error reading cpufreq table for cpu %d\n",
	__func__, cpu);
	continue;
	}
	for (i = 0; (table[i].frequency != CPUFREQ_TABLE_END); i++) {
	if (table[i].frequency > max)
	max = table[i].frequency;
	if (table[i].frequency < min)
	min = table[i].frequency;
	}
	limit->allowed_min = min;
	limit->allowed_max = max;
	limit->min = min;
	limit->max = max;
	limit->limits_init = 1;
	}

	return 0;
	}

	int msm_cpufreq_set_freq_limits(uint32_t cpu, uint32_t min, uint32_t max)
	{
	struct cpu_freq *limit = &per_cpu(cpu_freq_info, cpu);

	if (!limit->limits_init)
	msm_cpufreq_limits_init();

	if ((min != MSM_CPUFREQ_NO_LIMIT) &&
	min >= limit->min && min <= limit->max)
	limit->allowed_min = min;
	else
	limit->allowed_min = limit->min;


	if ((max != MSM_CPUFREQ_NO_LIMIT) &&
	max <= limit->max && max >= limit->min)
	limit->allowed_max = max;
	else
	limit->allowed_max = limit->max;

	pr_debug("%s: Limiting cpu %d min = %d, max = %d\n",
	__func__, cpu,
	limit->allowed_min, limit->allowed_max);

	return 0;
	}
	EXPORT_SYMBOL(msm_cpufreq_set_freq_limits);

	static int __cpuinit msm_cpufreq_init(struct cpufreq_policy *policy)
	{
	int cur_freq;
	int index;
	int ret = 0;
	struct cpufreq_frequency_table *table;
	struct cpufreq_work_struct *cpu_work = NULL;

	table = cpufreq_frequency_get_table(policy->cpu);
	if (table == NULL)
	return -ENODEV;
	/*
	* In 8625, 8610, and 8226 both cpu core's frequency can not
	* be changed independently. Each cpu is bound to
	* same frequency. Hence set the cpumask to all cpu.
	*/
	if (cpu_is_msm8625() \|\| cpu_is_msm8625q() \|\| cpu_is_msm8226()
	\|\| cpu_is_msm8610())
	cpumask_setall(policy->cpus);

	if (cpufreq_frequency_table_cpuinfo(policy, table)) {
	#ifdef CONFIG_MSM_CPU_FREQ_SET_MIN_MAX
	policy->cpuinfo.min_freq = CONFIG_MSM_CPU_FREQ_MIN;
	policy->cpuinfo.max_freq = CONFIG_MSM_CPU_FREQ_MAX;
	#endif
	}
	#ifdef CONFIG_MSM_CPU_FREQ_SET_MIN_MAX
	policy->min = CONFIG_MSM_CPU_FREQ_MIN;
	policy->max = CONFIG_MSM_CPU_FREQ_MAX;
	#endif

	cur_freq = acpuclk_get_rate(policy->cpu);
	if (cpufreq_frequency_table_target(policy, table, cur_freq,
	CPUFREQ_RELATION_H, &index) &&
	cpufreq_frequency_table_target(policy, table, cur_freq,
	CPUFREQ_RELATION_L, &index)) {
	pr_info("cpufreq: cpu%d at invalid freq: %d\n",
	policy->cpu, cur_freq);
	return -EINVAL;
	}
	/*
	* Call set_cpu_freq unconditionally so that when cpu is set to
	* online, frequency limit will always be updated.
	*/
	ret = set_cpu_freq(policy, table[index].frequency);
	if (ret)
	return ret;
	pr_debug("cpufreq: cpu%d init at %d switching to %d\n",
	policy->cpu, cur_freq, table[index].frequency);
	policy->cur = table[index].frequency;

	policy->cpuinfo.transition_latency =
	acpuclk_get_switch_time() * NSEC_PER_USEC;

	cpu_work = &per_cpu(cpufreq_work, policy->cpu);
	INIT_WORK(&cpu_work->work, set_cpu_work);
	init_completion(&cpu_work->complete);

	return 0;
	}

	static int __cpuinit msm_cpufreq_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:
	per_cpu(cpufreq_suspend, cpu).device_suspended = 0;
	break;
	case CPU_DOWN_PREPARE:
	case CPU_DOWN_PREPARE_FROZEN:
	mutex_lock(&per_cpu(cpufreq_suspend, cpu).suspend_mutex);
	per_cpu(cpufreq_suspend, cpu).device_suspended = 1;
	mutex_unlock(&per_cpu(cpufreq_suspend, cpu).suspend_mutex);
	break;
	case CPU_DOWN_FAILED:
	case CPU_DOWN_FAILED_FROZEN:
	per_cpu(cpufreq_suspend, cpu).device_suspended = 0;
	break;
	}

	return NOTIFY_OK;
	}

	static struct notifier_block __refdata msm_cpufreq_cpu_notifier = {
	.notifier_call = msm_cpufreq_cpu_callback,
	};

	/*
	* Define suspend/resume for cpufreq_driver. Kernel will call
	* these during suspend/resume with interrupts disabled. This
	* helps the suspend/resume variable get's updated before cpufreq
	* governor tries to change the frequency after coming out of suspend.
	*/
	static int msm_cpufreq_suspend(struct cpufreq_policy *policy)
	{
	int cpu;

	for_each_possible_cpu(cpu) {
	per_cpu(cpufreq_suspend, cpu).device_suspended = 1;
	}

	return 0;
	}

	static int msm_cpufreq_resume(struct cpufreq_policy *policy)
	{
	int cpu;

	for_each_possible_cpu(cpu) {
	per_cpu(cpufreq_suspend, cpu).device_suspended = 0;
	}

	return 0;
	}

	static struct freq_attr *msm_freq_attr[] = {
	&cpufreq_freq_attr_scaling_available_freqs,
	NULL,
	};

	static struct cpufreq_driver msm_cpufreq_driver = {
	/* lps calculations are handled here. */
	.flags = CPUFREQ_STICKY \| CPUFREQ_CONST_LOOPS,
	.init = msm_cpufreq_init,
	.verify = msm_cpufreq_verify,
	.target = msm_cpufreq_target,
	.get = msm_cpufreq_get_freq,
	.suspend = msm_cpufreq_suspend,
	.resume = msm_cpufreq_resume,
	.name = "msm",
	.attr = msm_freq_attr,
	};

	static int __init msm_cpufreq_register(void)
	{
	int cpu;

	for_each_possible_cpu(cpu) {
	mutex_init(&(per_cpu(cpufreq_suspend, cpu).suspend_mutex));
	per_cpu(cpufreq_suspend, cpu).device_suspended = 0;
	}

	msm_cpufreq_wq = alloc_workqueue("msm-cpufreq", WQ_HIGHPRI, 0);
	register_hotcpu_notifier(&msm_cpufreq_cpu_notifier);

	return cpufreq_register_driver(&msm_cpufreq_driver);
	}

	device_initcall(msm_cpufreq_register);