drivers/cpufreq/cpufreq-dt.c - linux - Git at Google

 /*
  * Copyright (C) 2012 Freescale Semiconductor, Inc.
  *
  * Copyright (C) 2014 Linaro.
  * Viresh Kumar <viresh.kumar@linaro.org>
  *
  * 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/clk.h>
 #include <linux/cpu.h>
 #include <linux/cpu_cooling.h>
 #include <linux/cpufreq.h>
 #include <linux/cpumask.h>
 #include <linux/err.h>
 #include <linux/module.h>
 #include <linux/of.h>
 #include <linux/pm_opp.h>
 #include <linux/platform_device.h>
 #include <linux/regulator/consumer.h>
 #include <linux/slab.h>
 #include <linux/thermal.h>

 #include "cpufreq-dt.h"

 struct private_data {
 	struct opp_table *opp_table;
 	struct device *cpu_dev;
 	struct thermal_cooling_device *cdev;
 	const char *reg_name;
 };

 static struct freq_attr *cpufreq_dt_attr[] = {
 	&cpufreq_freq_attr_scaling_available_freqs,
 	NULL,   /* Extra space for boost-attr if required */
 	NULL,
 };

 static int set_target(struct cpufreq_policy *policy, unsigned int index)
 {
 	struct private_data *priv = policy->driver_data;

 	return dev_pm_opp_set_rate(priv->cpu_dev,
 				   policy->freq_table[index].frequency * 1000);
 }

 /*
  * An earlier version of opp-v1 bindings used to name the regulator
  * "cpu0-supply", we still need to handle that for backwards compatibility.
  */
 static const char *find_supply_name(struct device *dev)
 {
 	struct device_node *np;
 	struct property *pp;
 	int cpu = dev->id;
 	const char *name = NULL;

 	np = of_node_get(dev->of_node);

 	/* This must be valid for sure */
 	if (WARN_ON(!np))
 		return NULL;

 	/* Try "cpu0" for older DTs */
 	if (!cpu) {
 		pp = of_find_property(np, "cpu0-supply", NULL);
 		if (pp) {
 			name = "cpu0";
 			goto node_put;
 		}
 	}

 	pp = of_find_property(np, "cpu-supply", NULL);
 	if (pp) {
 		name = "cpu";
 		goto node_put;
 	}

 	dev_dbg(dev, "no regulator for cpu%d\n", cpu);
 node_put:
 	of_node_put(np);
 	return name;
 }

 static int resources_available(void)
 {
 	struct device *cpu_dev;
 	struct regulator *cpu_reg;
 	struct clk *cpu_clk;
 	int ret = 0;
 	const char *name;

 	cpu_dev = get_cpu_device(0);
 	if (!cpu_dev) {
 		pr_err("failed to get cpu0 device\n");
 		return -ENODEV;
 	}

 	cpu_clk = clk_get(cpu_dev, NULL);
 	ret = PTR_ERR_OR_ZERO(cpu_clk);
 	if (ret) {
 		/*
 		 * If cpu's clk node is present, but clock is not yet
 		 * registered, we should try defering probe.
 		 */
 		if (ret == -EPROBE_DEFER)
 			dev_dbg(cpu_dev, "clock not ready, retry\n");
 		else
 			dev_err(cpu_dev, "failed to get clock: %d\n", ret);

 		return ret;
 	}

 	clk_put(cpu_clk);

 	name = find_supply_name(cpu_dev);
 	/* Platform doesn't require regulator */
 	if (!name)
 		return 0;

 	cpu_reg = regulator_get_optional(cpu_dev, name);
 	ret = PTR_ERR_OR_ZERO(cpu_reg);
 	if (ret) {
 		/*
 		 * If cpu's regulator supply node is present, but regulator is
 		 * not yet registered, we should try defering probe.
 		 */
 		if (ret == -EPROBE_DEFER)
 			dev_dbg(cpu_dev, "cpu0 regulator not ready, retry\n");
 		else
 			dev_dbg(cpu_dev, "no regulator for cpu0: %d\n", ret);

 		return ret;
 	}

 	regulator_put(cpu_reg);
 	return 0;
 }

 static int cpufreq_init(struct cpufreq_policy *policy)
 {
 	struct cpufreq_frequency_table *freq_table;
 	struct opp_table *opp_table = NULL;
 	struct private_data *priv;
 	struct device *cpu_dev;
 	struct clk *cpu_clk;
 	struct dev_pm_opp *suspend_opp;
 	unsigned int transition_latency;
 	bool fallback = false;
 	const char *name;
 	int ret;

 	cpu_dev = get_cpu_device(policy->cpu);
 	if (!cpu_dev) {
 		pr_err("failed to get cpu%d device\n", policy->cpu);
 		return -ENODEV;
 	}

 	cpu_clk = clk_get(cpu_dev, NULL);
 	if (IS_ERR(cpu_clk)) {
 		ret = PTR_ERR(cpu_clk);
 		dev_err(cpu_dev, "%s: failed to get clk: %d\n", __func__, ret);
 		return ret;
 	}

 	/* Get OPP-sharing information from "operating-points-v2" bindings */
 	ret = dev_pm_opp_of_get_sharing_cpus(cpu_dev, policy->cpus);
 	if (ret) {
 		if (ret != -ENOENT)
 			goto out_put_clk;

 		/*
 		 * operating-points-v2 not supported, fallback to old method of
 		 * finding shared-OPPs for backward compatibility if the
 		 * platform hasn't set sharing CPUs.
 		 */
 		if (dev_pm_opp_get_sharing_cpus(cpu_dev, policy->cpus))
 			fallback = true;
 	}

 	/*
 	 * OPP layer will be taking care of regulators now, but it needs to know
 	 * the name of the regulator first.
 	 */
 	name = find_supply_name(cpu_dev);
 	if (name) {
 		opp_table = dev_pm_opp_set_regulators(cpu_dev, &name, 1);
 		if (IS_ERR(opp_table)) {
 			ret = PTR_ERR(opp_table);
 			dev_err(cpu_dev, "Failed to set regulator for cpu%d: %d\n",
 				policy->cpu, ret);
 			goto out_put_clk;
 		}
 	}

 	/*
 	 * Initialize OPP tables for all policy->cpus. They will be shared by
 	 * all CPUs which have marked their CPUs shared with OPP bindings.
 	 *
 	 * For platforms not using operating-points-v2 bindings, we do this
 	 * before updating policy->cpus. Otherwise, we will end up creating
 	 * duplicate OPPs for policy->cpus.
 	 *
 	 * OPPs might be populated at runtime, don't check for error here
 	 */
 	dev_pm_opp_of_cpumask_add_table(policy->cpus);

 	/*
 	 * But we need OPP table to function so if it is not there let's
 	 * give platform code chance to provide it for us.
 	 */
 	ret = dev_pm_opp_get_opp_count(cpu_dev);
 	if (ret <= 0) {
 		dev_dbg(cpu_dev, "OPP table is not ready, deferring probe\n");
 		ret = -EPROBE_DEFER;
 		goto out_free_opp;
 	}

 	if (fallback) {
 		cpumask_setall(policy->cpus);

 		/*
 		 * OPP tables are initialized only for policy->cpu, do it for
 		 * others as well.
 		 */
 		ret = dev_pm_opp_set_sharing_cpus(cpu_dev, policy->cpus);
 		if (ret)
 			dev_err(cpu_dev, "%s: failed to mark OPPs as shared: %d\n",
 				__func__, ret);
 	}

 	priv = kzalloc(sizeof(*priv), GFP_KERNEL);
 	if (!priv) {
 		ret = -ENOMEM;
 		goto out_free_opp;
 	}

 	priv->reg_name = name;
 	priv->opp_table = opp_table;

 	ret = dev_pm_opp_init_cpufreq_table(cpu_dev, &freq_table);
 	if (ret) {
 		dev_err(cpu_dev, "failed to init cpufreq table: %d\n", ret);
 		goto out_free_priv;
 	}

 	priv->cpu_dev = cpu_dev;
 	policy->driver_data = priv;
 	policy->clk = cpu_clk;

 	rcu_read_lock();
 	suspend_opp = dev_pm_opp_get_suspend_opp(cpu_dev);
 	if (suspend_opp)
 		policy->suspend_freq = dev_pm_opp_get_freq(suspend_opp) / 1000;
 	rcu_read_unlock();

 	ret = cpufreq_table_validate_and_show(policy, freq_table);
 	if (ret) {
 		dev_err(cpu_dev, "%s: invalid frequency table: %d\n", __func__,
 			ret);
 		goto out_free_cpufreq_table;
 	}

 	/* Support turbo/boost mode */
 	if (policy_has_boost_freq(policy)) {
 		/* This gets disabled by core on driver unregister */
 		ret = cpufreq_enable_boost_support();
 		if (ret)
 			goto out_free_cpufreq_table;
 		cpufreq_dt_attr[1] = &cpufreq_freq_attr_scaling_boost_freqs;
 	}

 	transition_latency = dev_pm_opp_get_max_transition_latency(cpu_dev);
 	if (!transition_latency)
 		transition_latency = CPUFREQ_ETERNAL;

 	policy->cpuinfo.transition_latency = transition_latency;

 	return 0;

 out_free_cpufreq_table:
 	dev_pm_opp_free_cpufreq_table(cpu_dev, &freq_table);
 out_free_priv:
 	kfree(priv);
 out_free_opp:
 	dev_pm_opp_of_cpumask_remove_table(policy->cpus);
 	if (name)
 		dev_pm_opp_put_regulators(opp_table);
 out_put_clk:
 	clk_put(cpu_clk);

 	return ret;
 }

 static int cpufreq_exit(struct cpufreq_policy *policy)
 {
 	struct private_data *priv = policy->driver_data;

 	cpufreq_cooling_unregister(priv->cdev);
 	dev_pm_opp_free_cpufreq_table(priv->cpu_dev, &policy->freq_table);
 	dev_pm_opp_of_cpumask_remove_table(policy->related_cpus);
 	if (priv->reg_name)
 		dev_pm_opp_put_regulators(priv->opp_table);

 	clk_put(policy->clk);
 	kfree(priv);

 	return 0;
 }

 static void cpufreq_ready(struct cpufreq_policy *policy)
 {
 	struct private_data *priv = policy->driver_data;
 	struct device_node *np = of_node_get(priv->cpu_dev->of_node);

 	if (WARN_ON(!np))
 		return;

 	/*
 	 * For now, just loading the cooling device;
 	 * thermal DT code takes care of matching them.
 	 */
 	if (of_find_property(np, "#cooling-cells", NULL)) {
 		u32 power_coefficient = 0;

 		of_property_read_u32(np, "dynamic-power-coefficient",
 				     &power_coefficient);

 		priv->cdev = of_cpufreq_power_cooling_register(np,
 				policy->related_cpus, power_coefficient, NULL);
 		if (IS_ERR(priv->cdev)) {
 			dev_err(priv->cpu_dev,
 				"running cpufreq without cooling device: %ld\n",
 				PTR_ERR(priv->cdev));

 			priv->cdev = NULL;
 		}
 	}

 	of_node_put(np);
 }

 static struct cpufreq_driver dt_cpufreq_driver = {
 	.flags = CPUFREQ_STICKY | CPUFREQ_NEED_INITIAL_FREQ_CHECK,
 	.verify = cpufreq_generic_frequency_table_verify,
 	.target_index = set_target,
 	.get = cpufreq_generic_get,
 	.init = cpufreq_init,
 	.exit = cpufreq_exit,
 	.ready = cpufreq_ready,
 	.name = "cpufreq-dt",
 	.attr = cpufreq_dt_attr,
 	.suspend = cpufreq_generic_suspend,
 };

 static int dt_cpufreq_probe(struct platform_device *pdev)
 {
 	struct cpufreq_dt_platform_data *data = dev_get_platdata(&pdev->dev);
 	int ret;

 	/*
 	 * All per-cluster (CPUs sharing clock/voltages) initialization is done
 	 * from ->init(). In probe(), we just need to make sure that clk and
 	 * regulators are available. Else defer probe and retry.
 	 *
 	 * FIXME: Is checking this only for CPU0 sufficient ?
 	 */
 	ret = resources_available();
 	if (ret)
 		return ret;

 	if (data && data->have_governor_per_policy)
 		dt_cpufreq_driver.flags |= CPUFREQ_HAVE_GOVERNOR_PER_POLICY;

 	ret = cpufreq_register_driver(&dt_cpufreq_driver);
 	if (ret)
 		dev_err(&pdev->dev, "failed register driver: %d\n", ret);

 	return ret;
 }

 static int dt_cpufreq_remove(struct platform_device *pdev)
 {
 	cpufreq_unregister_driver(&dt_cpufreq_driver);
 	return 0;
 }

 static struct platform_driver dt_cpufreq_platdrv = {
 	.driver = {
 		.name	= "cpufreq-dt",
 	},
 	.probe		= dt_cpufreq_probe,
 	.remove		= dt_cpufreq_remove,
 };
 module_platform_driver(dt_cpufreq_platdrv);

 MODULE_ALIAS("platform:cpufreq-dt");
 MODULE_AUTHOR("Viresh Kumar <viresh.kumar@linaro.org>");
 MODULE_AUTHOR("Shawn Guo <shawn.guo@linaro.org>");
 MODULE_DESCRIPTION("Generic cpufreq driver");
 MODULE_LICENSE("GPL");
	/*
	* Copyright (C) 2012 Freescale Semiconductor, Inc.
	*
	* Copyright (C) 2014 Linaro.
	* Viresh Kumar <viresh.kumar@linaro.org>
	*
	* 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/clk.h>
	#include <linux/cpu.h>
	#include <linux/cpu_cooling.h>
	#include <linux/cpufreq.h>
	#include <linux/cpumask.h>
	#include <linux/err.h>
	#include <linux/module.h>
	#include <linux/of.h>
	#include <linux/pm_opp.h>
	#include <linux/platform_device.h>
	#include <linux/regulator/consumer.h>
	#include <linux/slab.h>
	#include <linux/thermal.h>

	#include "cpufreq-dt.h"

	struct private_data {
	struct opp_table *opp_table;
	struct device *cpu_dev;
	struct thermal_cooling_device *cdev;
	const char *reg_name;
	};

	static struct freq_attr *cpufreq_dt_attr[] = {
	&cpufreq_freq_attr_scaling_available_freqs,
	NULL, /* Extra space for boost-attr if required */
	NULL,
	};

	static int set_target(struct cpufreq_policy *policy, unsigned int index)
	{
	struct private_data *priv = policy->driver_data;

	return dev_pm_opp_set_rate(priv->cpu_dev,
	policy->freq_table[index].frequency * 1000);
	}

	/*
	* An earlier version of opp-v1 bindings used to name the regulator
	* "cpu0-supply", we still need to handle that for backwards compatibility.
	*/
	static const char find_supply_name(struct device dev)
	{
	struct device_node *np;
	struct property *pp;
	int cpu = dev->id;
	const char *name = NULL;

	np = of_node_get(dev->of_node);

	/* This must be valid for sure */
	if (WARN_ON(!np))
	return NULL;

	/* Try "cpu0" for older DTs */
	if (!cpu) {
	pp = of_find_property(np, "cpu0-supply", NULL);
	if (pp) {
	name = "cpu0";
	goto node_put;
	}
	}

	pp = of_find_property(np, "cpu-supply", NULL);
	if (pp) {
	name = "cpu";
	goto node_put;
	}

	dev_dbg(dev, "no regulator for cpu%d\n", cpu);
	node_put:
	of_node_put(np);
	return name;
	}

	static int resources_available(void)
	{
	struct device *cpu_dev;
	struct regulator *cpu_reg;
	struct clk *cpu_clk;
	int ret = 0;
	const char *name;

	cpu_dev = get_cpu_device(0);
	if (!cpu_dev) {
	pr_err("failed to get cpu0 device\n");
	return -ENODEV;
	}

	cpu_clk = clk_get(cpu_dev, NULL);
	ret = PTR_ERR_OR_ZERO(cpu_clk);
	if (ret) {
	/*
	* If cpu's clk node is present, but clock is not yet
	* registered, we should try defering probe.
	*/
	if (ret == -EPROBE_DEFER)
	dev_dbg(cpu_dev, "clock not ready, retry\n");
	else
	dev_err(cpu_dev, "failed to get clock: %d\n", ret);

	return ret;
	}

	clk_put(cpu_clk);

	name = find_supply_name(cpu_dev);
	/* Platform doesn't require regulator */
	if (!name)
	return 0;

	cpu_reg = regulator_get_optional(cpu_dev, name);
	ret = PTR_ERR_OR_ZERO(cpu_reg);
	if (ret) {
	/*
	* If cpu's regulator supply node is present, but regulator is
	* not yet registered, we should try defering probe.
	*/
	if (ret == -EPROBE_DEFER)
	dev_dbg(cpu_dev, "cpu0 regulator not ready, retry\n");
	else
	dev_dbg(cpu_dev, "no regulator for cpu0: %d\n", ret);

	return ret;
	}

	regulator_put(cpu_reg);
	return 0;
	}

	static int cpufreq_init(struct cpufreq_policy *policy)
	{
	struct cpufreq_frequency_table *freq_table;
	struct opp_table *opp_table = NULL;
	struct private_data *priv;
	struct device *cpu_dev;
	struct clk *cpu_clk;
	struct dev_pm_opp *suspend_opp;
	unsigned int transition_latency;
	bool fallback = false;
	const char *name;
	int ret;

	cpu_dev = get_cpu_device(policy->cpu);
	if (!cpu_dev) {
	pr_err("failed to get cpu%d device\n", policy->cpu);
	return -ENODEV;
	}

	cpu_clk = clk_get(cpu_dev, NULL);
	if (IS_ERR(cpu_clk)) {
	ret = PTR_ERR(cpu_clk);
	dev_err(cpu_dev, "%s: failed to get clk: %d\n", __func__, ret);
	return ret;
	}

	/* Get OPP-sharing information from "operating-points-v2" bindings */
	ret = dev_pm_opp_of_get_sharing_cpus(cpu_dev, policy->cpus);
	if (ret) {
	if (ret != -ENOENT)
	goto out_put_clk;

	/*
	* operating-points-v2 not supported, fallback to old method of
	* finding shared-OPPs for backward compatibility if the
	* platform hasn't set sharing CPUs.
	*/
	if (dev_pm_opp_get_sharing_cpus(cpu_dev, policy->cpus))
	fallback = true;
	}

	/*
	* OPP layer will be taking care of regulators now, but it needs to know
	* the name of the regulator first.
	*/
	name = find_supply_name(cpu_dev);
	if (name) {
	opp_table = dev_pm_opp_set_regulators(cpu_dev, &name, 1);
	if (IS_ERR(opp_table)) {
	ret = PTR_ERR(opp_table);
	dev_err(cpu_dev, "Failed to set regulator for cpu%d: %d\n",
	policy->cpu, ret);
	goto out_put_clk;
	}
	}

	/*
	* Initialize OPP tables for all policy->cpus. They will be shared by
	* all CPUs which have marked their CPUs shared with OPP bindings.
	*
	* For platforms not using operating-points-v2 bindings, we do this
	* before updating policy->cpus. Otherwise, we will end up creating
	* duplicate OPPs for policy->cpus.
	*
	* OPPs might be populated at runtime, don't check for error here
	*/
	dev_pm_opp_of_cpumask_add_table(policy->cpus);

	/*
	* But we need OPP table to function so if it is not there let's
	* give platform code chance to provide it for us.
	*/
	ret = dev_pm_opp_get_opp_count(cpu_dev);
	if (ret <= 0) {
	dev_dbg(cpu_dev, "OPP table is not ready, deferring probe\n");
	ret = -EPROBE_DEFER;
	goto out_free_opp;
	}

	if (fallback) {
	cpumask_setall(policy->cpus);

	/*
	* OPP tables are initialized only for policy->cpu, do it for
	* others as well.
	*/
	ret = dev_pm_opp_set_sharing_cpus(cpu_dev, policy->cpus);
	if (ret)
	dev_err(cpu_dev, "%s: failed to mark OPPs as shared: %d\n",
	__func__, ret);
	}

	priv = kzalloc(sizeof(*priv), GFP_KERNEL);
	if (!priv) {
	ret = -ENOMEM;
	goto out_free_opp;
	}

	priv->reg_name = name;
	priv->opp_table = opp_table;

	ret = dev_pm_opp_init_cpufreq_table(cpu_dev, &freq_table);
	if (ret) {
	dev_err(cpu_dev, "failed to init cpufreq table: %d\n", ret);
	goto out_free_priv;
	}

	priv->cpu_dev = cpu_dev;
	policy->driver_data = priv;
	policy->clk = cpu_clk;

	rcu_read_lock();
	suspend_opp = dev_pm_opp_get_suspend_opp(cpu_dev);
	if (suspend_opp)
	policy->suspend_freq = dev_pm_opp_get_freq(suspend_opp) / 1000;
	rcu_read_unlock();

	ret = cpufreq_table_validate_and_show(policy, freq_table);
	if (ret) {
	dev_err(cpu_dev, "%s: invalid frequency table: %d\n", __func__,
	ret);
	goto out_free_cpufreq_table;
	}

	/* Support turbo/boost mode */
	if (policy_has_boost_freq(policy)) {
	/* This gets disabled by core on driver unregister */
	ret = cpufreq_enable_boost_support();
	if (ret)
	goto out_free_cpufreq_table;
	cpufreq_dt_attr[1] = &cpufreq_freq_attr_scaling_boost_freqs;
	}

	transition_latency = dev_pm_opp_get_max_transition_latency(cpu_dev);
	if (!transition_latency)
	transition_latency = CPUFREQ_ETERNAL;

	policy->cpuinfo.transition_latency = transition_latency;

	return 0;

	out_free_cpufreq_table:
	dev_pm_opp_free_cpufreq_table(cpu_dev, &freq_table);
	out_free_priv:
	kfree(priv);
	out_free_opp:
	dev_pm_opp_of_cpumask_remove_table(policy->cpus);
	if (name)
	dev_pm_opp_put_regulators(opp_table);
	out_put_clk:
	clk_put(cpu_clk);

	return ret;
	}

	static int cpufreq_exit(struct cpufreq_policy *policy)
	{
	struct private_data *priv = policy->driver_data;

	cpufreq_cooling_unregister(priv->cdev);
	dev_pm_opp_free_cpufreq_table(priv->cpu_dev, &policy->freq_table);
	dev_pm_opp_of_cpumask_remove_table(policy->related_cpus);
	if (priv->reg_name)
	dev_pm_opp_put_regulators(priv->opp_table);

	clk_put(policy->clk);
	kfree(priv);

	return 0;
	}

	static void cpufreq_ready(struct cpufreq_policy *policy)
	{
	struct private_data *priv = policy->driver_data;
	struct device_node *np = of_node_get(priv->cpu_dev->of_node);

	if (WARN_ON(!np))
	return;

	/*
	* For now, just loading the cooling device;
	* thermal DT code takes care of matching them.
	*/
	if (of_find_property(np, "#cooling-cells", NULL)) {
	u32 power_coefficient = 0;

	of_property_read_u32(np, "dynamic-power-coefficient",
	&power_coefficient);

	priv->cdev = of_cpufreq_power_cooling_register(np,
	policy->related_cpus, power_coefficient, NULL);
	if (IS_ERR(priv->cdev)) {
	dev_err(priv->cpu_dev,
	"running cpufreq without cooling device: %ld\n",
	PTR_ERR(priv->cdev));

	priv->cdev = NULL;
	}
	}

	of_node_put(np);
	}

	static struct cpufreq_driver dt_cpufreq_driver = {
	.flags = CPUFREQ_STICKY \| CPUFREQ_NEED_INITIAL_FREQ_CHECK,
	.verify = cpufreq_generic_frequency_table_verify,
	.target_index = set_target,
	.get = cpufreq_generic_get,
	.init = cpufreq_init,
	.exit = cpufreq_exit,
	.ready = cpufreq_ready,
	.name = "cpufreq-dt",
	.attr = cpufreq_dt_attr,
	.suspend = cpufreq_generic_suspend,
	};

	static int dt_cpufreq_probe(struct platform_device *pdev)
	{
	struct cpufreq_dt_platform_data *data = dev_get_platdata(&pdev->dev);
	int ret;

	/*
	* All per-cluster (CPUs sharing clock/voltages) initialization is done
	* from ->init(). In probe(), we just need to make sure that clk and
	* regulators are available. Else defer probe and retry.
	*
	* FIXME: Is checking this only for CPU0 sufficient ?
	*/
	ret = resources_available();
	if (ret)
	return ret;

	if (data && data->have_governor_per_policy)
	dt_cpufreq_driver.flags \|= CPUFREQ_HAVE_GOVERNOR_PER_POLICY;

	ret = cpufreq_register_driver(&dt_cpufreq_driver);
	if (ret)
	dev_err(&pdev->dev, "failed register driver: %d\n", ret);

	return ret;
	}

	static int dt_cpufreq_remove(struct platform_device *pdev)
	{
	cpufreq_unregister_driver(&dt_cpufreq_driver);
	return 0;
	}

	static struct platform_driver dt_cpufreq_platdrv = {
	.driver = {
	.name = "cpufreq-dt",
	},
	.probe = dt_cpufreq_probe,
	.remove = dt_cpufreq_remove,
	};
	module_platform_driver(dt_cpufreq_platdrv);

	MODULE_ALIAS("platform:cpufreq-dt");
	MODULE_AUTHOR("Viresh Kumar <viresh.kumar@linaro.org>");
	MODULE_AUTHOR("Shawn Guo <shawn.guo@linaro.org>");
	MODULE_DESCRIPTION("Generic cpufreq driver");
	MODULE_LICENSE("GPL");