Commit dc279ac6 authored by Stephan Gerhold's avatar Stephan Gerhold Committed by Viresh Kumar
Browse files

cpufreq: dt: Refactor initialization to handle probe deferral properly 



cpufreq-dt is currently unable to handle -EPROBE_DEFER properly
because the error code is not propagated for the cpufreq_driver->init()
callback. Instead, it attempts to avoid the situation by temporarily
requesting all resources within resources_available() and releasing them
again immediately after. This has several disadvantages:

  - Whenever we add something like interconnect handling to the OPP core
    we need to patch cpufreq-dt to request these resources early.

  - resources_available() is only run for CPU0, but other clusters may
    eventually depend on other resources that are not available yet.
    (See FIXME comment removed by this commit...)

  - All resources need to be looked up several times.

Now that the OPP core can propagate -EPROBE_DEFER during initialization,
it would be nice to avoid all that trouble and just propagate its error
code when necessary.

This commit refactors the cpufreq-dt driver to initialize private_data
before registering the cpufreq driver. We do this by iterating over
all possible CPUs and ensure that all resources are initialized:

  1. dev_pm_opp_get_opp_table() ensures the OPP table is allocated
     and initialized with clock and interconnects.

  2. dev_pm_opp_set_regulators() requests the regulators and assigns
     them to the OPP table.

  3. We call dev_pm_opp_of_get_sharing_cpus() early so that we only
     initialize the OPP table once for each shared policy.

With these changes, we actually end up saving a few lines of code,
the resources are no longer looked up multiple times and everything
should be much more robust.

Signed-off-by: default avatarStephan Gerhold <stephan@gerhold.net>
[ Viresh: Use list_head structure for maintaining the list and minor
	  changes ]
Signed-off-by: default avatarViresh Kumar <viresh.kumar@linaro.org>
parent 90d46d71

drivers/cpufreq/cpufreq-dt.c

+143 −143
Original line number Diff line number Diff line
@@ -13,6 +13,7 @@ 
#include <linux/cpufreq.h>

#include <linux/cpumask.h>

#include <linux/err.h>

#include <linux/list.h>

#include <linux/module.h>

#include <linux/of.h>

#include <linux/pm_opp.h>
@@ -24,18 +25,35 @@ 
#include "cpufreq-dt.h"



struct private_data {

	struct opp_table *opp_table;

	struct list_head node;



	cpumask_var_t cpus;

	struct device *cpu_dev;

	const char *reg_name;

	struct opp_table *opp_table;

	struct opp_table *reg_opp_table;

	bool have_static_opps;

};



static LIST_HEAD(priv_list);



static struct freq_attr *cpufreq_dt_attr[] = {

	&cpufreq_freq_attr_scaling_available_freqs,

	NULL,   /* Extra space for boost-attr if required */

	NULL,

};



static struct private_data *cpufreq_dt_find_data(int cpu)

{

	struct private_data *priv;



	list_for_each_entry(priv, &priv_list, node) {

		if (cpumask_test_cpu(cpu, priv->cpus))

			return priv;

	}



	return NULL;

}



static int set_target(struct cpufreq_policy *policy, unsigned int index)

{

	struct private_data *priv = policy->driver_data;
@@ -90,83 +108,24 @@ node_put: 
	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);



	ret = dev_pm_opp_of_find_icc_paths(cpu_dev, NULL);

	if (ret)

		return ret;



	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;

	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);

	priv = cpufreq_dt_find_data(policy->cpu);

	if (!priv) {

		pr_err("failed to find data for cpu%d\n", policy->cpu);

		return -ENODEV;

	}



	cpu_dev = priv->cpu_dev;

	cpumask_copy(policy->cpus, priv->cpus);



	cpu_clk = clk_get(cpu_dev, NULL);

	if (IS_ERR(cpu_clk)) {

		ret = PTR_ERR(cpu_clk);
@@ -174,45 +133,6 @@ static int cpufreq_init(struct cpufreq_policy *policy) 
		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;

		}

	}



	priv = kzalloc(sizeof(*priv), GFP_KERNEL);

	if (!priv) {

		ret = -ENOMEM;

		goto out_put_regulator;

	}



	priv->reg_name = name;

	priv->opp_table = opp_table;



	/*

	 * Initialize OPP tables for all policy->cpus. They will be shared by

	 * all CPUs which have marked their CPUs shared with OPP bindings.
@@ -232,31 +152,17 @@ static int cpufreq_init(struct cpufreq_policy *policy) 
	 */

	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;

		dev_err(cpu_dev, "OPP table can't be empty\n");

		ret = -ENODEV;

		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);

	}



	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_opp;

	}



	priv->cpu_dev = cpu_dev;

	policy->driver_data = priv;

	policy->clk = cpu_clk;

	policy->freq_table = freq_table;
@@ -288,11 +194,6 @@ out_free_cpufreq_table: 
out_free_opp:

	if (priv->have_static_opps)

		dev_pm_opp_of_cpumask_remove_table(policy->cpus);

	kfree(priv);

out_put_regulator:

	if (name)

		dev_pm_opp_put_regulators(opp_table);

out_put_clk:

	clk_put(cpu_clk);



	return ret;
@@ -320,12 +221,7 @@ static int cpufreq_exit(struct cpufreq_policy *policy) 
	dev_pm_opp_free_cpufreq_table(priv->cpu_dev, &policy->freq_table);

	if (priv->have_static_opps)

		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;

}
@@ -344,21 +240,119 @@ static struct cpufreq_driver dt_cpufreq_driver = { 
	.suspend = cpufreq_generic_suspend,

};



static int dt_cpufreq_probe(struct platform_device *pdev)

static int dt_cpufreq_early_init(struct device *dev, int cpu)

{

	struct cpufreq_dt_platform_data *data = dev_get_platdata(&pdev->dev);

	struct private_data *priv;

	struct device *cpu_dev;

	const char *reg_name;

	int ret;



	/* Check if this CPU is already covered by some other policy */

	if (cpufreq_dt_find_data(cpu))

		return 0;



	cpu_dev = get_cpu_device(cpu);

	if (!cpu_dev)

		return -EPROBE_DEFER;



	priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);

	if (!priv)

		return -ENOMEM;



	if (!alloc_cpumask_var(&priv->cpus, GFP_KERNEL))

		return -ENOMEM;



	priv->cpu_dev = cpu_dev;



	/* Try to get OPP table early to ensure resources are available */

	priv->opp_table = dev_pm_opp_get_opp_table(cpu_dev);

	if (IS_ERR(priv->opp_table)) {

		ret = PTR_ERR(priv->opp_table);

		if (ret != -EPROBE_DEFER)

			dev_err(cpu_dev, "failed to get OPP table: %d\n", ret);

		goto free_cpumask;

	}



	/*

	 * 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 ?

	 * OPP layer will be taking care of regulators now, but it needs to know

	 * the name of the regulator first.

	 */

	ret = resources_available();

	reg_name = find_supply_name(cpu_dev);

	if (reg_name) {

		priv->reg_opp_table = dev_pm_opp_set_regulators(cpu_dev,

								&reg_name, 1);

		if (IS_ERR(priv->reg_opp_table)) {

			ret = PTR_ERR(priv->reg_opp_table);

			if (ret != -EPROBE_DEFER)

				dev_err(cpu_dev, "failed to set regulators: %d\n",

					ret);

			goto put_table;

		}

	}



	/* Find OPP sharing information so we can fill pri->cpus here */

	/* Get OPP-sharing information from "operating-points-v2" bindings */

	ret = dev_pm_opp_of_get_sharing_cpus(cpu_dev, priv->cpus);

	if (ret) {

		if (ret != -ENOENT)

			goto put_reg;



		/*

		 * operating-points-v2 not supported, fallback to all CPUs share

		 * OPP for backward compatibility if the platform hasn't set

		 * sharing CPUs.

		 */

		if (dev_pm_opp_get_sharing_cpus(cpu_dev, priv->cpus)) {

			cpumask_setall(priv->cpus);



			/*

			 * OPP tables are initialized only for cpu, do it for

			 * others as well.

			 */

			ret = dev_pm_opp_set_sharing_cpus(cpu_dev, priv->cpus);

			if (ret)

				dev_err(cpu_dev, "%s: failed to mark OPPs as shared: %d\n",

					__func__, ret);

		}

	}



	list_add(&priv->node, &priv_list);

	return 0;



put_reg:

	if (priv->reg_opp_table)

		dev_pm_opp_put_regulators(priv->reg_opp_table);

put_table:

	dev_pm_opp_put_opp_table(priv->opp_table);

free_cpumask:

	free_cpumask_var(priv->cpus);

	return ret;

}



static void dt_cpufreq_release(void)

{

	struct private_data *priv, *tmp;



	list_for_each_entry_safe(priv, tmp, &priv_list, node) {

		if (priv->reg_opp_table)

			dev_pm_opp_put_regulators(priv->reg_opp_table);

		dev_pm_opp_put_opp_table(priv->opp_table);

		free_cpumask_var(priv->cpus);

		list_del(&priv->node);

	}

}



static int dt_cpufreq_probe(struct platform_device *pdev)

{

	struct cpufreq_dt_platform_data *data = dev_get_platdata(&pdev->dev);

	int ret, cpu;



	/* Request resources early so we can return in case of -EPROBE_DEFER */

	for_each_possible_cpu(cpu) {

		ret = dt_cpufreq_early_init(&pdev->dev, cpu);

		if (ret)

			goto err;

	}



	if (data) {

		if (data->have_governor_per_policy)
@@ -374,15 +368,21 @@ static int dt_cpufreq_probe(struct platform_device *pdev) 
	}



	ret = cpufreq_register_driver(&dt_cpufreq_driver);

	if (ret)

	if (ret) {

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

		goto err;

	}



	return 0;

err:

	dt_cpufreq_release();

	return ret;

}



static int dt_cpufreq_remove(struct platform_device *pdev)

{

	cpufreq_unregister_driver(&dt_cpufreq_driver);

	dt_cpufreq_release();

	return 0;

}

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