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cpufreq: dt: Refactor initialization to handle probe deferral properly
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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: Stephan Gerhold <stephan@gerhold.net>
[ Viresh: Use list_head structure for maintaining the list and minor
	  changes ]
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
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@stephan-gh @vireshk
stephan-gh authored and vireshk committed Sep 16, 2020
1 parent 90d46d7 commit dc279ac
Showing 1 changed file with 143 additions and 143 deletions.
286 changes: 143 additions & 143 deletions drivers/cpufreq/cpufreq-dt.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -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>
Expand All @@ -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;
Expand Down Expand Up @@ -90,129 +108,31 @@ static const char *find_supply_name(struct device *dev)
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);
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;
}
}

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.
Expand All @@ -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;
Expand Down Expand Up @@ -288,11 +194,6 @@ static int cpufreq_init(struct cpufreq_policy *policy)
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;
Expand Down Expand Up @@ -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;
}

Expand All @@ -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();
if (ret)
return ret;
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)
Expand All @@ -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;
}

Expand Down

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