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linux/drivers/cpufreq/s3c2416-cpufreq.c
chenqiwu 8ead819f1b cpufreq: s3c: fix unbalances of cpufreq policy refcount
The cpufreq_reboot_notifier_evt() call cpufreq_cpu_get() to get the
cpufreq policy of cpu0, meanwhile, it also increments the kobject
reference count to mark it busy. However, a corresponding call of
cpufreq_cpu_put() is ignored to decrement the kobject reference count
back, which may lead to a potential stuck risk that the cpuhp thread
deadly waits for dropping of kobject refcount when cpufreq policy free.

With this patch, the cpuhp thread can be easily exercised by attempting
to force an unbind of the CPUfreq driver.

Signed-off-by: chenqiwu <chenqiwu@xiaomi.com>
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
2020-01-07 13:31:01 +05:30

493 lines
12 KiB
C

// SPDX-License-Identifier: GPL-2.0-only
/*
* S3C2416/2450 CPUfreq Support
*
* Copyright 2011 Heiko Stuebner <heiko@sntech.de>
*
* based on s3c64xx_cpufreq.c
*
* Copyright 2009 Wolfson Microelectronics plc
*/
#include <linux/kernel.h>
#include <linux/types.h>
#include <linux/init.h>
#include <linux/cpufreq.h>
#include <linux/clk.h>
#include <linux/err.h>
#include <linux/regulator/consumer.h>
#include <linux/reboot.h>
#include <linux/module.h>
static DEFINE_MUTEX(cpufreq_lock);
struct s3c2416_data {
struct clk *armdiv;
struct clk *armclk;
struct clk *hclk;
unsigned long regulator_latency;
#ifdef CONFIG_ARM_S3C2416_CPUFREQ_VCORESCALE
struct regulator *vddarm;
#endif
struct cpufreq_frequency_table *freq_table;
bool is_dvs;
bool disable_dvs;
};
static struct s3c2416_data s3c2416_cpufreq;
struct s3c2416_dvfs {
unsigned int vddarm_min;
unsigned int vddarm_max;
};
/* pseudo-frequency for dvs mode */
#define FREQ_DVS 132333
/* frequency to sleep and reboot in
* it's essential to leave dvs, as some boards do not reconfigure the
* regulator on reboot
*/
#define FREQ_SLEEP 133333
/* Sources for the ARMCLK */
#define SOURCE_HCLK 0
#define SOURCE_ARMDIV 1
#ifdef CONFIG_ARM_S3C2416_CPUFREQ_VCORESCALE
/* S3C2416 only supports changing the voltage in the dvs-mode.
* Voltages down to 1.0V seem to work, so we take what the regulator
* can get us.
*/
static struct s3c2416_dvfs s3c2416_dvfs_table[] = {
[SOURCE_HCLK] = { 950000, 1250000 },
[SOURCE_ARMDIV] = { 1250000, 1350000 },
};
#endif
static struct cpufreq_frequency_table s3c2416_freq_table[] = {
{ 0, SOURCE_HCLK, FREQ_DVS },
{ 0, SOURCE_ARMDIV, 133333 },
{ 0, SOURCE_ARMDIV, 266666 },
{ 0, SOURCE_ARMDIV, 400000 },
{ 0, 0, CPUFREQ_TABLE_END },
};
static struct cpufreq_frequency_table s3c2450_freq_table[] = {
{ 0, SOURCE_HCLK, FREQ_DVS },
{ 0, SOURCE_ARMDIV, 133500 },
{ 0, SOURCE_ARMDIV, 267000 },
{ 0, SOURCE_ARMDIV, 534000 },
{ 0, 0, CPUFREQ_TABLE_END },
};
static unsigned int s3c2416_cpufreq_get_speed(unsigned int cpu)
{
struct s3c2416_data *s3c_freq = &s3c2416_cpufreq;
if (cpu != 0)
return 0;
/* return our pseudo-frequency when in dvs mode */
if (s3c_freq->is_dvs)
return FREQ_DVS;
return clk_get_rate(s3c_freq->armclk) / 1000;
}
static int s3c2416_cpufreq_set_armdiv(struct s3c2416_data *s3c_freq,
unsigned int freq)
{
int ret;
if (clk_get_rate(s3c_freq->armdiv) / 1000 != freq) {
ret = clk_set_rate(s3c_freq->armdiv, freq * 1000);
if (ret < 0) {
pr_err("cpufreq: Failed to set armdiv rate %dkHz: %d\n",
freq, ret);
return ret;
}
}
return 0;
}
static int s3c2416_cpufreq_enter_dvs(struct s3c2416_data *s3c_freq, int idx)
{
#ifdef CONFIG_ARM_S3C2416_CPUFREQ_VCORESCALE
struct s3c2416_dvfs *dvfs;
#endif
int ret;
if (s3c_freq->is_dvs) {
pr_debug("cpufreq: already in dvs mode, nothing to do\n");
return 0;
}
pr_debug("cpufreq: switching armclk to hclk (%lukHz)\n",
clk_get_rate(s3c_freq->hclk) / 1000);
ret = clk_set_parent(s3c_freq->armclk, s3c_freq->hclk);
if (ret < 0) {
pr_err("cpufreq: Failed to switch armclk to hclk: %d\n", ret);
return ret;
}
#ifdef CONFIG_ARM_S3C2416_CPUFREQ_VCORESCALE
/* changing the core voltage is only allowed when in dvs mode */
if (s3c_freq->vddarm) {
dvfs = &s3c2416_dvfs_table[idx];
pr_debug("cpufreq: setting regulator to %d-%d\n",
dvfs->vddarm_min, dvfs->vddarm_max);
ret = regulator_set_voltage(s3c_freq->vddarm,
dvfs->vddarm_min,
dvfs->vddarm_max);
/* when lowering the voltage failed, there is nothing to do */
if (ret != 0)
pr_err("cpufreq: Failed to set VDDARM: %d\n", ret);
}
#endif
s3c_freq->is_dvs = 1;
return 0;
}
static int s3c2416_cpufreq_leave_dvs(struct s3c2416_data *s3c_freq, int idx)
{
#ifdef CONFIG_ARM_S3C2416_CPUFREQ_VCORESCALE
struct s3c2416_dvfs *dvfs;
#endif
int ret;
if (!s3c_freq->is_dvs) {
pr_debug("cpufreq: not in dvs mode, so can't leave\n");
return 0;
}
#ifdef CONFIG_ARM_S3C2416_CPUFREQ_VCORESCALE
if (s3c_freq->vddarm) {
dvfs = &s3c2416_dvfs_table[idx];
pr_debug("cpufreq: setting regulator to %d-%d\n",
dvfs->vddarm_min, dvfs->vddarm_max);
ret = regulator_set_voltage(s3c_freq->vddarm,
dvfs->vddarm_min,
dvfs->vddarm_max);
if (ret != 0) {
pr_err("cpufreq: Failed to set VDDARM: %d\n", ret);
return ret;
}
}
#endif
/* force armdiv to hclk frequency for transition from dvs*/
if (clk_get_rate(s3c_freq->armdiv) > clk_get_rate(s3c_freq->hclk)) {
pr_debug("cpufreq: force armdiv to hclk frequency (%lukHz)\n",
clk_get_rate(s3c_freq->hclk) / 1000);
ret = s3c2416_cpufreq_set_armdiv(s3c_freq,
clk_get_rate(s3c_freq->hclk) / 1000);
if (ret < 0) {
pr_err("cpufreq: Failed to set the armdiv to %lukHz: %d\n",
clk_get_rate(s3c_freq->hclk) / 1000, ret);
return ret;
}
}
pr_debug("cpufreq: switching armclk parent to armdiv (%lukHz)\n",
clk_get_rate(s3c_freq->armdiv) / 1000);
ret = clk_set_parent(s3c_freq->armclk, s3c_freq->armdiv);
if (ret < 0) {
pr_err("cpufreq: Failed to switch armclk clock parent to armdiv: %d\n",
ret);
return ret;
}
s3c_freq->is_dvs = 0;
return 0;
}
static int s3c2416_cpufreq_set_target(struct cpufreq_policy *policy,
unsigned int index)
{
struct s3c2416_data *s3c_freq = &s3c2416_cpufreq;
unsigned int new_freq;
int idx, ret, to_dvs = 0;
mutex_lock(&cpufreq_lock);
idx = s3c_freq->freq_table[index].driver_data;
if (idx == SOURCE_HCLK)
to_dvs = 1;
/* switching to dvs when it's not allowed */
if (to_dvs && s3c_freq->disable_dvs) {
pr_debug("cpufreq: entering dvs mode not allowed\n");
ret = -EINVAL;
goto out;
}
/* When leavin dvs mode, always switch the armdiv to the hclk rate
* The S3C2416 has stability issues when switching directly to
* higher frequencies.
*/
new_freq = (s3c_freq->is_dvs && !to_dvs)
? clk_get_rate(s3c_freq->hclk) / 1000
: s3c_freq->freq_table[index].frequency;
if (to_dvs) {
pr_debug("cpufreq: enter dvs\n");
ret = s3c2416_cpufreq_enter_dvs(s3c_freq, idx);
} else if (s3c_freq->is_dvs) {
pr_debug("cpufreq: leave dvs\n");
ret = s3c2416_cpufreq_leave_dvs(s3c_freq, idx);
} else {
pr_debug("cpufreq: change armdiv to %dkHz\n", new_freq);
ret = s3c2416_cpufreq_set_armdiv(s3c_freq, new_freq);
}
out:
mutex_unlock(&cpufreq_lock);
return ret;
}
#ifdef CONFIG_ARM_S3C2416_CPUFREQ_VCORESCALE
static void s3c2416_cpufreq_cfg_regulator(struct s3c2416_data *s3c_freq)
{
int count, v, i, found;
struct cpufreq_frequency_table *pos;
struct s3c2416_dvfs *dvfs;
count = regulator_count_voltages(s3c_freq->vddarm);
if (count < 0) {
pr_err("cpufreq: Unable to check supported voltages\n");
return;
}
if (!count)
goto out;
cpufreq_for_each_valid_entry(pos, s3c_freq->freq_table) {
dvfs = &s3c2416_dvfs_table[pos->driver_data];
found = 0;
/* Check only the min-voltage, more is always ok on S3C2416 */
for (i = 0; i < count; i++) {
v = regulator_list_voltage(s3c_freq->vddarm, i);
if (v >= dvfs->vddarm_min)
found = 1;
}
if (!found) {
pr_debug("cpufreq: %dkHz unsupported by regulator\n",
pos->frequency);
pos->frequency = CPUFREQ_ENTRY_INVALID;
}
}
out:
/* Guessed */
s3c_freq->regulator_latency = 1 * 1000 * 1000;
}
#endif
static int s3c2416_cpufreq_reboot_notifier_evt(struct notifier_block *this,
unsigned long event, void *ptr)
{
struct s3c2416_data *s3c_freq = &s3c2416_cpufreq;
int ret;
struct cpufreq_policy *policy;
mutex_lock(&cpufreq_lock);
/* disable further changes */
s3c_freq->disable_dvs = 1;
mutex_unlock(&cpufreq_lock);
/* some boards don't reconfigure the regulator on reboot, which
* could lead to undervolting the cpu when the clock is reset.
* Therefore we always leave the DVS mode on reboot.
*/
if (s3c_freq->is_dvs) {
pr_debug("cpufreq: leave dvs on reboot\n");
policy = cpufreq_cpu_get(0);
if (!policy) {
pr_debug("cpufreq: get no policy for cpu0\n");
return NOTIFY_BAD;
}
ret = cpufreq_driver_target(policy, FREQ_SLEEP, 0);
cpufreq_cpu_put(policy);
if (ret < 0)
return NOTIFY_BAD;
}
return NOTIFY_DONE;
}
static struct notifier_block s3c2416_cpufreq_reboot_notifier = {
.notifier_call = s3c2416_cpufreq_reboot_notifier_evt,
};
static int s3c2416_cpufreq_driver_init(struct cpufreq_policy *policy)
{
struct s3c2416_data *s3c_freq = &s3c2416_cpufreq;
struct cpufreq_frequency_table *pos;
struct clk *msysclk;
unsigned long rate;
int ret;
if (policy->cpu != 0)
return -EINVAL;
msysclk = clk_get(NULL, "msysclk");
if (IS_ERR(msysclk)) {
ret = PTR_ERR(msysclk);
pr_err("cpufreq: Unable to obtain msysclk: %d\n", ret);
return ret;
}
/*
* S3C2416 and S3C2450 share the same processor-ID and also provide no
* other means to distinguish them other than through the rate of
* msysclk. On S3C2416 msysclk runs at 800MHz and on S3C2450 at 533MHz.
*/
rate = clk_get_rate(msysclk);
if (rate == 800 * 1000 * 1000) {
pr_info("cpufreq: msysclk running at %lukHz, using S3C2416 frequency table\n",
rate / 1000);
s3c_freq->freq_table = s3c2416_freq_table;
policy->cpuinfo.max_freq = 400000;
} else if (rate / 1000 == 534000) {
pr_info("cpufreq: msysclk running at %lukHz, using S3C2450 frequency table\n",
rate / 1000);
s3c_freq->freq_table = s3c2450_freq_table;
policy->cpuinfo.max_freq = 534000;
}
/* not needed anymore */
clk_put(msysclk);
if (s3c_freq->freq_table == NULL) {
pr_err("cpufreq: No frequency information for this CPU, msysclk at %lukHz\n",
rate / 1000);
return -ENODEV;
}
s3c_freq->is_dvs = 0;
s3c_freq->armdiv = clk_get(NULL, "armdiv");
if (IS_ERR(s3c_freq->armdiv)) {
ret = PTR_ERR(s3c_freq->armdiv);
pr_err("cpufreq: Unable to obtain ARMDIV: %d\n", ret);
return ret;
}
s3c_freq->hclk = clk_get(NULL, "hclk");
if (IS_ERR(s3c_freq->hclk)) {
ret = PTR_ERR(s3c_freq->hclk);
pr_err("cpufreq: Unable to obtain HCLK: %d\n", ret);
goto err_hclk;
}
/* chech hclk rate, we only support the common 133MHz for now
* hclk could also run at 66MHz, but this not often used
*/
rate = clk_get_rate(s3c_freq->hclk);
if (rate < 133 * 1000 * 1000) {
pr_err("cpufreq: HCLK not at 133MHz\n");
ret = -EINVAL;
goto err_armclk;
}
s3c_freq->armclk = clk_get(NULL, "armclk");
if (IS_ERR(s3c_freq->armclk)) {
ret = PTR_ERR(s3c_freq->armclk);
pr_err("cpufreq: Unable to obtain ARMCLK: %d\n", ret);
goto err_armclk;
}
#ifdef CONFIG_ARM_S3C2416_CPUFREQ_VCORESCALE
s3c_freq->vddarm = regulator_get(NULL, "vddarm");
if (IS_ERR(s3c_freq->vddarm)) {
ret = PTR_ERR(s3c_freq->vddarm);
pr_err("cpufreq: Failed to obtain VDDARM: %d\n", ret);
goto err_vddarm;
}
s3c2416_cpufreq_cfg_regulator(s3c_freq);
#else
s3c_freq->regulator_latency = 0;
#endif
cpufreq_for_each_entry(pos, s3c_freq->freq_table) {
/* special handling for dvs mode */
if (pos->driver_data == 0) {
if (!s3c_freq->hclk) {
pr_debug("cpufreq: %dkHz unsupported as it would need unavailable dvs mode\n",
pos->frequency);
pos->frequency = CPUFREQ_ENTRY_INVALID;
} else {
continue;
}
}
/* Check for frequencies we can generate */
rate = clk_round_rate(s3c_freq->armdiv,
pos->frequency * 1000);
rate /= 1000;
if (rate != pos->frequency) {
pr_debug("cpufreq: %dkHz unsupported by clock (clk_round_rate return %lu)\n",
pos->frequency, rate);
pos->frequency = CPUFREQ_ENTRY_INVALID;
}
}
/* Datasheet says PLL stabalisation time must be at least 300us,
* so but add some fudge. (reference in LOCKCON0 register description)
*/
cpufreq_generic_init(policy, s3c_freq->freq_table,
(500 * 1000) + s3c_freq->regulator_latency);
register_reboot_notifier(&s3c2416_cpufreq_reboot_notifier);
return 0;
#ifdef CONFIG_ARM_S3C2416_CPUFREQ_VCORESCALE
err_vddarm:
clk_put(s3c_freq->armclk);
#endif
err_armclk:
clk_put(s3c_freq->hclk);
err_hclk:
clk_put(s3c_freq->armdiv);
return ret;
}
static struct cpufreq_driver s3c2416_cpufreq_driver = {
.flags = CPUFREQ_NEED_INITIAL_FREQ_CHECK,
.verify = cpufreq_generic_frequency_table_verify,
.target_index = s3c2416_cpufreq_set_target,
.get = s3c2416_cpufreq_get_speed,
.init = s3c2416_cpufreq_driver_init,
.name = "s3c2416",
.attr = cpufreq_generic_attr,
};
static int __init s3c2416_cpufreq_init(void)
{
return cpufreq_register_driver(&s3c2416_cpufreq_driver);
}
module_init(s3c2416_cpufreq_init);