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authorBoris BREZILLON <boris.brezillon@free-electrons.com>2016-03-30 22:03:27 +0200
committerThierry Reding <thierry.reding@gmail.com>2016-05-17 14:44:59 +0200
commit459a25afe97cb3d7f978b90c881f4d7aac8fb755 (patch)
tree233902a29b5d0f418de168ffe531149b997cbcf4
parent4ff66efd59102280a71d432c9f0e89cdaf66b849 (diff)
pwm: Get rid of pwm->lock
PWM devices are not protected against concurrent accesses. The lock in struct pwm_device might let PWM users think it is, but it's actually only protecting the enabled state. Removing this lock should be fine as long as all PWM users are aware that accesses to the PWM device have to be serialized, which seems to be the case for all of them except the sysfs interface. Patch the sysfs code by adding a lock to the pwm_export struct and making sure it's taken for all relevant accesses to the exported PWM device. Signed-off-by: Boris Brezillon <boris.brezillon@free-electrons.com> Signed-off-by: Thierry Reding <thierry.reding@gmail.com>
-rw-r--r--drivers/pwm/core.c19
-rw-r--r--drivers/pwm/sysfs.c24
-rw-r--r--include/linux/pwm.h2
3 files changed, 24 insertions, 21 deletions
diff --git a/drivers/pwm/core.c b/drivers/pwm/core.c
index 22cf395..cb762cf 100644
--- a/drivers/pwm/core.c
+++ b/drivers/pwm/core.c
@@ -269,7 +269,6 @@ int pwmchip_add_with_polarity(struct pwm_chip *chip,
pwm->pwm = chip->base + i;
pwm->hwpwm = i;
pwm->polarity = polarity;
- mutex_init(&pwm->lock);
radix_tree_insert(&pwm_tree, pwm->pwm, pwm);
}
@@ -474,22 +473,16 @@ int pwm_set_polarity(struct pwm_device *pwm, enum pwm_polarity polarity)
if (!pwm->chip->ops->set_polarity)
return -ENOSYS;
- mutex_lock(&pwm->lock);
-
- if (pwm_is_enabled(pwm)) {
- err = -EBUSY;
- goto unlock;
- }
+ if (pwm_is_enabled(pwm))
+ return -EBUSY;
err = pwm->chip->ops->set_polarity(pwm->chip, pwm, polarity);
if (err)
- goto unlock;
+ return err;
pwm->polarity = polarity;
-unlock:
- mutex_unlock(&pwm->lock);
- return err;
+ return 0;
}
EXPORT_SYMBOL_GPL(pwm_set_polarity);
@@ -506,16 +499,12 @@ int pwm_enable(struct pwm_device *pwm)
if (!pwm)
return -EINVAL;
- mutex_lock(&pwm->lock);
-
if (!test_and_set_bit(PWMF_ENABLED, &pwm->flags)) {
err = pwm->chip->ops->enable(pwm->chip, pwm);
if (err)
clear_bit(PWMF_ENABLED, &pwm->flags);
}
- mutex_unlock(&pwm->lock);
-
return err;
}
EXPORT_SYMBOL_GPL(pwm_enable);
diff --git a/drivers/pwm/sysfs.c b/drivers/pwm/sysfs.c
index 9c90886..187ca08 100644
--- a/drivers/pwm/sysfs.c
+++ b/drivers/pwm/sysfs.c
@@ -26,6 +26,7 @@
struct pwm_export {
struct device child;
struct pwm_device *pwm;
+ struct mutex lock;
};
static struct pwm_export *child_to_pwm_export(struct device *child)
@@ -53,7 +54,8 @@ static ssize_t period_store(struct device *child,
struct device_attribute *attr,
const char *buf, size_t size)
{
- struct pwm_device *pwm = child_to_pwm_device(child);
+ struct pwm_export *export = child_to_pwm_export(child);
+ struct pwm_device *pwm = export->pwm;
unsigned int val;
int ret;
@@ -61,7 +63,9 @@ static ssize_t period_store(struct device *child,
if (ret)
return ret;
+ mutex_lock(&export->lock);
ret = pwm_config(pwm, pwm_get_duty_cycle(pwm), val);
+ mutex_unlock(&export->lock);
return ret ? : size;
}
@@ -79,7 +83,8 @@ static ssize_t duty_cycle_store(struct device *child,
struct device_attribute *attr,
const char *buf, size_t size)
{
- struct pwm_device *pwm = child_to_pwm_device(child);
+ struct pwm_export *export = child_to_pwm_export(child);
+ struct pwm_device *pwm = export->pwm;
unsigned int val;
int ret;
@@ -87,7 +92,9 @@ static ssize_t duty_cycle_store(struct device *child,
if (ret)
return ret;
+ mutex_lock(&export->lock);
ret = pwm_config(pwm, val, pwm_get_period(pwm));
+ mutex_unlock(&export->lock);
return ret ? : size;
}
@@ -105,13 +112,16 @@ static ssize_t enable_store(struct device *child,
struct device_attribute *attr,
const char *buf, size_t size)
{
- struct pwm_device *pwm = child_to_pwm_device(child);
+ struct pwm_export *export = child_to_pwm_export(child);
+ struct pwm_device *pwm = export->pwm;
int val, ret;
ret = kstrtoint(buf, 0, &val);
if (ret)
return ret;
+ mutex_lock(&export->lock);
+
switch (val) {
case 0:
pwm_disable(pwm);
@@ -124,6 +134,8 @@ static ssize_t enable_store(struct device *child,
break;
}
+ mutex_unlock(&export->lock);
+
return ret ? : size;
}
@@ -151,7 +163,8 @@ static ssize_t polarity_store(struct device *child,
struct device_attribute *attr,
const char *buf, size_t size)
{
- struct pwm_device *pwm = child_to_pwm_device(child);
+ struct pwm_export *export = child_to_pwm_export(child);
+ struct pwm_device *pwm = export->pwm;
enum pwm_polarity polarity;
int ret;
@@ -162,7 +175,9 @@ static ssize_t polarity_store(struct device *child,
else
return -EINVAL;
+ mutex_lock(&export->lock);
ret = pwm_set_polarity(pwm, polarity);
+ mutex_unlock(&export->lock);
return ret ? : size;
}
@@ -203,6 +218,7 @@ static int pwm_export_child(struct device *parent, struct pwm_device *pwm)
}
export->pwm = pwm;
+ mutex_init(&export->lock);
export->child.release = pwm_export_release;
export->child.parent = parent;
diff --git a/include/linux/pwm.h b/include/linux/pwm.h
index b78d27c..d2e7430 100644
--- a/include/linux/pwm.h
+++ b/include/linux/pwm.h
@@ -106,7 +106,6 @@ enum {
* @pwm: global index of the PWM device
* @chip: PWM chip providing this PWM device
* @chip_data: chip-private data associated with the PWM device
- * @lock: used to serialize accesses to the PWM device where necessary
* @period: period of the PWM signal (in nanoseconds)
* @duty_cycle: duty cycle of the PWM signal (in nanoseconds)
* @polarity: polarity of the PWM signal
@@ -119,7 +118,6 @@ struct pwm_device {
unsigned int pwm;
struct pwm_chip *chip;
void *chip_data;
- struct mutex lock;
unsigned int period;
unsigned int duty_cycle;