From 3f4e6dcb3d2d9eefb04e6356a03696e30887ab65 Mon Sep 17 00:00:00 2001 From: Boris BREZILLON Date: Wed, 30 Mar 2016 22:03:27 +0200 Subject: [PATCH] UPSTREAM: 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 Signed-off-by: Thierry Reding (cherry picked from commit 459a25afe97cb3d7f978b90c881f4d7aac8fb755) Change-Id: I30d97ebaf1db8b80c353da5ebebd0fc5d5c57bb0 Signed-off-by: David Wu --- drivers/pwm/core.c | 19 ++++--------------- drivers/pwm/sysfs.c | 24 ++++++++++++++++++++---- include/linux/pwm.h | 2 -- 3 files changed, 24 insertions(+), 21 deletions(-) diff --git a/drivers/pwm/core.c b/drivers/pwm/core.c index 7bb31429886e..01de925be0f3 100644 --- a/drivers/pwm/core.c +++ b/drivers/pwm/core.c @@ -270,7 +270,6 @@ 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); } @@ -477,22 +476,16 @@ 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); @@ -509,16 +502,12 @@ 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 375008e2be20..a9bf1dcdc049 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 f4120e495f69..661ece188a51 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; -- 2.34.1