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 <boris.brezillon@free-electrons.com>
Signed-off-by: Thierry Reding <thierry.reding@gmail.com>
(cherry picked from commit 459a25afe97cb3d7f978b90c881f4d7aac8fb755)

Change-Id: I30d97ebaf1db8b80c353da5ebebd0fc5d5c57bb0
Signed-off-by: David Wu <david.wu@rock-chips.com>

diff --git a/drivers/pwm/core.c b/drivers/pwm/core.c
index 7bb31429886eb7baa1bdd14a652cf014c4443c33..01de925be0f3db6b8307d6d649cf5292c180531a 100644 (file)
--- 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 375008e2be20a5ae057f72fef7898988314cbdc4..a9bf1dcdc0492a9f4a57f4c9fa14cb1c104e5431 100644 (file)
--- 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 f4120e495f697b0d5e882b8252ea2854a825da43..661ece188a5161d1ef2fd8a87b9c585adfd68a11 100644 (file)
--- 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;