diff options
| -rw-r--r-- | Documentation/driver-api/pwm.rst | 9 | ||||
| -rw-r--r-- | MAINTAINERS | 2 | ||||
| -rw-r--r-- | drivers/pwm/core.c | 62 | ||||
| -rw-r--r-- | include/linux/pwm.h | 25 |
4 files changed, 86 insertions, 12 deletions
diff --git a/Documentation/driver-api/pwm.rst b/Documentation/driver-api/pwm.rst index f1d8197c8c43..3c28ccc4b611 100644 --- a/Documentation/driver-api/pwm.rst +++ b/Documentation/driver-api/pwm.rst @@ -46,6 +46,15 @@ After being requested, a PWM has to be configured using:: This API controls both the PWM period/duty_cycle config and the enable/disable state. +PWM devices can be used from atomic context, if the PWM does not sleep. You +can check if this the case with:: + + bool pwm_might_sleep(struct pwm_device *pwm); + +If false, the PWM can also be configured from atomic context with:: + + int pwm_apply_atomic(struct pwm_device *pwm, struct pwm_state *state); + As a consumer, don't rely on the output's state for a disabled PWM. If it's easily possible, drivers are supposed to emit the inactive state, but some drivers cannot. If you rely on getting the inactive state, use .duty_cycle=0, diff --git a/MAINTAINERS b/MAINTAINERS index c58480595220..5342cf32d73f 100644 --- a/MAINTAINERS +++ b/MAINTAINERS @@ -17576,7 +17576,7 @@ F: drivers/video/backlight/pwm_bl.c F: include/dt-bindings/pwm/ F: include/linux/pwm.h F: include/linux/pwm_backlight.h -K: pwm_(config|apply_might_sleep|ops) +K: pwm_(config|apply_might_sleep|apply_atomic|ops) PXA GPIO DRIVER M: Robert Jarzmik <robert.jarzmik@free.fr> diff --git a/drivers/pwm/core.c b/drivers/pwm/core.c index c6228843a1a7..f1ded8ce5ea4 100644 --- a/drivers/pwm/core.c +++ b/drivers/pwm/core.c @@ -433,24 +433,15 @@ static void pwm_apply_debug(struct pwm_device *pwm, } /** - * pwm_apply_might_sleep() - atomically apply a new state to a PWM device + * __pwm_apply() - atomically apply a new state to a PWM device * @pwm: PWM device * @state: new state to apply */ -int pwm_apply_might_sleep(struct pwm_device *pwm, const struct pwm_state *state) +static int __pwm_apply(struct pwm_device *pwm, const struct pwm_state *state) { struct pwm_chip *chip; int err; - /* - * Some lowlevel driver's implementations of .apply() make use of - * mutexes, also with some drivers only returning when the new - * configuration is active calling pwm_apply_might_sleep() from atomic context - * is a bad idea. So make it explicit that calling this function might - * sleep. - */ - might_sleep(); - if (!pwm || !state || !state->period || state->duty_cycle > state->period) return -EINVAL; @@ -479,9 +470,58 @@ int pwm_apply_might_sleep(struct pwm_device *pwm, const struct pwm_state *state) return 0; } + +/** + * pwm_apply_might_sleep() - atomically apply a new state to a PWM device + * Cannot be used in atomic context. + * @pwm: PWM device + * @state: new state to apply + */ +int pwm_apply_might_sleep(struct pwm_device *pwm, const struct pwm_state *state) +{ + int err; + + /* + * Some lowlevel driver's implementations of .apply() make use of + * mutexes, also with some drivers only returning when the new + * configuration is active calling pwm_apply_might_sleep() from atomic context + * is a bad idea. So make it explicit that calling this function might + * sleep. + */ + might_sleep(); + + if (IS_ENABLED(CONFIG_PWM_DEBUG) && pwm->chip->atomic) { + /* + * Catch any drivers that have been marked as atomic but + * that will sleep anyway. + */ + non_block_start(); + err = __pwm_apply(pwm, state); + non_block_end(); + } else { + err = __pwm_apply(pwm, state); + } + + return err; +} EXPORT_SYMBOL_GPL(pwm_apply_might_sleep); /** + * pwm_apply_atomic() - apply a new state to a PWM device from atomic context + * Not all PWM devices support this function, check with pwm_might_sleep(). + * @pwm: PWM device + * @state: new state to apply + */ +int pwm_apply_atomic(struct pwm_device *pwm, const struct pwm_state *state) +{ + WARN_ONCE(!pwm->chip->atomic, + "sleeping PWM driver used in atomic context\n"); + + return __pwm_apply(pwm, state); +} +EXPORT_SYMBOL_GPL(pwm_apply_atomic); + +/** * pwm_capture() - capture and report a PWM signal * @pwm: PWM device * @result: structure to fill with capture result diff --git a/include/linux/pwm.h b/include/linux/pwm.h index c9cb87b59ac8..495af3627939 100644 --- a/include/linux/pwm.h +++ b/include/linux/pwm.h @@ -285,6 +285,7 @@ struct pwm_ops { * @npwm: number of PWMs controlled by this chip * @of_xlate: request a PWM device given a device tree PWM specifier * @of_pwm_n_cells: number of cells expected in the device tree PWM specifier + * @atomic: can the driver's ->apply() be called in atomic context * @pwms: array of PWM devices allocated by the framework */ struct pwm_chip { @@ -297,6 +298,7 @@ struct pwm_chip { struct pwm_device * (*of_xlate)(struct pwm_chip *chip, const struct of_phandle_args *args); unsigned int of_pwm_n_cells; + bool atomic; /* only used internally by the PWM framework */ struct pwm_device *pwms; @@ -305,6 +307,7 @@ struct pwm_chip { #if IS_ENABLED(CONFIG_PWM) /* PWM user APIs */ int pwm_apply_might_sleep(struct pwm_device *pwm, const struct pwm_state *state); +int pwm_apply_atomic(struct pwm_device *pwm, const struct pwm_state *state); int pwm_adjust_config(struct pwm_device *pwm); /** @@ -375,6 +378,17 @@ static inline void pwm_disable(struct pwm_device *pwm) pwm_apply_might_sleep(pwm, &state); } +/** + * pwm_might_sleep() - is pwm_apply_atomic() supported? + * @pwm: PWM device + * + * Returns: false if pwm_apply_atomic() can be called from atomic context. + */ +static inline bool pwm_might_sleep(struct pwm_device *pwm) +{ + return !pwm->chip->atomic; +} + /* PWM provider APIs */ int pwm_capture(struct pwm_device *pwm, struct pwm_capture *result, unsigned long timeout); @@ -403,6 +417,11 @@ struct pwm_device *devm_fwnode_pwm_get(struct device *dev, struct fwnode_handle *fwnode, const char *con_id); #else +static inline bool pwm_might_sleep(struct pwm_device *pwm) +{ + return true; +} + static inline int pwm_apply_might_sleep(struct pwm_device *pwm, const struct pwm_state *state) { @@ -410,6 +429,12 @@ static inline int pwm_apply_might_sleep(struct pwm_device *pwm, return -EOPNOTSUPP; } +static inline int pwm_apply_atomic(struct pwm_device *pwm, + const struct pwm_state *state) +{ + return -EOPNOTSUPP; +} + static inline int pwm_adjust_config(struct pwm_device *pwm) { return -EOPNOTSUPP; |