Add an ->apply() method to the pwm_ops struct to allow PWM drivers to implement atomic update. This method will be preferred over the ->enable(), ->disable() and ->config() methods if available.
Add the pwm_apply_state() function to the PWM user API.
Note that the pwm_apply_state() does not guarantee the atomicity of the update operation, it all depends on the availability and implementation of the ->apply() method.
pwm_enable/disable/set_polarity/config() are now implemented as wrappers around the pwm_apply_state() function.
Signed-off-by: Boris Brezillon boris.brezillon@free-electrons.com --- drivers/pwm/core.c | 155 ++++++++++++++++++--------------------- include/linux/pwm.h | 207 +++++++++++++++++++++++++++++++++++++--------------- 2 files changed, 220 insertions(+), 142 deletions(-)
diff --git a/drivers/pwm/core.c b/drivers/pwm/core.c index a909c64..62e6b3c 100644 --- a/drivers/pwm/core.c +++ b/drivers/pwm/core.c @@ -226,6 +226,19 @@ void *pwm_get_chip_data(struct pwm_device *pwm) } EXPORT_SYMBOL_GPL(pwm_get_chip_data);
+static bool pwm_ops_check(const struct pwm_ops *ops) +{ + /* driver supports legacy, non-atomic operation */ + if (ops->config && ops->enable && ops->disable) + return true; + + /* driver supports atomic operation */ + if (ops->apply) + return true; + + return false; +} + /** * pwmchip_add_with_polarity() - register a new PWM chip * @chip: the PWM chip to add @@ -244,8 +257,10 @@ int pwmchip_add_with_polarity(struct pwm_chip *chip, unsigned int i; int ret;
- if (!chip || !chip->dev || !chip->ops || !chip->ops->config || - !chip->ops->enable || !chip->ops->disable || !chip->npwm) + if (!chip || !chip->dev || !chip->ops || !chip->npwm) + return -EINVAL; + + if (!pwm_ops_check(chip->ops)) return -EINVAL;
mutex_lock(&pwm_lock); @@ -431,102 +446,72 @@ void pwm_free(struct pwm_device *pwm) EXPORT_SYMBOL_GPL(pwm_free);
/** - * pwm_config() - change a PWM device configuration + * pwm_apply_state() - atomically apply a new state to a PWM device * @pwm: PWM device - * @duty_ns: "on" time (in nanoseconds) - * @period_ns: duration (in nanoseconds) of one cycle - * - * Returns: 0 on success or a negative error code on failure. + * @state: new state to apply. This can be adjusted by the PWM driver + * if the requested config is not achievable, for example, + * ->duty_cycle and ->period might be approximated. */ -int pwm_config(struct pwm_device *pwm, int duty_ns, int period_ns) +int pwm_apply_state(struct pwm_device *pwm, struct pwm_state *state) { int err;
- if (!pwm || duty_ns < 0 || period_ns <= 0 || duty_ns > period_ns) - return -EINVAL; - - err = pwm->chip->ops->config(pwm->chip, pwm, duty_ns, period_ns); - if (err) - return err; - - pwm->state.duty_cycle = duty_ns; - pwm->state.period = period_ns; - - return 0; -} -EXPORT_SYMBOL_GPL(pwm_config); - -/** - * pwm_set_polarity() - configure the polarity of a PWM signal - * @pwm: PWM device - * @polarity: new polarity of the PWM signal - * - * Note that the polarity cannot be configured while the PWM device is - * enabled. - * - * Returns: 0 on success or a negative error code on failure. - */ -int pwm_set_polarity(struct pwm_device *pwm, enum pwm_polarity polarity) -{ - int err; - - if (!pwm || !pwm->chip->ops) - return -EINVAL; - - if (!pwm->chip->ops->set_polarity) - return -ENOSYS; - - if (pwm_is_enabled(pwm)) - return -EBUSY; - - err = pwm->chip->ops->set_polarity(pwm->chip, pwm, polarity); - if (err) - return err; - - pwm->state.polarity = polarity; - - return 0; -} -EXPORT_SYMBOL_GPL(pwm_set_polarity); - -/** - * pwm_enable() - start a PWM output toggling - * @pwm: PWM device - * - * Returns: 0 on success or a negative error code on failure. - */ -int pwm_enable(struct pwm_device *pwm) -{ - int err = 0; - if (!pwm) return -EINVAL;
- if (!pwm_is_enabled(pwm)) { - err = pwm->chip->ops->enable(pwm->chip, pwm); - if (!err) - pwm->state.enabled = true; - } + if (!memcmp(state, &pwm->state, sizeof(*state))) + return 0;
- return err; -} -EXPORT_SYMBOL_GPL(pwm_enable); + if (pwm->chip->ops->apply) { + err = pwm->chip->ops->apply(pwm->chip, pwm, state); + if (err) + return err; + } else { + /* + * FIXME: restore the initial state in case of error. + */ + if (state->polarity != pwm->state.polarity) { + if (!pwm->chip->ops->set_polarity) + return -ENOTSUPP; + + /* + * Changing the polarity of a running PWM is + * only allowed when the PWM driver implements + * ->apply(). + */ + if (pwm->state.enabled) + return -EBUSY; + + err = pwm->chip->ops->set_polarity(pwm->chip, pwm, + state->polarity); + if (err) + return err; + }
-/** - * pwm_disable() - stop a PWM output toggling - * @pwm: PWM device - */ -void pwm_disable(struct pwm_device *pwm) -{ - if (!pwm) - return; + if (state->period != pwm->state.period || + state->duty_cycle != pwm->state.duty_cycle) { + err = pwm->chip->ops->config(pwm->chip, pwm, + state->period, + state->duty_cycle); + if (err) + return err; + }
- if (pwm_is_enabled(pwm)) { - pwm->chip->ops->disable(pwm->chip, pwm); - pwm->state.enabled = false; + if (state->enabled != pwm->state.enabled) { + if (state->enabled) { + err = pwm->chip->ops->enable(pwm->chip, pwm); + if (err) + return err; + } else { + pwm->chip->ops->disable(pwm->chip, pwm); + } + } } + + pwm->state = *state; + return 0; } -EXPORT_SYMBOL_GPL(pwm_disable); +EXPORT_SYMBOL_GPL(pwm_apply_state);
static struct pwm_chip *of_node_to_pwmchip(struct device_node *np) { diff --git a/include/linux/pwm.h b/include/linux/pwm.h index ceedcf8..4aad4eb 100644 --- a/include/linux/pwm.h +++ b/include/linux/pwm.h @@ -5,59 +5,7 @@ #include <linux/mutex.h> #include <linux/of.h>
-struct pwm_device; struct seq_file; - -#if IS_ENABLED(CONFIG_PWM) -/* - * pwm_request - request a PWM device - */ -struct pwm_device *pwm_request(int pwm_id, const char *label); - -/* - * pwm_free - free a PWM device - */ -void pwm_free(struct pwm_device *pwm); - -/* - * pwm_config - change a PWM device configuration - */ -int pwm_config(struct pwm_device *pwm, int duty_ns, int period_ns); - -/* - * pwm_enable - start a PWM output toggling - */ -int pwm_enable(struct pwm_device *pwm); - -/* - * pwm_disable - stop a PWM output toggling - */ -void pwm_disable(struct pwm_device *pwm); -#else -static inline struct pwm_device *pwm_request(int pwm_id, const char *label) -{ - return ERR_PTR(-ENODEV); -} - -static inline void pwm_free(struct pwm_device *pwm) -{ -} - -static inline int pwm_config(struct pwm_device *pwm, int duty_ns, int period_ns) -{ - return -EINVAL; -} - -static inline int pwm_enable(struct pwm_device *pwm) -{ - return -EINVAL; -} - -static inline void pwm_disable(struct pwm_device *pwm) -{ -} -#endif - struct pwm_chip;
/** @@ -183,11 +131,6 @@ static inline unsigned int pwm_get_duty_cycle(const struct pwm_device *pwm) return pstate.duty_cycle; }
-/* - * pwm_set_polarity - configure the polarity of a PWM signal - */ -int pwm_set_polarity(struct pwm_device *pwm, enum pwm_polarity polarity); - static inline enum pwm_polarity pwm_get_polarity(const struct pwm_device *pwm) { struct pwm_state pstate; @@ -211,6 +154,10 @@ static inline void pwm_get_args(const struct pwm_device *pwm, * @set_polarity: configure the polarity of this PWM * @enable: enable PWM output toggling * @disable: disable PWM output toggling + * @apply: atomically apply a new PWM config. The state argument + * should be adjusted with the real hardware config (if the + * approximate the period or duty_cycle value, state should + * reflect it) * @get_state: get the current PWM state. This function is only * called once per PWM device when the PWM chip is * registered. @@ -226,6 +173,8 @@ struct pwm_ops { enum pwm_polarity polarity); int (*enable)(struct pwm_chip *chip, struct pwm_device *pwm); void (*disable)(struct pwm_chip *chip, struct pwm_device *pwm); + int (*apply)(struct pwm_chip *chip, struct pwm_device *pwm, + struct pwm_state *state); void (*get_state)(struct pwm_chip *chip, struct pwm_device *pwm, struct pwm_state *pstate); #ifdef CONFIG_DEBUG_FS @@ -263,6 +212,114 @@ struct pwm_chip { };
#if IS_ENABLED(CONFIG_PWM) +/* PWM user APIs */ +struct pwm_device *pwm_request(int pwm_id, const char *label); +void pwm_free(struct pwm_device *pwm); +int pwm_apply_state(struct pwm_device *pwm, struct pwm_state *state); + +/** + * pwm_config() - change a PWM device configuration + * @pwm: PWM device + * @duty_ns: "on" time (in nanoseconds) + * @period_ns: duration (in nanoseconds) of one cycle + * + * Returns: 0 on success or a negative error code on failure. + */ +static inline int pwm_config(struct pwm_device *pwm, int duty_ns, + int period_ns) +{ + struct pwm_state pstate; + + if (!pwm) + return -EINVAL; + + pwm_get_state(pwm, &pstate); + if (pstate.duty_cycle == duty_ns && pstate.period == period_ns) + return 0; + + pstate.duty_cycle = duty_ns; + pstate.period = period_ns; + return pwm_apply_state(pwm, &pstate); +} + +/** + * pwm_set_polarity() - configure the polarity of a PWM signal + * @pwm: PWM device + * @polarity: new polarity of the PWM signal + * + * Note that the polarity cannot be configured while the PWM device is + * enabled. + * + * Returns: 0 on success or a negative error code on failure. + */ +static inline int pwm_set_polarity(struct pwm_device *pwm, + enum pwm_polarity polarity) +{ + struct pwm_state pstate; + + if (!pwm) + return -EINVAL; + + pwm_get_state(pwm, &pstate); + if (pstate.polarity == polarity) + return 0; + + /* + * Changing the polarity of a running PWM without adjusting the + * dutycycle/period value is a bit risky (can introduce glitches). + * Return -EBUSY in this case. + * Note that this is allowed when using pwm_apply_state() because + * the user specifies all the parameters. + */ + if (pstate.enabled) + return -EBUSY; + + pstate.polarity = polarity; + return pwm_apply_state(pwm, &pstate); +} + +/** + * pwm_enable() - start a PWM output toggling + * @pwm: PWM device + * + * Returns: 0 on success or a negative error code on failure. + */ +static inline int pwm_enable(struct pwm_device *pwm) +{ + struct pwm_state pstate; + + if (!pwm) + return -EINVAL; + + pwm_get_state(pwm, &pstate); + if (pstate.enabled) + return 0; + + pstate.enabled = true; + return pwm_apply_state(pwm, &pstate); +} + +/** + * pwm_disable() - stop a PWM output toggling + * @pwm: PWM device + */ +static inline void pwm_disable(struct pwm_device *pwm) +{ + struct pwm_state pstate; + + if (!pwm) + return; + + pwm_get_state(pwm, &pstate); + if (!pstate.enabled) + return; + + pstate.enabled = false; + pwm_apply_state(pwm, &pstate); +} + + +/* PWM provider APIs */ int pwm_set_chip_data(struct pwm_device *pwm, void *data); void *pwm_get_chip_data(struct pwm_device *pwm);
@@ -288,6 +345,42 @@ void devm_pwm_put(struct device *dev, struct pwm_device *pwm);
bool pwm_can_sleep(struct pwm_device *pwm); #else +static inline struct pwm_device *pwm_request(int pwm_id, const char *label) +{ + return ERR_PTR(-ENODEV); +} + +static inline void pwm_free(struct pwm_device *pwm) +{ +} + +static inline int pwm_apply_state(struct pwm_device *pwm, + const struct pwm_state *state) +{ + return -ENOTSUPP; +} + +static inline int pwm_config(struct pwm_device *pwm, int duty_ns, + int period_ns) +{ + return -EINVAL; +} + +static inline int pwm_set_polarity(struct pwm_device *pwm, + enum pwm_polarity polarity) +{ + return -ENOTSUPP; +} + +static inline int pwm_enable(struct pwm_device *pwm) +{ + return -EINVAL; +} + +static inline void pwm_disable(struct pwm_device *pwm) +{ +} + static inline int pwm_set_chip_data(struct pwm_device *pwm, void *data) { return -EINVAL;