diff options
Diffstat (limited to 'include/linux/pwm.h')
| -rw-r--r-- | include/linux/pwm.h | 429 |
1 files changed, 353 insertions, 76 deletions
diff --git a/include/linux/pwm.h b/include/linux/pwm.h index b78d27c42629..f1bbae014889 100644 --- a/include/linux/pwm.h +++ b/include/linux/pwm.h @@ -5,59 +5,9 @@ #include <linux/mutex.h> #include <linux/of.h> -struct pwm_device; +struct pwm_capture; 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; /** @@ -94,8 +44,21 @@ struct pwm_args { enum { PWMF_REQUESTED = 1 << 0, - PWMF_ENABLED = 1 << 1, - PWMF_EXPORTED = 1 << 2, + PWMF_EXPORTED = 1 << 1, +}; + +/* + * struct pwm_state - state of a PWM channel + * @period: PWM period (in nanoseconds) + * @duty_cycle: PWM duty cycle (in nanoseconds) + * @polarity: PWM polarity + * @enabled: PWM enabled status + */ +struct pwm_state { + unsigned int period; + unsigned int duty_cycle; + enum pwm_polarity polarity; + bool enabled; }; /** @@ -106,11 +69,8 @@ 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 * @args: PWM arguments + * @state: curent PWM channel state */ struct pwm_device { const char *label; @@ -119,50 +79,68 @@ struct pwm_device { unsigned int pwm; struct pwm_chip *chip; void *chip_data; - struct mutex lock; - - unsigned int period; - unsigned int duty_cycle; - enum pwm_polarity polarity; struct pwm_args args; + struct pwm_state state; }; +/** + * pwm_get_state() - retrieve the current PWM state + * @pwm: PWM device + * @state: state to fill with the current PWM state + */ +static inline void pwm_get_state(const struct pwm_device *pwm, + struct pwm_state *state) +{ + *state = pwm->state; +} + static inline bool pwm_is_enabled(const struct pwm_device *pwm) { - return test_bit(PWMF_ENABLED, &pwm->flags); + struct pwm_state state; + + pwm_get_state(pwm, &state); + + return state.enabled; } static inline void pwm_set_period(struct pwm_device *pwm, unsigned int period) { if (pwm) - pwm->period = period; + pwm->state.period = period; } static inline unsigned int pwm_get_period(const struct pwm_device *pwm) { - return pwm ? pwm->period : 0; + struct pwm_state state; + + pwm_get_state(pwm, &state); + + return state.period; } static inline void pwm_set_duty_cycle(struct pwm_device *pwm, unsigned int duty) { if (pwm) - pwm->duty_cycle = duty; + pwm->state.duty_cycle = duty; } static inline unsigned int pwm_get_duty_cycle(const struct pwm_device *pwm) { - return pwm ? pwm->duty_cycle : 0; -} + struct pwm_state state; -/* - * pwm_set_polarity - configure the polarity of a PWM signal - */ -int pwm_set_polarity(struct pwm_device *pwm, enum pwm_polarity polarity); + pwm_get_state(pwm, &state); + + return state.duty_cycle; +} static inline enum pwm_polarity pwm_get_polarity(const struct pwm_device *pwm) { - return pwm ? pwm->polarity : PWM_POLARITY_NORMAL; + struct pwm_state state; + + pwm_get_state(pwm, &state); + + return state.polarity; } static inline void pwm_get_args(const struct pwm_device *pwm, @@ -171,10 +149,92 @@ static inline void pwm_get_args(const struct pwm_device *pwm, *args = pwm->args; } -static inline void pwm_apply_args(struct pwm_device *pwm) +/** + * pwm_init_state() - prepare a new state to be applied with pwm_apply_state() + * @pwm: PWM device + * @state: state to fill with the prepared PWM state + * + * This functions prepares a state that can later be tweaked and applied + * to the PWM device with pwm_apply_state(). This is a convenient function + * that first retrieves the current PWM state and the replaces the period + * and polarity fields with the reference values defined in pwm->args. + * Once the function returns, you can adjust the ->enabled and ->duty_cycle + * fields according to your needs before calling pwm_apply_state(). + * + * ->duty_cycle is initially set to zero to avoid cases where the current + * ->duty_cycle value exceed the pwm_args->period one, which would trigger + * an error if the user calls pwm_apply_state() without adjusting ->duty_cycle + * first. + */ +static inline void pwm_init_state(const struct pwm_device *pwm, + struct pwm_state *state) { - pwm_set_period(pwm, pwm->args.period); - pwm_set_polarity(pwm, pwm->args.polarity); + struct pwm_args args; + + /* First get the current state. */ + pwm_get_state(pwm, state); + + /* Then fill it with the reference config */ + pwm_get_args(pwm, &args); + + state->period = args.period; + state->polarity = args.polarity; + state->duty_cycle = 0; +} + +/** + * pwm_get_relative_duty_cycle() - Get a relative duty cycle value + * @state: PWM state to extract the duty cycle from + * @scale: target scale of the relative duty cycle + * + * This functions converts the absolute duty cycle stored in @state (expressed + * in nanosecond) into a value relative to the period. + * + * For example if you want to get the duty_cycle expressed in percent, call: + * + * pwm_get_state(pwm, &state); + * duty = pwm_get_relative_duty_cycle(&state, 100); + */ +static inline unsigned int +pwm_get_relative_duty_cycle(const struct pwm_state *state, unsigned int scale) +{ + if (!state->period) + return 0; + + return DIV_ROUND_CLOSEST_ULL((u64)state->duty_cycle * scale, + state->period); +} + +/** + * pwm_set_relative_duty_cycle() - Set a relative duty cycle value + * @state: PWM state to fill + * @duty_cycle: relative duty cycle value + * @scale: scale in which @duty_cycle is expressed + * + * This functions converts a relative into an absolute duty cycle (expressed + * in nanoseconds), and puts the result in state->duty_cycle. + * + * For example if you want to configure a 50% duty cycle, call: + * + * pwm_init_state(pwm, &state); + * pwm_set_relative_duty_cycle(&state, 50, 100); + * pwm_apply_state(pwm, &state); + * + * This functions returns -EINVAL if @duty_cycle and/or @scale are + * inconsistent (@scale == 0 or @duty_cycle > @scale). + */ +static inline int +pwm_set_relative_duty_cycle(struct pwm_state *state, unsigned int duty_cycle, + unsigned int scale) +{ + if (!scale || duty_cycle > scale) + return -EINVAL; + + state->duty_cycle = DIV_ROUND_CLOSEST_ULL((u64)duty_cycle * + state->period, + scale); + + return 0; } /** @@ -183,8 +243,16 @@ static inline void pwm_apply_args(struct pwm_device *pwm) * @free: optional hook for freeing a PWM * @config: configure duty cycles and period length for this PWM * @set_polarity: configure the polarity of this PWM + * @capture: capture and report PWM signal * @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. * @dbg_show: optional routine to show contents in debugfs * @owner: helps prevent removal of modules exporting active PWMs */ @@ -195,8 +263,14 @@ struct pwm_ops { int duty_ns, int period_ns); int (*set_polarity)(struct pwm_chip *chip, struct pwm_device *pwm, enum pwm_polarity polarity); + int (*capture)(struct pwm_chip *chip, struct pwm_device *pwm, + struct pwm_capture *result, unsigned long timeout); 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 *state); #ifdef CONFIG_DEBUG_FS void (*dbg_show)(struct pwm_chip *chip, struct seq_file *s); #endif @@ -231,7 +305,130 @@ struct pwm_chip { bool can_sleep; }; +/** + * struct pwm_capture - PWM capture data + * @period: period of the PWM signal (in nanoseconds) + * @duty_cycle: duty cycle of the PWM signal (in nanoseconds) + */ +struct pwm_capture { + unsigned int period; + unsigned int duty_cycle; +}; + #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); +int pwm_adjust_config(struct pwm_device *pwm); + +/** + * 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 state; + + if (!pwm) + return -EINVAL; + + if (duty_ns < 0 || period_ns < 0) + return -EINVAL; + + pwm_get_state(pwm, &state); + if (state.duty_cycle == duty_ns && state.period == period_ns) + return 0; + + state.duty_cycle = duty_ns; + state.period = period_ns; + return pwm_apply_state(pwm, &state); +} + +/** + * 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 state; + + if (!pwm) + return -EINVAL; + + pwm_get_state(pwm, &state); + if (state.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 (state.enabled) + return -EBUSY; + + state.polarity = polarity; + return pwm_apply_state(pwm, &state); +} + +/** + * 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 state; + + if (!pwm) + return -EINVAL; + + pwm_get_state(pwm, &state); + if (state.enabled) + return 0; + + state.enabled = true; + return pwm_apply_state(pwm, &state); +} + +/** + * pwm_disable() - stop a PWM output toggling + * @pwm: PWM device + */ +static inline void pwm_disable(struct pwm_device *pwm) +{ + struct pwm_state state; + + if (!pwm) + return; + + pwm_get_state(pwm, &state); + if (!state.enabled) + return; + + state.enabled = false; + pwm_apply_state(pwm, &state); +} + +/* PWM provider APIs */ +int pwm_capture(struct pwm_device *pwm, struct pwm_capture *result, + unsigned long timeout); int pwm_set_chip_data(struct pwm_device *pwm, void *data); void *pwm_get_chip_data(struct pwm_device *pwm); @@ -257,6 +454,54 @@ 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_adjust_config(struct pwm_device *pwm) +{ + return -ENOTSUPP; +} + +static inline int pwm_config(struct pwm_device *pwm, int duty_ns, + int period_ns) +{ + return -EINVAL; +} + +static inline int pwm_capture(struct pwm_device *pwm, + struct pwm_capture *result, + unsigned long timeout) +{ + 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; @@ -328,6 +573,38 @@ static inline bool pwm_can_sleep(struct pwm_device *pwm) } #endif +static inline void pwm_apply_args(struct pwm_device *pwm) +{ + struct pwm_state state = { }; + + /* + * PWM users calling pwm_apply_args() expect to have a fresh config + * where the polarity and period are set according to pwm_args info. + * The problem is, polarity can only be changed when the PWM is + * disabled. + * + * PWM drivers supporting hardware readout may declare the PWM device + * as enabled, and prevent polarity setting, which changes from the + * existing behavior, where all PWM devices are declared as disabled + * at startup (even if they are actually enabled), thus authorizing + * polarity setting. + * + * To fulfill this requirement, we apply a new state which disables + * the PWM device and set the reference period and polarity config. + * + * Note that PWM users requiring a smooth handover between the + * bootloader and the kernel (like critical regulators controlled by + * PWM devices) will have to switch to the atomic API and avoid calling + * pwm_apply_args(). + */ + + state.enabled = false; + state.polarity = pwm->args.polarity; + state.period = pwm->args.period; + + pwm_apply_state(pwm, &state); +} + struct pwm_lookup { struct list_head list; const char *provider; |