pwm: Add core infrastructure to allow atomic updates
Add an ->apply() method to the pwm_ops struct to allow PWM drivers to implement atomic updates. This method is 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. pwm_adjust_config() is allowing smooth handover between the bootloader and the kernel. This function tries to adapt the current PWM state to the PWM arguments coming from a PWM lookup table or a DT definition without changing the duty_cycle/period proportion. Signed-off-by: Boris Brezillon <boris.brezillon@free-electrons.com> [thierry.reding@gmail.com: fix a couple of typos] Signed-off-by: Thierry Reding <thierry.reding@gmail.com>
This commit is contained in:
Boris Brezillon
committed by
Thierry Reding
Thierry Reding
parent
15fa8a43c1
commit
5ec803edcb
@@ -5,59 +5,7 @@
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#include <linux/mutex.h>
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#include <linux/of.h>
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struct pwm_device;
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struct seq_file;
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#if IS_ENABLED(CONFIG_PWM)
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/*
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* pwm_request - request a PWM device
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*/
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struct pwm_device *pwm_request(int pwm_id, const char *label);
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/*
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* pwm_free - free a PWM device
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*/
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void pwm_free(struct pwm_device *pwm);
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/*
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* pwm_config - change a PWM device configuration
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*/
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int pwm_config(struct pwm_device *pwm, int duty_ns, int period_ns);
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/*
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* pwm_enable - start a PWM output toggling
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*/
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int pwm_enable(struct pwm_device *pwm);
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/*
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* pwm_disable - stop a PWM output toggling
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*/
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void pwm_disable(struct pwm_device *pwm);
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#else
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static inline struct pwm_device *pwm_request(int pwm_id, const char *label)
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{
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return ERR_PTR(-ENODEV);
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}
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static inline void pwm_free(struct pwm_device *pwm)
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{
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}
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static inline int pwm_config(struct pwm_device *pwm, int duty_ns, int period_ns)
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{
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return -EINVAL;
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}
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static inline int pwm_enable(struct pwm_device *pwm)
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{
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return -EINVAL;
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}
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static inline void pwm_disable(struct pwm_device *pwm)
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{
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}
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#endif
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struct pwm_chip;
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/**
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@@ -184,11 +132,6 @@ static inline unsigned int pwm_get_duty_cycle(const struct pwm_device *pwm)
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return state.duty_cycle;
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}
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/*
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* pwm_set_polarity - configure the polarity of a PWM signal
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*/
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int pwm_set_polarity(struct pwm_device *pwm, enum pwm_polarity polarity);
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static inline enum pwm_polarity pwm_get_polarity(const struct pwm_device *pwm)
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{
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struct pwm_state state;
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@@ -204,34 +147,6 @@ static inline void pwm_get_args(const struct pwm_device *pwm,
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*args = pwm->args;
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}
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static inline void pwm_apply_args(struct pwm_device *pwm)
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{
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/*
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* PWM users calling pwm_apply_args() expect to have a fresh config
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* where the polarity and period are set according to pwm_args info.
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* The problem is, polarity can only be changed when the PWM is
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* disabled.
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*
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* PWM drivers supporting hardware readout may declare the PWM device
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* as enabled, and prevent polarity setting, which changes from the
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* existing behavior, where all PWM devices are declared as disabled
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* at startup (even if they are actually enabled), thus authorizing
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* polarity setting.
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*
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* Instead of setting ->enabled to false, we call pwm_disable()
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* before pwm_set_polarity() to ensure that everything is configured
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* as expected, and the PWM is really disabled when the user request
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* it.
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*
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* Note that PWM users requiring a smooth handover between the
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* bootloader and the kernel (like critical regulators controlled by
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* PWM devices) will have to switch to the atomic API and avoid calling
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* pwm_apply_args().
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*/
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pwm_disable(pwm);
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pwm_set_polarity(pwm, pwm->args.polarity);
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}
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/**
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* struct pwm_ops - PWM controller operations
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* @request: optional hook for requesting a PWM
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@@ -240,6 +155,10 @@ static inline void pwm_apply_args(struct pwm_device *pwm)
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* @set_polarity: configure the polarity of this PWM
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* @enable: enable PWM output toggling
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* @disable: disable PWM output toggling
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* @apply: atomically apply a new PWM config. The state argument
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* should be adjusted with the real hardware config (if the
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* approximate the period or duty_cycle value, state should
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* reflect it)
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* @get_state: get the current PWM state. This function is only
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* called once per PWM device when the PWM chip is
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* registered.
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@@ -255,6 +174,8 @@ struct pwm_ops {
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enum pwm_polarity polarity);
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int (*enable)(struct pwm_chip *chip, struct pwm_device *pwm);
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void (*disable)(struct pwm_chip *chip, struct pwm_device *pwm);
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int (*apply)(struct pwm_chip *chip, struct pwm_device *pwm,
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struct pwm_state *state);
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void (*get_state)(struct pwm_chip *chip, struct pwm_device *pwm,
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struct pwm_state *state);
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#ifdef CONFIG_DEBUG_FS
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@@ -292,6 +213,115 @@ struct pwm_chip {
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};
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#if IS_ENABLED(CONFIG_PWM)
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/* PWM user APIs */
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struct pwm_device *pwm_request(int pwm_id, const char *label);
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void pwm_free(struct pwm_device *pwm);
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int pwm_apply_state(struct pwm_device *pwm, struct pwm_state *state);
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int pwm_adjust_config(struct pwm_device *pwm);
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/**
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* pwm_config() - change a PWM device configuration
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* @pwm: PWM device
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* @duty_ns: "on" time (in nanoseconds)
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* @period_ns: duration (in nanoseconds) of one cycle
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*
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* Returns: 0 on success or a negative error code on failure.
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*/
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static inline int pwm_config(struct pwm_device *pwm, int duty_ns,
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int period_ns)
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{
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struct pwm_state state;
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if (!pwm)
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return -EINVAL;
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pwm_get_state(pwm, &state);
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if (state.duty_cycle == duty_ns && state.period == period_ns)
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return 0;
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state.duty_cycle = duty_ns;
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state.period = period_ns;
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return pwm_apply_state(pwm, &state);
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}
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/**
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* pwm_set_polarity() - configure the polarity of a PWM signal
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* @pwm: PWM device
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* @polarity: new polarity of the PWM signal
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*
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* Note that the polarity cannot be configured while the PWM device is
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* enabled.
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*
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* Returns: 0 on success or a negative error code on failure.
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*/
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static inline int pwm_set_polarity(struct pwm_device *pwm,
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enum pwm_polarity polarity)
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{
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struct pwm_state state;
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if (!pwm)
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return -EINVAL;
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pwm_get_state(pwm, &state);
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if (state.polarity == polarity)
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return 0;
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/*
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* Changing the polarity of a running PWM without adjusting the
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* dutycycle/period value is a bit risky (can introduce glitches).
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* Return -EBUSY in this case.
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* Note that this is allowed when using pwm_apply_state() because
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* the user specifies all the parameters.
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*/
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if (state.enabled)
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return -EBUSY;
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state.polarity = polarity;
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return pwm_apply_state(pwm, &state);
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}
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/**
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* pwm_enable() - start a PWM output toggling
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* @pwm: PWM device
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*
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* Returns: 0 on success or a negative error code on failure.
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*/
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static inline int pwm_enable(struct pwm_device *pwm)
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{
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struct pwm_state state;
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if (!pwm)
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return -EINVAL;
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pwm_get_state(pwm, &state);
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if (state.enabled)
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return 0;
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state.enabled = true;
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return pwm_apply_state(pwm, &state);
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}
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/**
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* pwm_disable() - stop a PWM output toggling
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* @pwm: PWM device
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*/
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static inline void pwm_disable(struct pwm_device *pwm)
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{
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struct pwm_state state;
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if (!pwm)
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return;
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pwm_get_state(pwm, &state);
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if (!state.enabled)
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return;
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state.enabled = false;
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pwm_apply_state(pwm, &state);
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}
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/* PWM provider APIs */
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int pwm_set_chip_data(struct pwm_device *pwm, void *data);
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void *pwm_get_chip_data(struct pwm_device *pwm);
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@@ -317,6 +347,47 @@ void devm_pwm_put(struct device *dev, struct pwm_device *pwm);
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bool pwm_can_sleep(struct pwm_device *pwm);
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#else
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static inline struct pwm_device *pwm_request(int pwm_id, const char *label)
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{
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return ERR_PTR(-ENODEV);
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}
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static inline void pwm_free(struct pwm_device *pwm)
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{
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}
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static inline int pwm_apply_state(struct pwm_device *pwm,
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const struct pwm_state *state)
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{
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return -ENOTSUPP;
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}
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static inline int pwm_adjust_config(struct pwm_device *pwm)
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{
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return -ENOTSUPP;
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}
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static inline int pwm_config(struct pwm_device *pwm, int duty_ns,
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int period_ns)
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{
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return -EINVAL;
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}
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static inline int pwm_set_polarity(struct pwm_device *pwm,
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enum pwm_polarity polarity)
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{
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return -ENOTSUPP;
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}
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static inline int pwm_enable(struct pwm_device *pwm)
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{
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return -EINVAL;
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}
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static inline void pwm_disable(struct pwm_device *pwm)
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{
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}
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static inline int pwm_set_chip_data(struct pwm_device *pwm, void *data)
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{
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return -EINVAL;
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@@ -388,6 +459,34 @@ static inline bool pwm_can_sleep(struct pwm_device *pwm)
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}
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#endif
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static inline void pwm_apply_args(struct pwm_device *pwm)
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{
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/*
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* PWM users calling pwm_apply_args() expect to have a fresh config
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* where the polarity and period are set according to pwm_args info.
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* The problem is, polarity can only be changed when the PWM is
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* disabled.
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*
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* PWM drivers supporting hardware readout may declare the PWM device
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* as enabled, and prevent polarity setting, which changes from the
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* existing behavior, where all PWM devices are declared as disabled
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* at startup (even if they are actually enabled), thus authorizing
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* polarity setting.
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*
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* Instead of setting ->enabled to false, we call pwm_disable()
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* before pwm_set_polarity() to ensure that everything is configured
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* as expected, and the PWM is really disabled when the user request
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* it.
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*
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* Note that PWM users requiring a smooth handover between the
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* bootloader and the kernel (like critical regulators controlled by
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* PWM devices) will have to switch to the atomic API and avoid calling
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* pwm_apply_args().
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*/
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pwm_disable(pwm);
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pwm_set_polarity(pwm, pwm->args.polarity);
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}
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struct pwm_lookup {
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struct list_head list;
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const char *provider;
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