Commit 5ec803ed authored by Boris Brezillon's avatar Boris Brezillon Committed by Thierry Reding
Browse files

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: default avatarBoris Brezillon <boris.brezillon@free-electrons.com>
[thierry.reding@gmail.com: fix a couple of typos]
Signed-off-by: default avatarThierry Reding <thierry.reding@gmail.com>
parent 15fa8a43

drivers/pwm/core.c

+119 −68
Original line number Diff line number Diff line
@@ -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 +446,138 @@ 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)

	if (!pwm)

		return -EINVAL;



	err = pwm->chip->ops->config(pwm->chip, pwm, duty_ns, period_ns);

	if (!memcmp(state, &pwm->state, sizeof(*state)))

		return 0;



	if (pwm->chip->ops->apply) {

		err = pwm->chip->ops->apply(pwm->chip, pwm, state);

		if (err)

			return err;



	pwm->state.duty_cycle = duty_ns;

	pwm->state.period = period_ns;

		pwm->state = *state;

	} else {

		/*

		 * FIXME: restore the initial state in case of error.

		 */

		if (state->polarity != pwm->state.polarity) {

			if (!pwm->chip->ops->set_polarity)

				return -ENOTSUPP;



	return 0;

			/*

			 * Changing the polarity of a running PWM is

			 * only allowed when the PWM driver implements

			 * ->apply().

			 */

			if (pwm->state.enabled) {

				pwm->chip->ops->disable(pwm->chip, pwm);

				pwm->state.enabled = false;

			}

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;

			err = pwm->chip->ops->set_polarity(pwm->chip, pwm,

							   state->polarity);

			if (err)

				return err;



	if (!pwm || !pwm->chip->ops)

		return -EINVAL;

			pwm->state.polarity = state->polarity;

		}



	if (!pwm->chip->ops->set_polarity)

		return -ENOSYS;

		if (state->period != pwm->state.period ||

		    state->duty_cycle != pwm->state.duty_cycle) {

			err = pwm->chip->ops->config(pwm->chip, pwm,

						     state->duty_cycle,

						     state->period);

			if (err)

				return err;



	if (pwm_is_enabled(pwm))

		return -EBUSY;

			pwm->state.duty_cycle = state->duty_cycle;

			pwm->state.period = state->period;

		}



	err = pwm->chip->ops->set_polarity(pwm->chip, pwm, polarity);

		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.polarity = polarity;

			pwm->state.enabled = state->enabled;

		}

	}



	return 0;

}

EXPORT_SYMBOL_GPL(pwm_set_polarity);

EXPORT_SYMBOL_GPL(pwm_apply_state);



/**

 * pwm_enable() - start a PWM output toggling

 * pwm_adjust_config() - adjust the current PWM config to the PWM arguments

 * @pwm: PWM device

 *

 * Returns: 0 on success or a negative error code on failure.

 * This function will adjust the PWM config to the PWM arguments provided

 * by the DT or PWM lookup table. This is particularly useful to adapt

 * the bootloader config to the Linux one.

 */

int pwm_enable(struct pwm_device *pwm)

int pwm_adjust_config(struct pwm_device *pwm)

{

	int err = 0;

	struct pwm_state state;

	struct pwm_args pargs;



	if (!pwm)

		return -EINVAL;

	pwm_get_args(pwm, &pargs);

	pwm_get_state(pwm, &state);



	if (!pwm_is_enabled(pwm)) {

		err = pwm->chip->ops->enable(pwm->chip, pwm);

		if (!err)

			pwm->state.enabled = true;

	}

	/*

	 * If the current period is zero it means that either the PWM driver

	 * does not support initial state retrieval or the PWM has not yet

	 * been configured.

	 *

	 * In either case, we setup the new period and polarity, and assign a

	 * duty cycle of 0.

	 */

	if (!state.period) {

		state.duty_cycle = 0;

		state.period = pargs.period;

		state.polarity = pargs.polarity;



	return err;

		return pwm_apply_state(pwm, &state);

	}

EXPORT_SYMBOL_GPL(pwm_enable);



/**

 * pwm_disable() - stop a PWM output toggling

 * @pwm: PWM device

	/*

	 * Adjust the PWM duty cycle/period based on the period value provided

	 * in PWM args.

	 */

void pwm_disable(struct pwm_device *pwm)

{

	if (!pwm)

		return;

	if (pargs.period != state.period) {

		u64 dutycycle = (u64)state.duty_cycle * pargs.period;



	if (pwm_is_enabled(pwm)) {

		pwm->chip->ops->disable(pwm->chip, pwm);

		pwm->state.enabled = false;

		do_div(dutycycle, state.period);

		state.duty_cycle = dutycycle;

		state.period = pargs.period;

	}



	/*

	 * If the polarity changed, we should also change the duty cycle.

	 */

	if (pargs.polarity != state.polarity) {

		state.polarity = pargs.polarity;

		state.duty_cycle = state.period - state.duty_cycle;

	}



	return pwm_apply_state(pwm, &state);

}

EXPORT_SYMBOL_GPL(pwm_disable);

EXPORT_SYMBOL_GPL(pwm_adjust_config);



static struct pwm_chip *of_node_to_pwmchip(struct device_node *np)

{

include/linux/pwm.h

+184 −85
Original line number Diff line number Diff line
@@ -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;



/**
@@ -184,11 +132,6 @@ static inline unsigned int pwm_get_duty_cycle(const struct pwm_device *pwm) 
	return state.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 state;
@@ -204,34 +147,6 @@ 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 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.

	 *

	 * Instead of setting ->enabled to false, we call pwm_disable()

	 * before pwm_set_polarity() to ensure that everything is configured

	 * as expected, and the PWM is really disabled when the user request

	 * it.

	 *

	 * 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().

	 */

	pwm_disable(pwm);

	pwm_set_polarity(pwm, pwm->args.polarity);

}



/**

 * struct pwm_ops - PWM controller operations

 * @request: optional hook for requesting a PWM
@@ -240,6 +155,10 @@ static inline void pwm_apply_args(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.
@@ -255,6 +174,8 @@ 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 *state);

#ifdef CONFIG_DEBUG_FS
@@ -292,6 +213,115 @@ 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);

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;



	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_set_chip_data(struct pwm_device *pwm, void *data);

void *pwm_get_chip_data(struct pwm_device *pwm);
@@ -317,6 +347,47 @@ 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_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;
@@ -388,6 +459,34 @@ static inline bool pwm_can_sleep(struct pwm_device *pwm) 
}

#endif



static inline void pwm_apply_args(struct pwm_device *pwm)

{

	/*

	 * 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.

	 *

	 * Instead of setting ->enabled to false, we call pwm_disable()

	 * before pwm_set_polarity() to ensure that everything is configured

	 * as expected, and the PWM is really disabled when the user request

	 * it.

	 *

	 * 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().

	 */

	pwm_disable(pwm);

	pwm_set_polarity(pwm, pwm->args.polarity);

}



struct pwm_lookup {

	struct list_head list;

	const char *provider;

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