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Commit b2c200e3 authored by Fabrice Gasnier's avatar Fabrice Gasnier Committed by Thierry Reding
Browse files

pwm: Add consumer device link 

Add a device link between the PWM consumer and the PWM provider. This
enforces the PWM user to get suspended before the PWM provider. It
allows proper synchronization of suspend/resume sequences: the PWM user
is responsible for properly stopping PWM, before the provider gets
suspended: see [1]. Add the device link in:
- of_pwm_get()
- pwm_get()
- devm_*pwm_get() variants
as it requires a reference to the device for the PWM consumer.

[1] https://lkml.org/lkml/2019/2/5/770



Suggested-by: default avatarThierry Reding <thierry.reding@gmail.com>
Acked-by: default avatarUwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: default avatarFabrice Gasnier <fabrice.gasnier@st.com>
Signed-off-by: default avatarThierry Reding <thierry.reding@gmail.com>
parent cce4a833

drivers/pwm/core.c

+47 −3
Original line number Original line Diff line number Diff line
@@ -639,8 +639,35 @@ static struct pwm_chip *of_node_to_pwmchip(struct device_node *np) 
	return ERR_PTR(-EPROBE_DEFER);

	return ERR_PTR(-EPROBE_DEFER);

}

}





static struct device_link *pwm_device_link_add(struct device *dev,

					       struct pwm_device *pwm)

{

	struct device_link *dl;



	if (!dev) {

		/*

		 * No device for the PWM consumer has been provided. It may

		 * impact the PM sequence ordering: the PWM supplier may get

		 * suspended before the consumer.

		 */

		dev_warn(pwm->chip->dev,

			 "No consumer device specified to create a link to\n");

		return NULL;

	}



	dl = device_link_add(dev, pwm->chip->dev, DL_FLAG_AUTOREMOVE_CONSUMER);

	if (!dl) {

		dev_err(dev, "failed to create device link to %s\n",

			dev_name(pwm->chip->dev));

		return ERR_PTR(-EINVAL);

	}



	return dl;

}



/**

/**

 * of_pwm_get() - request a PWM via the PWM framework

 * of_pwm_get() - request a PWM via the PWM framework

 * @dev: device for PWM consumer

 * @np: device node to get the PWM from

 * @np: device node to get the PWM from

 * @con_id: consumer name

 * @con_id: consumer name

 *

 *
@@ -658,10 +685,12 @@ static struct pwm_chip *of_node_to_pwmchip(struct device_node *np) 
 * Returns: A pointer to the requested PWM device or an ERR_PTR()-encoded

 * Returns: A pointer to the requested PWM device or an ERR_PTR()-encoded

 * error code on failure.

 * error code on failure.

 */

 */

struct pwm_device *of_pwm_get(struct device_node *np, const char *con_id)

struct pwm_device *of_pwm_get(struct device *dev, struct device_node *np,

			      const char *con_id)

{

{

	struct pwm_device *pwm = NULL;

	struct pwm_device *pwm = NULL;

	struct of_phandle_args args;

	struct of_phandle_args args;

	struct device_link *dl;

	struct pwm_chip *pc;

	struct pwm_chip *pc;

	int index = 0;

	int index = 0;

	int err;

	int err;
@@ -692,6 +721,14 @@ struct pwm_device *of_pwm_get(struct device_node *np, const char *con_id) 
	if (IS_ERR(pwm))

	if (IS_ERR(pwm))

		goto put;

		goto put;





	dl = pwm_device_link_add(dev, pwm);

	if (IS_ERR(dl)) {

		/* of_xlate ended up calling pwm_request_from_chip() */

		pwm_free(pwm);

		pwm = ERR_CAST(dl);

		goto put;

	}



	/*

	/*

	 * If a consumer name was not given, try to look it up from the

	 * If a consumer name was not given, try to look it up from the

	 * "pwm-names" property if it exists. Otherwise use the name of

	 * "pwm-names" property if it exists. Otherwise use the name of
@@ -767,6 +804,7 @@ struct pwm_device *pwm_get(struct device *dev, const char *con_id) 
	const char *dev_id = dev ? dev_name(dev) : NULL;

	const char *dev_id = dev ? dev_name(dev) : NULL;

	struct pwm_device *pwm;

	struct pwm_device *pwm;

	struct pwm_chip *chip;

	struct pwm_chip *chip;

	struct device_link *dl;

	unsigned int best = 0;

	unsigned int best = 0;

	struct pwm_lookup *p, *chosen = NULL;

	struct pwm_lookup *p, *chosen = NULL;

	unsigned int match;

	unsigned int match;
@@ -774,7 +812,7 @@ struct pwm_device *pwm_get(struct device *dev, const char *con_id) 




	/* look up via DT first */

	/* look up via DT first */

	if (IS_ENABLED(CONFIG_OF) && dev && dev->of_node)

	if (IS_ENABLED(CONFIG_OF) && dev && dev->of_node)

		return of_pwm_get(dev->of_node, con_id);

		return of_pwm_get(dev, dev->of_node, con_id);





	/*

	/*

	 * We look up the provider in the static table typically provided by

	 * We look up the provider in the static table typically provided by
@@ -851,6 +889,12 @@ struct pwm_device *pwm_get(struct device *dev, const char *con_id) 
	if (IS_ERR(pwm))

	if (IS_ERR(pwm))

		return pwm;

		return pwm;





	dl = pwm_device_link_add(dev, pwm);

	if (IS_ERR(dl)) {

		pwm_free(pwm);

		return ERR_CAST(dl);

	}



	pwm->args.period = chosen->period;

	pwm->args.period = chosen->period;

	pwm->args.polarity = chosen->polarity;

	pwm->args.polarity = chosen->polarity;
@@ -943,7 +987,7 @@ struct pwm_device *devm_of_pwm_get(struct device *dev, struct device_node *np, 
	if (!ptr)

	if (!ptr)

		return ERR_PTR(-ENOMEM);

		return ERR_PTR(-ENOMEM);





	pwm = of_pwm_get(np, con_id);

	pwm = of_pwm_get(dev, np, con_id);

	if (!IS_ERR(pwm)) {

	if (!IS_ERR(pwm)) {

		*ptr = pwm;

		*ptr = pwm;

		devres_add(dev, ptr);

		devres_add(dev, ptr);

include/linux/pwm.h

+4 −2
Original line number Original line Diff line number Diff line
@@ -405,7 +405,8 @@ struct pwm_device *of_pwm_xlate_with_flags(struct pwm_chip *pc, 
		const struct of_phandle_args *args);

		const struct of_phandle_args *args);





struct pwm_device *pwm_get(struct device *dev, const char *con_id);

struct pwm_device *pwm_get(struct device *dev, const char *con_id);

struct pwm_device *of_pwm_get(struct device_node *np, const char *con_id);

struct pwm_device *of_pwm_get(struct device *dev, struct device_node *np,

			      const char *con_id);

void pwm_put(struct pwm_device *pwm);

void pwm_put(struct pwm_device *pwm);





struct pwm_device *devm_pwm_get(struct device *dev, const char *con_id);

struct pwm_device *devm_pwm_get(struct device *dev, const char *con_id);
@@ -493,7 +494,8 @@ static inline struct pwm_device *pwm_get(struct device *dev, 
	return ERR_PTR(-ENODEV);

	return ERR_PTR(-ENODEV);

}

}





static inline struct pwm_device *of_pwm_get(struct device_node *np,

static inline struct pwm_device *of_pwm_get(struct device *dev,

					    struct device_node *np,

					    const char *con_id)

					    const char *con_id)

{

{

	return ERR_PTR(-ENODEV);

	return ERR_PTR(-ENODEV);