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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: Thierry Reding <thierry.reding@gmail.com>
Acked-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Fabrice Gasnier <fabrice.gasnier@st.com>
Signed-off-by: Thierry Reding <thierry.reding@gmail.com>
This commit is contained in:
Fabrice Gasnier 2019-04-18 11:37:47 +02:00 committed by Thierry Reding
parent cce4a833fc
commit b2c200e3f2
2 changed files with 51 additions and 5 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

50
drivers/pwm/core.c
View File

@ -639,8 +639,35 @@ static struct pwm_chip *of_node_to_pwmchip(struct device_node *np)
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
* @dev: device for PWM consumer
* @np: device node to get the PWM from
* @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
* 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 of_phandle_args args;
struct device_link *dl;
struct pwm_chip *pc;
int index = 0;
int err;
@ -692,6 +721,14 @@ struct pwm_device *of_pwm_get(struct device_node *np, const char *con_id)
if (IS_ERR(pwm))
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
* "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;
struct pwm_device *pwm;
struct pwm_chip *chip;
struct device_link *dl;
unsigned int best = 0;
struct pwm_lookup *p, *chosen = NULL;
unsigned int match;
@ -774,7 +812,7 @@ struct pwm_device *pwm_get(struct device *dev, const char *con_id)
/* look up via DT first */
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
@ -851,6 +889,12 @@ struct pwm_device *pwm_get(struct device *dev, const char *con_id)
if (IS_ERR(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.polarity = chosen->polarity;
@ -943,7 +987,7 @@ struct pwm_device *devm_of_pwm_get(struct device *dev, struct device_node *np,
if (!ptr)
return ERR_PTR(-ENOMEM);
pwm = of_pwm_get(np, con_id);
pwm = of_pwm_get(dev, np, con_id);
if (!IS_ERR(pwm)) {
*ptr = pwm;
devres_add(dev, ptr);

6
include/linux/pwm.h
View File

@ -405,7 +405,8 @@ struct pwm_device *of_pwm_xlate_with_flags(struct pwm_chip *pc,
const struct of_phandle_args *args);
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);
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);
}
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)
{
return ERR_PTR(-ENODEV);