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Subject[PATCH v3 3/3] pwm: core: add consumer device link
Date
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_ 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>
Signed-off-by: Fabrice Gasnier <fabrice.gasnier@st.com>
---
Changes in v3:
- add struct device to of_get_pwm() arguments to handle device link from
there.
---
drivers/pwm/core.c | 14 +++++++++++---
include/linux/pwm.h | 6 ++++--
2 files changed, 15 insertions(+), 5 deletions(-)

diff --git a/drivers/pwm/core.c b/drivers/pwm/core.c
index 1581f6a..8cb5d4bc 100644
--- a/drivers/pwm/core.c
+++ b/drivers/pwm/core.c
@@ -638,6 +638,7 @@ static struct pwm_chip *of_node_to_pwmchip(struct device_node *np)

/**
* 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
*
@@ -655,7 +656,8 @@ 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;
@@ -689,6 +691,9 @@ struct pwm_device *of_pwm_get(struct device_node *np, const char *con_id)
if (IS_ERR(pwm))
goto put;

+ if (!device_link_add(dev, pwm->chip->dev, DL_FLAG_AUTOREMOVE_CONSUMER))
+ pr_debug("%s(): device link not added\n", __func__);
+
/*
* 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
@@ -771,7 +776,7 @@ 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 +856,9 @@ struct pwm_device *pwm_get(struct device *dev, const char *con_id)
pwm->args.period = chosen->period;
pwm->args.polarity = chosen->polarity;

+ if (!device_link_add(dev, pwm->chip->dev, DL_FLAG_AUTOREMOVE_CONSUMER))
+ pr_debug("%s(): device link not added\n", __func__);
+
return pwm;
}
EXPORT_SYMBOL_GPL(pwm_get);
@@ -939,7 +947,7 @@ 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);
diff --git a/include/linux/pwm.h b/include/linux/pwm.h
index d5199b5..895e074 100644
--- a/include/linux/pwm.h
+++ b/include/linux/pwm.h
@@ -406,7 +406,8 @@ 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);
@@ -494,7 +495,8 @@ 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);
--
1.9.1
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