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Date: Thu, 14 Feb 2019 11:25:51 +0100
From: Fabrice Gasnier <fabrice.gasnier@...com>
To: <thierry.reding@...il.com>, <robh+dt@...nel.org>
CC: <u.kleine-koenig@...gutronix.de>, <tduszyns@...il.com>,
<mark.rutland@....com>, <alexandre.torgue@...com>,
<mcoquelin.stm32@...il.com>, <fabrice.gasnier@...com>,
<devicetree@...r.kernel.org>,
<linux-arm-kernel@...ts.infradead.org>,
<linux-kernel@...r.kernel.org>, <linux-pwm@...r.kernel.org>,
<linux-stm32@...md-mailman.stormreply.com>
Subject: [PATCH v4 3/3] pwm: core: 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@...il.com>
Signed-off-by: Fabrice Gasnier <fabrice.gasnier@...com>
---
Changes in v4:
- rework error handling following Thierry's comments
- turn/split pr_debug() into dev_err()/pr_warn().
Changes in v3:
- add struct device to of_get_pwm() arguments to handle device link from
there as discussed with Uwe.
---
drivers/pwm/core.c | 50 +++++++++++++++++++++++++++++++++++++++++++++++---
include/linux/pwm.h | 6 ++++--
2 files changed, 51 insertions(+), 5 deletions(-)
diff --git a/drivers/pwm/core.c b/drivers/pwm/core.c
index 1581f6a..64e10a6 100644
--- a/drivers/pwm/core.c
+++ b/drivers/pwm/core.c
@@ -636,8 +636,35 @@ 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.
+ */
+ pr_warn("no consumer dev, can't create device link to %s\n",
+ dev_name(pwm->chip->dev));
+ 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
*
@@ -655,10 +682,12 @@ 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;
@@ -689,6 +718,14 @@ 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
@@ -764,6 +801,7 @@ 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;
@@ -771,7 +809,7 @@ 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
@@ -848,6 +886,12 @@ 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;
@@ -939,7 +983,7 @@ 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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