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.red...@gmail.com> Signed-off-by: Fabrice Gasnier <fabrice.gasn...@st.com> --- Changes in v5: - fix a style issue - use dev_warn() instead of pr_warn 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..03aa1b5 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. + */ + 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 * @@ -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); -- 2.7.4
