[PATCH v4 0/3] Add PM support to STM32 LP Timer drivers

[PATCH v4 0/3] Add PM support to STM32 LP Timer drivers

[Fabrice Gasnier]

This patch series adds power management support for STM32 LP Timer:
- PWM driver
- Document the pinctrl states for sleep mode

It also adds device link between the PWM consumer and the PWM provider.
This allows proper sequencing for suspend/resume (e.g. user will likely
do a pwm_disable() before the PWM provider suspend executes), see [1].

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

---
Changes in v4:
- improve error handling when adding the PWM consumer device link.

Changes in v3:
- Move the device_link_add() call to of_pwm_get() as discussed with Uwe.

Changes in v2:
- Don't disable PWM channel in PWM provider: rather refuse to suspend
  and report an error as suggested by Uwe and Thierry.
- Add patch 3/3 to propose device link addition.
- No updates for STM32 LP Timer IIO driver. Patches can be send separately.

Fabrice Gasnier (3):
  dt-bindings: pwm-stm32-lp: document pinctrl sleep state
  pwm: stm32-lp: Add power management support
  pwm: core: add consumer device link

 .../devicetree/bindings/pwm/pwm-stm32-lp.txt       |  9 ++--
 drivers/pwm/core.c                                 | 50 ++++++++++++++++++++--
 drivers/pwm/pwm-stm32-lp.c                         | 25 +++++++++++
 include/linux/pwm.h                                |  6 ++-
 4 files changed, 82 insertions(+), 8 deletions(-)

-- 
1.9.1

[PATCH v4 1/3] dt-bindings: pwm-stm32-lp: document pinctrl sleep state

[Fabrice Gasnier]

Add documentation for pinctrl sleep state on STM32 LPTimer PWM.

Signed-off-by: Fabrice Gasnier <fabrice.gasnier@st.com>
---
 Documentation/devicetree/bindings/pwm/pwm-stm32-lp.txt | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/Documentation/devicetree/bindings/pwm/pwm-stm32-lp.txt b/Documentation/devicetree/bindings/pwm/pwm-stm32-lp.txt
index bd23302..6521bc4 100644
--- a/Documentation/devicetree/bindings/pwm/pwm-stm32-lp.txt
+++ b/Documentation/devicetree/bindings/pwm/pwm-stm32-lp.txt
@@ -11,8 +11,10 @@ Required parameters:
 			bindings defined in pwm.txt.
 
 Optional properties:
-- pinctrl-names: 	Set to "default".
-- pinctrl-0: 		Phandle pointing to pin configuration node for PWM.
+- pinctrl-names: 	Set to "default". An additional "sleep" state can be
+			defined to set pins in sleep state when in low power.
+- pinctrl-n: 		Phandle(s) pointing to pin configuration node for PWM,
+			respectively for "default" and "sleep" states.
 
 Example:
 	timer@40002400 {
@@ -21,7 +23,8 @@ Example:
 		pwm {
 			compatible = "st,stm32-pwm-lp";
 			#pwm-cells = <3>;
-			pinctrl-names = "default";
+			pinctrl-names = "default", "sleep";
 			pinctrl-0 = <&lppwm1_pins>;
+			pinctrl-1 = <&lppwm1_sleep_pins>;
 		};
 	};
-- 
1.9.1

[PATCH v4 2/3] pwm: stm32-lp: Add power management support

[Fabrice Gasnier]

Add suspend/resume PM sleep ops. When going to low power, enforce the PWM
channel isn't active. Let the PWM consumers disable it during their own
suspend sequence. Only perform a check here, and handle the pinctrl states.
See [1].
[1] https://lkml.org/lkml/2019/2/5/770

Signed-off-by: Fabrice Gasnier <fabrice.gasnier@st.com>
---
Changes in v2:
- Don't disable PWM channel: let the PWM user disable it. Refuse to
  suspend in case it's been left enabled.
- Drop the ifdefs, use __maybe_unused instead.
---
 drivers/pwm/pwm-stm32-lp.c | 25 +++++++++++++++++++++++++
 1 file changed, 25 insertions(+)

diff --git a/drivers/pwm/pwm-stm32-lp.c b/drivers/pwm/pwm-stm32-lp.c
index 0059b24c..2211a64 100644
--- a/drivers/pwm/pwm-stm32-lp.c
+++ b/drivers/pwm/pwm-stm32-lp.c
@@ -13,6 +13,7 @@
 #include <linux/mfd/stm32-lptimer.h>
 #include <linux/module.h>
 #include <linux/of.h>
+#include <linux/pinctrl/consumer.h>
 #include <linux/platform_device.h>
 #include <linux/pwm.h>
 
@@ -223,6 +224,29 @@ static int stm32_pwm_lp_remove(struct platform_device *pdev)
 	return pwmchip_remove(&priv->chip);
 }
 
+static int __maybe_unused stm32_pwm_lp_suspend(struct device *dev)
+{
+	struct stm32_pwm_lp *priv = dev_get_drvdata(dev);
+	struct pwm_state state;
+
+	pwm_get_state(&priv->chip.pwms[0], &state);
+	if (state.enabled) {
+		dev_err(dev, "The consumer didn't stop us (%s)\n",
+			priv->chip.pwms[0].label);
+		return -EBUSY;
+	}
+
+	return pinctrl_pm_select_sleep_state(dev);
+}
+
+static int __maybe_unused stm32_pwm_lp_resume(struct device *dev)
+{
+	return pinctrl_pm_select_default_state(dev);
+}
+
+static SIMPLE_DEV_PM_OPS(stm32_pwm_lp_pm_ops, stm32_pwm_lp_suspend,
+			 stm32_pwm_lp_resume);
+
 static const struct of_device_id stm32_pwm_lp_of_match[] = {
 	{ .compatible = "st,stm32-pwm-lp", },
 	{},
@@ -235,6 +259,7 @@ static int stm32_pwm_lp_remove(struct platform_device *pdev)
 	.driver	= {
 		.name = "stm32-pwm-lp",
 		.of_match_table = of_match_ptr(stm32_pwm_lp_of_match),
+		.pm = &stm32_pwm_lp_pm_ops,
 	},
 };
 module_platform_driver(stm32_pwm_lp_driver);
-- 
1.9.1

[PATCH v4 3/3] pwm: core: add consumer device link

[Fabrice Gasnier]

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>
Signed-off-by: Fabrice Gasnier <fabrice.gasnier@st.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

Re: [PATCH v4 1/3] dt-bindings: pwm-stm32-lp: document pinctrl sleep state

[Rob Herring]

On Thu, 14 Feb 2019 11:25:49 +0100, Fabrice Gasnier wrote:
> Add documentation for pinctrl sleep state on STM32 LPTimer PWM.
> 
> Signed-off-by: Fabrice Gasnier <fabrice.gasnier@st.com>
> ---
>  Documentation/devicetree/bindings/pwm/pwm-stm32-lp.txt | 9 ++++++---
>  1 file changed, 6 insertions(+), 3 deletions(-)
> 

Reviewed-by: Rob Herring <robh@kernel.org>

Re: [PATCH v4 3/3] pwm: core: add consumer device link

[Uwe Kleine-König]

Hello,

On Thu, Feb 14, 2019 at 11:25:51AM +0100, Fabrice Gasnier wrote:
> 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>
> Signed-off-by: Fabrice Gasnier <fabrice.gasnier@st.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));

Maybe use dev_warn(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);

broken indention.

> +	}
> +
> +	return dl;
> +}
> +

Best regards
Uwe

-- 
Pengutronix e.K.                           | Uwe Kleine-König            |
Industrial Linux Solutions                 | http://www.pengutronix.de/  |

Re: [PATCH v4 3/3] pwm: core: add consumer device link

[Fabrice Gasnier]

On 2/18/19 6:22 PM, Uwe Kleine-König wrote:
> Hello,
> 
> On Thu, Feb 14, 2019 at 11:25:51AM +0100, Fabrice Gasnier wrote:
>> 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>
>> Signed-off-by: Fabrice Gasnier <fabrice.gasnier@st.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));
> 
> Maybe use dev_warn(pwm->chip->dev, ...) ?

Hi Uwe,

I'm wondering a bit about this: In this case, the caller that doesn't
provide a struct device *, PWM provider isn't responsible for that. So I
just hope this wouldn't be miss-leading ?

> 
>> +		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);
> 
> broken indention.

Oops, I'll fix it.

Thanks,
Fabrice

> 
>> +	}
>> +
>> +	return dl;
>> +}
>> +
> 
> Best regards
> Uwe
> 

Re: [PATCH v4 3/3] pwm: core: add consumer device link

[Uwe Kleine-König]

On Tue, Feb 19, 2019 at 09:46:32AM +0100, Fabrice Gasnier wrote:
> On 2/18/19 6:22 PM, Uwe Kleine-König wrote:
> > Hello,
> > 
> > On Thu, Feb 14, 2019 at 11:25:51AM +0100, Fabrice Gasnier wrote:
> >> 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>
> >> Signed-off-by: Fabrice Gasnier <fabrice.gasnier@st.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));
> > 
> > Maybe use dev_warn(pwm->chip->dev, ...) ?
> 
> Hi Uwe,
> 
> I'm wondering a bit about this: In this case, the caller that doesn't
> provide a struct device *, PWM provider isn't responsible for that. So I
> just hope this wouldn't be miss-leading ?

IMHO it's more the wording that might make the message misleading. If
you use

	dev_warn(pwm->chip->dev, "No consumer device specified to create a device link to\n");

that's completely fine in my eyes.
 
Best regards
Uwe

-- 
Pengutronix e.K.                           | Uwe Kleine-König            |
Industrial Linux Solutions                 | http://www.pengutronix.de/  |

Re: [PATCH v4 3/3] pwm: core: add consumer device link

[Fabrice Gasnier]

On 2/19/19 9:55 AM, Uwe Kleine-König wrote:
> On Tue, Feb 19, 2019 at 09:46:32AM +0100, Fabrice Gasnier wrote:
>> On 2/18/19 6:22 PM, Uwe Kleine-König wrote:
>>> Hello,
>>>
>>> On Thu, Feb 14, 2019 at 11:25:51AM +0100, Fabrice Gasnier wrote:
>>>> 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>
>>>> Signed-off-by: Fabrice Gasnier <fabrice.gasnier@st.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));
>>>
>>> Maybe use dev_warn(pwm->chip->dev, ...) ?
>>
>> Hi Uwe,
>>
>> I'm wondering a bit about this: In this case, the caller that doesn't
>> provide a struct device *, PWM provider isn't responsible for that. So I
>> just hope this wouldn't be miss-leading ?
> 
> IMHO it's more the wording that might make the message misleading. If
> you use
> 
> 	dev_warn(pwm->chip->dev, "No consumer device specified to create a device link to\n");
> 
> that's completely fine in my eyes.

Thanks for the suggestion, I'll update this as well in v5.

Best regards,
Fabrice
>  
> Best regards
> Uwe
>