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

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(-)

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

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
>

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

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
>