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

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