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