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