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

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