Re: [PATCH v4 1/3] dt-bindings: hwmon: fan: Add fan binding to schema

[Naresh Solanki <naresh.solanki@9elements.com>]

Hi Rob,

On 02-11-2022 12:14 am, Rob Herring wrote:
> On Mon, Oct 31, 2022 at 01:35:09PM +0530, Naresh Solanki wrote:
>> Hi Rob,
>>
>> On 26-10-2022 07:07 pm, Rob Herring wrote:
>>> fanc: fan-controller {
>>>     #pwm-cells = <3>;
>>>     ...
>>>
>>>     fan {
>>>       pwms = <&fanc 0 500000  PWM_POLARITY_INVERTED>;
>>>       ...
>>>     };
>>> };
>>>
>>> 0 is PWM number and 500000 is the PWM frequency. The 3rd cell are per
>>> consumer flags. See pwm.txt for more details.
>>
>> Did the implementation & while testing getting the below err:
>> [63.626505] max6639 166-002e: failed to create device link to 166-002e
> 
> Does turning off fw_devlink help (fw_devlink=off)?

Will supplier == consumer, device link creation fails.
Not sure what is best approach but not creating device link in this 
scenario help & for that below additional changes needed in pwm core.

diff --git a/drivers/pwm/core.c b/drivers/pwm/core.c
index 4527f09a5c50..afea51c49138 100644
--- a/drivers/pwm/core.c
+++ b/drivers/pwm/core.c
@@ -730,6 +730,12 @@ static struct device_link 
*pwm_device_link_add(struct device *dev,
  		return NULL;
  	}

+	/*
+	 * Do not attempt to create link if consumer itself is supplier.
+	 */
+	if (dev == pwm->chip->dev)
+		return 0;
+
  	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",



Regards,
Naresh