linux-kernel - Re: [PATCH v7 1/3] dt-bindings: hwmon: Add adt7475 fan/pwm properties

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Message-ID: <bc99a27e-74ec-45a0-b77c-48f993269586@alliedtelesis.co.nz>
Date: Tue, 27 May 2025 20:24:56 +0000
From: Chris Packham <Chris.Packham@...iedtelesis.co.nz>
To: Uwe Kleine-König <ukleinek@...nel.org>
CC: "jdelvare@...e.com" <jdelvare@...e.com>, "linux@...ck-us.net"
	<linux@...ck-us.net>, "robh@...nel.org" <robh@...nel.org>,
	"krzk+dt@...nel.org" <krzk+dt@...nel.org>, "conor+dt@...nel.org"
	<conor+dt@...nel.org>, "linux-hwmon@...r.kernel.org"
	<linux-hwmon@...r.kernel.org>, "devicetree@...r.kernel.org"
	<devicetree@...r.kernel.org>, "linux-kernel@...r.kernel.org"
	<linux-kernel@...r.kernel.org>, "linux-pwm@...r.kernel.org"
	<linux-pwm@...r.kernel.org>
Subject: Re: [PATCH v7 1/3] dt-bindings: hwmon: Add adt7475 fan/pwm properties

Hi Uwe,

On 28/05/2025 04:12, Uwe Kleine-König wrote:
> Hello,
>
> On Tue, Jul 23, 2024 at 10:17:35AM +1200, Chris Packham wrote:
>> Add fan child nodes that allow describing the connections for the
>> ADT7475 to the fans it controls. This also allows setting some
>> initial values for the pwm duty cycle and frequency.
>>
>> Signed-off-by: Chris Packham <chris.packham@...iedtelesis.co.nz>
>> Reviewed-by: Rob Herring (Arm) <robh@...nel.org>
>> ---
>>
>> Notes:
>>      Changes in v7:
>>      - None
>>      Changes in v6:
>>      - Collect r-by from Rob
>>      Changes in v5:
>>      - Use nanoseconds for PWM frequency and duty cycle as per existing
>>        conventions for PWMs
>>      - Set flags to 0 in example to match adi,pwm-active-state setting
>>      Changes in v4:
>>      - 0 is not a valid frequency value
>>      Changes in v3:
>>      - Use the pwm provider/consumer bindings
>>      Changes in v2:
>>      - Document 0 as a valid value (leaves hardware as-is)
>>
>>   .../devicetree/bindings/hwmon/adt7475.yaml    | 35 ++++++++++++++++++-
>>   1 file changed, 34 insertions(+), 1 deletion(-)
>>
>> diff --git a/Documentation/devicetree/bindings/hwmon/adt7475.yaml b/Documentation/devicetree/bindings/hwmon/adt7475.yaml
>> index 051c976ab711..df2b5b889e4d 100644
>> --- a/Documentation/devicetree/bindings/hwmon/adt7475.yaml
>> +++ b/Documentation/devicetree/bindings/hwmon/adt7475.yaml
>> @@ -51,6 +51,24 @@ properties:
>>         enum: [0, 1]
>>         default: 1
>>   
>> +  "#pwm-cells":
>> +    const: 4
> I asked to add support for #pwm-cells = <4> to the pwm core in reply to
> v4 (see
> https://lore.kernel.org/linux-pwm/drqvaon5lb2ei3jqofutbr6demibyfdhbmr24sva27gzpqdnon@fxa7rpl33iih/).
>
> I'm unhappy to see this merged anyhow in combination with ad-hoc parsing
> of the pwm properties in the driver :-\

As I mentioned at the time the adt7475 is not currently pwm_chip so I 
need the ad-hoc parsing in that driver. I'd be happy to take you 
prototype patch for pwm/core.c and polish it although I don't really 
have a good way of testing it.

>> +    description: |
>> +      Number of cells in a PWM specifier.
>> +      - 0: The PWM channel
>> +      - 1: The PWM period in nanoseconds
>> +           - 90909091 (11 Hz)
>> +           - 71428571 (14 Hz)
>> +           - 45454545 (22 Hz)
>> +           - 34482759 (29 Hz)
>> +           - 28571429 (35 Hz)
>> +           - 22727273 (44 Hz)
>> +           - 17241379 (58 Hz)
>> +           - 11363636 (88 Hz)
>> +           - 44444 (22 kHz)
>> +      - 2: PWM flags 0 or PWM_POLARITY_INVERTED
>> +      - 3: The default PWM duty cycle in nanoseconds
>> +
> Best regards
> Uwe