Re: [PATCH 1/2] dt-bindings: hwmon: Add binding for max6639

[Naresh Solanki]

Thanks Guenter, to summarize below properties that can be configured
based on input from
fan datasheet:
pwm controlled fan:
1.  max-rpm : Defines maximum rpm the fan supports
2.  tach-pulse/pulse-per-revolution( also referred as prescale) :
Determines the number of
 pulses received from the sensor/tach pin of fan per revolution.
3.  rpm-init (also ref. as fan-target-rpm): Determines the fan rpm
driver needs to configure
during probe.
4. pwm-input-polarity(normal or inverse) : Specifies fan pwm input
polarity as specified in
 fan datasheet. a fan controller driver can use this data to configure
pwm output polarity
accordingly during driver probe.

For a DC output controlled fan, voltage across fan is controlled to control rpm.
Below is what I can think of:
5. voltage-range : Specifies valid voltage range for rpm control
example for 3V to 5V range:
     voltage-range=<3000 5000>;

Above mentioned properties are within the scope of fan.
Fan controllers like max6639/max6650 etc can have additional
properties specific to the
feather supported by the chip.

Let me know if I can go ahead with this.

Thanks,
Naresh Solanki

Regards,
Naresh Solanki



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On Thu, 6 Oct 2022 at 00:10, Guenter Roeck <linux@xxxxxxxxxxxx> wrote:
>
> On 9/21/22 23:34, Krzysztof Kozlowski wrote:
> > On 22/09/2022 07:07, Naresh Solanki wrote:
> >> From: Marcello Sylvester Bauer <sylv@xxxxxxx>
> >>
> >> Add Devicetree binding documentation for Maxim MAX6639 temperature
> >> monitor with PWM fan-speed controller.
> >>
> >> Signed-off-by: Marcello Sylvester Bauer <sylv@xxxxxxx>
> >> Signed-off-by: Naresh Solanki <Naresh.Solanki@xxxxxxxxxxxxx>
> >> ---
> >>   .../bindings/hwmon/maxim,max6639.yaml         | 112 ++++++++++++++++++
> >>   1 file changed, 112 insertions(+)
> >>   create mode 100644 Documentation/devicetree/bindings/hwmon/maxim,max6639.yaml
> >>
> >> diff --git a/Documentation/devicetree/bindings/hwmon/maxim,max6639.yaml b/Documentation/devicetree/bindings/hwmon/maxim,max6639.yaml
> >> new file mode 100644
> >> index 000000000000..c845fb989af2
> >> --- /dev/null
> >> +++ b/Documentation/devicetree/bindings/hwmon/maxim,max6639.yaml
> >> @@ -0,0 +1,112 @@
> >> +# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
> >> +%YAML 1.2
> >> +---
> >> +
> >> +$id: http://devicetree.org/schemas/hwmon/maxim,max6639.yaml#
> >> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> >> +
> >> +title: Maxim max6639
> >> +
> >> +maintainers:
> >> +  - Roland Stigge <stigge@xxxxxxxxx>
> >
> > Ack from Roland is needed here.
> >
> >> +
> >> +description: |
> >> +  The MAX6639 is a 2-channel temperature monitor with dual, automatic, PWM
> >> +  fan-speed controller.  It monitors its own temperature and one external
> >> +  diode-connected transistor or the temperatures of two external diode-connected
> >> +  transistors, typically available in CPUs, FPGAs, or GPUs.
> >> +
> >> +  Datasheets:
> >> +    https://datasheets.maximintegrated.com/en/ds/MAX6639-MAX6639F.pdf
> >> +
> >> +properties:
> >> +  compatible:
> >> +    enum:
> >> +      - maxim,max6639
> >> +
> >> +  reg:
> >> +    maxItems: 1
> >> +
> >> +  '#address-cells':
> >> +    const: 1
> >> +
> >> +  '#size-cells':
> >> +    const: 0
> >> +
> >> +required:
> >> +  - compatible
> >> +  - reg
> >> +  - "fan@0"
> >> +  - "fan@1"
> >> +
> >> +additionalProperties: false
> >> +
> >> +patternProperties:
> >
> > This goes after properties.
> >
> >> +  "^fan@[0-1]$":
> >> +    type: object
> >> +    description: |
> >> +      Represents the two fans and their specific configuration.
> >> +
> >> +    properties:
> >> +      reg:
> >> +        description: |
> >> +          The fan number.
> >> +        items:
> >
> > Skip items.
> >
> >> +          minimum: 0
> >> +          maximum: 1
> >> +
> >> +      pwm-polarity:
> >
> > Why is this property of fan, not of PWM source?
> >
>
> The chip provides pwm output to the fan. That typical for fan
> controller chips. Typically they also have options to configure
> the pwm frequency and either pwm or DC output (max6639 does not
> have the latter option).
>
> Guenter