Re: [PATCH v4 1/2] dt-binding: hwmon: Add NPCM7xx PWM and Fan controller documentation

[Tomer Maimon <tmaimon77@gmail.com>]

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Hi Rob,

On 26 June 2018 at 18:03, Rob Herring <robh@kernel.org> wrote:

> On Mon, Jun 25, 2018 at 4:20 PM Tomer Maimon <tmaimon77@gmail.com> wrote:
> >
> > Hi Rob,
> >
> >
> > On 25 June 2018 at 20:14, Rob Herring <robh@kernel.org> wrote:
> >>
> >> On Sun, Jun 24, 2018 at 03:41:54PM +0300, Tomer Maimon wrote:
> >> > Added device tree binding documentation for Nuvoton BMC
> >> > NPCM7xx Pulse Width Modulation (PWM)  and Fan tach controller.
> >> > The PWM controller can support upto 8 PWM output ports.
> >> > The Fan tach controller can support upto 16 tachometer inputs.
> >> >
> >> > Signed-off-by: Tomer Maimon <tmaimon77@gmail.com>
> >> > ---
> >> >  .../devicetree/bindings/hwmon/npcm750-pwm-fan.txt  | 84
> ++++++++++++++++++++++
> >> >  1 file changed, 84 insertions(+)
> >> >  create mode 100644 Documentation/devicetree/
> bindings/hwmon/npcm750-pwm-fan.txt
> >> >
> >> > diff --git a/Documentation/devicetree/bindings/hwmon/npcm750-pwm-fan.txt
> b/Documentation/devicetree/bindings/hwmon/npcm750-pwm-fan.txt
> >> > new file mode 100644
> >> > index 000000000000..a9eacda34f92
> >> > --- /dev/null
> >> > +++ b/Documentation/devicetree/bindings/hwmon/npcm750-pwm-fan.txt
> >> > @@ -0,0 +1,84 @@
> >> > +Nuvoton NPCM7xx PWM and Fan Tacho controller device driver
> >>
> >> Bindings are for h/w, not drivers.
> >>
> >> > +
> >> > +The NPCM7xx has two identical Pulse-width modulation (PWM)
> controller modules,
> >> > +Each PWM module has four PWM controller outputs, Totally 8 PWM
> controller outputs.
> >> > +
> >> > +The NPCM7xx has eight identical Fan tachometer controller modules,
> >> > +Each Fan module has two Fan controller inputs, Totally 16 Fan
> controller inputs.
> >>
> >> Have you looked at other fan ctrlr bindings?f This looks like similar
> >> h/w to ASpeed. Really, I'd like to see a common doc that describes the
> >
> >
> > We do not have the same H/W as Aspeed, I believe in the near future we
> will need to add
> > more DT properties that will used only in the NPCM7xx module.
>
> I didn't say it was the same. Both are multi-channel PWMs with tach
> inputs. Presumably, they can attach to the same types of fans as there
> are only a limited number of types of fans and none of them are
> specific to any fan controller.
>
> >> structure and common properties.
> >
> >
> > what do you mean by common structure and common properties?
>
> When we have multiple bindings for the same class of device/hw, we
> define all the common parts in a common binding doc. This often
> doesn't happen at first, so we end up with a variety of bindings until
> we see some commonality.
>
> In this case, for structure, having sub-nodes for fans. As fans are
> not specific to the controllers, their node should not be defined by
> the controller binding. It's also how you describe the fan type,
> number of fans, the PWM connections, the tach connections, etc.
>
> Rob
>

Thanks a lot for the clarification, indeed we can do a common binding doc.
is it O.K. for now to stay with the same binding document (V5 - that  i
will send toady),
and later on we will work on creating common binding document for the
fan-nodes.

also I will like to know how to represent the fan-nodes properties in
the common
binding document,
the property name "aspeed,fan-tach-ch" is something related Aspeed.

Do I need to ask the Aspeed hwmon maintainer to modify his driver to
use fan-tach-ch
property?
or to mention both fan-tach properties (NPCM and Aspeed) in the  common
binding document ?

Thanks,

Tomer

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