[RFC PATCH 05/10] dt-bindings: pwm: Add bindings for PWM function in Netronix EC

[Jonathan Neuschäfer]

On Sun, Jun 21, 2020 at 08:41:23PM +0200, Andreas Kemnade wrote:
> On Sun, 21 Jun 2020 00:42:16 +0200
> Jonathan Neuschäfer <j.neuschaefer at gmx.net> wrote:
> 
> > The Netronix embedded controller as found in Kobo Aura and Tolino Shine
> > supports one PWM channel, which is used to control the frontlight
> > brightness on these devices.
> > 
> > Known problems:
> > - `make dt_binding_check` shows the following warnings:
> >   Documentation/devicetree/bindings/mfd/netronix,ntxec.example.dts:49.17-42:
> >   Warning (pwms_property): /example-0/backlight:pwms: cell 2 is not a
> >   phandle reference
> >   Documentation/devicetree/bindings/mfd/netronix,ntxec.example.dts:49.17-42:
> >   Warning (pwms_property): /example-0/backlight:pwms: Could not get
> >   phandle node for (cell 2)
> > 
> In the tolino sources in ./drivers/misc/ntx-misc.c I find this line
> 
>         if(4==gptHWCFG->m_val.bFL_PWM) {
> 
> No idea what it does but I would expect to have a kind of translation to
> a dt property?

As far as I understand it, FL_PWM=4 means that there is a second PWM
channel, in order to provide different backlight colors.

I think it should be possible to simply extend the binding to list
another available PWM channel, once we add support for such hardware.

> > +                    ec_pwm: pwm {
> > +                            compatible = "netronix,ntxec-pwm";
> > +                            #pwm-cells = <1>;
> shouldn't that be 2?
> > +                    };
> >              };
> >      };
> > +
> > +    backlight {
> > +            compatible = "pwm-backlight";
> > +            pwms = <&ec_pwm 0 50000>;
> since you have 2 values after the &ec_pwm 
[...]
> > +properties:
> > +  compatible:
> > +    const: netronix,ntxec-pwm
> > +
> > +  "#pwm-cells":
> > +    const: 1
> 
> shouln't that be 2?

Right, I'll fix that.


Thanks,
Jonathan
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