Hello Florian,
[adding Linus and linux-gpio to Cc:]
On Tue, Oct 29, 2024 at 09:03:57AM -0700, Florian Fainelli wrote:
> On 10/29/24 03:44, Uwe Kleine-König wrote:
> > On Tue, Oct 15, 2024 at 10:07:10AM -0700, Florian Fainelli wrote:
> > > On 10/15/24 09:32, Rob Herring wrote:
> > > > Another thing to consider is for any PWM controller with more than
> > > > 1 output, you might want this to be per output and therefore should be
> > > > a flag in the cells.
> > >
> > > Yes, that is a good point, this controller has two channels, so it seems
> > > like increasing the #pwm-cells might be the way to go.
> >
> > So the idea is something like:
> >
> > diff --git a/include/dt-bindings/pwm/pwm.h b/include/dt-bindings/pwm/pwm.h
> > index ab9a077e3c7d..d18b006a7399 100644
> > --- a/include/dt-bindings/pwm/pwm.h
> > +++ b/include/dt-bindings/pwm/pwm.h
> > @@ -11,5 +11,6 @@
> > #define _DT_BINDINGS_PWM_PWM_H
> > #define PWM_POLARITY_INVERTED (1 << 0)
> > +#define PWM_OUTPUT_OPEN_DRAIN (1 << 1)
> > #endif
> >
> > and then add support for that to the core and drivers? There is some
> > intersection with pinctrl (depending on hardware). I wonder if
> > abstracting this somehow using the typical pinctrl properties would be a
> > saner option??
>
> But what if the pin is not managed by a pinctrl provider?
Then create one? If that's the PWM itself that is the pinctrl device it
would look as follows:
pwm@f0408000 {
compatible = "brcm,bcm7038-pwm";
pinctrl-0 = <&pwm_pins>;
reg = <0xf0408000 0x28>;
#pwm-cells = <2>;
#pinctrl-cells = <0>;
clocks = <&upg_fixed>;
pinctrl {
pwm_pins: pwm-pins {
pins = "A", "B";
drive-open-drain;
};
};
};
Maybe this is difficult if there is a pinctrl that configures the output
as "PWM" and then there is that additional register in the PWM IP to
make this pin open drain? One could just use
pinctrl-0 = <&pwm_pins>, <&system_pinctrl_pwm>;
then. Not entirely sure this is overengineered, but the dt
representation would be nice (IMHO). Thoughts?
> I have started
> going the route of implementing the PWM_OUTPUT_OPEN_DRAIN bit as an
> additional specifier in the #pwm-cells, but I am not sure to what extent
> this should be allowed to be changed at runtime.
I would not expect that the open-drainness needs to change at runtime.
Best regards
Uwe
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