Re: [RFC PATCH 7/7] dt-bindings: motion: Add motion-simple-pwm bindings

David Jander
2025-02-28T10:09:34Z

On Fri, 28 Feb 2025 10:37:48 +0100
Krzysztof Kozlowski <krzk@kernel.org> wrote:

> On 28/02/2025 10:22, David Jander wrote:
> >
> >>> +
> >>> + motion,pwm-inverted:
> >>> + $ref: /schemas/types.yaml#/definitions/flag
> >>
> >> And PWM flag does not work?
> >
> > I have seen PWM controllers that don't seem to support the
> > PWM_POLARITY_INVERTED flag and those where it just doesn't work. Should all
>
>
> Shouldn't the controllers be fixed? Or let's rephrase the question: why
> only this PWM consumer needs this property and none of others need it?

CCing Uwe Kleine-Koenig and linux-pwm mailing list.

I know that at least in kernel 6.11 the pwm-stm32.c PWM driver doesn't
properly invert the PWM signal when specifying PWM_POLARITY_INVERTED. I agree
this is a probably bug that needs fixing if still present in 6.14-rc. Besides
that, if linux-pwm agrees that every single PWM driver _must_ properly support
this flag, I will drop this consumer flag an start fixing broken PWM drivers
that I encounter. I agree that it makes more sense this way, but I wanted to
be sure.

Best regards,

--
David Jander