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

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Message-ID: <20250228110931.7bdae7fd@erd003.prtnl>
Date: Fri, 28 Feb 2025 11:09:31 +0100
From: David Jander <david@...tonic.nl>
To: Krzysztof Kozlowski <krzk@...nel.org>
Cc: linux-kernel@...r.kernel.org, linux-iio@...r.kernel.org, Jonathan Corbet
 <corbet@....net>, Rob Herring <robh@...nel.org>, Krzysztof Kozlowski
 <krzk+dt@...nel.org>, Conor Dooley <conor+dt@...nel.org>,
 devicetree@...r.kernel.org, linux-doc@...r.kernel.org, Nuno Sa
 <nuno.sa@...log.com>, Jonathan Cameron <jic23@...nel.org>, Oleksij Rempel
 <o.rempel@...gutronix.de>, Uwe Kleine-König
 <ukleinek@...nel.org>, linux-pwm@...r.kernel.org
Subject: Re: [RFC PATCH 7/7] dt-bindings: motion: Add motion-simple-pwm
 bindings

On Fri, 28 Feb 2025 10:37:48 +0100
Krzysztof Kozlowski <krzk@...nel.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