linux-kernel - Re: [PATCH v2 2/9] dt-bindings: pincfg-node: Add property "skew-delay-direction"

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Message-ID: <4de485fc717a1b469979c32852f58fa3c4b20607.camel@foss.st.com>
Date: Wed, 1 Oct 2025 16:36:17 +0200
From: Antonio Borneo <antonio.borneo@...s.st.com>
To: Linus Walleij <linus.walleij@...aro.org>
CC: Rob Herring <robh@...nel.org>, Krzysztof Kozlowski <krzk+dt@...nel.org>,
        Conor Dooley <conor+dt@...nel.org>,
        Maxime Coquelin
	<mcoquelin.stm32@...il.com>,
        Alexandre Torgue <alexandre.torgue@...s.st.com>,
        Bartosz Golaszewski <brgl@...ev.pl>, <linux-gpio@...r.kernel.org>,
        <devicetree@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <linux-stm32@...md-mailman.stormreply.com>,
        <linux-arm-kernel@...ts.infradead.org>,
        Christophe Roullier
	<christophe.roullier@...s.st.com>,
        Fabien Dessenne
	<fabien.dessenne@...s.st.com>,
        Valentin Caron <valentin.caron@...s.st.com>
Subject: Re: [PATCH v2 2/9] dt-bindings: pincfg-node: Add property
 "skew-delay-direction"

On Tue, 2025-09-30 at 14:23 +0200, Linus Walleij wrote:
> Hi Antonio,
> 
> thanks for your patch!
> 
> And sorry that it takes so long for me to review it! :(

Hi Linus,

no problem, thanks for your review!

> 
> On Fri, Sep 5, 2025 at 3:56 PM Antonio Borneo
> <antonio.borneo@...s.st.com> wrote:
> 
> > Add the property "skew-delay-direction" to specify on which pin's
> > direction (either input, output or both) the value of the generic
> > property 'skew-delay' applies.
> > For backward compatibility, 'skew-delay' applies on both input and
> > output directions when the new property is not present or has
> > value '0'.
> > 
> > Signed-off-by: Antonio Borneo <antonio.borneo@...s.st.com>
> (...)
> > +  skew-delay-direction:
> > +    $ref: /schemas/types.yaml#/definitions/uint32
> > +    enum: [0, 1, 2]
> > +    default: 0
> > +    description: |
> > +      0: skew-delay applies to both input and output directions
> > +      1: skew-delay applies only to the output direction
> > +      2: skew-delay applies only to the input direction
> 
> Unfortunately I don't think this will work, because skew-delay
> has a value, and with this scheme we can only specify that we
> want this value to affect both in/out, only in or only out.
> 
> What happens when someone want to configure different
> skew delay for input and output?

It makes sense!

I will address it in V3.

> I think it is better to add:
> 
> skew-delay-input = <u32>;
> skew-delay-output = <u32>;
> 
> So the drivers that need this explicitly specified will need
> to just define one of these instead.
> 
> If you want to be very determined, make the schema
> not accept skew-delay if either skew-delay-input
> or skew-delay-output is specified.

Sure, I will add the proper test.

Regards,
Antonio