linux-kernel - Re: [PATCH 2/2] dt-bindings: phy: lan966x: Add optional microchip,sx-tx/rx-inverted

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Message-ID: <20251112-junkman-buckle-31fcfcbfa3c5@spud>
Date: Wed, 12 Nov 2025 18:32:01 +0000
From: Conor Dooley <conor@...nel.org>
To: Horatiu Vultur <horatiu.vultur@...rochip.com>
Cc: Krzysztof Kozlowski <krzk@...nel.org>, vkoul@...nel.org,
	kishon@...nel.org, robh@...nel.org, krzk+dt@...nel.org,
	conor+dt@...nel.org, linux-phy@...ts.infradead.org,
	devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] dt-bindings: phy: lan966x: Add optional
 microchip,sx-tx/rx-inverted

On Wed, Nov 12, 2025 at 09:02:35AM +0100, Horatiu Vultur wrote:
> The 11/11/2025 17:39, Conor Dooley wrote:
> > On Tue, Nov 11, 2025 at 11:06:02AM +0100, Krzysztof Kozlowski wrote:
> > > On 11/11/2025 10:58, Horatiu Vultur wrote:
> > > > The 11/10/2025 18:43, Conor Dooley wrote:
> > > > 
> > > > Hi Conor,
> > > > 
> > > >> On Mon, Nov 10, 2025 at 12:05:36PM +0100, Horatiu Vultur wrote:
> > > >>> This allows to invert the N and P signals of the RX and TX Serdes
> > > >>> signals. This option allows the board designer to trace their signals
> > > >>> easier on the boards.
> > > >>
> > > >> Why can't this just be done in software, debugfs or something like that?
> > > >> Maybe it's just your description is poor, but sounds like the intention
> > > >> here is to just switch things around for debug purposes.
> > > > 
> > > > I don't think it should be done through debugfs. As this describes the
> > > > board layout and I don't think someone will want to change it at
> > > > runtime to see how things behave. So maybe the description is poor.
> > > 
> > > You said it is purely for hardware designer to trace signals, so sorry,
> > > but that's not DTs purpose.
> > 
> > If it is not purely some sort of debug helper, then please explain
> > better in your commit message.
> 
> Yes, I will do so because I don't see how this is a debug helper
> functionality. I see it as changing the polarity of some pins and there

The word "trace" here might be problematic? Maybe you meant something
like "lay out", but all of the use of the word tracing in electronics
that I have ever seen refers to troubleshooting - be that physically
following signals to see if there's degradation or things like the
trace framework in linux.

> are few examples in the devicetree bindings where pins change the
> polarity. Why I see it as changing the polarity is because the
> N(negative) will become P(positive) and the P(positive) will become the
> N(negative), so we just invert the signals.

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