linux-kernel - Re: [PATCH 0/2] phy: microchip: lan966x: Allow to invert N and P signals

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Message-ID: <20251111095016.42byrgj33lp4bouo@DEN-DL-M31836.microchip.com>
Date: Tue, 11 Nov 2025 10:50:16 +0100
From: Horatiu Vultur <horatiu.vultur@...rochip.com>
To: Vladimir Oltean <vladimir.oltean@....com>
CC: <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>, Daniel Golle
	<daniel@...rotopia.org>
Subject: Re: [PATCH 0/2] phy: microchip: lan966x: Allow to invert N and P
 signals

The 11/10/2025 13:42, Vladimir Oltean wrote:
> 
> Hi Horatiu,

Hi Vladimir,

> 
> On Mon, Nov 10, 2025 at 12:05:34PM +0100, Horatiu Vultur wrote:
> > Allow to invert the N and P signals of the Serdes for both RX and TX. This
> > is used to allow the board designer to trace more easily the signals.
> >
> > Horatiu Vultur (2):
> >   phy: microchip: lan966x: Add support for inverting the rx/tx lanes
> >   dt-bindings: phy: lan966x: Add optional microchip,sx-tx/rx-inverted
> >
> >  .../phy/microchip,lan966x-serdes.yaml         | 24 +++++++++++++++++++
> >  drivers/phy/microchip/lan966x_serdes.c        | 23 ++++++++++++++++++
> >  2 files changed, 47 insertions(+)
> >
> > --
> > 2.34.1
> 
> For context, I am trying to describe the lane polarity property
> generically, and I've already blocked Daniel Golle's attempt to
> introduce the similar in intent "maxlinear,rx-inverted" and
> "maxlinear,tx-inverted".
> https://lore.kernel.org/netdev/20251028000959.3kiac5kwo5pcl4ft@skbuf/
> 
> I am trying to find out all there is to know in order about this
> feature, and I just noticed your patch, so I have to ask some questions
> in order to understand, had a generic property existed, whether you
> would have used it.

Yes, if there was something generic that would fit, I would like to use it.

> 
> So I see that you don't have OF nodes for individual SerDes lanes, so
> this makes your device tree structure incompatible with simple
> "tx-polarity"/"rx-polarity" properties. Are those something you're not
> willing to introduce? 

Do you propose to change the device tree to describe each SerDes lane
individualy?
Apparently in the lan966x_serdes we have also the port muxing which I am
not sure it should be there as it should be in the switch. I have done
it this way because I have use the phy-ocelot-serdes.c as an example.
If I change the device tree to describe each lane, then first I need to
take the port muxing which is fine for me. But there might be a problem,
if someone will use a newer kernel with an older device tree, it would
break the things?

> What about other stuff that's in
> Documentation/devicetree/bindings/phy/transmit-amplitude.yaml?
> You also won't be able to make use of the existing device tree
> properties if you don't have OF node containers for each lane.

To be honest, I haven't look at transmit-amplitude.yaml yet.

-- 
/Horatiu