linux-kernel - Re: [PATCH net-next v4 14/17] dt-bindings: net: pse-pd: Add bindings for PD692x0 PSE controller

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Date: Tue, 20 Feb 2024 11:40:29 +0100
From: Köry Maincent <kory.maincent@...tlin.com>
To: Oleksij Rempel <o.rempel@...gutronix.de>
Cc: "David S. Miller" <davem@...emloft.net>, Eric Dumazet
 <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>, Paolo Abeni
 <pabeni@...hat.com>, Jonathan Corbet <corbet@....net>, Luis Chamberlain
 <mcgrof@...nel.org>, Russ Weight <russ.weight@...ux.dev>, Greg
 Kroah-Hartman <gregkh@...uxfoundation.org>, "Rafael J. Wysocki"
 <rafael@...nel.org>, Rob Herring <robh+dt@...nel.org>, Krzysztof Kozlowski
 <krzysztof.kozlowski+dt@...aro.org>, Conor Dooley <conor+dt@...nel.org>,
 Mark Brown <broonie@...nel.org>, Frank Rowand <frowand.list@...il.com>,
 Andrew Lunn <andrew@...n.ch>, Heiner Kallweit <hkallweit1@...il.com>,
 Russell King <linux@...linux.org.uk>, Thomas Petazzoni
 <thomas.petazzoni@...tlin.com>, netdev@...r.kernel.org,
 linux-kernel@...r.kernel.org, linux-doc@...r.kernel.org,
 devicetree@...r.kernel.org, Dent Project <dentproject@...uxfoundation.org>
Subject: Re: [PATCH net-next v4 14/17] dt-bindings: net: pse-pd: Add
 bindings for PD692x0 PSE controller

On Sat, 17 Feb 2024 13:14:29 +0100
Oleksij Rempel <o.rempel@...gutronix.de> wrote:

> On Thu, Feb 15, 2024 at 05:02:55PM +0100, Kory Maincent wrote:
> > Add the PD692x0 I2C Power Sourcing Equipment controller device tree
> > bindings documentation.
> > 
> > This patch is sponsored by Dent Project <dentproject@...uxfoundation.org>.
> > 
> > Signed-off-by: Kory Maincent <kory.maincent@...tlin.com>
> > ---  
> ...
> > +        pse_pis {
> > +          #address-cells = <1>;
> > +          #size-cells = <0>;
> > +
> > +          pse_pi0: pse_pi@0 {
> > +            reg = <0>;
> > +            #pse-cells = <0>;
> > +            pairset-names = "alternative-a", "alternative-b";
> > +            pairsets = <&phys0>, <&phys1>;
> > +          };
> > +          pse_pi1: pse_pi@1 {
> > +            reg = <1>;
> > +            #pse-cells = <0>;
> > +            pairset-names = "alternative-a";
> > +            pairsets = <&phys2>;  
> 
> According to latest discussions, PSE PI nodes will need some
> additional, board specific, information:
> - this controller do not implements polarity switching, we need to know
>   what polarity is implemented on this board. The 802.3 spec provide not
>   really consistent names for polarity configurations:
>   - Alternative A MDI-X
>   - Alternative A MDI
>   - Alternative B X
>   - Alternative B S
>   The board may implement one of polarity configurations per alternative
>   or have additional helpers to switch them without using PSE
>   controller.
>   Even if specification explicitly say:
>   "The PD shall be implemented to be insensitive to the polarity of the power
>    supply and shall be able to operate per the PD Mode A column and the PD
>    Mode B column in Table 33–13"
>   it is possible to find reports like this:
>   https://community.ui.com/questions/M5-cant-take-reversed-power-polarity-/d834d9a8-579d-4f08-80b1-623806cc5070
> 
>   Probably this kind of property is a good fit:
>   polarity-supported = "MDI-X", "MDI", "X", "S";

This property should be on the PD side.
Isn't it better to name it "polarity-provided" for each PSE PIs binding? What
do you think?
We agreed that it is mainly for ethtool to show the polarity of a PI, right?

Regards,
-- 
Köry Maincent, Bootlin
Embedded Linux and kernel engineering
https://bootlin.com