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Date: Tue, 20 Feb 2024 11:40:29 +0100
From: =?UTF-8?B?S8O2cnk=?= Maincent <kory.maincent@bootlin.com>
To: Oleksij Rempel <o.rempel@pengutronix.de>
Cc: "David S. Miller" <davem@davemloft.net>, Eric Dumazet
 <edumazet@google.com>, Jakub Kicinski <kuba@kernel.org>, Paolo Abeni
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 devicetree@vger.kernel.org, Dent Project <dentproject@linuxfoundation.org>
Subject: Re: [PATCH net-next v4 14/17] dt-bindings: net: pse-pd: Add
 bindings for PD692x0 PSE controller
Message-ID: <20240220114029.6b1a445d@kmaincent-XPS-13-7390>
In-Reply-To: <ZdCjJcPbbBGYVtuo@pengutronix.de>
References: <20240215-feature_poe-v4-0-35bb4c23266c@bootlin.com>
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	<ZdCjJcPbbBGYVtuo@pengutronix.de>
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On Sat, 17 Feb 2024 13:14:29 +0100
Oleksij Rempel <o.rempel@pengutronix.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.
> >=20
> > This patch is sponsored by Dent Project <dentproject@linuxfoundation.or=
g>.
> >=20
> > Signed-off-by: Kory Maincent <kory.maincent@bootlin.com>
> > --- =20
> ...
> > +        pse_pis {
> > +          #address-cells =3D <1>;
> > +          #size-cells =3D <0>;
> > +
> > +          pse_pi0: pse_pi@0 {
> > +            reg =3D <0>;
> > +            #pse-cells =3D <0>;
> > +            pairset-names =3D "alternative-a", "alternative-b";
> > +            pairsets =3D <&phys0>, <&phys1>;
> > +          };
> > +          pse_pi1: pse_pi@1 {
> > +            reg =3D <1>;
> > +            #pse-cells =3D <0>;
> > +            pairset-names =3D "alternative-a";
> > +            pairsets =3D <&phys2>; =20
>=20
> 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 p=
ower
>    supply and shall be able to operate per the PD Mode A column and the PD
>    Mode B column in Table 33=E2=80=9313"
>   it is possible to find reports like this:
>   https://community.ui.com/questions/M5-cant-take-reversed-power-polarity=
-/d834d9a8-579d-4f08-80b1-623806cc5070
>=20
>   Probably this kind of property is a good fit:
>   polarity-supported =3D "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? Wh=
at
do you think?
We agreed that it is mainly for ethtool to show the polarity of a PI, right?

Regards,
--=20
K=C3=B6ry Maincent, Bootlin
Embedded Linux and kernel engineering
https://bootlin.com