[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-ID: <20240215114123.128e7907@kmaincent-XPS-13-7390>
Date: Thu, 15 Feb 2024 11:41:23 +0100
From: Köry Maincent <kory.maincent@...tlin.com>
To: Oleksij Rempel <o.rempel@...gutronix.de>
Cc: Andrew Lunn <andrew@...n.ch>, Rob Herring <robh@...nel.org>, "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>, Krzysztof Kozlowski
<krzysztof.kozlowski+dt@...aro.org>, Conor Dooley <conor+dt@...nel.org>,
Mark Brown <broonie@...nel.org>, Frank Rowand <frowand.list@...il.com>,
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 v3 14/17] dt-bindings: net: pse-pd: Add
bindings for PD692x0 PSE controller
On Thu, 15 Feb 2024 09:17:48 +0100
Oleksij Rempel <o.rempel@...gutronix.de> wrote:
> On Wed, Feb 14, 2024 at 06:41:54PM +0100, Andrew Lunn wrote:
> > > Alternative A and B Overview
> > > ----------------------------
> > >
> > > - **Alternative A:** Utilizes the data-carrying pairs for power
> > > transmission in 10/100BaseT networks. The power delivery's polarity in
> > > this alternative can vary based on the MDI (Medium Dependent Interface)
> > > or MDI-X (Medium Dependent Interface Crossover) configuration.
> > >
> > > - **Alternative B:** Delivers power over the spare pairs not used for
> > > data in 10/100BaseT networks. Unlike Alternative A, Alternative B's
> > > method separates power from data lines within the cable. Though it is
> > > less influenced by data transmission direction, Alternative B includes
> > > two configurations with different polarities, known as variant X and
> > > variant S, to accommodate different network requirements and device
> > > specifications.
> >
> > Thanks for this documentation.
> >
> > It might be worth pointing out that RJ-45 supports up to 4
> > pairs. However, 10/100BaseT only makes use of two pairs for data
> > transfer from the four. 1000BaseT and above make use of all four pairs
> > for data transfer. If you don't know this, it is not so obvious what
> > 'data-carrying pairs' and 'spare pairs' mean.
>
> @Kory, can you please update it.
>
> > And what happens for 1000BaseT when all four pairs are in use?
>
> Hm.. good question. I didn't found the answer in the spec. By combining all
> puzzle parts I assume, different Alternative configurations are designed
> to handle conflict between "PSE Physical Layer classification" and PHY
> autoneg.
Oleksij how did you get the definition of Alternative A uses the "data-carrying"
pairs for power transmission and Alternative B Delivers power over the "spare
pairs"?
On my understanding of the 2022 standard the definition is:
- Alternative A is for pinout conductors 1, 2, 3 and 6
- Alternative B is for pinout conductors 4, 5, 7, 8.
Then indeed if we are in 10/100BaseT Alternative A are "data-carrying
pairs" and Alternative B are "spare pairs" but that's not the case on
1000BaseT.
You can see it in the figures in the paragraph 145.2.3.
Regards,
--
Köry Maincent, Bootlin
Embedded Linux and kernel engineering
https://bootlin.com
Powered by blists - more mailing lists