On Fri, 16 Feb 2024 08:47:14 +0100 Oleksij Rempel <o.rempel@xxxxxxxxxxxxxx> wrote: > > > > So, either somebody needs to understand 1000BaseT and can say the > > proposed binding works, or we explicitly document the binding is > > limited to 10BaseT and 100BaseT. > > I asked the internet and found the answer: Some PSE/PD implementations > are not compatible with 1000BaseT. > > See Figure 33–4—10BASE-T/100BASE-TX Endpoint PSE location overview. > Alternative B show a variant where power is injected directly to pairs > without using magnetics as it is done for Alternative A (phantom > delivery - over magnetics). > > So, we have following variants of 2 pairs PoE: > +---------+---------------+-------------------+---------------------+--------------------+ > | Variant | Alternative | Polarity | Power Feeding Type | > Compatibility with | | | (a/b) | (Direct/Reverse) | > (Direct/Phantom) | 1000BaseT | > +=========+===============+===================+=====================+====================+ > | 1 | a | Direct | Phantom | Yes > | > +---------+---------------+-------------------+---------------------+--------------------+ > | 2 | a | Reverse | Phantom | Yes > | > +---------+---------------+-------------------+---------------------+--------------------+ > | 3 | b | Direct | Phantom | Yes > | > +---------+---------------+-------------------+---------------------+--------------------+ > | 4 | b | Reverse | Phantom | Yes > | > +---------+---------------+-------------------+---------------------+--------------------+ > | 5 | b | Direct | Direct | No > | > +---------+---------------+-------------------+---------------------+--------------------+ > | 6 | b | Reverse | Direct | No > | > +---------+---------------+-------------------+---------------------+--------------------+ Maybe we could remove the polarity column on this table as it does not bring more information. It is also already explained on the PI pinout alternatives table. Also we should document that a 4pairs PSE supporting only 10/100BaseT (which mean no magnetics on pinout AlternativeB) may not be compatible with a 4pairs 1GBaseT PD. > For this case, it will be good if systems knows supported modes, so user > can get this information directly. For example with ethtool Yes. Regards, -- Köry Maincent, Bootlin Embedded Linux and kernel engineering https://bootlin.com
