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@xxxxxxxxxxxxxxxxxxx>.
>
> Signed-off-by: Kory Maincent <kory.maincent@xxxxxxxxxxx>
> ---
...
> + 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";
- Except of polarity, we have alternative-b variant with direct or
phantom feeding (No idea if it is proper description). Theoretically, this
difference would affect electrical rating specifications.
For example direct path for alternate-b (10/100Mbit only), would have
higher rating as the path over coils/magnetics. Practically, vendors do not
make different ratings for this paths, so no need to care about it for now
until someone will be able to provide good reason.
Here is example of RJ45 connector with integrated magnetics with PoE support
where alternative-a feed over magnetics and alternative-b is feed directly:
https://www.te.com/commerce/DocumentDelivery/DDEController?Action=srchrtrv&DocNm=5-2337992-4&DocType=Customer+Drawing&DocLang=English&PartCntxt=5-2337992-4&DocFormat=pdf
(the last topic is more an answer to my self and for archive :))
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