On Thu, 20 Jan 2022 09:49:14 +0100 Marc Kleine-Budde <mkl@xxxxxxxxxxxxxx> wrote: > On 19.01.2022 14:11:17, Marek Behún wrote: > > Common PHYs and network PCSes often have the possibility to specify > > peak-to-peak voltage on the differential pair - the default voltage > > sometimes needs to be changed for a particular board. > > > > Add properties `tx-p2p-microvolt` and `tx-p2p-microvolt-names` for this > > purpose. The second property is needed to specify the mode for the > > corresponding voltage in the `tx-p2p-microvolt` property, if the voltage > > is to be used only for speficic mode. More voltage-mode pairs can be > > specified. > > > > Example usage with only one voltage (it will be used for all supported > > PHY modes, the `tx-p2p-microvolt-names` property is not needed in this > > case): > > > > tx-p2p-microvolt = <915000>; > > > > Example usage with voltages for multiple modes: > > > > tx-p2p-microvolt = <915000>, <1100000>, <1200000>; > > tx-p2p-microvolt-names = "2500base-x", "usb", "pcie"; > > > > Add these properties into a separate file phy/transmit-amplitude.yaml, > > which should be referenced by any binding that uses it. > > If I understand your use-case correctly, you need different voltage p2p > levels in the connection between the Ethernet MAC and the Ethernet > switch or Ethernet-PHY? This is a SerDes differential pair amplitude. So yes to your question, if the MII interface uses differential pair, like sgmii, 10gbase-r, ... > Some of the two wire Ethernet standards (10base-T1S, 10base-T1L, > 100base-T1, 1000base-T1) defines several p2p voltage levels on the wire, > i.e. between the PHYs. Alexandru has posed a series where you can > specify the between-PHY voltage levels: > > | https://lore.kernel.org/all/20211210110509.20970-8-alexandru.tachici@xxxxxxxxxx/ Copper ethernet is something different, so no conflict > Can we make clear that your binding specifies the voltage level on the > MII interface, in contrast Alexandru's binding? The binding explicitly says "common PHY", not ethernet PHY. I don't thing there will be any confusion. It can also be specified for USB3+ differential pairs, or PCIe differential pairs, or DisplayPort differential pairs... Marek
