> > I'm not saying whether this is good or bad, I'm just worried about > > mixing quantities having different measurement units into the same > > address space. > > > > Just like in the case of an mdio-mux, there is no address space isolation > > between the parent bus and the child bus. AKA you can't have this, > > because there would be clashes: > > > > host_bus: mdio@abcd { > > ethernet-phy@2 { > > reg = <2>; > > }; > > }; > > > > child_bus: mdio@efgh { > > mdio-parent-bus = <&host_bus>; > > > > ethernet-phy@2 { > > reg = <2>; > > }; > > }; > > > > But there is a big difference. With an mdio-mux, you could statically > > detect address space clashes by inspecting the PHY addresses on the 2 > > buses. But with the lan937x child MDIO bus, in this design, you can't, > > because the "reg" values don't represent MDIO addresses, but switch port > > numbers (this is kind of important, but I don't see it mentioned in the > > dt-binding). > > In current state, the driver still require properly configured addresses > in the devicetree. So, it will be visible in the DT. This is not what i was expecting, especially from mv88e6xxx perspective. The older generation of devices had the PHYs available on the 'host bus', as well as the 'child bus', using a 1:1 address mapping. You could in theory even skip the 'child bus' and list the PHYs on the 'host bus' and phy-handle would make it work. However i see from a later comment that does not work here, you need some configuration done over SPI, which mv88e6xx does not need. > > > These are translated by lan937x_create_phy_addr_map() using > > the CASCADE_ID/VPHY_ADD pin strapping information read over SPI. > > I.e. with the same device tree, you may or may not have address space > > clashes depending on pin strapping. No way to tell. > > The PHY address to port mapping in the driver is needed to make the > internal switch interrupt controller assign interrupts to proper PHYs. You are talking about: ds->user_mii_bus->irq[phy] = irq; in ksz_irq_phy_setup. I naively expect 'phy' to be the 'reg' value in DT, and the 'dev' value which passed to mdiobus_read_nested(bus, dev, reg) ? Andrew