On Thu, Sep 14, 2017 at 2:19 PM, Andrew Lunn <andrew@xxxxxxx> wrote: >> > Is the MDIO controller "allwinner,sun8i-h3-emac" or "snps,dwmac-mdio"? >> > If the latter, then I think the node is fine, but then the mux should be >> > a child node of it. IOW, the child of an MDIO controller should either >> > be a mux node or slave devices. > > Hi Rob > > Up until now, children of an MDIO bus have been MDIO devices. Those > MDIO devices are either Ethernet PHYs, Ethernet Switches, or the > oddball devices that Broadcom iProc has, like generic PHYs. > > We have never had MDIO-muxes as MDIO children. A Mux is not an MDIO > device, and does not have the properties of an MDIO device. It is not > addressable on the MDIO bus. The current MUXes are addressed via GPIOs > or MMIO. The DT parent/child relationship defines the bus topology. We describe MDIO buses in that way and if a mux is sitting between the controller and the devices, then the DT hierarchy should reflect that. Now sometimes we have 2 options for what interface has the parent/child relationship (e.g. an I2C controlled USB hub chip), but in this case we don't. > There other similar cases. i2c-mux-gpio is not a child of an i2c bus, > nor i2c-mux-reg or gpio-mux. nxp,pca9548 is however a child of the i2c > bus, because it is an i2c device itself... Some are i2c controlled mux devices, but some can be GPIO controlled. > > If the MDIO mux was an MDIO device, i would agree with you. Bit it is > not, so lets not make it a child. > > Andrew > > _______________________________________________ > linux-arm-kernel mailing list > linux-arm-kernel@xxxxxxxxxxxxxxxxxxx > http://lists.infradead.org/mailman/listinfo/linux-arm-kernel -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
