Hi Andrew, Russell Sorry for the delay with response. I had to refresh my understanding of the series since it was created sometime ago and I already managed to forget some of its aspects (particularly regarding the MDIO-bus PHY-mask semantics). On Tue, Dec 05, 2023 at 02:50:58PM +0000, Russell King (Oracle) wrote: > On Tue, Dec 05, 2023 at 02:52:24PM +0100, Andrew Lunn wrote: > > On Tue, Dec 05, 2023 at 02:31:41PM +0300, Serge Semin wrote: > > > On Tue, Dec 05, 2023 at 10:49:47AM +0000, Russell King (Oracle) wrote: > > > > On Tue, Dec 05, 2023 at 01:35:27PM +0300, Serge Semin wrote: > > > > > If the DW XPCS MDIO devices are either left unmasked for being auto-probed > > > > > or explicitly registered in the MDIO subsystem by means of the > > > > > mdiobus_register_board_info() method there is no point in creating the > > > > > dummy MDIO device instance in order to get the DW XPCS handler since the > > > > > MDIO core subsystem will create the device during the MDIO bus > > > > > registration procedure. > > > > > > > > > > > Please reword this overly long sentence. > > > > > > Ok. > > > > > > > > > > > If they're left unmasked, what prevents them being created as PHY > > > > devices? > > > > > > Not sure I fully get what you meant. If they are left unmasked the > > > MDIO-device descriptor will be created by the MDIO subsystem anyway. > > > What the point in creating another one? > > > > Saying what Russell said, in a different way: > > > > /* > > * Return true if the child node is for a phy. It must either: > > * o Compatible string of "ethernet-phy-idX.X" > > * o Compatible string of "ethernet-phy-ieee802.3-c45" > > * o Compatible string of "ethernet-phy-ieee802.3-c22" > > * o In the white list above (and issue a warning) > > * o No compatibility string > > * > > * A device which is not a phy is expected to have a compatible string > > * indicating what sort of device it is. > > */ > > bool of_mdiobus_child_is_phy(struct device_node *child) > > > > So when walking the bus, if a node is found which fits these criteria, > > its assumed to be a PHY. > > > > Anything on the MDIO bus which is not a PHY needs to use a compatible. > > Right. I'd actually forgotten about the firmware-based walking, and > was thinking more of the non-firmware bus scanning as the commit > message was talking about being _unmasked_ and the only mask we have > is bus->phy_mask. Back then when I was working on the series and up until last week I had thought that having a device unmasked in mii_bus->phy_mask was a correct way to do for _any_ device including our DW XPCS (which BTW looks like a normal C45 PHY and if synthesized with a PMA attached could be passed to be handled by the PHY subsystem). Can't remember why exactly I came to that thought, but likely it was due to finding out examples of having mii_bus->phy_mask uninitialized in some of the PCS use-cases, like in drivers/net/dsa/ocelot/felix_vsc9959.c (but in case of DW XPCS the mask is always set indeed). Anyway obviously I was wrong and PHY-device is supposed to be created only if a device is actual PHY and handled by the PHY subsystem drivers. So the correct ways to create PHY MDIO-devices are: 1. Call mdiobus_register() with PHY-addresses unmasked 2. Call of_mdiobus_register() for a DT-node with sub-nodes for which of_mdiobus_child_is_phy() returns true. and the correct ways to create non-PHY MDIO-devices are: 1. Call mdiobus_register() with non-PHY-addresses masked and have those non-PHY device registered by mdiobus_register_board_info() beforehand. 2. Call of_mdiobus_register() with DT sub-nodes having specific compatible string (based on the of_mdiobus_child_is_phy() semantics). Only in case of having a non-PHY device registered it's allowed to use it in in non-PHY MDIO driver, like PCS, etc. Right? Please correct me if I am wrong or miss something. > > It seems to me that this is yet another case of a really confusing > commit message making review harder than it needs to be. >From the perspective described above the patch log is indeed partly wrong. Sorry about that. I shouldn't have mentioned the mask at all but instead just listed two use-cases of creating the non-PHY MDIO-devices. I'll fix that in v2. -Serge(y) > > -- > RMK's Patch system: https://www.armlinux.org.uk/developer/patches/ > FTTP is here! 80Mbps down 10Mbps up. Decent connectivity at last! >
