On 04/11/2017 04:23 PM, Florian Fainelli wrote: > On 04/11/2017 04:14 PM, Andrew Lunn wrote: >>> To give some more background and rational for this change. >>> >>> On a platform where we have a parent MDIO bus, backed by the >>> mdio-bcm-unimac.c driver, we also register a slave MII bus (through >>> net/dsa/dsa2.c) which is parented to this UniMAC MDIO bus through an >>> assignment of of_node. This slave MII bus is created in order to >>> intercept reads/writes to problematic addresses (e.g: that clashes with >>> another piece of hardware). >>> >>> This means that the slave DSA MII bus inherits all child nodes from the >>> originating master MII bus. This also means that when the slave MII bus >>> is probed via of_mdiobus_register(), we probe the same devices twice: >>> once through the master, another time through the slave. >> >> Ah, O.K. This makes more sense. On the hardware i have, we get three >> deep in MDIO busses. We have the FEC mdio bus. On top of that we have >> a gpio-mux-mdio, and on top of that we have the mv88e6xxx mdio >> bus. And i've never seen issues. >> >> So your real problem here is you have two mdio busses using the same >> device tree properties. I would actually say that is just plain >> broken. > > From a Device Tree/HW representation perspective, we do have the > external BCM53125 switch physically attached to the 7445/7278 > SWITCH_MDIO bus (backed by mdio-bcm-unimac) so in that regard the > representation is correct. There is also an integrated Gigabit PHY > (bcm7xxx) which is attached to that bus. > > From a SW perspective though, we want to talk to the integrated Gigabit > PHY using mdio-bcm-unimac but talk to the external BCM53125 switch using > the slave MII bus created by the bcm_sf2 driver in order to create an > isolation. We need to inherit some of the parent (mdio-bcm-unimac) child > DT nodes (such as the BCM53125), but not the GPHY. The easiest solution > I found was to use this patch. > > Using mdiobus_register() instead of of_mdiobus_register() was > considered, but then, the child BCM53125 has no more "visbility" into > the OF world at all, and it matters, because this switch is also driven > via a DSA switch driver and its Ethernet data-path is connected to one > port of the bcm_sf2 switch.. > > Thankfully the HW bug was fixed eventually ;) In fact, all I need is to flag the internal Gigabit PHY for the slave MII bus node with something that makes it appear as "disabled" which I can presumably do with of_update_property() and putting a status = "disabled" property in there. Let me do something like that and see how big of a hack this becomes. -- Florian -- 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
