On Sun, May 24, 2020 at 11:20:01PM -0500, Jeremy Linton wrote: > Hi, > > On 5/23/20 1:44 PM, Russell King - ARM Linux admin wrote: > > On Fri, May 22, 2020 at 04:30:55PM -0500, Jeremy Linton wrote: > > > MMD's in the device list sometimes return 0 for their id. > > > When that happens lets reset the id back to 0xfffffff so > > > that we don't get a stub device created for it. > > > > > > This is a questionable commit, but i'm tossing it out > > > there along with the comment that reading the spec > > > seems to indicate that maybe there are further registers > > > that could be probed in an attempt to resolve some futher > > > "bad" phys. It sort of comes down to do we want unused phy > > > devices floating around (potentially unmatched in dt) or > > > do we want to cut them off early and let DT create them > > > directly. > > > > I'm not sure what you mean "stub device" or "unused phy devices > > floating around" - the individual MMDs are not treated as separate > > "phy devices", but as one PHY device as a whole. > > > > Well, I guess its clearer to say phy/mmd devices with a phy_id=0. Which is a > problem if we don't have DT overriding the phy_id for a given address. > Although AFAIK given a couple of the /sys/bus/mdio_bus/devices lists I've > seen, and after studying this code for a while now, I think "bogus" phy's > might be getting created*. I was far to easy, to upset the cart when I was > hacking on this set, and end up with a directory chuck full of phys. > > So this gets close to one of the questions I asked in the cover letter. This > patch and 09/11 serve to cut off possibly valid phy's which are failing to > identify themselves using the standard registers. Which per the 802.3 spec > there is a blurb about 0 in the id registers for some cases. Its not really > a critical problem for ACPI machines to have these phys around (OTOH, there > might be issues with c22 phys on c45 electrical buses that respond to c45 > reg requests but don't set the c22 regs flag, I haven't seen that yet.).
If you have a classical clause 22 PHY on a clause 45 bus, it isn't going to respond to clause 45 cycles, so it isn't going to respond to a request to read the devices-in-package register, so there is no "c22 regs" flag. > I > considered dropping this patch, and 9/11 was a last minute addition. I kept > it because I was worried all those extra "reserved" MMDs would end up with > id = 0's in there and break something. > > * In places where there isn't actually a phy, likely a large part of the > problem was clearing the c22 bit, which allowed 0xFFFFFFFF returns to slip > through the devices list. -- RMK's Patch system: https://www.armlinux.org.uk/developer/patches/ FTTC for 0.8m (est. 1762m) line in suburbia: sync at 13.1Mbps down 424kbps up
