On 2/5/19 1:28 AM, Joe Hershberger wrote: > On Fri, Jan 25, 2019 at 7:12 AM Vladimir Oltean <vladimir.olt...@nxp.com> > wrote: >> >> On 25.01.2019 12:12, Carlo Caione wrote: >>> On 24/01/2019 20:48, Vladimir Oltean wrote: >>>> On 1/24/19 10:19 PM, Carlo Caione wrote: >>>>> On 24/01/2019 20:12, Vladimir Oltean wrote: >>>>>> >>>> >>>> I can't completely answer that, TBH I don't even know who is supposed to >>>> make that distinction. >>> >>> In the kernel that distinction is made by the driver itself, hence my >>> question. See [0]. >>> >>>> For Freescale parts that is a call for the MDIO bus driver to make, for >>>> good or bad (see drivers/net/fm/memac_phy.c where dev_addr is compared >>>> to MDIO_DEVAD_NONE). >>> >>>> And in your patch, phy_write_mmd is only a wrapper over bus->write in >>>> the end, with some more logic to handle C22 indirection. >>>> So my question of unifying "mdio rmmd" with "mdio read" translates into: >>> >>>> Does it make sense to also handle the check with MDIO_DEVAD_NONE in >>>> phy_write_mmd, instead of jumping straight ahead to perform indirection? >>> >>> Honestly I'm not quite sure of all the possible implications here IMO >>> the safest bet here is just to follow what's done by the kernel. Maybe >>> Joe can step in about this. >>> >>> In general we have 3 possible cases: >>> >>> 1) your driver is doing something non-standard when accessing the MMDs >>> and we deal with that using the PHY driver hooks >>> 2) your PHY is C22 and you have to use the indirect method >>> 3) your PHY is C45 and you can use the direct register reading (mangling >>> a bit the address apparently) >>> >>> The kernel is dealing with all the cases, U-Boot is only dealing with >>> C22 PHYs (cases 1 and 2) because AFAICT there isn't yet a generic way to >>> detect if the PHY is C22 or C45. >>> >>> I'm not sure if the indirect method works also for C45 PHYs. >>> >>>> The goal would then be to just call phy_write_mmd from cmd/mdio.c >>>> regardless of the target PHY's clause. >>> >>> Again I wrote that patch only assuming that we were going to deal with >>> C22 PHYs. At this point I wonder if the C22 indirect method works also >>> for C45 PHYs. If that's the case than the phy_write_mmd should already >>> work regardless of the target PHY clause. >>> >>> Cheers. >>> >>> [0] >>> https://emea01.safelinks.protection.outlook.com/?url=https%3A%2F%2Felixir.bootlin.com%2Flinux%2Flatest%2Fsource%2Fdrivers%2Fnet%2Fphy%2Fphy-core.c%23L296&data=02%7C01%7Cvladimir.oltean%40nxp.com%7C826fd741578446f6f36908d68af87b27%7C686ea1d3bc2b4c6fa92cd99c5c301635%7C0%7C0%7C636849197162094704&sdata=r9AlGZbzGtLC2z7u2HgKKZt17Cl1OcHncjeY00xlVWE%3D&reserved=0 >>> >> >> I'm not suggesting to use C22 indirection if the PHY already supports >> native C45 addressing. Even if that worked, it would be a pointless >> exercise in all but a few cases (like the MDIO controller does not >> support C22, but the PHY does support both C22 and C45). >> I was just wondering out loud whether the introduction of the "mdio >> rmmd" command is justified or not. I now understand that using e.g. >> "mdio read 1.3" will confuse the command for clause 45 PHY's because it >> won't know whether it should access the PHY via native C45 or via >> indirect C22 (obviously it shouldn't do the latter). So in lack of a >> clear distinction mechanism, I now think that a new command truly is >> necessary for performing indirect C45 access on C22. >> What I am still not convinced of, however, is whether those commands >> should be called "rmmd" and "wmmd". It is not immediately obvious from >> the command description that this is what they are for, and a user may >> attempt to use them for C45 PHY's as well, which will probably not yield >> the intended result. > > I agree. The MMD in the register name is simply "MDIO Manageable > Devices"... i.e. the phys. > > I think the commands should be "iread" and "iwrite" to denote the > indirect access in use. >
Which brings me to my next point. If we can't properly make the distinction between an indirect C22 MMD access and a proper C45 MMD access, and hence not keeping proper API compatibility with Linux kernel, aren't we better off going back to square 1 and using phy_read_mmd_indirect and phy_write_mmd_indirect? -Vladimir _______________________________________________ U-Boot mailing list U-Boot@lists.denx.de https://lists.denx.de/listinfo/u-boot
