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make menuconfig can't select MDIO_I2C (ksz9567 in 4.14 would be nice too)

Question asked by Brian Hutchinson on Feb 27, 2020
Latest reply on Mar 5, 2020 by Brian Hutchinson

On 4.14 kernel for imx8mm-evk, make menuconfig will not select CONFIG_MDIO_I2C.  Looks like some kind of bug around PHYLINK and some other Kconfig options that get set based on what is picked.  No matter what I do I can't get option turned on.  Looks like SFP (SFP cage support) has something to do with selecting MDIO_I2C but I can't get that to show up in make menuconfig to select.


I'd like to use the MDIO I2C bridge (drivers/net/phy/mdio-i2c.c)

because I have a custom board based on the imx8mm-evk and it uses a Microchip switch (ksz9567) that we wired up RGMII with I2C for management (no MDIO).  The linux driver that I need didn't get upstreamed until 5.x series kernel and there doesn't appear to be an imx8 supported kernel past 4.14 so it looks like I either have to cherry pick/back port a bunch (and I mean a bunch) of dsa stuff or find another option and since the switch is strapped to basically come up and run in PHY mode I thought using the generic PHY Linux driver and MDIO to I2C bridge might be a easy workaround for now ... if I could figure out how to get my .config to build it!


So I'm pulling my hair out and striking out every which way I turn trying to find a solution to get our Ethernet going on this new custom board.


Grateful for any ideas or suggestions,