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.
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,