I notice the imx6 (in my case the imx6qp) has multiple mii mac to phy interface options. I tried searching the kernel device tree options to see if there are settings specifically for the IC used on the sabresd board (Qualcomm AR8031) but there aren't. There are some pin mux settings and FEC settings that all seem pretty generic. The AR8031 is RGMII which allows for gigbit ethernet, but I don't need that and am wondering, in order to reduce pcb complexity and device size, if I use a simpler mac-to-phy IC like the Microchip LAN8742 which uses RMII, do I simply swap it out and connect only the appropriate pins (it appears the RGMII has dedicated 4-bit tx and rx pins, among other dedicated pins) to the enet mac interface, leaving the RGMII pins disconnected? I can't find anything in the documentation how to modify the linux kernel settings or the device tree or u-boot (via yocto of course, though I would use menuconfig if i need to modify either) in order to specify that i'm using rmii instead of rgmii.
as a side question, is there an even simpler interface for 100Mbps? For example, Microchip has the LAN9514 which is a USB hub IC with intergrated ethernet mac and phy. Of course that would only work if I figure out how to configure linux to recognize the ethernet interface.
