Hi mingming yuan,
I have confirm it for you that if you do not use the AR8031, there is no need to disable it. It more like a module, if you do not use it and it will not work. If you want to disable about phy, you can configure it in the Make Menuconfig and cancel the Mac configuration.
If you are using other phy chip, you need to check and config the phy initialization address.
Hope this can help you. Any questions contact me easily.
Have a great day
Dan
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