On Mon, Dec 07, 2015 at 11:58:33AM +0100, Neil Armstrong wrote:
> On some platforms, the macb integration does not use the USRIO
> register to configure the (R)MII port and clocks.
> When the register is not implemented and the MACB error signal
> is connected to the bus error, reading or writing to the USRIO
> register can trigger some Imprecise External Aborts on ARM platforms.
> ---

Does this make sense to even be a separate bool device tree property?

This sort of configuration is typically done by:
   1. Creating a new 'caps' bit; relevant codepaths check that bit
   2. Creating a new "compatible" string for your platform's macb
      instance
   3. Creating a new 'struct macb_config' instance for your platform,
      setting any relevant caps bits when it is selected.

  Josh