The initial configuration is done by the memory's sequencer block, from the IP settings, so in the simple case, you don't need to use this interface at all and you can disable it.
U-Boot could use these registers during a memory test, and the operating system could use those registers to detect ECC errors at runtime, so if that is desired, you'd connect the interface to the soft CPU's data bus.
Thanks Simon for providing the explanations.
The Memory Mode Register (MMR) interface is the Avalon based interface through which core can access debug signals and sideband operation requests in the hard memory controller.
Do you have further question about this?
I believe that the timing parameter setting is at the tRFC.
tRFC is refers to the Refresh Cycle Time where the amount of delay after a refresh command before an activate command can be accepted by the memory.