Accessing 64bit address

I am using ppc440 based board. Board is having 64bit memory controll register. To access the memory controll region i have added one tlb entry i.e tlbentry( 0xc70e0000, SZ_64K, 0xc70e0000, 0xf,??AC_R|AC_X|AC_W|SA_I) ?
What is the way to access the 64bit register in u-boot?