ioremap and page table

Hello all, I'm almost sure but want to check if my understanding is correct. To use a memory mapped IO, we use functions like request_mem_region and ioremap, iounmap functions. I guess when we call ioremap function, the kernel sets up page table for the region so that the region becomes non-cacheable, and I don't also have to worry about reordering problem. Is my understanding correct? Thanks! Chan Kim