mmap slower than ioremap

Question

I am developing for an ARM device running Linux 2.6.37. I am trying to toggle an IO pin as fast as possible. I made a little kernel module and a user space application. I tried

Answer 1

This is because ioremap_nocache() still enables the CPU write buffer in your VM mapping whereas pgprot_noncached() disables both bufferability and cacheability.

Apples to apples comparison would be to use ioremap_strongly_ordered() instead.