OMAP-L138 GPIO Interrupt

I am using Code Composer Studio/C Language to program OMAP-L138, trying to generate an GPIO Interrupt at a frequency ~1MHz. I have looked over the sample C libraries functions, as well as the L138 Manual, but I found them confusing and still don't know how to do so. Are there any sample codes I can look at? More particularly, I don't know exactly how to set the frequency of interrupt and how to write to/read from a register in L138.

Thanks