Why not call up_udelay or up_mdelay? The arch/soc should provide a best implementation for you.
I was wondering that too.Also, as a side note, it is very important to calibrate the delay loop using in those functions. If the delay loop is properly calibrated, these can be very accurate (but I suspect most people no longer calibrate the delay loop).
There is an app at apps/examples/calib_udelay that can be used to do that.
