udelay vs usleep_range

Hi all, I ran the checkpatch script over drivers/staging/nvec.c and got the following warning udelay(33); CHECK: usleep_range is preferred over udelay; see Documentation/timers/timers-howto.txt I checked out the timers-howto.txt and for usleep_range, one has to specify the lower and upper limit for the timer. How does one decide what the upper limit will be if one is to change the function from udelay to usleep_range? Thanks! Gargi