Hi Mike,

+ *
+ * @recalc_rate	Recalculate the rate of this clock, by quering hardware
+ * 		and/or the clock's parent. It is up to the caller to insure
+ * 		that the prepare_mutex is held across this call.  Returns the
+ * 		calculated rate.  Optional, but recommended - if this op is not
+ * 		set then clock rate will be initialized to 0.

I'm still concerned, if it's NULL, why don't just retrun parent's rate if it has? 
 
Thanks
Richard