Toast cumin, fennel and mustard seeds in a dry cast iron skillet until they
begin to smoke, about 5 minutes
Combine seeds and remaining ingredients(except pork) in a spice grinder,
mortar and pestle or food processor. Grind to a powder.
Coat Pork with spice mixture. Refrigerate at least 30 minutes.
Prepare charcoal grill. When coals have turned amber and become ashy on the outside, push them to one side. Remove hardwood chips from water and pile them on top of coals. Position grate on grill and heat until chips begin to smoke, about 10 minutes.
Sear tenderloin over coals on each side for 3 minutes, then move to the side
of the grill with no coals, cover grill and cook 5-10 minutes.