I'm planning an electrical upgrade to give my vastly underpowered garage some more future capabilities. I'm going to be feeding a 75 or 100amp subpanel from a 200amp main service panel. About 125' worth of cable (on the entire other side of the house, go figure). About 40' worth of the run to the garage (attached BTW), will be going though IMC buried in my backyard. The rest will be running along in some more IMC connected to the side of the concrete foundation. The subpanel will contain only GFCI protected branches, per code. The main question is do I need to have big GFCI's on the main service panel circuit that feeds the sub panel. I know why it's needed on branch circuits, but is it required on a feed to a sub panel? Thanks!