GM ASCM: don't apply gas when stopping (#28699)

* don't apply gas when stopping

* simpler?

* todo

* fixme

selfdrive/car/gm/carcontroller.py

@@ -85,6 +85,7 @@ class CarController:
     if self.CP.openpilotLongitudinalControl:
       # Gas/regen, brakes, and UI commands - all at 25Hz
       if self.frame % 4 == 0:
+        stopping = actuators.longControlState == LongCtrlState.stopping
         if not CC.longActive:
           # ASCM sends max regen when not enabled
           self.apply_gas = self.params.INACTIVE_REGEN
@@ -92,6 +93,10 @@ class CarController:
         else:
           self.apply_gas = int(round(interp(actuators.accel, self.params.GAS_LOOKUP_BP, self.params.GAS_LOOKUP_V)))
           self.apply_brake = int(round(interp(actuators.accel, self.params.BRAKE_LOOKUP_BP, self.params.BRAKE_LOOKUP_V)))
+          # Don't allow any gas above inactive regen while stopping
+          # FIXME: brakes aren't applied immediately when enabling at a stop
+          if stopping:
+            self.apply_gas = self.params.INACTIVE_REGEN
 
         idx = (self.frame // 4) % 4
 
@@ -101,7 +106,7 @@ class CarController:
         # GM Camera exceptions
         # TODO: can we always check the longControlState?
         if self.CP.networkLocation == NetworkLocation.fwdCamera:
-          at_full_stop = at_full_stop and actuators.longControlState == LongCtrlState.stopping
+          at_full_stop = at_full_stop and stopping
           friction_brake_bus = CanBus.POWERTRAIN
 
         # GasRegenCmdActive needs to be 1 to avoid cruise faults. It describes the ACC state, not actuation