allow multiple current helpers per rail

klippy/extras/homing.py

@@ -259,9 +259,10 @@ def _set_current_homing(self, homing_axes):
             affected_rails = affected_rails | set(partial_rails)
 
         for rail in affected_rails:
-            ch = rail.get_tmc_current_helper()
-            if ch is not None and ch.needs_home_current_change():
-                ch.set_current_for_homing(print_time)
+            chs = rail.get_tmc_current_helpers()
+            for ch in chs:
+                if ch is not None and ch.needs_home_current_change():
+                    ch.set_current_for_homing(print_time)
                 self.toolhead.dwell(ch.current_change_dwell_time)
 
     def _set_current_post_homing(self, homing_axes):

klippy/stepper.py

@@ -400,10 +400,12 @@ def __init__(
         self.endstop_map = {}
         self.add_extra_stepper(config)
         mcu_stepper = self.steppers[0]
+        self._tmc_current_helpers = [
+            s.get_tmc_current_helper() for s in self.steppers
+        ]
         self.get_name = mcu_stepper.get_name
         self.get_commanded_position = mcu_stepper.get_commanded_position
         self.calc_position_from_coord = mcu_stepper.calc_position_from_coord
-        self.get_tmc_current_helper = mcu_stepper.get_tmc_current_helper
         # Primary endstop position
         mcu_endstop = self.endstops[0][0]
         if hasattr(mcu_endstop, "get_position_endstop"):
@@ -482,6 +484,9 @@ def __init__(
                 % (config.get_name(),)
             )
 
+    def get_tmc_current_helpers(self):
+        return self._tmc_current_helpers
+
     def get_range(self):
         return self.position_min, self.position_max