tech: Make power_grid configurable

this is the first step to allow engineers, porting technologies, more room
for routing their handmade cells.

For now, we don't allow the specification of power_grids where the lower layer
prefers to be routed vertically. This is due to the router not
connecting some pins properly in that case.

Signed-off-by: Bastian Koppelmann <kbastian@mail.uni-paderborn.de>

compiler/base/hierarchy_layout.py

@@ -39,6 +39,12 @@ class layout():
         self.visited = []    # List of modules we have already visited
         self.is_library_cell = False # Flag for library cells 
         self.gds_read()
+        try:
+            from tech import power_grid
+            self.pwr_grid_layer = power_grid[0]
+        except ImportError:
+            self.pwr_grid_layer = "m3"
+
 
     ############################################################
     # GDS layout
@@ -1169,12 +1175,12 @@ class layout():
 
     def copy_power_pins(self, inst, name):
         """
-        This will copy a power pin if it is on M3.
+        This will copy a power pin if it is on the lowest power_grid layer.
         If it is on M1, it will add a power via too.
         """
         pins = inst.get_pins(name)
         for pin in pins:
-            if pin.layer == "m3":
+            if pin.layer == self.pwr_grid_layer:
                 self.add_layout_pin(name,
                                     pin.layer,
                                     pin.ll(),
@@ -1183,14 +1189,17 @@ class layout():
             elif pin.layer == "m1":
                 self.add_power_pin(name, pin.center())
             else:
-                debug.warning("{0} pins of {1} should be on metal3 or metal1 for supply router.".format(name,inst.name))
+                debug.warning("{0} pins of {1} should be on {2} or metal1 for "\
+                              "supply router."
+                              .format(name,inst.name,self.pwr_grid_layer))
 
                 
         
     def add_power_pin(self, name, loc, size=[1, 1], vertical=False, start_layer="m1"):
         """
-        Add a single power pin from M3 down to M1 at the given center location.
-        The starting layer is specified to determine which vias are needed.
+        Add a single power pin from the lowest power_grid layer down to M1 at
+        the given center location. The starting layer is specified to determine
+        which vias are needed.
         """
         if vertical:
             direction = ("V", "V")
@@ -1198,18 +1207,18 @@ class layout():
             direction = ("H", "H")
             
         via = self.add_via_stack_center(from_layer=start_layer,
-                                        to_layer="m3",
+                                        to_layer=self.pwr_grid_layer,
                                         size=size,
                                         offset=loc,
                                         direction=direction)
 
-        if start_layer == "m3":
+        if start_layer == self.pwr_grid_layer:
             self.add_layout_pin_rect_center(text=name,
-                                            layer="m3",
+                                            layer=self.pwr_grid_layer,
                                             offset=loc)
         else:
             self.add_layout_pin_rect_center(text=name,
-                                            layer="m3",
+                                            layer=self.pwr_grid_layer,
                                             offset=loc,
                                             width=via.width,
                                             height=via.height)

compiler/router/router_tech.py

@@ -5,7 +5,7 @@
 # (acting for and on behalf of Oklahoma State University)
 # All rights reserved.
 #
-from tech import drc, layer
+from tech import drc, layer, preferred_directions
 from contact import contact
 from vector import vector
 import debug
@@ -26,6 +26,9 @@ class router_tech:
         self.rail_track_width = rail_track_width
 
         if len(self.layers) == 1:
+            if preferred_directions[self.layers[0]] != "H":
+                debug.warning("Using '{}' for horizontal routing, but it " \
+                              "prefers vertical routing".format(self.layers[0]))
             self.horiz_layer_name = self.vert_layer_name = self.layers[0]
             self.horiz_lpp = self.vert_lpp = layer[self.layers[0]]
             
@@ -35,7 +38,17 @@ class router_tech:
             self.horiz_track_width = self.horiz_layer_minwidth + self.horiz_layer_spacing
             self.vert_track_width = self.vert_layer_minwidth + self.vert_layer_spacing
         else:
-            (self.horiz_layer_name, self.via_layer_name, self.vert_layer_name) = self.layers
+            (try_horiz_layer, self.via_layer_name, try_vert_layer) = self.layers
+
+            # figure out wich of the two layers prefers horizontal/vertical
+            # routing
+            if preferred_directions[try_horiz_layer] == "H" and preferred_directions[try_vert_layer] == "V":
+                self.horiz_layer_name = try_horiz_layer
+                self.vert_layer_name = try_vert_layer
+            else:
+                raise ValueError("Layer '{}' and '{}' are using the wrong " \
+                            "preferred_directions '{}' and '{}'. Only "\
+                            "('H', 'V') are supported")
 
             via_connect = contact(self.layers, (1, 1))
             max_via_size = max(via_connect.width,via_connect.height)

compiler/sram/sram_base.py

@@ -148,14 +148,21 @@ class sram_base(design, verilog, lef):
         if not OPTS.route_supplies:
             # Do not route the power supply (leave as must-connect pins)
             return
-        elif "m4" in tech.layer:
-            # Route a M3/M4 grid
-            from supply_grid_router import supply_grid_router as router
-            rtr=router(self.m3_stack, self)
-        elif "m3" in tech.layer:
-            from supply_tree_router import supply_tree_router as router
-            rtr=router(("m3",), self)
 
+        grid_stack = set()
+        try:
+            from tech import power_grid
+            grid_stack = power_grid
+        except ImportError:
+            # if no power_grid is specified by tech we use sensible defaults
+            if "m4" in tech.layer:
+                # Route a M3/M4 grid
+                grid_stack = self.m3_stack
+            elif "m3" in tech.layer:
+                grid_stack =("m3",)
+
+        from supply_grid_router import supply_grid_router as router
+        rtr=router(grid_stack, self)
         rtr.route()