soc_core: add automatic down-conversion of CPU buses to 32-bit (if needed)

litex/soc/integration/soc_core.py

@@ -184,6 +184,12 @@ class SoCCore(Module):
 
             # Add CPU buses as Wisbone masters
             for bus in self.cpu.buses:
+                assert bus.data_width in [32, 64, 128]
+                # Down Convert CPU buses to 32-bit if needed
+                if bus.data_width != 32:
+                    dc_bus = wishbone.Interface()
+                    self.submodules += wishbone.Converter(bus, dc_bus)
+                    bus = dc_bus
                 self.add_wb_master(bus)
 
             # Add CPU CSR (dynamic)

litex/soc/interconnect/wishbone.py

@@ -34,6 +34,8 @@ _layout = [
 
 class Interface(Record):
     def __init__(self, data_width=32, adr_width=30):
+        self.data_width = data_width
+        self.adr_width  = adr_width
         Record.__init__(self, set_layout_parameters(_layout,
             adr_width=adr_width,
             data_width=data_width,