mac/preamble: Add 32/64 bit support in checker

Only tested for 32/8 bit

liteeth/mac/preamble.py

@@ -81,7 +81,7 @@ class LiteEthMACPreambleChecker(Module):
         Pulses every time a preamble error is detected.
     """
     def __init__(self, dw):
-        assert dw == 8
+        assert dw in [8, 16, 32, 64]
         self.sink   = sink   = stream.Endpoint(eth_phy_description(dw))
         self.source = source = stream.Endpoint(eth_phy_description(dw))
 
@@ -89,10 +89,12 @@ class LiteEthMACPreambleChecker(Module):
 
         # # #
 
+        preamble = Signal(64, reset=eth_preamble)
         self.submodules.fsm = fsm = FSM(reset_state="PREAMBLE")
         fsm.act("PREAMBLE",
             sink.ready.eq(1),
-            If(sink.valid & ~sink.last & (sink.data == (eth_preamble >> 56)),
+            # Match to end of preamble
+            If(sink.valid & ~sink.last & (sink.data == preamble[-dw:]),
                 NextState("COPY")
             ),
             If(sink.valid & sink.last, self.error.eq(1))