build/gowin/gowin: workaround Ethernet clock port name

LiteETH will rename clock port names, which makes Gowin tools unhappy
(because the name specified is no longer a "port" but a "net").

Add a hack to workaround this.

This is tested by applying Etherbone on Tang Primer 20K.

Signed-off-by: Icenowy Zheng <[email protected]>

litex/build/gowin/gowin.py

@@ -90,7 +90,13 @@ def build_io_constraints(self):
     def build_timing_constraints(self, vns):
         sdc = []
         for clk, period in sorted(self.clocks.items(), key=lambda x: x[0].duid):
-            sdc.append(f"create_clock -name {vns.get_name(clk)} -period {str(period)} [get_ports {{{vns.get_name(clk)}}}]")
+            clk_name = vns.get_name(clk)
+            # FIXME: Hack for Ethernet requesting a net name instead of port name
+            if clk_name == "eth_rx_clk":
+                clk_name = "eth_clocks_rx"
+            if clk_name == "eth_tx_clk":
+                clk_name = "eth_clocks_tx"
+            sdc.append(f"create_clock -name {clk_name} -period {str(period)} [get_ports {{{clk_name}}}]")
         tools.write_to_file(f"{self._build_name}.sdc", "\n".join(sdc))
         return (f"{self._build_name}.sdc", "SDC")