build/microsemi/common: add async reset synchronizer (using DFN1P0)

litex/build/microsemi/common.py

@@ -1,2 +1,24 @@
+from migen import *
+from migen.genlib.resetsync import AsyncResetSynchronizer
+
+
+class MicrosemiPolarfireAsyncResetSynchronizerImpl(Module):
+    def __init__(self, cd, async_reset):
+        rst1 = Signal()
+        self.specials += [
+            Instance("DFN1P0", i_D=0, i_PRE=~async_reset,
+                     i_CLK=cd.clk, o_Q=rst1),
+            Instance("DFN1P0", i_D=rst1, i_PRE=~async_reset,
+                     i_CLK=cd.clk, o_Q=cd.rst)
+        ]
+
+
+class MicrosemiPolarfireAsyncResetSynchronizer:
+    @staticmethod
+    def lower(dr):
+        return MicrosemiPolarfireAsyncResetSynchronizerImpl(dr.cd, dr.async_reset)
+
+
 microsemi_polarfire_special_overrides = {
+    AsyncResetSynchronizer: MicrosemiPolarfireAsyncResetSynchronizer,
 }