core: fix refresh (bug was reducing controller throughput by 2)

litedram/core/multiplexer.py

@@ -229,7 +229,7 @@ class Multiplexer(Module, AutoCSR):
         fsm.act("REFRESH",
             steerer.sel[0].eq(STEER_REFRESH),
             refresher.cmd.ready.eq(1),
-            If(refresher.cmd.valid & refresher.cmd.last,
+            If(refresher.cmd.last,
                 NextState("READ")
             )
         )

litedram/core/refresher.py

@@ -59,9 +59,10 @@ class Refresher(Module):
             )
         )
         fsm.act("WAIT_SEQ",
-            cmd.valid.eq(1),
             If(seq_done,
                 cmd.last.eq(1),
                 NextState("IDLE")
+            ).Else(
+                cmd.valid.eq(1)
             )
         )