[otbn,dv] Tidy up how we handle "start-of-time RMA" in model

Signed-off-by: Rupert Swarbrick <[email protected]>

hw/ip/otbn/dv/otbnsim/sim/sim.py

@@ -346,7 +346,7 @@ def _step_pre_wipe(self, verbose: bool) -> StepRes:
         # complex might not be up, so we don't want to wait for a seed. Handle
         # this by jumping straight to the WIPING state and setting the number
         # of rounds to 1 (so that we don't wait again for a seed afterwards)
-        if self.state.rma_req == LcTx.ON and self.state.wipe_rounds_done == 0:
+        if self.state.rma_req == LcTx.ON and not self.state.edn_seen_running:
             self.state.lock_after_wipe = True
             self.state.wipe_rounds_to_do = 1
             self.state.set_fsm_state(FsmState.WIPING)

hw/ip/otbn/dv/otbnsim/sim/state.py

@@ -175,6 +175,13 @@ def __init__(self) -> None:
         # in IDLE.
         self.delayed_lock = False
 
+        # We set this flag when the first URND seed comes back from the EDN. If
+        # we get an RMA request before this flag is set, we'll be in the
+        # PRE_WIPE state and the EDN might not actually be running. In that
+        # situation, we do a shortened secure wipe (just one round and no
+        # random data).
+        self.edn_seen_running = False
+
     def get_next_pc(self) -> int:
         if self._pc_next_override is not None:
             return self._pc_next_override
@@ -217,6 +224,8 @@ def urnd_completed(self) -> None:
         # it back into four 64-bit words.
         w64s = [(w256 >> (64 * i)) & ((1 << 64) - 1) for i in range(4)]
 
+        self.edn_seen_running = True
+
         self.wsrs.URND.set_seed(w64s)
 
     def start_init_sec_wipe(self) -> None: