tilelink2 Parameters: poison ports with unsafe atomics

We need to detect if an AtomicAutomata's output ever gets mixed
with some other source of operations.

src/main/scala/uncore/tilelink2/Parameters.scala

@@ -289,7 +289,10 @@ case class TLClientParameters(
   val name = nodePath.lastOption.map(_.lazyModule.name).getOrElse("disconnected")
 }
 
-case class TLClientPortParameters(clients: Seq[TLClientParameters]) {
+case class TLClientPortParameters(
+  clients:       Seq[TLClientParameters],
+  unsafeAtomics: Boolean = false) // Atomics are executed as get+put
+{
   require (!clients.isEmpty)
 
   // Require disjoint ranges for Ids

src/main/scala/uncore/tilelink2/Xbar.scala

@@ -45,24 +45,24 @@ class TLXbar(policy: (Vec[Bool], Bool) => Seq[Bool] = TLXbar.lowestIndex) extend
     numClientPorts  = 1 to 32,
     numManagerPorts = 1 to 32,
     clientFn  = { seq =>
-      val clients = (mapInputIds(seq) zip seq) flatMap { case (range, port) =>
+      // An unsafe atomic port can not be combined with any other!
+      require (!seq.exists(_.unsafeAtomics) || seq.size == 1)
+      seq(0).copy(clients = (mapInputIds(seq) zip seq) flatMap { case (range, port) =>
         port.clients map { client => client.copy(
           sourceId = client.sourceId.shift(range.start)
         )}
-      }
-      TLClientPortParameters(clients)
+      })
     },
     managerFn = { seq =>
       val fifoIdFactory = relabeler()
-      val managers = (mapOutputIds(seq) zip seq) flatMap { case (range, port) =>
+      seq(0).copy(managers = (mapOutputIds(seq) zip seq) flatMap { case (range, port) =>
         require (port.beatBytes == seq(0).beatBytes)
         val fifoIdMapper = fifoIdFactory()
         port.managers map { manager => manager.copy(
           sinkId = manager.sinkId.shift(range.start),
           fifoId = manager.fifoId.map(fifoIdMapper(_))
         )}
-      }
-      TLManagerPortParameters(managers, seq(0).beatBytes)
+      })
     })
 
   lazy val module = new LazyModuleImp(this) {