ControlBus diplomacy breaks when CBus atomics is disabled

[richardyrh]

Related issue:

Type of change: bug report

Impact: API modification

Development Phase: implementation

Release Notes

To reproduce:

class WithNoAtomicsCBus extends Config ((site, here, up) => {
  case ControlBusKey => up(ControlBusKey).copy(
    atomics = None,
  )
})

class RocketWithNoAtomicsCBusConfig extends Config(
  new WithNoAtomicsCBus ++
  new RocketConfig)

This will cause this:

Caused by: java.lang.IllegalArgumentException: requirement failed: Diplomacy has detected a problem with your graph:
The following node appears left of a :*= 2 times and right of a :=* 0 times, at most once is allowed.
adapter cbus_fixer.$anon node:
parents: cbus_fixer/cbus/system/chiptop0
locator:  (generators/rocket-chip/src/main/scala/subsystem/PeripheryBus.scala:54:33)

2 inward nodes bound: [flex-buffer.node,flex-coupler_from_port_named_custom_boot_pin.tl]
1 outward nodes bound: [query-xbar.$anon]


        at scala.Predef$.require(Predef.scala:337)
        at org.chipsalliance.diplomacy.nodes.MixedAdapterNode.resolveStar(AdapterNode.scala:37)
        at org.chipsalliance.diplomacy.nodes.MixedNode.liftedTree1$1(MixedNode.scala:381)
        at org.chipsalliance.diplomacy.nodes.MixedNode.x$19$lzycompute(MixedNode.scala:342)
        at org.chipsalliance.diplomacy.nodes.MixedNode.x$19(MixedNode.scala:336)
        at org.chipsalliance.diplomacy.nodes.MixedNode.iStar$lzycompute(MixedNode.scala:340)
        at org.chipsalliance.diplomacy.nodes.MixedNode.iStar(MixedNode.scala:340)
        at org.chipsalliance.diplomacy.nodes.MixedNode.$anonfun$x$19$5(MixedNode.scala:363)
        at org.chipsalliance.diplomacy.nodes.MixedNode.edgeAritySelect(MixedNode.scala:319)
        at org.chipsalliance.diplomacy.nodes.MixedNode.$anonfun$x$19$3(MixedNode.scala:363)
        at org.chipsalliance.diplomacy.nodes.MixedNode.$anonfun$x$19$3$adapted(MixedNode.scala:360)
        at scala.collection.immutable.List.map(List.scala:247)
        at scala.collection.immutable.List.map(List.scala:79)
        at org.chipsalliance.diplomacy.nodes.MixedNode.liftedTree1$1(MixedNode.scala:360)
(and so on)

Fix is the commit