Difference between crossToBus and crossFromBus

[Tong-Lin]

I changed cross function between cbus and sbus like follow:

trait HasHierarchicalBusTopology { this: BaseSubsystem =>
  // The sbus masters the cbus; here we convert TL-UH -> TL-UL
  //sbus.crossToBus(cbus, NoCrossing)
  cbus.crossFromBus(sbus, SynchronousCrossing(FastToSlow))

It because that I want adapt modules like 'TLWidthWidget' and 'TLFragmenter' been instanced in cbus which is slower side; And then got following error:

[error] (run-main-0) java.lang.reflect.InvocationTargetException
[error] java.lang.reflect.InvocationTargetException
[error] at java.base/jdk.internal.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
[error] at java.base/jdk.internal.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:62)
[error] at java.base/jdk.internal.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
[error] at java.base/java.lang.reflect.Constructor.newInstance(Constructor.java:490)
[error] at freechips.rocketchip.util.HasGeneratorUtilities.$anonfun$elaborate$1(GeneratorUtils.scala:54)
[error] at chisel3.core.Module$.do_apply(Module.scala:52)
[error] at chisel3.Driver$.$anonfun$elaborate$1(Driver.scala:95)
[error] at chisel3.internal.Builder$.$anonfun$build$2(Builder.scala:343)
[error] at scala.util.DynamicVariable.withValue(DynamicVariable.scala:58)
[error] at chisel3.internal.Builder$.$anonfun$build$1(Builder.scala:341)
[error] at scala.util.DynamicVariable.withValue(DynamicVariable.scala:58)
[error] at chisel3.internal.Builder$.build(Builder.scala:341)
[error] at chisel3.Driver$.elaborate(Driver.scala:95)
[error] at freechips.rocketchip.util.HasGeneratorUtilities.elaborate(GeneratorUtils.scala:59)
[error] Caused by: java.lang.IllegalArgumentException: requirement failed: The nodes List(buffer.node, sbus.bus_xing, coupler_from_bus_named_system_bus.bus_xing, system_bus_xbar.node) which are inter-connected by := have 2 := operators and 3 := operators connected to them, making it impossible to determine cardinality inference direction.
[error] at scala.Predef$.require(Predef.scala:277)
[error] at freechips.rocketchip.diplomacy.MixedNode.flexOffset$lzycompute(Nodes.scala:254)
[error] at freechips.rocketchip.diplomacy.MixedNode.flexOffset(Nodes.scala:242)
[error] at freechips.rocketchip.diplomacy.MixedNode.$anonfun$x$29$1(Nodes.scala:263)
[error] at freechips.rocketchip.diplomacy.MixedNode.$anonfun$x$29$1$adapted(Nodes.scala:263)
[error] at scala.collection.TraversableOnce.$anonfun$count$1(TraversableOnce.scala:116)
[error] at scala.collection.TraversableOnce.$anonfun$count$1$adapted(TraversableOnce.scala:115)
[error] at scala.collection.immutable.List.foreach(List.scala:389)
[error] at scala.collection.TraversableOnce.count(TraversableOnce.scala:115)
[error] at scala.collection.TraversableOnce.count$(TraversableOnce.scala:113)
[error] at scala.collection.AbstractTraversable.count(Traversable.scala:104)
[error] at freechips.rocketchip.diplomacy.MixedNode.liftedTree1$1(Nodes.scala:263)
[error] at freechips.rocketchip.diplomacy.MixedNode.x$29$lzycompute(Nodes.scala:260)
[error] at freechips.rocketchip.diplomacy.MixedNode.x$29(Nodes.scala:259)
[error] Nonzero exit code: 1
[error] (Compile / runMain) Nonzero exit code: 1
[error] Total time: 6 s, completed Jul 6, 2019, 1:39:06 PM

[michael-etzkorn]

Given that the PR that mentions this removed HasHierarchicalBusTopology has removed this, and the age of this issue, I'll go ahead and close it. If you have any questions, feel free to post on Stack Overflow and we can follow-up there.