Merge pull request #3731 from tymcauley/axi4-buffer-chain

AXI4 buffer chain

Author: jerryz123

Diff for: src/main/scala/amba/axi4/Buffer.scala

@@ -68,4 +68,16 @@ object AXI4Buffer
     val axi4buf = LazyModule(new AXI4Buffer(aw, w, b, ar, r))
     axi4buf.node
   }
+
+  def chain(depth: Int, name: Option[String] = None)(implicit p: Parameters): Seq[AXI4Node] = {
+    val buffers = Seq.fill(depth) { LazyModule(new AXI4Buffer()) }
+    name.foreach { n => buffers.zipWithIndex.foreach { case (b, i) => b.suggestName(s"${n}_${i}") } }
+    buffers.map(_.node)
+  }
+
+  def chainNode(depth: Int, name: Option[String] = None)(implicit p: Parameters): AXI4Node = {
+    chain(depth, name)
+      .reduceLeftOption(_ :*=* _)
+      .getOrElse(AXI4NameNode("no_buffer"))
+  }
 }