From eb9e998c085589f60efb30f79ef5509b0a83b16a Mon Sep 17 00:00:00 2001
From: Megan Wachs <megan@sifive.com>
Date: Mon, 18 Jul 2016 13:09:44 -0700
Subject: [PATCH] Add ManagerToClientStatelessBridge

---
 .../main/scala/agents/StatelessBridge.scala   | 61 +++++++++++++++++++
 1 file changed, 61 insertions(+)
 create mode 100644 uncore/src/main/scala/agents/StatelessBridge.scala

diff --git a/uncore/src/main/scala/agents/StatelessBridge.scala b/uncore/src/main/scala/agents/StatelessBridge.scala
new file mode 100644
index 00000000..efc7e2ab
--- /dev/null
+++ b/uncore/src/main/scala/agents/StatelessBridge.scala
@@ -0,0 +1,61 @@
+// See LICENSE for license details.
+
+package uncore.agents
+
+import Chisel._
+import uncore.coherence._
+import uncore.tilelink._
+import uncore.constants._
+import uncore.devices._
+import cde.{Parameters, Field, Config}
+
+/** The ManagerToClientStateless Bridge does not maintain any state for the messages
+  *  which pass through it. It simply passes the messages back and forth without any
+  *  tracking or translation. 
+  *  
+  * This can reduce area and timing in very constrained situations:
+  *   - The Manager and Client implement the same coherence protocol
+  *   - There are no probe or finish messages.
+  *   - The outer transaction ID is large enough to handle all possible inner
+  *     transaction IDs, such that no remapping state must be maintained.
+  *
+  */
+
+class ManagerToClientStatelessBridge(implicit p: Parameters) extends HierarchicalCoherenceAgent()(p) {
+
+  val icid = io.inner.acquire.bits.client_id.getWidth
+  val ixid = io.inner.acquire.bits.client_xact_id.getWidth
+  val oxid = io.outer.acquire.bits.client_xact_id.getWidth
+
+  // Stateless Bridge is only usable in certain constrained situations.
+  // Sanity check its usage here.
+  // Additional requirements are that the inner and outer Coherence policies
+  // are the same (e.g. MEI != MESI), and that NTiles == 1,
+  // but this is not checked here.
+  require (p(NTiles) == 1)
+
+  require(icid + ixid <= oxid)
+  require(icid == io.inner.release.bits.client_id.getWidth)
+  require(ixid == io.inner.release.bits.client_xact_id.getWidth)
+  require(oxid == io.outer.release.bits.client_xact_id.getWidth)
+
+  io.outer.acquire.valid := io.inner.acquire.valid
+  io.inner.acquire.ready := io.outer.acquire.ready
+  io.outer.acquire.bits := io.inner.acquire.bits
+  io.outer.acquire.bits.client_xact_id := Cat(io.inner.acquire.bits.client_id, io.inner.acquire.bits.client_xact_id)
+
+  io.outer.release.valid := io.inner.release.valid
+  io.inner.release.ready := io.outer.release.ready
+  io.outer.release.bits := io.inner.release.bits
+  io.outer.release.bits.client_xact_id := Cat(io.inner.release.bits.client_id, io.inner.release.bits.client_xact_id)
+
+  io.inner.grant.valid := io.outer.grant.valid
+  io.outer.grant.ready := io.inner.grant.ready
+  io.inner.grant.bits := io.outer.grant.bits
+  io.inner.grant.bits.client_xact_id := io.outer.grant.bits.client_xact_id(ixid-1, 0)
+  io.inner.grant.bits.client_id := io.outer.grant.bits.client_xact_id(icid+ixid-1, ixid)
+
+  io.inner.probe.valid := Bool(false)
+  io.inner.finish.ready := Bool(true)
+}
+