Merge pull request #533 from ucb-bar/rational-crossing

Rational clock crossing

src/main/scala/uncore/tilelink2/AsyncCrossing.scala

@@ -137,7 +137,7 @@ class TLAsyncCrossing(depth: Int = 8, sync: Int = 3)(implicit p: Parameters) ext
 /** Synthesizeable unit tests */
 import unittest._
 
-class TLRAMCrossing(implicit p: Parameters) extends LazyModule {
+class TLRAMAsyncCrossing(implicit p: Parameters) extends LazyModule {
   val model = LazyModule(new TLRAMModel)
   val ram  = LazyModule(new TLRAM(AddressSet(0x0, 0x3ff)))
   val fuzz = LazyModule(new TLFuzzer(5000))
@@ -168,6 +168,6 @@ class TLRAMCrossing(implicit p: Parameters) extends LazyModule {
   }
 }
 
-class TLRAMCrossingTest(implicit p: Parameters) extends UnitTest(timeout = 500000) {
+class TLRAMAsyncCrossingTest(implicit p: Parameters) extends UnitTest(timeout = 500000) {
-  io.finished := Module(LazyModule(new TLRAMCrossing).module).io.finished
+  io.finished := Module(LazyModule(new TLRAMAsyncCrossing).module).io.finished
 }

src/main/scala/uncore/tilelink2/Bundles.scala

@@ -251,3 +251,12 @@ class TLAsyncBundle(params: TLAsyncBundleParameters) extends TLAsyncBundleBase(p
   val d = new AsyncBundle(params.depth, new TLBundleD(params.base)).flip
   val e = new AsyncBundle(params.depth, new TLBundleE(params.base))
 }
+
+class TLRationalBundle(params: TLBundleParameters) extends TLBundleBase(params)
+{
+  val a = RationalIO(new TLBundleA(params))
+  val b = RationalIO(new TLBundleB(params)).flip
+  val c = RationalIO(new TLBundleC(params))
+  val d = RationalIO(new TLBundleD(params)).flip
+  val e = RationalIO(new TLBundleE(params))
+}

src/main/scala/uncore/tilelink2/Nodes.scala

@@ -180,3 +180,39 @@ case class TLAsyncSinkNode(depth: Int, sync: Int) extends MixedNode(TLAsyncImp,
   uFn = { case (1, Seq(p)) => Seq(TLAsyncManagerPortParameters(depth, p)) },
   numPO = 1 to 1,
   numPI = 1 to 1)
+
+object TLRationalImp extends NodeImp[TLClientPortParameters, TLManagerPortParameters, TLEdgeParameters, TLEdgeParameters, TLRationalBundle]
+{
+  def edgeO(pd: TLClientPortParameters, pu: TLManagerPortParameters): TLEdgeParameters = TLEdgeParameters(pd, pu)
+  def edgeI(pd: TLClientPortParameters, pu: TLManagerPortParameters): TLEdgeParameters = TLEdgeParameters(pd, pu)
+
+  def bundleO(eo: Seq[TLEdgeParameters]): Vec[TLRationalBundle] = Vec(eo.size, new TLRationalBundle(TLBundleParameters.union(eo.map(_.bundle))))
+  def bundleI(ei: Seq[TLEdgeParameters]): Vec[TLRationalBundle] = Vec(ei.size, new TLRationalBundle(TLBundleParameters.union(ei.map(_.bundle))))
+
+  def colour = "#00ff00" // green
+
+  def connect(bo: => TLRationalBundle, bi: => TLRationalBundle, ei: => TLEdgeParameters)(implicit p: Parameters, sourceInfo: SourceInfo): (Option[LazyModule], () => Unit) = {
+    (None, () => { bi <> bo })
+  }
+
+  override def mixO(pd: TLClientPortParameters, node: OutwardNode[TLClientPortParameters, TLManagerPortParameters, TLRationalBundle]): TLClientPortParameters  =
+   pd.copy(clients  = pd.clients.map  { c => c.copy (nodePath = node +: c.nodePath) })
+  override def mixI(pu: TLManagerPortParameters, node: InwardNode[TLClientPortParameters, TLManagerPortParameters, TLRationalBundle]): TLManagerPortParameters =
+   pu.copy(managers = pu.managers.map { m => m.copy (nodePath = node +: m.nodePath) })
+}
+
+case class TLRationalIdentityNode() extends IdentityNode(TLRationalImp)
+case class TLRationalOutputNode() extends OutputNode(TLRationalImp)
+case class TLRationalInputNode() extends InputNode(TLRationalImp)
+
+case class TLRationalSourceNode() extends MixedNode(TLImp, TLRationalImp)(
+  dFn = { case (_, s) => s },
+  uFn = { case (_, s) => s.map(p => p.copy(minLatency = 1)) }, // discard cycles from other clock domain
+  numPO = 0 to 999,
+  numPI = 0 to 999)
+
+case class TLRationalSinkNode() extends MixedNode(TLRationalImp, TLImp)(
+  dFn = { case (_, s) => s.map(p => p.copy(minLatency = 1)) },
+  uFn = { case (_, s) => s },
+  numPO = 0 to 999,
+  numPI = 0 to 999)

src/main/scala/uncore/tilelink2/RationalCrossing.scala

@@ -0,0 +1,184 @@
+// See LICENSE.SiFive for license details.
+
+// If you know two clocks are related with a N:1 or 1:N relationship, you
+// can cross the clock domains with lower latency than an AsyncQueue.
+// This clock crossing behaves almost identically to a TLBuffer(2):
+//   - It adds one cycle latency to each clock domain.
+//   - All outputs of TLRational are registers (bits, valid, and ready).
+//   - It costs 3*bits registers as opposed to 2*bits in a TLBuffer(2)
+
+package uncore.tilelink2
+
+import Chisel._
+import chisel3.internal.sourceinfo.SourceInfo
+import config._
+import diplomacy._
+import util._
+
+class TLRationalCrossingSource(implicit p: Parameters) extends LazyModule
+{
+  val node = TLRationalSourceNode()
+
+  lazy val module = new LazyModuleImp(this) {
+    val io = new Bundle {
+      val in  = node.bundleIn
+      val out = node.bundleOut
+    }
+
+    ((io.in zip io.out) zip (node.edgesIn zip node.edgesOut)) foreach { case ((in, out), (edgeIn, edgeOut)) =>
+      val bce = edgeIn.manager.anySupportAcquireB && edgeIn.client.anySupportProbe
+
+      out.a <> ToRational(in.a)
+      in.d <> FromRational(out.d)
+
+      if (bce) {
+        in.b <> FromRational(out.b)
+        out.c <> ToRational(in.c)
+        out.e <> ToRational(in.e)
+      } else {
+        in.b.valid   := Bool(false)
+        in.c.ready   := Bool(true)
+        in.e.ready   := Bool(true)
+        out.b.ready  := Bool(true)
+        out.c.valid  := Bool(false)
+        out.e.valid  := Bool(false)
+        out.b.sink   := UInt(0)
+        out.c.source := UInt(0)
+        out.e.source := UInt(0)
+      }
+    }
+  }
+}
+
+class TLRationalCrossingSink(implicit p: Parameters) extends LazyModule
+{
+  val node = TLRationalSinkNode()
+
+  lazy val module = new LazyModuleImp(this) {
+    val io = new Bundle {
+      val in  = node.bundleIn
+      val out = node.bundleOut
+    }
+
+    ((io.in zip io.out) zip (node.edgesIn zip node.edgesOut)) foreach { case ((in, out), (edgeIn, edgeOut)) =>
+      val bce = edgeOut.manager.anySupportAcquireB && edgeOut.client.anySupportProbe
+
+      out.a <> FromRational(in.a)
+      in.d <> ToRational(out.d)
+
+      if (bce) {
+        in.b <> ToRational(out.b)
+        out.c <> FromRational(in.c)
+        out.e <> FromRational(in.e)
+      } else {
+        out.b.ready := Bool(true)
+        out.c.valid := Bool(false)
+        out.e.valid := Bool(false)
+        in.b.valid  := Bool(false)
+        in.c.ready  := Bool(true)
+        in.e.ready  := Bool(true)
+        in.b.source := UInt(0)
+        in.c.sink   := UInt(0)
+        in.e.sink   := UInt(0)
+      }
+    }
+  }
+}
+
+object TLRationalCrossingSource
+{
+  // applied to the TL source node; y.node := TLRationalCrossingSource()(x.node)
+  def apply()(x: TLOutwardNode)(implicit p: Parameters, sourceInfo: SourceInfo): TLRationalOutwardNode = {
+    val source = LazyModule(new TLRationalCrossingSource)
+    source.node := x
+    source.node
+  }
+}
+
+object TLRationalCrossingSink
+{
+  // applied to the TL source node; y.node := TLRationalCrossingSink()(x.node)
+  def apply()(x: TLRationalOutwardNode)(implicit p: Parameters, sourceInfo: SourceInfo): TLOutwardNode = {
+    val sink = LazyModule(new TLRationalCrossingSink)
+    sink.node := x
+    sink.node
+  }
+}
+
+class TLRationalCrossing(implicit p: Parameters) extends LazyModule
+{
+  val nodeIn = TLInputNode()
+  val nodeOut = TLOutputNode()
+  val node = NodeHandle(nodeIn, nodeOut)
+
+  val source = LazyModule(new TLRationalCrossingSource)
+  val sink = LazyModule(new TLRationalCrossingSink)
+
+  val _    = (sink.node := source.node) // no monitor
+  val in   = (source.node := nodeIn)
+  val out  = (nodeOut := sink.node)
+
+  lazy val module = new LazyModuleImp(this) {
+    val io = new Bundle {
+      val in        = nodeIn.bundleIn
+      val in_clock  = Clock(INPUT)
+      val in_reset  = Bool(INPUT)
+      val out       = nodeOut.bundleOut
+      val out_clock = Clock(INPUT)
+      val out_reset = Bool(INPUT)
+    }
+
+    source.module.clock := io.in_clock
+    source.module.reset := io.in_reset
+    in.foreach { lm =>
+      lm.module.clock := io.in_clock
+      lm.module.reset := io.in_reset
+    }
+
+    sink.module.clock := io.out_clock
+    sink.module.reset := io.out_reset
+    out.foreach { lm =>
+      lm.module.clock := io.out_clock
+      lm.module.reset := io.out_reset
+    }
+  }
+}
+
+/** Synthesizeable unit tests */
+import unittest._
+
+class TLRAMRationalCrossing(implicit p: Parameters) extends LazyModule {
+  val fuzz  = LazyModule(new TLFuzzer(5000))
+  val model = LazyModule(new TLRAMModel)
+  val cross = LazyModule(new TLRationalCrossing)
+  val delay = LazyModule(new TLDelayer(0.25))
+  val ram   = LazyModule(new TLRAM(AddressSet(0x0, 0x3ff)))
+
+  model.node := fuzz.node
+  cross.node := TLDelayer(0.25)(TLFragmenter(4, 256)(model.node))
+  val monitor1 = (delay.node := cross.node)
+  val monitor2 = (ram.node := delay.node)
+  val monitors = monitor1.toList ++ monitor2.toList
+
+  lazy val module = new LazyModuleImp(this) with HasUnitTestIO {
+    io.finished := fuzz.module.io.finished
+
+    // Shove the RAM into another clock domain
+    val clocks = Module(new util.Pow2ClockDivider(2))
+    ram.module.clock := clocks.io.clock_out
+    delay.module.clock := clocks.io.clock_out
+
+    // ... and safely cross TL2 into it
+    cross.module.io.in_clock := clock
+    cross.module.io.in_reset := reset
+    cross.module.io.out_clock := clocks.io.clock_out
+    cross.module.io.out_reset := reset
+
+    // Push the Monitors into the right clock domain
+    monitors.foreach { m => m.module.clock := clocks.io.clock_out }
+  }
+}
+
+class TLRAMRationalCrossingTest(implicit p: Parameters) extends UnitTest(timeout = 500000) {
+  io.finished := Module(LazyModule(new TLRAMRationalCrossing).module).io.finished
+}

src/main/scala/uncore/tilelink2/package.scala

@@ -10,6 +10,7 @@ package object tilelink2
   type TLInwardNode = InwardNodeHandle[TLClientPortParameters, TLManagerPortParameters, TLBundle]
   type TLOutwardNode = OutwardNodeHandle[TLClientPortParameters, TLManagerPortParameters, TLBundle]
   type TLAsyncOutwardNode = OutwardNodeHandle[TLAsyncClientPortParameters, TLAsyncManagerPortParameters, TLAsyncBundle]
+  type TLRationalOutwardNode = OutwardNodeHandle[TLClientPortParameters, TLManagerPortParameters, TLRationalBundle]
   type IntOutwardNode = OutwardNodeHandle[IntSourcePortParameters, IntSinkPortParameters, Vec[Bool]]
 
   def OH1ToOH(x: UInt) = (x << 1 | UInt(1)) & ~Cat(UInt(0, width=1), x)

src/main/scala/unittest/Configs.scala

@@ -30,7 +30,8 @@ class WithTLSimpleUnitTests extends Config((site, here, up) => {
       Module(new uncore.tilelink2.TLRAMSimpleTest(16)),
       Module(new uncore.tilelink2.TLRR0Test),
       Module(new uncore.tilelink2.TLRR1Test),
-      Module(new uncore.tilelink2.TLRAMCrossingTest) ) }
+      Module(new uncore.tilelink2.TLRAMRationalCrossingTest),
+      Module(new uncore.tilelink2.TLRAMAsyncCrossingTest) ) }
 })
 
 class WithTLWidthUnitTests extends Config((site, here, up) => {

src/main/scala/util/RationalCrossing.scala

@@ -0,0 +1,101 @@
+// See LICENSE.SiFive for license details.
+
+// If you know two clocks are related with a N:1 or 1:N relationship, you
+// can cross the clock domains with lower latency than an AsyncQueue. This
+// crossing adds 1 cycle in the target clock domain.
+
+package util
+import Chisel._
+
+final class RationalIO[T <: Data](gen: T) extends Bundle
+{
+  val bits   = gen.chiselCloneType
+  val valid  = Bool()
+  val source = UInt(width = 2)
+  val ready  = Bool().flip
+  val sink   = UInt(width = 2).flip
+
+  override def cloneType: this.type = new RationalIO(gen).asInstanceOf[this.type]
+}
+
+object RationalIO
+{
+  def apply[T <: Data](gen: T) = new RationalIO(gen)
+}
+
+class RationalCrossingSource[T <: Data](gen: T) extends Module
+{
+  val io = new Bundle {
+    val enq = DecoupledIO(gen).flip
+    val deq = RationalIO(gen)
+  }
+
+  val enq = Queue(io.enq, 1, flow=true)
+  val deq = io.deq
+
+  val count = RegInit(UInt(0, width = 2))
+  val equal = count === deq.sink
+
+  deq.valid  := enq.valid
+  deq.source := count
+  deq.bits   := Mux(equal, enq.bits, RegEnable(enq.bits, equal))
+  enq.ready  := Mux(equal, deq.ready, count(1) =/= deq.sink(0))
+
+  when (enq.fire()) { count := Cat(count(0), !count(1)) }
+}
+
+class RationalCrossingSink[T <: Data](gen: T) extends Module
+{
+  val io = new Bundle {
+    val enq = RationalIO(gen).flip
+    val deq = DecoupledIO(gen)
+  }
+
+  val enq = io.enq
+  val deq = Wire(io.deq)
+  io.deq <> Queue(deq, 1, pipe=true)
+
+  val count = RegInit(UInt(0, width = 2))
+  val equal = count === enq.source
+
+  enq.ready := deq.ready
+  enq.sink  := count
+  deq.bits  := enq.bits
+  deq.valid := Mux(equal, enq.valid, count(1) =/= enq.source(0))
+
+  when (deq.fire()) { count := Cat(count(0), !count(1)) }
+}
+
+class RationalCrossing[T <: Data](gen: T) extends Module
+{
+  val io = new CrossingIO(gen)
+
+  val source = Module(new RationalCrossingSource(gen))
+  val sink   = Module(new RationalCrossingSink(gen))
+
+  source.clock := io.enq_clock
+  source.reset := io.enq_reset
+  sink  .clock := io.deq_clock
+  sink  .reset := io.deq_reset
+
+  source.io.enq <> io.enq
+  io.deq <> sink.io.deq
+}
+
+object ToRational
+{
+  def apply[T <: Data](x: DecoupledIO[T]): RationalIO[T] = {
+    val source = Module(new RationalCrossingSource(x.bits))
+    source.io.enq <> x
+    source.io.deq
+  }
+}
+
+object FromRational
+{
+  def apply[T <: Data](x: RationalIO[T]): DecoupledIO[T] = {
+    val sink = Module(new RationalCrossingSink(x.bits))
+    sink.io.enq <> x
+    sink.io.deq
+  }
+}