tilelink: add PatternPusher, a device to inject a fixed traffic pattern (#950)

src/main/scala/tilelink/PatternPusher.scala

@@ -0,0 +1,74 @@
+// See LICENSE.SiFive for license details.
+
+package freechips.rocketchip.tilelink
+
+import Chisel._
+import chisel3.internal.sourceinfo.SourceInfo
+import freechips.rocketchip.config.Parameters
+import freechips.rocketchip.diplomacy._
+
+sealed trait Pattern {
+  def address: BigInt
+  def size: Int
+  def bits(edge: TLEdgeOut): (Bool, TLBundleA)
+  require ((address & ((BigInt(1) << size) - 1)) == 0)
+}
+
+case class WritePattern(address: BigInt, size: Int, data: BigInt) extends Pattern
+{
+  require (log2Floor(data) < (BigInt(8) << size))
+  def bits(edge: TLEdgeOut) = edge.Put(UInt(0), UInt(address), UInt(size), UInt(data))
+}
+
+case class ReadPattern(address: BigInt, size: Int) extends Pattern
+{
+  def bits(edge: TLEdgeOut) = edge.Get(UInt(0), UInt(address), UInt(size))
+}
+
+class TLPatternPusher(name: String, pattern: Seq[Pattern])(implicit p: Parameters) extends LazyModule
+{
+  val node = TLClientNode(Seq(TLClientPortParameters(Seq(TLClientParameters(name = name)))))
+
+  lazy val module = new LazyModuleImp(this) {
+    val io = new Bundle {
+      val tl_out = node.bundleOut
+      val run = Bool(INPUT)
+      val done = Bool(OUTPUT)
+    }
+
+    val edgeOut = node.edgesOut(0)
+    pattern.foreach { p =>
+      require (p.size <= log2Ceil(edgeOut.manager.beatBytes), "Patterns must fit in a single beat")
+    }
+
+    val step   = RegInit(UInt(0, width = log2Ceil(pattern.size+1)))
+    val flight = RegInit(Bool(false))
+    val ready  = RegNext(Bool(true), Bool(false))
+
+    val end = step === UInt(pattern.size)
+    io.done := end && !flight
+
+    val a = io.tl_out(0).a
+    val d = io.tl_out(0).d
+
+    when (a.fire()) {
+      flight := Bool(true)
+      step := step + UInt(1)
+    }
+    when (d.fire()) {
+      flight := Bool(false)
+    }
+
+    val (plegal, pbits) = pattern.map(_.bits(edgeOut)).unzip
+    assert (end || Vec(plegal)(step), s"Pattern pusher ${name} tried to push an illegal request")
+
+    a.valid := io.run && ready && !end && !flight
+    a.bits  := Vec(pbits)(step)
+    d.ready := Bool(true)
+
+    // Tie off unused channels
+    io.tl_out(0).b.ready := Bool(true)
+    io.tl_out(0).c.valid := Bool(false)
+    io.tl_out(0).e.valid := Bool(false)
+  }
+}