From 6fc3ec3d63f01a173a36d45c0e5ef9ddc8812d9e Mon Sep 17 00:00:00 2001
From: "Wesley W. Terpstra" <wesley@sifive.com>
Date: Mon, 13 Mar 2017 16:03:21 -0700
Subject: [PATCH] tileink2: add a TestRAM; a zero-delay RAM useful for testing

TLRAM always answers after 1 cycle. We need a RAM that answers in 0.
---
 src/main/scala/uncore/tilelink2/TestRAM.scala | 83 +++++++++++++++++++
 src/main/scala/unittest/Configs.scala         |  1 +
 2 files changed, 84 insertions(+)
 create mode 100644 src/main/scala/uncore/tilelink2/TestRAM.scala

diff --git a/src/main/scala/uncore/tilelink2/TestRAM.scala b/src/main/scala/uncore/tilelink2/TestRAM.scala
new file mode 100644
index 00000000..74dd2f75
--- /dev/null
+++ b/src/main/scala/uncore/tilelink2/TestRAM.scala
@@ -0,0 +1,83 @@
+// See LICENSE.SiFive for license details.
+
+package uncore.tilelink2
+
+import Chisel._
+import config._
+import diplomacy._
+import util._
+
+// Do not use this for synthesis! Only for simulation.
+class TLTestRAM(address: AddressSet, executable: Boolean = true, beatBytes: Int = 4)(implicit p: Parameters) extends LazyModule
+{
+  val device = new MemoryDevice
+
+  val node = TLManagerNode(Seq(TLManagerPortParameters(
+    Seq(TLManagerParameters(
+      address            = List(address),
+      resources          = device.reg,
+      regionType         = RegionType.UNCACHED,
+      executable         = executable,
+      supportsGet        = TransferSizes(1, beatBytes),
+      supportsPutPartial = TransferSizes(1, beatBytes),
+      supportsPutFull    = TransferSizes(1, beatBytes),
+      fifoId             = Some(0))), // requests are handled in order
+    beatBytes  = beatBytes)))
+
+  // We require the address range to include an entire beat (for the write mask)
+  require ((address.mask & (beatBytes-1)) == beatBytes-1)
+
+  lazy val module = new LazyModuleImp(this) {
+    val io = new Bundle {
+      val in = node.bundleIn
+    }
+
+    def bigBits(x: BigInt, tail: List[Boolean] = List.empty[Boolean]): List[Boolean] =
+      if (x == 0) tail.reverse else bigBits(x >> 1, ((x & 1) == 1) :: tail)
+    val mask = bigBits(address.mask >> log2Ceil(beatBytes))
+
+    val in = io.in(0)
+    val edge = node.edgesIn(0)
+
+    val addrBits = (mask zip edge.addr_hi(in.a.bits).toBools).filter(_._1).map(_._2)
+    val memAddress = Cat(addrBits.reverse)
+    val mem = Mem(1 << addrBits.size, Vec(beatBytes, Bits(width = 8)))
+
+    // "Flow control"
+    in.a.ready := in.d.ready
+    in.d.valid := in.a.valid
+
+    val hasData = edge.hasData(in.a.bits)
+    val wdata = Vec.tabulate(beatBytes) { i => in.a.bits.data(8*(i+1)-1, 8*i) }
+
+    in.d.bits := edge.AccessAck(in.a.bits, UInt(0))
+    in.d.bits.data := Cat(mem(memAddress).reverse)
+    in.d.bits.opcode := Mux(hasData, TLMessages.AccessAck, TLMessages.AccessAckData)
+    when (in.a.fire() && hasData) { mem.write(memAddress, wdata, in.a.bits.mask.toBools) }
+
+    // Tie off unused channels
+    in.b.valid := Bool(false)
+    in.c.ready := Bool(true)
+    in.e.ready := Bool(true)
+  }
+}
+
+/** Synthesizeable unit testing */
+import unittest._
+
+class TLRAMZeroDelay(ramBeatBytes: Int)(implicit p: Parameters) extends LazyModule {
+  val fuzz = LazyModule(new TLFuzzer(5000))
+  val model = LazyModule(new TLRAMModel)
+  val ram  = LazyModule(new TLTestRAM(AddressSet(0x0, 0x3ff), beatBytes = ramBeatBytes))
+
+  model.node := fuzz.node
+  ram.node := TLDelayer(0.25)(model.node)
+
+  lazy val module = new LazyModuleImp(this) with HasUnitTestIO {
+    io.finished := fuzz.module.io.finished
+  }
+}
+
+class TLRAMZeroDelayTest(ramBeatBytes: Int)(implicit p: Parameters) extends UnitTest(timeout = 500000) {
+  io.finished := Module(LazyModule(new TLRAMZeroDelay(ramBeatBytes)).module).io.finished
+}
diff --git a/src/main/scala/unittest/Configs.scala b/src/main/scala/unittest/Configs.scala
index 95a22002..a927eeda 100644
--- a/src/main/scala/unittest/Configs.scala
+++ b/src/main/scala/unittest/Configs.scala
@@ -28,6 +28,7 @@ class WithTLSimpleUnitTests extends Config((site, here, up) => {
       Module(new uncore.tilelink2.TLRAMSimpleTest(1)),
       Module(new uncore.tilelink2.TLRAMSimpleTest(4)),
       Module(new uncore.tilelink2.TLRAMSimpleTest(16)),
+      Module(new uncore.tilelink2.TLRAMZeroDelayTest(4)),
       Module(new uncore.tilelink2.TLRR0Test),
       Module(new uncore.tilelink2.TLRR1Test),
       Module(new uncore.tilelink2.TLRAMRationalCrossingTest),