tilelink: add the ErrorEvaluator, a test bench error helper

src/main/scala/tilelink/ErrorEvaluator.scala

@@ -0,0 +1,50 @@
+// See LICENSE.SiFive for license details.
+
+package freechips.rocketchip.tilelink
+
+import Chisel._
+import freechips.rocketchip.config.Parameters
+import freechips.rocketchip.diplomacy._
+import freechips.rocketchip.util._
+
+// An ErrorEvaluator is used for test harnesses.
+// It creates errors in transactions which overlap an address in pattern.
+// If testOn is true, it will assert fail if these transactions do not already error.
+// If testOff is true, it will assert fail if these transactions otherwise error.
+// This helps when building unit tests to confirm that errors are propagated correctly.
+class TLErrorEvaluator(pattern: Seq[AddressSet], testOn: Boolean, testOff: Boolean)(implicit p: Parameters) extends LazyModule
+{
+  val node = TLAdapterNode()
+  lazy val module = new LazyModuleImp(this) {
+    (node.in zip node.out) foreach { case ((in, edgeIn), (out, edgeOut)) =>
+      out <> in
+
+      // Does the request overlap the pattern ?
+      val abase = in.a.bits.address
+      val amask = UIntToOH1(in.a.bits.size, log2Up(edgeIn.maxTransfer))
+      val overlaps = pattern.map { case a =>
+        val pbase = UInt(a.base)
+        val pmask = UInt(a.mask & ((BigInt(1) << edgeIn.bundle.addressBits) - 1))
+        (amask | pmask | ~(abase ^ pbase)).andR
+      }.reduce(_ || _)
+
+      val (d_first, d_last, _) = edgeOut.firstlast(out.d)
+
+      val inject = Mem(edgeIn.client.endSourceId, Bool())
+      when (in.a.fire()) { inject.write(in.a.bits.source, overlaps) }
+
+      val bypass = in.a.fire() && in.a.bits.source === in.d.bits.source
+      val d_inject = Mux(bypass, overlaps, inject.read(in.d.bits.source)) holdUnless d_first
+      in.d.bits.error := out.d.bits.error || (d_last && d_inject)
+
+      assert (Bool(!testOn)  || !out.d.fire() || !d_last || !d_inject ||  out.d.bits.error, "Error flag was not set!")
+      assert (Bool(!testOff) || !out.d.fire() || !d_last ||  d_inject || !out.d.bits.error, "Error flag was set!")
+    }
+  }
+}
+
+object TLErrorEvaluator
+{
+  def apply(pattern: Seq[AddressSet], testOn: Boolean = false, testOff: Boolean = false)(implicit p: Parameters): TLNode =
+    LazyModule(new TLErrorEvaluator(pattern, testOn, testOff)).node
+}