From 44ce96cff9da557be080dd3b327f91d13a8cfe84 Mon Sep 17 00:00:00 2001
From: Schuyler Eldridge <schuyler.eldridge@sifive.com>
Date: Fri, 5 May 2023 18:31:57 -0400
Subject: [PATCH] Allow DataView of Reset <=> [UInt<1>, AsyncReset] (#3181)

Change what DataView allows in its type checking to enable Reset to be
viewed as either a UInt<1> or an AsyncReset.  This enables more flexible
DataViews which match already allowable Chisel and FIRRTL connection
semantics.

Signed-off-by: Schuyler Eldridge <schuyler.eldridge@sifive.com>
---
 .../experimental/dataview/package.scala       | 16 +++++++--
 .../chiselTests/experimental/DataView.scala   | 34 +++++++++++++++++++
 2 files changed, 47 insertions(+), 3 deletions(-)

diff --git a/core/src/main/scala/chisel3/experimental/dataview/package.scala b/core/src/main/scala/chisel3/experimental/dataview/package.scala
index 072ce6c6446..52c5bfdadf1 100644
--- a/core/src/main/scala/chisel3/experimental/dataview/package.scala
+++ b/core/src/main/scala/chisel3/experimental/dataview/package.scala
@@ -103,9 +103,19 @@ package object dataview {
       val tex = unfoldView(te).find(targetContains).getOrElse(err("Target", te))
       val vex = unfoldView(ve).find(viewFieldLookup.contains).getOrElse(err("View", ve))
 
-      if (tex.getClass != vex.getClass) {
-        val fieldName = viewFieldName(vex)
-        throw InvalidViewException(s"Field $fieldName specified as view of non-type-equivalent value $tex")
+      (tex, vex) match {
+        /* Allow views where the types are equal. */
+        case (a, b) if a.getClass == b.getClass =>
+        /* allow bool <=> reset views. */
+        case (a: Bool, _: Reset) =>
+        case (_: Reset, a: Bool) =>
+        /* Allow AsyncReset <=> Reset views. */
+        case (a: AsyncReset, _: Reset) =>
+        case (_: Reset, a: AsyncReset) =>
+        /* All other views produce a runtime error. */
+        case _ =>
+          val fieldName = viewFieldName(vex)
+          throw InvalidViewException(s"Field $fieldName specified as view of non-type-equivalent value $tex")
       }
       // View width must be unknown or match target width
       if (vex.widthKnown && vex.width != tex.width) {
diff --git a/src/test/scala/chiselTests/experimental/DataView.scala b/src/test/scala/chiselTests/experimental/DataView.scala
index a443fafe410..6b1d7785bed 100644
--- a/src/test/scala/chiselTests/experimental/DataView.scala
+++ b/src/test/scala/chiselTests/experimental/DataView.scala
@@ -546,6 +546,40 @@ class DataViewSpec extends ChiselFlatSpec {
     chirrtl should include("dataOut <= vec[addrReg]")
   }
 
+  it should "allow views between reset types" in {
+    class A extends Bundle {
+      val bool = Bool()
+      val asyncreset = AsyncReset()
+    }
+
+    class B extends Bundle {
+      val reset_0 = Reset()
+      val reset_1 = Reset()
+    }
+
+    class Foo extends RawModule {
+      val a = Wire(new A)
+      val b = Wire(new B)
+
+      implicit val view = DataView[A, B](
+        _ => new B,
+        _.bool -> _.reset_0,
+        _.asyncreset -> _.reset_1
+      )
+
+      a.viewAs[B] := b
+    }
+
+    (ChiselStage
+      .emitCHIRRTL(new Foo, Array("--full-stacktrace"))
+      .split('\n')
+      .map(_.takeWhile(_ != '@'))
+      .map(_.trim) should contain).allOf(
+      "a.bool <= b.reset_0",
+      "a.asyncreset <= b.reset_1"
+    )
+  }
+
   it should "error if you try to dynamically index a Vec view that does not correspond to a Vec target" in {
     class MyModule extends Module {
       val inA, inB = IO(Input(UInt(8.W)))