Fix broken GCD example

docs/Customization/Keys-Traits-Configs.rst

@@ -40,12 +40,12 @@ Top-level traits specify that the ``DigitalTop`` has been parameterized to read
 
 Top-level traits should be defined and documented in subprojects, alongside their corresponding keys. The traits should then be added to the ``DigitalTop`` being used by Chipyard.
 
-Below we see the traits for the GCD example. The Lazy trait connects the GCD module to the Diplomacy graph, while the Implementation trait causes the ``DigitalTop`` to instantiate an additional port and concretely connect it to the GCD module.
+Below we see the traits for the GCD example. The Lazy trait connects the GCD module to the Diplomacy graph.
 
 .. literalinclude:: ../../generators/chipyard/src/main/scala/example/GCD.scala
     :language: scala
     :start-after: DOC include start: GCD lazy trait
-    :end-before: DOC include end: GCD imp trait
+    :end-before: DOC include end: GCD lazy trait
 
 These traits are added to the default ``DigitalTop`` in Chipyard.
 

docs/Customization/MMIO-Peripherals.rst

@@ -79,13 +79,7 @@ Register routers have a TileLink node simply named "node", which we can hook up
 This will automatically add address map and device tree entries for the peripheral.
 Also observe how we have to place additional AXI4 buffers and converters for the AXI4 version of this peripheral.
 
-For peripherals which instantiate a concrete module, or which need to be connected to concrete IOs or wires, a matching concrete trait is necessary. We will make our GCD example output a ``gcd_busy`` signal as a top-level port to demonstrate. In the concrete module implementation trait, we instantiate the top level IO (a concrete object) and wire it to the IO of our lazy module.
-
-
-.. literalinclude:: ../../generators/chipyard/src/main/scala/example/GCD.scala
-    :language: scala
-    :start-after: DOC include start: GCD imp trait
-    :end-before: DOC include end: GCD imp trait
+Peripherals which expose I/O can use `InModuleBody` to punch their I/O to the `DigitalTop` module.
 
 Constructing the DigitalTop and Config
 --------------------------------------

generators/chipyard/src/main/scala/DigitalTop.scala

@@ -48,6 +48,5 @@ class DigitalTopModule[+L <: DigitalTop](l: L) extends ChipyardSystemModule(l)
   with sifive.blocks.devices.gpio.HasPeripheryGPIOModuleImp
   with sifive.blocks.devices.spi.HasPeripherySPIFlashModuleImp
   with sifive.blocks.devices.spi.HasPeripherySPIModuleImp
-  with chipyard.example.CanHavePeripheryGCDModuleImp
   with freechips.rocketchip.util.DontTouch
 // DOC include end: DigitalTop

generators/chipyard/src/main/scala/example/GCD.scala

@@ -161,45 +161,40 @@ trait CanHavePeripheryGCD { this: BaseSubsystem =>
   private val portName = "gcd"
 
   // Only build if we are using the TL (nonAXI4) version
-  val gcd = p(GCDKey) match {
+  val gcd_busy = p(GCDKey) match {
     case Some(params) => {
-      if (params.useAXI4) {
-        val gcd = LazyModule(new GCDAXI4(params, pbus.beatBytes)(p))
+      val gcd = if (params.useAXI4) {
+        val gcd = pbus { LazyModule(new GCDAXI4(params, pbus.beatBytes)(p)) }
         pbus.coupleTo(portName) {
           gcd.node :=
           AXI4Buffer () :=
           TLToAXI4 () :=
           // toVariableWidthSlave doesn't use holdFirstDeny, which TLToAXI4() needsx
           TLFragmenter(pbus.beatBytes, pbus.blockBytes, holdFirstDeny = true) := _
         }
-        Some(gcd)
+        gcd
       } else {
-        val gcd = LazyModule(new GCDTL(params, pbus.beatBytes)(p))
+        val gcd = pbus { LazyModule(new GCDTL(params, pbus.beatBytes)(p)) }
         pbus.coupleTo(portName) { gcd.node := TLFragmenter(pbus.beatBytes, pbus.blockBytes) := _ }
-        Some(gcd)
+        gcd
       }
+      val pbus_io = pbus { InModuleBody {
+        val busy = IO(Output(Bool()))
+        busy := gcd.module.io.gcd_busy
+        busy
+      }}
+      val gcd_busy = InModuleBody {
+        val busy = IO(Output(Bool())).suggestName("gcd_busy")
+        busy := pbus_io
+        busy
+      }
+      Some(gcd_busy)
     }
     case None => None
   }
 }
 // DOC include end: GCD lazy trait
 
-// DOC include start: GCD imp trait
-trait CanHavePeripheryGCDModuleImp extends LazyRawModuleImp {
-  val outer: CanHavePeripheryGCD
-  val gcd_busy = outer.gcd match {
-    case Some(gcd) => {
-      val busy = IO(Output(Bool()))
-      busy := gcd.module.io.gcd_busy
-      Some(busy)
-    }
-    case None => None
-  }
-}
-
-// DOC include end: GCD imp trait
-
-
 // DOC include start: GCD config fragment
 class WithGCD(useAXI4: Boolean = false, useBlackBox: Boolean = false) extends Config((site, here, up) => {
   case GCDKey => Some(GCDParams(useAXI4 = useAXI4, useBlackBox = useBlackBox))