Add EmptyChipTop example

docs/Advanced-Concepts/Top-Testharness.rst

@@ -25,6 +25,8 @@ The default standard ``ChipTop`` provides a mimimal, barebones template for ``IO
 For tapeouts, integrating Analog IP, or other non-standard use cases, Chipyard supports specifying a custom ``ChipTop`` using the ``BuildTop`` key.
 An example of a custom ChipTop which uses non-standard IOCells is provided in `generators/chipyard/src/main/scala/example/CustomChipTop.scala <https://github.com/ucb-bar/chipyard/blob/main/generators/chipyard/src/main/scala/example/CustomChipTop.scala>`__
 
+You can also specify a fully custom ChipTop that does not use any RocketChip or Chipyard SoC components. An example of this is provided in `generators/chipyard/src/main/scala/example/EmptyChipTop.scala <https://github.com/ucb-bar/chipyard/blob/main/generators/chipyard/src/main/scala/example/EmptyChipTop.scala>`__. The ``EmptyChipTop`` example can be built with ``make CONFIG=EmptyChipTopConfig TOP=EmptyChipTop``.
+
 
 System/DigitalTop
 -------------------------

generators/chipyard/src/main/scala/config/NoCoreConfigs.scala

@@ -17,3 +17,9 @@ class NoCoresConfig extends Config(
   new chipyard.config.WithNoDebug ++
   new chipyard.config.WithNoPLIC ++
   new chipyard.config.AbstractConfig)
+
+// A config that uses a empty chiptop module with no rocket-chip soc components
+class EmptyChipTopConfig extends Config(
+  new chipyard.example.WithEmptyChipTop ++
+  new chipyard.config.AbstractConfig             // since we aren't using rocket-chip, this doesn't do anything
+)

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

@@ -0,0 +1,21 @@
+package chipyard.example
+
+import chisel3._
+
+import org.chipsalliance.cde.config._
+import freechips.rocketchip.diplomacy._
+import freechips.rocketchip.util.{DontTouch}
+
+import chipyard._
+import chipyard.harness.{BuildTop}
+
+class EmptyChipTop(implicit p: Parameters) extends LazyModule {
+  override lazy val module = new Impl
+  class Impl extends LazyRawModuleImp(this) with DontTouch {
+    // Your custom non-rocketchip-soc stuff here
+  }
+}
+
+class WithEmptyChipTop extends Config((site, here, up) => {
+  case BuildTop => (p: Parameters) => new EmptyChipTop()(p)
+})

generators/chipyard/src/main/scala/harness/HasHarnessInstantiators.scala

@@ -99,6 +99,7 @@ trait HasHarnessInstantiators {
     if (p(DontTouchChipTopPorts)) {
       duts.map(_ match {
         case d: DontTouch => d.dontTouchPorts()
+        case _ =>
       })
     }
 

scripts/split-mems-conf.py

@@ -70,7 +70,10 @@ if __name__ == "__main__":
     imhj_data = json.load(imhj)
 
     dut_root = bfs_find_root(imhj_data, args.dut_module_name)
+    if dut_root:
       dut_submodules = bfs_collect_submodules(dut_root)
+    else:
+      dut_submodules = set()
 
     model_root = bfs_find_root(imhj_data, args.model_module_name)
     model_submodules = bfs_collect_submodules(model_root)