6.3. Integrating Custom Chisel Projects into the Generator Build System


This section assumes integration of custom Chisel through git submodules. While it is possible to directly commit custom Chisel into the Chipyard framework, we heavily recommend managing custom code through git submodules. Using submodules decouples development of custom features from development on the Chipyard framework.

While developing, you want to include Chisel code in a submodule so that it can be shared by different projects. To add a submodule to the Chipyard framework, make sure that your project is organized as follows.


Put this in a git repository and make it accessible. Then add it as a submodule to under the following directory hierarchy: generators/yourproject.

The build.sbt is a minimal file which describes metadata for a Chisel project. For a simple project, the build.sbt can even be empty, but below we provide an example build.sbt.

organization := "edu.berkeley.cs"

version := "1.0"

name := "yourproject"

scalaVersion := "2.12.4"
cd generators/
git submodule add https://git-repository.com/yourproject.git

Then add yourproject to the Chipyard top-level build.sbt file.

lazy val yourproject = (project in file("generators/yourproject")).settings(commonSettings).dependsOn(rocketchip)

You can then import the classes defined in the submodule in a new project if you add it as a dependency. For instance, if you want to use this code in the chipyard project, add your project to the list of sub-projects in the .dependsOn() for lazy val chipyard. The original code may change over time, but it should look something like this:

lazy val chipyard = (project in file("generators/chipyard"))
    .dependsOn(testchipip, rocketchip, boom, hwacha, rocketchip_blocks, rocketchip_inclusive_cache, iocell,
        sha3, dsptools, `rocket-dsp-utils`,
        gemmini, icenet, tracegen, cva6, nvdla, sodor, ibex, fft_generator,
        yourproject, // <- added to the middle of the list for simplicity
        constellation, mempress)
    .settings(libraryDependencies ++= rocketLibDeps.value)
        libraryDependencies ++= Seq(
        "org.reflections" % "reflections" % "0.10.2"