Building Tiles in chiesl (RocketChip)

Question

I'm working on RocketChip (RISC-V) and I ask if someone can explain this piece of code.

class WithNCores(n: Int) extends Config((pname,site,here) => pname match {
case NTiles => n
case BuildTiles => {
    List.tabulate(site(NTiles)){ i => (p: Parameters) =>
      LazyModule(new RocketTile()(p.alterPartial({
        case TileId => i
        case TLId => "L1toL2"
        case NUncachedTileLinkPorts => 1 + site(RoccNMemChannels)
      })))
    }
 }
case _ => throw new CDEMatchError})  

1. What is (pname,site,here) ? and what is it role ?
2. What does it mean (pname,site,here) => pname match { ... }

Thanks

Answer 1

RocketChip uses these configuration objects to feed parameters to the generator. The argument to Config is a function. (pname, site, here) are the arguments to the function. The first argument, pname, is the parameter name, which is how the function determines what setting is being requested. The match statement pname match { case Foo => Bar } is doing exactly that.

By the way, it seems that you are using a very old version of rocket-chip. I recommend upgrading to the latest version. There is documentation on how to use the parameter system.

https://github.com/freechipsproject/rocket-chip