cake_pattern.md

Cake pattern

Some notes of the cake pattern used in Rocket.

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• Class combination

For a design that uses cake pattern, 3 classes are needed.

• abstract class Design(implicit p: Parameters) extends LazyModule with BindingScope
  The design generator (LazyModule).
  • module LazyModuleImp
• class DesignBundle[+L <: Design](_outer: L) extends GenericParameterizedBundle(_outer)
  The I/O (bundle) definition of the design.
• class DesignModule[+L <: Design, +B <: DesignBundle[L]](_outer: L, _io: () => B) extends LazyModuleImp(_outer)
  The actual Chisel module that will be generated by the design generator.

Here is the cake pattern for the BaseCoreplex module:

abstract class BaseCoreplex(implicit p: Parameters) extends BareCoreplex
    with CoreplexNetwork
    with BankedL2CoherenceManagers {
  override lazy val module = new BaseCoreplexModule(this, () => new BaseCoreplexBundle(this))
}

class BaseCoreplexBundle[+L <: BaseCoreplex](_outer: L) extends BareCoreplexBundle(_outer)
    with CoreplexNetworkBundle
    with BankedL2CoherenceManagersBundle

class BaseCoreplexModule[+L <: BaseCoreplex, +B <: BaseCoreplexBundle[L]](_outer: L, _io: () => B) extends BareCoreplexModule(_outer, _io)
    with CoreplexNetworkModule
    with BankedL2CoherenceManagersModule

extra notes

• use module in LazyModule as a virtual variable, to enforce types. See the derived declaration in HasXXXX traits.

_{Last updated: 14/08/2017
CC BY-NC-SA 4.0, © (2017) Wei Song}