Wlink Configs¶

Wlink utilizes Configs for describing how each instance of Wlink looks. Each Config can be different to target a different instance of Wlink. Each Config is generally made up of several smaller config fragments. These are individual fragments that usually target a certain portion of the design.

Let’s take a look at a simple config fragment

class WithWlinkDisableTLMonitors extends  Config((site, here, up) => {
  case MonitorsEnabled => false
})

This config fragment disables TileLink Monitors by setting the MonitorsEnabled key to false.

One nice feature about Configs is that you can declare several fragments in one and then extend from that fragment for generating a larger Config. Let’s look at the BaseWlinkConfig which we usually extend from.

class BaseWlinkConfig extends Config(
  new WithWlinkDisableTLMonitors ++
  new WithWlinkOnlyGen ++
  new WithWavComponentPrefix("wlink")
)

Here we have defined the BaseWlinkConfig. It starts with the WithWavComponentPrefix config fragment. We then add WithWlinkOnlyGen to indicate we are generating Wlink as the top level component, and finally we add our WithWlinkDisableTLMonitors.

This Config doesn’t seem all that interesting, so let’s see what else we can create.

WithWlinkGPIOAXIConfig Example¶

Let’s say I want to use Wlink with the basic GPIO-based PHY and AXI. Depending on my implementation I want to be able to change the number of lanes and possibly the AXI parameters. Let’s create a config fragment that gives some configurability.

class WithWlinkGPIOAXIConfig(
  numTxLanes  : Int = 1,
  numRxLanes  : Int = 1,
  size        : BigInt = 0x100000,
  beatBytes   : Int = 4,
  idBits      : Int = 4,
) extends Config((site, here, up) => {

  case WlinkParamsKey => WlinkParams(
    phyParams = WlinkPHYGPIOExampleParams(
      numTxLanes = numTxLanes,
      numRxLanes = numRxLanes,
    ),
    axiParams = Some(Seq(WlinkAxiParams(
      base = 0x0,
      size = size,
      beatBytes = beatBytes,
      idBits = idBits)))
  )
})

This config fragment allows a user to pass the lanes, size, beatBytes, and id size anytime they mixin this config fragment. Let’s look below at how we can create two separate instances of the Wlink.

class Wlink1LaneAXI32bitConfig extends Config(
  new WithWlinkGPIOAXIConfig(
    numTxLanes = 1,
    numRxLanes = 1,
    beatBytes  = 4) ++
  new BaseWlinkConfig
)

class Wlink1LaneAXI64bitConfig extends Config(
  new WithWlinkGPIOAXIConfig(
    numTxLanes = 1,
    numRxLanes = 1,
    beatBytes  = 8) ++
  new BaseWlinkConfig
)


class Wlink8LaneAXI256bitConfig extends Config(
  new WithWlinkGPIOAXIConfig(
    numTxLanes = 8,
    numRxLanes = 8,
    beatBytes  = 32) ++
  new BaseWlinkConfig
)

For more details on Configs it is strongly recommend to look over the Chipyard project