rocket-chip/rocket/src/main/scala/arbiter.scala

// See LICENSE for license details.

package rocket

import Chisel._
import uncore._
import cde.{Parameters, Field}
import junctions.{ParameterizedBundle, DecoupledHelper}

class HellaCacheArbiter(n: Int)(implicit p: Parameters) extends Module
{
  val io = new Bundle {
    val requestor = Vec(n, new HellaCacheIO).flip
    val mem = new HellaCacheIO
  }

  val r_valid = io.requestor.map(r => Reg(next=r.req.valid))

  io.mem.req.valid := io.requestor.map(_.req.valid).reduce(_||_)
  io.requestor(0).req.ready := io.mem.req.ready
  for (i <- 1 until n)
    io.requestor(i).req.ready := io.requestor(i-1).req.ready && !io.requestor(i-1).req.valid

  io.mem.req.bits := io.requestor(n-1).req.bits
  io.mem.req.bits.tag := Cat(io.requestor(n-1).req.bits.tag, UInt(n-1, log2Up(n)))
  for (i <- n-2 to 0 by -1) {
    val req = io.requestor(i).req
    when (req.valid) {
      io.mem.req.bits.cmd := req.bits.cmd
      io.mem.req.bits.typ := req.bits.typ
      io.mem.req.bits.addr := req.bits.addr
      io.mem.req.bits.phys := req.bits.phys
      io.mem.req.bits.tag := Cat(req.bits.tag, UInt(i, log2Up(n)))
    }
    when (r_valid(i)) {
      io.mem.req.bits.kill := req.bits.kill
      io.mem.req.bits.data := req.bits.data
    }
  }

  for (i <- 0 until n) {
    val resp = io.requestor(i).resp
    val tag_hit = io.mem.resp.bits.tag(log2Up(n)-1,0) === UInt(i)
    resp.valid := io.mem.resp.valid && tag_hit
    io.requestor(i).xcpt := io.mem.xcpt
    io.requestor(i).ordered := io.mem.ordered
    resp.bits := io.mem.resp.bits
    resp.bits.tag := io.mem.resp.bits.tag >> log2Up(n)
    resp.bits.nack := io.mem.resp.bits.nack && tag_hit
    resp.bits.replay := io.mem.resp.bits.replay && tag_hit

    io.requestor(i).replay_next.valid := io.mem.replay_next.valid &&
      io.mem.replay_next.bits(log2Up(n)-1,0) === UInt(i)
    io.requestor(i).replay_next.bits := io.mem.replay_next.bits >> log2Up(n)
  }
}

class InOrderArbiter[T <: Data, U <: Data](reqTyp: T, respTyp: U, n: Int)
    (implicit p: Parameters) extends Module {
  val io = new Bundle {
    val in_req = Vec(n, Decoupled(reqTyp)).flip
    val in_resp = Vec(n, Decoupled(respTyp))
    val out_req = Decoupled(reqTyp)
    val out_resp = Decoupled(respTyp).flip
  }

  if (n > 1) {
    val route_q = Module(new Queue(UInt(width = log2Up(n)), 2))
    val req_arb = Module(new RRArbiter(reqTyp, n))
    req_arb.io.in <> io.in_req

    val req_helper = DecoupledHelper(
      req_arb.io.out.valid,
      route_q.io.enq.ready,
      io.out_req.ready)

    io.out_req.bits := req_arb.io.out.bits
    io.out_req.valid := req_helper.fire(io.out_req.ready)

    route_q.io.enq.bits := req_arb.io.chosen
    route_q.io.enq.valid := req_helper.fire(route_q.io.enq.ready)

    req_arb.io.out.ready := req_helper.fire(req_arb.io.out.valid)

    val resp_sel = route_q.io.deq.bits
    val resp_ready = io.in_resp(resp_sel).ready
    val resp_helper = DecoupledHelper(
      resp_ready,
      route_q.io.deq.valid,
      io.out_resp.valid)

    val resp_valid = resp_helper.fire(resp_ready)
    for (i <- 0 until n) {
      io.in_resp(i).bits := io.out_resp.bits
      io.in_resp(i).valid := resp_valid && resp_sel === UInt(i)
    }

    route_q.io.deq.ready := resp_helper.fire(route_q.io.deq.valid)
    io.out_resp.ready := resp_helper.fire(io.out_resp.valid)
  } else {
    io.out_req <> io.in_req.head
    io.in_resp.head <> io.out_resp
  }
}