rocket-chip/uncore/src/main/scala/devices/Rom.scala

package uncore.devices

import Chisel._
import junctions._
import uncore.tilelink._
import uncore.util._
import cde.{Parameters, Field}

class ROMSlave(contents: Seq[Byte])(implicit val p: Parameters) extends Module
    with HasTileLinkParameters
    with HasAddrMapParameters {
  val io = new ClientUncachedTileLinkIO().flip

  val acq = Queue(io.acquire, 1)
  val single_beat = acq.bits.isBuiltInType(Acquire.getType)
  val multi_beat = acq.bits.isBuiltInType(Acquire.getBlockType)
  assert(!acq.valid || single_beat || multi_beat, "unsupported ROMSlave operation")

  val addr_beat = Reg(UInt())
  when (io.grant.fire()) { addr_beat := addr_beat + UInt(1) }
  when (io.acquire.fire()) { addr_beat := io.acquire.bits.addr_beat }

  val byteWidth = tlDataBits / 8
  val rows = (contents.size + byteWidth - 1)/byteWidth
  val rom = Vec.tabulate(rows) { i =>
    val slice = contents.slice(i*byteWidth, (i+1)*byteWidth)
    UInt(slice.foldRight(BigInt(0)) { case (x,y) => (y << 8) + (x.toInt & 0xFF) }, byteWidth*8)
  }
  val raddr = Cat(acq.bits.addr_block, addr_beat)
  val rdata = rom(if (rows == 1) UInt(0) else raddr(log2Up(rom.size)-1,0))

  val last = !multi_beat || addr_beat === UInt(tlDataBeats-1)
  io.grant.valid := acq.valid
  acq.ready := io.grant.ready && last
  io.grant.bits := Grant(
    is_builtin_type = Bool(true),
    g_type = acq.bits.getBuiltInGrantType(),
    client_xact_id = acq.bits.client_xact_id,
    manager_xact_id = UInt(0),
    addr_beat = addr_beat,
    data = rdata)
}

class NastiROM(contents: Seq[Byte])(implicit p: Parameters) extends Module {
  val io = new NastiIO().flip
  val ar = Queue(io.ar, 1)

  // This assumes ROMs are in read-only parts of the address map.
  // Reuse b_queue code from NastiErrorSlave if this assumption is bad.
  when (ar.valid) { assert(ar.bits.len === UInt(0), "Can't burst-read from NastiROM") }
  assert(!(io.aw.valid || io.w.valid), "Can't write to NastiROM")
  io.aw.ready := Bool(false)
  io.w.ready := Bool(false)
  io.b.valid := Bool(false)

  val byteWidth = io.r.bits.nastiXDataBits / 8
  val rows = (contents.size + byteWidth - 1)/byteWidth
  val rom = Vec.tabulate(rows) { i =>
    val slice = contents.slice(i*byteWidth, (i+1)*byteWidth)
    UInt(slice.foldRight(BigInt(0)) { case (x,y) => (y << 8) + (x.toInt & 0xFF) }, byteWidth*8)
  }
  val rdata = rom(if (rows == 1) UInt(0) else ar.bits.addr(log2Up(contents.size)-1,log2Up(byteWidth)))

  io.r <> ar
  io.r.bits := NastiReadDataChannel(ar.bits.id, rdata)
}