rocket-chip/src/main/scala/uncore/tilelink2/Broadcast.scala

// See LICENSE for license details.

package uncore.tilelink2

import Chisel._
import diplomacy._
import scala.math.{min,max}

class TLBroadcast(lineBytes: Int, numTrackers: Int = 4, bufferless: Boolean = false) extends LazyModule
{
  require (lineBytes > 0 && isPow2(lineBytes))
  require (numTrackers > 0)

  val node = TLAdapterNode(
    clientFn  = { case Seq(cp) =>
      cp.copy(clients = Seq(TLClientParameters(
        sourceId = IdRange(0, 1 << log2Ceil(cp.endSourceId*4)))))
    },
    managerFn = { case Seq(mp) =>
      mp.copy(
        endSinkId  = numTrackers,
        minLatency = 1,
        managers   = mp.managers.map { m =>
          // We are the last level manager
          require (m.regionType != RegionType.CACHED)
          require (m.regionType != RegionType.TRACKED)
          require (!m.supportsAcquire)
          // We only manage addresses which are uncached
          if (m.regionType == RegionType.UNCACHED && m.supportsGet) {
            // The device had better support line transfers
            val lowerBound = max(m.supportsPutFull.min, m.supportsGet.min)
            require (!m.supportsPutFull || m.supportsPutFull.contains(lineBytes))
            require (!m.supportsGet     || m.supportsGet    .contains(lineBytes))
            m.copy(
              regionType         = RegionType.TRACKED,
              supportsAcquire    = TransferSizes(lowerBound, lineBytes),
              // truncate supported accesses to lineBytes (we only ever probe for one line)
              supportsPutFull    = TransferSizes(m.supportsPutFull   .min, min(m.supportsPutFull   .max, lineBytes)),
              supportsPutPartial = TransferSizes(m.supportsPutPartial.min, min(m.supportsPutPartial.max, lineBytes)),
              supportsGet        = TransferSizes(m.supportsGet       .min, min(m.supportsGet       .max, lineBytes)),
              fifoId             = None // trackers do not respond in FIFO order!
            )
          } else {
            m
          }
        }
      )
    }
  )

  lazy val module = new LazyModuleImp(this) {
    val io = new Bundle {
      val in  = node.bundleIn
      val out = node.bundleOut
    }

    val in = io.in(0)
    val out = io.out(0)
    val edgeIn = node.edgesIn(0)
    val edgeOut = node.edgesOut(0)
    val clients = edgeIn.client.clients
    val managers = edgeOut.manager.managers
    val lineShift = log2Ceil(lineBytes)

    import TLBroadcastConstants._

    require (lineBytes >= edgeOut.manager.beatBytes)
    // For the probe walker, we need to identify all the caches
    val caches = clients.filter(_.supportsProbe).map(_.sourceId)
    val cache_targets = caches.map(c => UInt(c.start))

    // Create the request tracker queues
    val trackers = Seq.tabulate(numTrackers) { id =>
      Module(new TLBroadcastTracker(id, lineBytes, log2Up(caches.size), bufferless, edgeIn, edgeOut)).io
    }

    // We always accept E
    in.e.ready := Bool(true)
    (trackers zip UIntToOH(in.e.bits.sink).toBools) foreach { case (tracker, select) =>
      tracker.e_last := select && in.e.fire()
    }

    // Depending on the high source bits, we might transform D
    val d_high = log2Ceil(edgeIn.client.endSourceId)
    val d_what = out.d.bits.source(d_high+1, d_high)
    val d_drop = d_what === DROP
    val d_hasData = edgeOut.hasData(out.d.bits)
    val d_normal = Wire(in.d)
    val d_trackerOH = Vec(trackers.map { t => !t.idle && t.source === d_normal.bits.source }).asUInt

    out.d.ready := d_normal.ready || d_drop
    d_normal.valid := out.d.valid && !d_drop
    d_normal.bits := out.d.bits // truncates source
    when (d_what(1)) { // TRANSFORM_*
      d_normal.bits.opcode := Mux(d_hasData, TLMessages.GrantData, TLMessages.ReleaseAck)
      d_normal.bits.param  := Mux(d_hasData, Mux(d_what(0), TLPermissions.toT, TLPermissions.toB), UInt(0))
    }
    d_normal.bits.sink := OHToUInt(d_trackerOH)
    assert (!d_normal.valid || (d_trackerOH.orR() || d_normal.bits.opcode === TLMessages.ReleaseAck))

    // A tracker response is anything neither dropped nor a ReleaseAck
    val d_response = d_hasData || !d_what(1)
    val (_, d_last, _) = edgeIn.firstlast(d_normal)
    (trackers zip d_trackerOH.toBools) foreach { case (tracker, select) =>
      tracker.d_last := select && d_normal.fire() && d_response && d_last
    }

    // Incoming C can be:
    // ProbeAck     => decrement tracker, drop 
    // ProbeAckData => decrement tracker, send out A as PutFull(DROP)
    // ReleaseData  =>                    send out A as PutFull(TRANSFORM)
    // Release      => send out D as ReleaseAck

    val c_probeack     = in.c.bits.opcode === TLMessages.ProbeAck
    val c_probeackdata = in.c.bits.opcode === TLMessages.ProbeAckData
    val c_releasedata  = in.c.bits.opcode === TLMessages.ReleaseData
    val c_release      = in.c.bits.opcode === TLMessages.Release

    // Decrement the tracker's outstanding probe counter
    val c_decrement = in.c.fire() && (c_probeack || c_probeackdata)
    val (_, c_last, _) = edgeIn.firstlast(in.c)
    trackers foreach { tracker =>
      tracker.probeack := c_decrement && c_last && tracker.line === (in.c.bits.address >> lineShift)
    }

    val releaseack = Wire(in.d)
    val putfull = Wire(out.a)

    in.c.ready := c_probeack || Mux(c_release, releaseack.ready, putfull.ready)

    releaseack.valid := in.c.valid && c_release
    releaseack.bits  := edgeIn.ReleaseAck(in.c.bits.address, UInt(0), in.c.bits.source, in.c.bits.size)

    val put_what = Mux(c_releasedata, TRANSFORM_B, DROP)
    putfull.valid := in.c.valid && (c_probeackdata || c_releasedata)
    putfull.bits := edgeOut.Put(Cat(put_what, in.c.bits.source), in.c.bits.address, in.c.bits.size, in.c.bits.data)._2

    // Combine ReleaseAck or the modified D
    TLArbiter(TLArbiter.lowestIndexFirst)(in.d, (UInt(0), releaseack), (edgeOut.numBeats1(d_normal.bits), d_normal))
    // Combine the PutFull with the trackers
    TLArbiter(TLArbiter.lowestIndexFirst)(out.a, 
      ((edgeOut.numBeats1(putfull.bits), putfull) +:
       trackers.map { t => (edgeOut.numBeats1(t.out_a.bits), t.out_a) }):_*)

    // The Probe FSM walks all caches and probes them
    val probe_todo = RegInit(UInt(0, width = max(1, caches.size)))
    val probe_line = Reg(UInt())
    val probe_perms = Reg(UInt(width = 2))
    val probe_next = probe_todo & ~(leftOR(probe_todo) << 1)
    val probe_busy = probe_todo.orR()
    val probe_target = if (caches.size == 0) UInt(0) else Mux1H(probe_next, cache_targets)

    // Probe whatever the FSM wants to do next
    in.b.valid := probe_busy
    if (caches.size != 0) {
      in.b.bits := edgeIn.Probe(probe_line << lineShift, probe_target, UInt(lineShift), probe_perms)._2
    }
    when (in.b.fire()) { probe_todo := probe_todo & ~probe_next }

    // Which cache does a request come from?
    val a_cache = if (caches.size == 0) UInt(1) else Vec(caches.map(_.contains(in.a.bits.source))).asUInt
    val (a_first, _, _) = edgeIn.firstlast(in.a)

    // To accept a request from A, the probe FSM must be idle and there must be a matching tracker
    val freeTrackers = Vec(trackers.map { t => t.idle }).asUInt
    val freeTracker = freeTrackers.orR()
    val matchTrackers = Vec(trackers.map { t => t.line === in.a.bits.address >> lineShift }).asUInt
    val matchTracker = matchTrackers.orR()
    val allocTracker = freeTrackers & ~(leftOR(freeTrackers) << 1)
    val selectTracker = Mux(matchTracker, matchTrackers, allocTracker)

    val trackerReady = Vec(trackers.map(_.in_a.ready)).asUInt
    in.a.ready := (!a_first || !probe_busy) && (selectTracker & trackerReady).orR()
    (trackers zip selectTracker.toBools) foreach { case (t, select) =>
      t.in_a.valid := in.a.valid && select && (!a_first || !probe_busy)
      t.in_a.bits := in.a.bits
      t.in_a_first := a_first
      t.probe := (if (caches.size == 0) UInt(0) else Mux(a_cache.orR(), UInt(caches.size-1), UInt(caches.size)))
    }

    when (in.a.fire() && a_first) {
      probe_todo  := ~a_cache // probe all but the cache who poked us
      probe_line  := in.a.bits.address >> lineShift
      probe_perms := MuxLookup(in.a.bits.opcode, Wire(UInt(width = 2)), Array(
        TLMessages.PutFullData    -> TLPermissions.toN,
        TLMessages.PutPartialData -> TLPermissions.toN,
        TLMessages.ArithmeticData -> TLPermissions.toN,
        TLMessages.LogicalData    -> TLPermissions.toN,
        TLMessages.Get            -> TLPermissions.toB,
        TLMessages.Hint           -> MuxLookup(in.a.bits.param, Wire(UInt(width = 2)), Array(
          TLHints.PREFETCH_READ   -> TLPermissions.toB,
          TLHints.PREFETCH_WRITE  -> TLPermissions.toN)),
        TLMessages.Acquire        -> MuxLookup(in.a.bits.param, Wire(UInt(width = 2)), Array(
          TLPermissions.NtoB      -> TLPermissions.toB,
          TLPermissions.NtoT      -> TLPermissions.toN,
          TLPermissions.BtoT      -> TLPermissions.toN))))
    }

    // The outer TL connections may not be cached
    out.b.ready := Bool(true)
    out.c.valid := Bool(false)
    out.e.valid := Bool(false)
  }
}

class TLBroadcastTracker(id: Int, lineBytes: Int, probeCountBits: Int, bufferless: Boolean, edgeIn: TLEdgeIn, edgeOut: TLEdgeOut) extends Module
{
  val io = new Bundle {
    val in_a_first = Bool(INPUT)
    val in_a  = Decoupled(new TLBundleA(edgeIn.bundle)).flip
    val out_a = Decoupled(new TLBundleA(edgeOut.bundle))
    val probe = UInt(INPUT, width = probeCountBits)
    val probeack = Bool(INPUT)
    val d_last = Bool(INPUT)
    val e_last = Bool(INPUT)
    val source = UInt(OUTPUT) // the source awaiting D response
    val line = UInt(OUTPUT)   // the line waiting for probes
    val idle = Bool(OUTPUT)
  }

  val lineShift = log2Ceil(lineBytes)
  import TLBroadcastConstants._

  // Only one operation can be inflight per line, because we need to be sure
  // we send the request after all the probes we sent and before all the next probes
  val idle    = RegInit(Bool(true))
  val opcode  = Reg(io.in_a.bits.opcode)
  val param   = Reg(io.in_a.bits.param)
  val size    = Reg(io.in_a.bits.size)
  val source  = Reg(io.in_a.bits.source)
  val address = RegInit(UInt(id << lineShift, width = io.in_a.bits.address.getWidth))
  val count   = Reg(UInt(width = probeCountBits))

  when (io.in_a.fire() && io.in_a_first) {
    assert (idle)
    idle    := Bool(false)
    opcode  := io.in_a.bits.opcode
    param   := io.in_a.bits.param
    size    := io.in_a.bits.size
    source  := io.in_a.bits.source
    address := io.in_a.bits.address
    count   := io.probe
  }
  when (io.d_last) {
    assert (!idle)
    idle := opcode =/= TLMessages.Acquire
  }
  when (io.e_last) {
    assert (!idle)
    idle := Bool(true)
  }
  when (io.probeack) {
    assert (count > UInt(0))
    count := count - UInt(1)
  }

  io.idle := idle
  io.source := source
  io.line := address >> lineShift

  val i_data = Wire(Decoupled(new TLBroadcastData(edgeIn.bundle)))
  val o_data = Queue(i_data, if (bufferless) 1 else (lineBytes / edgeIn.manager.beatBytes))

  io.in_a.ready := (idle || !io.in_a_first) && i_data.ready
  i_data.valid := (idle || !io.in_a_first) && io.in_a.valid
  i_data.bits.mask := io.in_a.bits.mask
  i_data.bits.data := io.in_a.bits.data

  val probe_done = count === UInt(0)
  val acquire = opcode === TLMessages.Acquire

  val transform = MuxLookup(param, Wire(UInt(width = 2)), Array(
    TLPermissions.NtoB -> TRANSFORM_B,
    TLPermissions.NtoT -> TRANSFORM_T,
    TLPermissions.BtoT -> TRANSFORM_T))

  o_data.ready := io.out_a.ready && probe_done
  io.out_a.valid := o_data.valid && probe_done
  io.out_a.bits.opcode  := Mux(acquire, TLMessages.Get, opcode)
  io.out_a.bits.param   := Mux(acquire, UInt(0), param)
  io.out_a.bits.size    := size
  io.out_a.bits.source  := Cat(Mux(acquire, transform, PASS), source)
  io.out_a.bits.address := address
  io.out_a.bits.mask    := o_data.bits.mask
  io.out_a.bits.data    := o_data.bits.data
}

object TLBroadcastConstants
{
  val TRANSFORM_T = UInt(3)
  val TRANSFORM_B = UInt(2)
  val DROP        = UInt(1)
  val PASS        = UInt(0)
}

class TLBroadcastData(params: TLBundleParameters) extends TLBundleBase(params)
{
  val mask = UInt(width = params.dataBits/8)
  val data = UInt(width = params.dataBits)
}