1
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rocket-chip/uncore/coherence.scala

540 lines
20 KiB
Scala

package rocket
import Chisel._
import Constants._
class MemData extends Bundle {
val data = Bits(width = MEM_DATA_BITS)
}
class MemReqCmd() extends Bundle
{
val rw = Bool()
val addr = UFix(width = PADDR_BITS - OFFSET_BITS)
val tag = Bits(width = MEM_TAG_BITS)
}
class MemResp () extends MemData
{
val tag = Bits(width = MEM_TAG_BITS)
}
class ioMem() extends Bundle
{
val req_cmd = (new ioDecoupled) { new MemReqCmd() }.flip
val req_data = (new ioDecoupled) { new MemData() }.flip
val resp = (new ioValid) { new MemResp() }
}
class HubMemReq extends Bundle {
val lock = Bool()
}
class TrackerProbeData extends Bundle {
val valid = Bool()
val data_tile_id = Bits(width = log2up(NTILES))
}
class TrackerAllocReq extends Bundle {
val xact_init = new TransactionInit()
val init_tile_id = Bits(width = TILE_ID_BITS)
val data_valid = Bool()
}
class TransactionInit extends Bundle {
val t_type = Bits(width = TTYPE_BITS)
val has_data = Bool()
val tile_xact_id = Bits(width = TILE_XACT_ID_BITS)
val address = UFix(width = PADDR_BITS)
}
class TransactionInitData extends MemData
class TransactionAbort extends Bundle {
val tile_xact_id = Bits(width = TILE_XACT_ID_BITS)
}
class ProbeRequest extends Bundle {
val p_type = Bits(width = PTYPE_BITS)
val global_xact_id = Bits(width = GLOBAL_XACT_ID_BITS)
val address = Bits(width = PADDR_BITS)
}
class ProbeReply extends Bundle {
val p_type = Bits(width = PTYPE_BITS)
val has_data = Bool()
val global_xact_id = Bits(width = GLOBAL_XACT_ID_BITS)
}
class ProbeReplyData extends MemData
class TransactionReply extends MemData {
val t_type = Bits(width = TTYPE_BITS)
val tile_xact_id = Bits(width = TILE_XACT_ID_BITS)
val global_xact_id = Bits(width = GLOBAL_XACT_ID_BITS)
}
class TransactionFinish extends Bundle {
val global_xact_id = Bits(width = GLOBAL_XACT_ID_BITS)
}
class ioTileLink extends Bundle {
val xact_init = (new ioDecoupled) { new TransactionInit() }.flip
val xact_init_data = (new ioDecoupled) { new TransactionInitData() }.flip
val xact_abort = (new ioDecoupled) { new TransactionAbort() }
val probe_req = (new ioDecoupled) { new ProbeRequest() }
val probe_rep = (new ioDecoupled) { new ProbeReply() }.flip
val probe_rep_data = (new ioDecoupled) { new ProbeReplyData() }.flip
val xact_rep = (new ioValid) { new TransactionReply() }
val xact_finish = (new ioDecoupled) { new TransactionFinish() }.flip
}
trait CoherencePolicy {
def cpuCmdToRW( cmd: Bits): (Bool, Bool) = {
val store = (cmd === M_XWR)
val load = (cmd === M_XRD)
val amo = cmd(3).toBool
val read = load || amo || (cmd === M_PFR)
val write = store || amo || (cmd === M_PFW)
(read, write)
}
}
trait ThreeStateIncoherence extends CoherencePolicy {
val tileInvalid :: tileClean :: tileDirty :: Nil = Enum(3){ UFix() }
def isHit ( cmd: Bits, state: UFix): Bool = {
val (read, write) = cpuCmdToRW(cmd)
( state === tileClean || state === tileDirty)
}
def isValid (state: UFix): Bool = {
state != tileInvalid
}
def needsWriteback (state: UFix): Bool = {
state === tileDirty
}
def newStateOnWriteback() = tileInvalid
def newStateOnFlush() = tileInvalid
def newState(cmd: Bits, state: UFix): UFix = {
val (read, write) = cpuCmdToRW(cmd)
Mux(write, tileDirty, Mux(read, Mux(state === tileDirty, tileDirty, tileClean), state))
}
def newStateOnHit(cmd: Bits, state: UFix): UFix = newState(cmd, state)
def newStateOnPrimaryMiss(cmd: Bits): UFix = newState(cmd, tileInvalid)
def newStateOnSecondaryMiss(cmd: Bits, state: UFix): UFix = {
val (read, write) = cpuCmdToRW(cmd)
Mux(write, tileDirty, state)
}
}
trait FourStateCoherence extends CoherencePolicy {
val tileInvalid :: tileShared :: tileExclusiveClean :: tileExclusiveDirty :: Nil = Enum(4){ UFix() }
val globalInvalid :: globalShared :: globalExclusiveClean :: Nil = Enum(3){ UFix() }
val probeInvalidate :: probeDowngrade :: probeCopy :: Nil = Enum(3){ UFix() }
def isHit ( cmd: Bits, state: UFix): Bool = {
val (read, write) = cpuCmdToRW(cmd)
((read && ( state === tileShared || state === tileExclusiveClean || state === tileExclusiveDirty)) ||
(write && (state === tileExclusiveClean || state === tileExclusiveDirty)))
}
def isValid (state: UFix): Bool = {
state != tileInvalid
}
def needsWriteback (state: UFix): Bool = {
state === tileExclusiveDirty
}
def newStateOnWriteback() = tileInvalid
def newStateOnFlush() = tileInvalid
// TODO: New funcs as compared to incoherent protocol:
def newState(cmd: Bits, state: UFix): UFix
def newStateOnHit(cmd: Bits, state: UFix): UFix
def newStateOnPrimaryMiss(cmd: Bits): UFix
def newStateOnSecondaryMiss(cmd: Bits, state: UFix): UFix
def needsSecondaryXact (cmd: Bits, outstanding: TransactionInit): Bool
def getMetaUpdateOnProbe (incoming: ProbeRequest): Bits = {
val state = UFix(0)
switch(incoming.p_type) {
is(probeInvalidate) { state := tileInvalid }
is(probeDowngrade) { state := tileShared }
}
state.toBits
}
def replyTypeHasData (reply: TransactionReply): Bool = {
(reply.t_type != X_WRITE_UNCACHED)
}
}
class XactTracker(id: Int) extends Component with CoherencePolicy {
val io = new Bundle {
val alloc_req = (new ioDecoupled) { new TrackerAllocReq() }
val probe_data = (new TrackerProbeData).asInput
val can_alloc = Bool(INPUT)
val xact_finish = Bool(INPUT)
val p_rep_cnt_dec = Bits(NTILES, INPUT)
val p_req_cnt_inc = Bits(NTILES, INPUT)
val p_rep_data = (new ioDecoupled) { new ProbeReplyData() }
val x_init_data = (new ioDecoupled) { new TransactionInitData() }
val mem_req_cmd = (new ioDecoupled) { new MemReqCmd() }
val mem_req_data = (new ioDecoupled) { new MemData() }
val mem_req_lock = Bool(OUTPUT)
val probe_req = (new ioDecoupled) { new ProbeRequest() }.flip
val busy = Bool(OUTPUT)
val addr = Bits(PADDR_BITS, OUTPUT)
val init_tile_id = Bits(TILE_ID_BITS, OUTPUT)
val p_rep_tile_id = Bits(log2up(NTILES), INPUT)
val tile_xact_id = Bits(TILE_XACT_ID_BITS, OUTPUT)
val sharer_count = Bits(TILE_ID_BITS, OUTPUT)
val t_type = Bits(TTYPE_BITS, OUTPUT)
val push_p_req = Bits(NTILES, OUTPUT)
val pop_p_rep = Bits(NTILES, OUTPUT)
val pop_p_rep_data = Bits(NTILES, OUTPUT)
val pop_x_init = Bool(OUTPUT)
val pop_x_init_data = Bool(OUTPUT)
val send_x_rep_ack = Bool(OUTPUT)
}
def sendProbeReqType(t_type: UFix, global_state: UFix): UFix = {
MuxCase(P_COPY, Array((t_type === X_READ_SHARED) -> P_DOWNGRADE,
(t_type === X_READ_EXCLUSIVE) -> P_INVALIDATE,
(t_type === X_READ_UNCACHED) -> P_COPY,
(t_type === X_WRITE_UNCACHED) -> P_INVALIDATE))
}
def needsMemRead(t_type: UFix, global_state: UFix): Bool = {
(t_type != X_WRITE_UNCACHED)
}
def needsAckRep(t_type: UFix, global_state: UFix): Bool = {
(t_type === X_WRITE_UNCACHED)
}
val s_idle :: s_mem :: s_probe :: s_busy :: Nil = Enum(4){ UFix() }
val state = Reg(resetVal = s_idle)
val addr_ = Reg{ UFix() }
val t_type_ = Reg{ Bits() }
val init_tile_id_ = Reg{ Bits() }
val tile_xact_id_ = Reg{ Bits() }
val p_rep_count = Reg(resetVal = UFix(0, width = log2up(NTILES)))
val p_req_flags = Reg(resetVal = Bits(0, width = NTILES))
val p_rep_tile_id_ = Reg{ Bits() }
val x_needs_read = Reg(resetVal = Bool(false))
val x_init_data_needs_write = Reg(resetVal = Bool(false))
val p_rep_data_needs_write = Reg(resetVal = Bool(false))
val mem_cmd_sent = Reg(resetVal = Bool(false))
val mem_cnt = Reg(resetVal = UFix(0, width = log2up(REFILL_CYCLES)))
val mem_cnt_next = mem_cnt + UFix(1)
def doMemReqWrite(req_cmd: ioDecoupled[MemReqCmd], req_data: ioDecoupled[MemData], lock: Bool, data: ioDecoupled[MemData], trigger: Bool, pop: Bool) {
req_cmd.valid := mem_cmd_sent
req_cmd.bits.rw := Bool(true)
req_data <> data
lock := Bool(true)
when(req_cmd.ready && req_cmd.valid) {
mem_cmd_sent := Bool(false)
}
when(req_data.ready && req_data.valid) {
pop := Bool(true)
mem_cnt := mem_cnt_next
}
when(mem_cnt === ~UFix(0)) {
trigger := Bool(false)
}
}
def doMemReqRead(req_cmd: ioDecoupled[MemReqCmd], trigger: Bool) {
req_cmd.valid := Bool(true)
req_cmd.bits.rw := Bool(false)
when(req_cmd.ready ) {
trigger := Bool(false)
}
}
io.busy := state != s_idle
io.addr := addr_
io.init_tile_id := init_tile_id_
io.tile_xact_id := tile_xact_id_
io.sharer_count := UFix(NTILES) // TODO: Broadcast only
io.t_type := t_type_
io.mem_req_cmd.valid := Bool(false)
io.mem_req_cmd.bits.rw := Bool(false)
io.mem_req_cmd.bits.addr := addr_
io.mem_req_cmd.bits.tag := UFix(id)
io.mem_req_data.valid := Bool(false)
io.mem_req_data.bits.data := UFix(0)
io.mem_req_lock := Bool(false)
io.probe_req.valid := Bool(false)
io.probe_req.bits.p_type := sendProbeReqType(t_type_, UFix(0))
io.probe_req.bits.global_xact_id := UFix(id)
io.probe_req.bits.address := addr_
io.push_p_req := Bits(0, width = NTILES)
io.pop_p_rep := Bits(0, width = NTILES)
io.pop_p_rep_data := Bits(0, width = NTILES)
io.pop_x_init := Bool(false)
io.pop_x_init_data := Bool(false)
io.send_x_rep_ack := Bool(false)
switch (state) {
is(s_idle) {
when( io.alloc_req.valid && io.can_alloc ) {
addr_ := io.alloc_req.bits.xact_init.address
t_type_ := io.alloc_req.bits.xact_init.t_type
init_tile_id_ := io.alloc_req.bits.init_tile_id
tile_xact_id_ := io.alloc_req.bits.xact_init.tile_xact_id
x_init_data_needs_write := io.alloc_req.bits.xact_init.has_data
x_needs_read := needsMemRead(io.alloc_req.bits.xact_init.t_type, UFix(0))
p_rep_count := UFix(NTILES-1)
p_req_flags := ~( UFix(1) << io.alloc_req.bits.init_tile_id )
state := Mux(p_req_flags.orR, s_probe, s_mem)
mem_cnt := UFix(0)
mem_cmd_sent := Bool(false)
io.pop_x_init := Bool(true)
}
}
is(s_probe) {
when(p_req_flags.orR) {
io.push_p_req := p_req_flags
io.probe_req.valid := Bool(true)
}
when(io.p_req_cnt_inc.orR) {
p_req_flags := p_req_flags & ~io.p_req_cnt_inc // unflag sent reqs
}
when(io.p_rep_cnt_dec.orR) {
val p_rep_count_next = p_rep_count - PopCount(io.p_rep_cnt_dec)
io.pop_p_rep := io.p_rep_cnt_dec
p_rep_count := p_rep_count_next
when(p_rep_count_next === UFix(0)) {
mem_cnt := UFix(0)
mem_cmd_sent := Bool(false)
state := s_mem
}
}
when(io.probe_data.valid) {
p_rep_data_needs_write := Bool(true)
p_rep_tile_id_ := io.p_rep_tile_id
}
}
is(s_mem) {
when (p_rep_data_needs_write) {
doMemReqWrite(io.mem_req_cmd, io.mem_req_data, io.mem_req_lock, io.p_rep_data, p_rep_data_needs_write, io.pop_p_rep_data)
} . elsewhen(x_init_data_needs_write) {
doMemReqWrite(io.mem_req_cmd, io.mem_req_data, io.mem_req_lock, io.x_init_data, x_init_data_needs_write, io.pop_x_init_data)
} . elsewhen (x_needs_read) {
doMemReqRead(io.mem_req_cmd, x_needs_read)
} . otherwise {
io.send_x_rep_ack := needsAckRep(t_type_, UFix(0))
state := s_busy
}
}
is(s_busy) { // Nothing left to do but wait for transaction to complete
when (io.xact_finish) {
state := s_idle
}
}
}
//TODO: Decrement the probe count when final data piece is written
// Connent io.mem.ready sig to correct pop* outputs
// P_rep and x_init must be popped on same cycle of receipt
}
abstract class CoherenceHub extends Component with CoherencePolicy {
val io = new Bundle {
val tiles = Vec(NTILES) { new ioTileLink() }.flip
val mem = new ioMem
}
}
class CoherenceHubNull extends CoherenceHub {
val x_init = io.tiles(0).xact_init
val is_write = x_init.bits.t_type === X_WRITE_UNCACHED
x_init.ready := io.mem.req_cmd.ready && !(is_write && io.mem.resp.valid) //stall write req/resp to handle previous read resp
io.mem.req_cmd.valid := x_init.valid && !(is_write && io.mem.resp.valid)
io.mem.req_cmd.bits.rw := is_write
io.mem.req_cmd.bits.tag := x_init.bits.tile_xact_id
io.mem.req_cmd.bits.addr := x_init.bits.address
io.mem.req_data <> io.tiles(0).xact_init_data
val x_rep = io.tiles(0).xact_rep
x_rep.bits.t_type := Mux(io.mem.resp.valid, X_READ_EXCLUSIVE, X_WRITE_UNCACHED)
x_rep.bits.tile_xact_id := Mux(io.mem.resp.valid, io.mem.resp.bits.tag, x_init.bits.tile_xact_id)
x_rep.bits.global_xact_id := UFix(0) // don't care
x_rep.bits.data := io.mem.resp.bits.data
x_rep.valid := io.mem.resp.valid || x_init.valid && is_write
}
class CoherenceHubBroadcast extends CoherenceHub {
def coherenceConflict(addr1: Bits, addr2: Bits): Bool = {
addr1(PADDR_BITS-1, OFFSET_BITS) === addr2(PADDR_BITS-1, OFFSET_BITS)
}
def getTransactionReplyType(t_type: UFix, count: UFix): Bits = {
val ret = Wire() { Bits(width = TTYPE_BITS) }
switch (t_type) {
is(X_READ_SHARED) { ret := Mux(count > UFix(0), X_READ_SHARED, X_READ_EXCLUSIVE) }
is(X_READ_EXCLUSIVE) { ret := X_READ_EXCLUSIVE }
is(X_READ_UNCACHED) { ret := X_READ_UNCACHED }
is(X_WRITE_UNCACHED) { ret := X_WRITE_UNCACHED }
}
ret
}
val trackerList = (0 until NGLOBAL_XACTS).map(new XactTracker(_))
/*
val busy_arr = Vec(NGLOBAL_XACTS){ Wire(){Bool()} }
val addr_arr = Vec(NGLOBAL_XACTS){ Wire(){Bits(width=PADDR_BITS)} }
val init_tile_id_arr = Vec(NGLOBAL_XACTS){ Wire(){Bits(width=TILE_ID_BITS)} }
val tile_xact_id_arr = Vec(NGLOBAL_XACTS){ Wire(){Bits(width=TILE_XACT_ID_BITS)} }
val t_type_arr = Vec(NGLOBAL_XACTS){ Wire(){Bits(width=TTYPE_BITS)} }
val sh_count_arr = Vec(NGLOBAL_XACTS){ Wire(){Bits(width=TILE_ID_BITS)} }
val send_x_rep_ack_arr = Vec(NGLOBAL_XACTS){ Wire(){Bool()} }
val do_free_arr = Vec(NGLOBAL_XACTS){ Wire(){Bool()} }
val p_rep_cnt_dec_arr = Vec(NGLOBAL_XACTS){ Wire(){Bits(width=NTILES)} }
val p_req_cnt_inc_arr = Vec(NGLOBAL_XACTS){ Wire(){Bits(width=NTILES)} }
for( i <- 0 until NGLOBAL_XACTS) {
busy_arr.write( UFix(i), trackerList(i).io.busy)
addr_arr.write( UFix(i), trackerList(i).io.addr)
init_tile_id_arr.write( UFix(i), trackerList(i).io.init_tile_id)
tile_xact_id_arr.write( UFix(i), trackerList(i).io.tile_xact_id)
t_type_arr.write( UFix(i), trackerList(i).io.t_type)
sh_count_arr.write( UFix(i), trackerList(i).io.sharer_count)
send_x_rep_ack_arr.write(UFix(i), trackerList(i).io.send_x_rep_ack)
trackerList(i).io.xact_finish := do_free_arr.read(UFix(i))
trackerList(i).io.p_rep_cnt_dec := p_rep_cnt_dec_arr.read(UFix(i))
trackerList(i).io.p_req_cnt_inc := p_req_cnt_inc_arr.read(UFix(i))
}
// Free finished transactions
for( j <- 0 until NTILES ) {
val finish = io.tiles(j).xact_finish
do_free_arr.write(finish.bits.global_xact_id, finish.valid)
finish.ready := Bool(true)
}
// Reply to initial requestor
// Forward memory responses from mem to tile
val idx = io.mem.resp.bits.tag
for( j <- 0 until NTILES ) {
io.tiles(j).xact_rep.bits.t_type := getTransactionReplyType(t_type_arr.read(idx), sh_count_arr.read(idx))
io.tiles(j).xact_rep.bits.tile_xact_id := tile_xact_id_arr.read(idx)
io.tiles(j).xact_rep.bits.global_xact_id := idx
io.tiles(j).xact_rep.bits.data := io.mem.resp.bits.data
io.tiles(j).xact_rep.valid := (UFix(j) === init_tile_id_arr.read(idx)) && (io.mem.resp.valid || send_x_rep_ack_arr.read(idx))
}
// If there were a ready signal due to e.g. intervening network use:
//io.mem.resp.ready := io.tiles(init_tile_id_arr.read(idx)).xact_rep.ready
// Create an arbiter for the one memory port
// We have to arbitrate between the different trackers' memory requests
// and once we have picked a request, get the right write data
val mem_req_cmd_arb = (new LockingArbiter(NGLOBAL_XACTS)) { new MemReqCmd() }
val mem_req_data_arb = (new LockingArbiter(NGLOBAL_XACTS)) { new MemData() }
for( i <- 0 until NGLOBAL_XACTS ) {
mem_req_cmd_arb.io.in(i) <> trackerList(i).io.mem_req_cmd
mem_req_cmd_arb.io.lock(i) <> trackerList(i).io.mem_req_lock
mem_req_data_arb.io.in(i) <> trackerList(i).io.mem_req_data
mem_req_data_arb.io.lock(i) <> trackerList(i).io.mem_req_lock
}
io.mem.req_cmd <> mem_req_cmd_arb.io.out
io.mem.req_data <> mem_req_data_arb.io.out
// Handle probe replies, which may or may not have data
for( j <- 0 until NTILES ) {
val p_rep = io.tiles(j).probe_rep
val p_rep_data = io.tiles(j).probe_rep_data
val idx = p_rep.bits.global_xact_id
p_rep.ready := foldR(trackerList.map(_.io.pop_p_rep(j)))(_ || _)
p_rep_data.ready := foldR(trackerList.map(_.io.pop_p_rep_data(j)))(_ || _)
}
for( i <- 0 until NGLOBAL_XACTS ) {
trackerList(i).io.p_rep_data <> io.tiles(trackerList(i).io.p_rep_tile_id).probe_rep_data
for( j <- 0 until NTILES) {
val p_rep = io.tiles(j).probe_rep
val dec = p_rep.valid && (p_rep.bits.global_xact_id === UFix(i))
p_rep_cnt_dec_arr(UFix(i)) := p_rep_cnt_dec_arr(UFix(i)).bitSet(UFix(j), dec)
}
}
// Nack conflicting transaction init attempts
val aborting = Wire() { Bits(width = NTILES) }
for( j <- 0 until NTILES ) {
val x_init = io.tiles(j).xact_init
val x_abort = io.tiles(j).xact_abort
val conflicts = Bits(width = NGLOBAL_XACTS)
for( i <- 0 until NGLOBAL_XACTS) {
val t = trackerList(i).io
conflicts(UFix(i), t.busy(i) && coherenceConflict(t.addr, x_init.bits.address) &&
!(x_init.bits.has_data && (UFix(j) === t.init_tile_id)))
// Don't abort writebacks stalled on mem.
// TODO: This assumes overlapped writeback init reqs to
// the same addr will never be issued; is this ok?
}
x_abort.bits.tile_xact_id := x_init.bits.tile_xact_id
val want_to_abort = conflicts.orR || busy_arr.toBits.andR
x_abort.valid := want_to_abort && x_init.valid
aborting.bitSet(UFix(j), want_to_abort && x_abort.ready)
}
// Handle transaction initiation requests
// Only one allocation per cycle
// Init requests may or may not have data
val alloc_arb = (new Arbiter(NGLOBAL_XACTS)) { Bool() }
val init_arb = (new Arbiter(NTILES)) { new TrackerAllocReq() }
for( i <- 0 until NGLOBAL_XACTS ) {
alloc_arb.io.in(i).valid := !trackerList(i).io.busy
trackerList(i).io.can_alloc := alloc_arb.io.in(i).ready
trackerList(i).io.alloc_req.bits <> init_arb.io.out.bits
trackerList(i).io.alloc_req.valid := init_arb.io.out.valid
trackerList(i).io.x_init_data <> io.tiles(trackerList(i).io.init_tile_id).xact_init_data
}
for( j <- 0 until NTILES ) {
val x_init = io.tiles(j).xact_init
val x_init_data = io.tiles(j).xact_init_data
init_arb.io.in(j).valid := x_init.valid
init_arb.io.in(j).bits.xact_init := x_init.bits
init_arb.io.in(j).bits.init_tile_id := UFix(j)
init_arb.io.in(j).bits.data_valid := x_init_data.valid
x_init.ready := aborting(j) || foldR(trackerList.map(_.io.pop_x_init && init_arb.io.out.bits.init_tile_id === UFix(j)))(_||_)
x_init_data.ready := aborting(j) || foldR(trackerList.map(_.io.pop_x_init_data && init_arb.io.out.bits.init_tile_id === UFix(j)))(_||_)
}
alloc_arb.io.out.ready := init_arb.io.out.valid && !busy_arr.toBits.andR &&
!foldR(trackerList.map(t => t.io.busy && coherenceConflict(t.io.addr, init_arb.io.out.bits.xact_init.address)))(_||_)
// Handle probe request generation
// Must arbitrate for each request port
val p_req_arb_arr = List.fill(NTILES)((new Arbiter(NGLOBAL_XACTS)) { new ProbeRequest() })
for( j <- 0 until NTILES ) {
for( i <- 0 until NGLOBAL_XACTS ) {
val t = trackerList(i).io
p_req_arb_arr(j).io.in(i).bits := t.probe_req.bits
p_req_arb_arr(j).io.in(i).valid := t.probe_req.valid && t.push_p_req(j)
p_rep_cnt_dec_arr(i) = p_rep_cnt_dec_arr(i).bitSet(UFix(j), p_req_arb_arr(j).io.in(i).ready)
}
p_req_arb_arr(j).io.out <> io.tiles(j).probe_req
}
*/
}