dcache/mainpipe/Probe.scala

/***************************************************************************************
* Copyright (c) 2020-2021 Institute of Computing Technology, Chinese Academy of Sciences
* Copyright (c) 2020-2021 Peng Cheng Laboratory
*
* XiangShan is licensed under Mulan PSL v2.
* You can use this software according to the terms and conditions of the Mulan PSL v2.
* You may obtain a copy of Mulan PSL v2 at:
*          http://license.coscl.org.cn/MulanPSL2
*
* THIS SOFTWARE IS PROVIDED ON AN "AS IS" BASIS, WITHOUT WARRANTIES OF ANY KIND,
* EITHER EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO NON-INFRINGEMENT,
* MERCHANTABILITY OR FIT FOR A PARTICULAR PURPOSE.
*
* See the Mulan PSL v2 for more details.
***************************************************************************************/

package xiangshan.cache

import chipsalliance.rocketchip.config.Parameters
import chisel3._
import chisel3.util._

import freechips.rocketchip.tilelink.{TLEdgeOut, TLBundleB, TLMessages, TLPermissions}

import utils.{HasTLDump, XSDebug, XSPerfAccumulate}

class ProbeReq(implicit p: Parameters) extends DCacheBundle
{
  val source = UInt()
  val opcode = UInt()
  val addr   = UInt(PAddrBits.W)
  // TODO: l2 should use vaddr index to probe l1
  val vaddr  = UInt(VAddrBits.W)
  val param  = UInt(TLPermissions.bdWidth.W)
  val needData = Bool()

  def dump() = {
    XSDebug("ProbeReq source: %d opcode: %d addr: %x param: %d\n",
      source, opcode, addr, param)
  }
}

class ProbeEntry(implicit p: Parameters) extends DCacheModule {
  val io = IO(new Bundle {
    val req = Flipped(Decoupled(new ProbeReq))
    val pipe_req  = DecoupledIO(new MainPipeReq)
    val lrsc_locked_block = Input(Valid(UInt()))

    // the block we are probing
    val block_addr  = Output(Valid(UInt()))
  })

  val s_invalid :: s_pipe_req :: Nil = Enum(2)

  val state = RegInit(s_invalid)

  val req = Reg(new ProbeReq)

  // assign default values to signals
  io.req.ready      := false.B
  io.pipe_req.valid := false.B
  io.pipe_req.bits  := DontCare

  io.block_addr.valid := state =/= s_invalid
  io.block_addr.bits  := req.addr

  when (state =/= s_invalid) {
    XSDebug("state: %d\n", state)
  }

  when (state =/= s_invalid) {
    XSDebug("ProbeEntry: state: %d block_addr: %x\n", state, io.block_addr.bits)
  }

  when (state === s_invalid) {
    io.req.ready := true.B
    when (io.req.fire()) {
      req := io.req.bits
      state := s_pipe_req
    }
  }

  when (state === s_pipe_req) {
    val lrsc_blocked = io.lrsc_locked_block.valid && io.lrsc_locked_block.bits === req.addr
    io.pipe_req.valid := !lrsc_blocked

    val pipe_req = io.pipe_req.bits
    pipe_req := DontCare
    pipe_req.miss := false.B
    pipe_req.probe := true.B
    pipe_req.probe_param := req.param
    pipe_req.addr   := req.addr
    pipe_req.vaddr  := req.vaddr
    pipe_req.probe_need_data := req.needData

    when (io.pipe_req.fire()) {
      state := s_invalid
    }
  }

  // perfoemance counters
  XSPerfAccumulate("probe_req", state === s_invalid && io.req.fire())
  XSPerfAccumulate("probe_penalty", state =/= s_invalid)
  XSPerfAccumulate("probe_penalty_blocked_by_lrsc", state === s_pipe_req && io.lrsc_locked_block.valid && io.lrsc_locked_block.bits === req.addr)
  XSPerfAccumulate("probe_penalty_blocked_by_pipeline", state === s_pipe_req && io.pipe_req.valid && !io.pipe_req.ready)
}

class ProbeQueue(edge: TLEdgeOut)(implicit p: Parameters) extends DCacheModule with HasTLDump
{
  val io = IO(new Bundle {
    val mem_probe = Flipped(Decoupled(new TLBundleB(edge.bundle)))
    val pipe_req  = DecoupledIO(new MainPipeReq)
    val lrsc_locked_block = Input(Valid(UInt()))
  })

  val pipe_req_arb = Module(new RRArbiter(new MainPipeReq, cfg.nProbeEntries))

  // allocate a free entry for incoming request
  val primary_ready  = Wire(Vec(cfg.nProbeEntries, Bool()))
  val allocate = primary_ready.asUInt.orR
  val alloc_idx = PriorityEncoder(primary_ready)

  // translate to inner req
  val req = Wire(new ProbeReq)
  val alias_addr_frag = io.mem_probe.bits.data(2, 1) // add extra 2 bits from vaddr to get vindex
  req.source := io.mem_probe.bits.source
  req.opcode := io.mem_probe.bits.opcode
  req.addr := io.mem_probe.bits.address
  if(DCacheAboveIndexOffset > DCacheTagOffset) {
    // have alias problem, extra alias bits needed for index
    req.vaddr := Cat(
      io.mem_probe.bits.address(VAddrBits - 1, DCacheAboveIndexOffset), // dontcare
      alias_addr_frag(DCacheAboveIndexOffset - DCacheTagOffset - 1, 0), // index
      io.mem_probe.bits.address(DCacheTagOffset - 1, 0)                 // index & others
    )
  } else { // no alias problem
    req.vaddr := io.mem_probe.bits.address
  }
  req.param := io.mem_probe.bits.param
  req.needData := io.mem_probe.bits.data(0)

  io.mem_probe.ready := allocate

  val entries = (0 until cfg.nProbeEntries) map { i =>
    val entry = Module(new ProbeEntry)

    // entry req
    entry.io.req.valid := (i.U === alloc_idx) && allocate && io.mem_probe.valid
    primary_ready(i)   := entry.io.req.ready
    entry.io.req.bits  := req

    // pipe_req
    pipe_req_arb.io.in(i) <> entry.io.pipe_req

    entry.io.lrsc_locked_block := io.lrsc_locked_block

    entry
  }

  io.pipe_req <> pipe_req_arb.io.out

  // print all input/output requests for debug purpose
  when (io.mem_probe.valid) {
    // before a probe finishes, L2 should not further issue probes on this block
    val probe_conflict = VecInit(entries.map(e => e.io.block_addr.valid && e.io.block_addr.bits === io.mem_probe.bits.address)).asUInt.orR
    assert (!probe_conflict)
    // for now, we can only deal with ProbeBlock
    assert (io.mem_probe.bits.opcode === TLMessages.Probe)
  }

  // debug output
  when (io.mem_probe.fire()) {
    XSDebug("mem_probe: ")
    io.mem_probe.bits.dump
  }

  when (io.pipe_req.fire()) {
    io.pipe_req.bits.dump()
  }

  when (io.lrsc_locked_block.valid) {
    XSDebug("lrsc_locked_block: %x\n", io.lrsc_locked_block.bits)
  }
}