hw/ip/dma/chisel/src/frontend/TLULReader.scala

/*
Copyright 2024 Google LLC

http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.

SPDX-License-Identifier: Apache-2.0
*/

package DMAController.Frontend

import DMAController.Bus._
import DMAController.Worker.{XferDescBundle}
import chisel3._
import chisel3.util._

class TLULReader(val addrWidth : Int, val dataWidth : Int) extends IOBus[TLULHost]{
  val io = IO(new Bundle{
    val bus = new TLULHost(addrWidth, dataWidth)
    val dataIO = EnqIO(UInt(dataWidth.W))
    val xfer = Flipped(new XferDescBundle(addrWidth))
  })

  val sIdle :: sTransfer :: sWait :: Nil = Enum(3)

  val state = RegInit(sIdle)

  val xferCnt = RegInit(0.U(addrWidth.W))
  val addr = RegInit(0.U(addrWidth.W))
  val valid = RegInit(false.B)

  val done = WireInit(false.B)
  val xferValid = WireInit(false.B)
  val xfer = WireInit(io.dataIO.ready && io.xfer.valid)

  io.bus.d <> TLULD.tieOff(addrWidth, dataWidth)

  // Producer to fifo
  io.dataIO.bits := io.bus.d.data
  io.dataIO.valid := xferValid

  io.bus.a.valid := valid
  io.bus.a.data := 0.U

  io.bus.a.opcode := TLOp.Get
  io.bus.a.param := 0.U
  io.bus.a.size := 2.U
  io.bus.a.source := 0.U
  io.bus.a.address := addr
  io.bus.a.corrupt := 0.U
  io.bus.a.mask := 0xF.U

  io.xfer.done := done

  switch(state){
    is(sIdle){
      valid := false.B
      io.bus.d.ready := false.B
      done := false.B
      xferValid := false.B
      when(xfer) {
        valid := true.B
        state := sTransfer
        xferCnt := io.xfer.length
        addr := io.xfer.address
      }
    }
    is(sTransfer){
      io.bus.d.ready := true.B
      xferValid := false.B
      when(io.bus.a.ready) {
        valid := false.B
        state := sWait

        when(xferCnt =/= 0.U) {
          addr := addr + (dataWidth / 8).U
          xferCnt := xferCnt - 1.U
        }

        // Don't stall if we receive same cycle d_valid
        when(io.bus.d.valid) {
          xferValid := true.B

          when(xferCnt === 1.U) {
            state := sIdle
            done := true.B
          }.otherwise {
            valid := true.B
            state := sTransfer
          }
        }
      }
    }
    is(sWait){
      valid := false.B
      xferValid := false.B
      io.bus.d.ready := true.B
      when(io.bus.d.valid) {
        xferValid := true.B
        when(xferCnt === 0.U) {
          state := sIdle
          done := true.B
        }.otherwise {
          valid := true.B
          state := sTransfer
        }
      }
    }
  }
}