From 872b162e1bff591e679bb50c2743d0e9e578725c Mon Sep 17 00:00:00 2001
From: Howard Mao <zhehao.mao@gmail.com>
Date: Tue, 17 Nov 2015 18:13:50 -0800
Subject: [PATCH] implement DMA engine

---
 uncore/src/main/scala/dma.scala  | 316 +++++++++++++++++++++++++++++++
 uncore/src/main/scala/util.scala |   4 +
 2 files changed, 320 insertions(+)
 create mode 100644 uncore/src/main/scala/dma.scala

diff --git a/uncore/src/main/scala/dma.scala b/uncore/src/main/scala/dma.scala
new file mode 100644
index 00000000..3170eec3
--- /dev/null
+++ b/uncore/src/main/scala/dma.scala
@@ -0,0 +1,316 @@
+package uncore
+
+import Chisel._
+import cde.{Parameters, Field}
+import junctions._
+
+case object NDmaTransactors extends Field[Int]
+case object NDmaClients extends Field[Int]
+case object NDmaXactsPerClient extends Field[Int]
+
+trait HasDmaParameters {
+  implicit val p: Parameters
+  val nDmaTransactors = p(NDmaTransactors)
+  val nDmaClients = p(NDmaClients)
+  val nDmaXactsPerClient = p(NDmaXactsPerClient)
+  val dmaClientXactIdBits = log2Up(nDmaClients * nDmaXactsPerClient)
+  val addrBits = p(PAddrBits)
+  val dmaStatusBits = 2
+}
+
+abstract class DmaModule(implicit val p: Parameters) extends Module with HasDmaParameters
+abstract class DmaBundle(implicit val p: Parameters) extends ParameterizedBundle()(p) with HasDmaParameters
+
+class DmaRequest(implicit p: Parameters) extends DmaBundle()(p) {
+  val client_xact_id = UInt(width = dmaClientXactIdBits)
+  val cmd = UInt(width = DmaRequest.DMA_CMD_SZ)
+  val source = UInt(width = addrBits)
+  val dest = UInt(width = addrBits)
+  val length = UInt(width = addrBits)
+}
+
+class DmaResponse(implicit p: Parameters) extends DmaBundle()(p) {
+  val client_xact_id = UInt(width = dmaClientXactIdBits)
+  val status = UInt(width = dmaStatusBits)
+}
+
+object DmaRequest {
+  val DMA_CMD_SZ = 2
+
+  val DMA_CMD_COPY = UInt(0, DMA_CMD_SZ)
+  val DMA_CMD_PFR = UInt(2, DMA_CMD_SZ)
+  val DMA_CMD_PFW = UInt(3, DMA_CMD_SZ)
+
+  def apply(client_xact_id: UInt = UInt(0),
+            cmd: UInt,
+            source: UInt,
+            dest: UInt,
+            length: UInt)(implicit p: Parameters): DmaRequest = {
+    val req = Wire(new DmaRequest)
+    req.client_xact_id := client_xact_id
+    req.cmd := cmd
+    req.source := source
+    req.dest := dest
+    req.length := length
+    req
+  }
+}
+import DmaRequest._
+
+class DmaIO(implicit p: Parameters) extends DmaBundle()(p) {
+  val req = Decoupled(new DmaRequest)
+  val resp = Decoupled(new DmaResponse).flip
+}
+
+class DmaEngine(implicit p: Parameters) extends DmaModule()(p) {
+  val io = new Bundle {
+    val dma = (new DmaIO).flip
+    val mem = new ClientUncachedTileLinkIO
+  }
+
+  val trackers = List.fill(nDmaTransactors) { Module(new DmaTracker) }
+  val reqReadys = Vec(trackers.map(_.io.dma.req.ready)).toBits
+
+  if (nDmaTransactors > 1) {
+    val mem_arb = Module(new ClientUncachedTileLinkIOArbiter(nDmaTransactors))
+    mem_arb.io.in <> trackers.map(_.io.mem)
+    io.mem <> mem_arb.io.out
+
+    val resp_arb = Module(new RRArbiter(new DmaResponse, nDmaTransactors))
+    resp_arb.io.in <> trackers.map(_.io.dma.resp)
+    io.dma.resp <> resp_arb.io.out
+
+    val selection = PriorityEncoder(reqReadys)
+    trackers.zipWithIndex.foreach { case (tracker, i) =>
+      tracker.io.dma.req.valid := io.dma.req.valid && selection === UInt(i)
+      tracker.io.dma.req.bits := io.dma.req.bits
+    }
+    io.dma.req.ready := reqReadys.orR
+  } else {
+    io.mem <> trackers.head.io.mem
+    io.dma <> trackers.head.io.dma
+  }
+}
+
+class DmaTracker(implicit p: Parameters) extends DmaModule()(p)
+    with HasTileLinkParameters {
+  val io = new Bundle {
+    val dma = (new DmaIO).flip
+    val mem = new ClientUncachedTileLinkIO
+  }
+
+  private val blockOffset = tlBeatAddrBits + tlByteAddrBits
+  private val blockBytes = tlDataBeats * tlDataBytes
+
+  val data_buffer = Reg(Vec(2 * tlDataBeats, Bits(width = tlDataBits)))
+  val get_inflight = Reg(UInt(2 * tlDataBeats))
+  val put_inflight = Reg(Bool())
+  val put_half = Reg(UInt(width = 1))
+  val get_half = Reg(UInt(width = 1))
+  val prefetch_put = Reg(Bool())
+  val get_done = !get_inflight.orR
+
+  val src_block = Reg(UInt(width = tlBlockAddrBits))
+  val dst_block = Reg(UInt(width = tlBlockAddrBits))
+  val offset    = Reg(UInt(width = blockOffset))
+  val alignment = Reg(UInt(width = blockOffset))
+  val shift_dir = Reg(Bool())
+
+  val bytes_left = Reg(UInt(width = addrBits))
+
+  val acq = io.mem.acquire.bits
+  val gnt = io.mem.grant.bits
+
+  val (s_idle :: s_get :: s_put :: s_prefetch ::
+       s_wait :: s_resp :: Nil) = Enum(Bits(), 6)
+  val state = Reg(init = s_idle)
+
+  val (put_beat, put_done) = Counter(
+    io.mem.acquire.fire() && acq.hasData(), tlDataBeats)
+
+  val put_mask = Vec.tabulate(tlDataBytes) { i =>
+    val byte_index = Cat(put_beat, UInt(i, tlByteAddrBits))
+    byte_index >= offset && byte_index < bytes_left
+  }.toBits
+
+  val prefetch_sent = io.mem.acquire.fire() && io.mem.acquire.bits.isPrefetch()
+  val prefetch_busy = Reg(init = UInt(0, tlMaxClientXacts))
+  val (prefetch_id, _) = Counter(prefetch_sent, tlMaxClientXacts)
+
+  val base_index = Cat(put_half, put_beat)
+  val put_data = Wire(init = Bits(0, tlDataBits))
+  val beat_align = alignment(blockOffset - 1, tlByteAddrBits)
+  val bit_align = Cat(alignment(tlByteAddrBits - 1, 0), UInt(0, 3))
+  val rev_align = UInt(tlDataBits) - bit_align
+
+  def getBit(value: UInt, sel: UInt): Bool =
+    (value >> sel)(0)
+
+  when (alignment === UInt(0)) {
+    put_data := data_buffer.read(base_index)
+  } .elsewhen (shift_dir) {
+    val shift_index = base_index - beat_align
+    when (bit_align === UInt(0)) {
+      put_data := data_buffer.read(shift_index)
+    } .otherwise {
+      val upper_bits = data_buffer.read(shift_index)
+      val lower_bits = data_buffer.read(shift_index - UInt(1))
+      val upper_shifted = upper_bits << bit_align
+      val lower_shifted = lower_bits >> rev_align
+      put_data := upper_shifted | lower_shifted
+    }
+  } .otherwise {
+    val shift_index = base_index + beat_align
+    when (bit_align === UInt(0)) {
+      put_data := data_buffer.read(shift_index)
+    } .otherwise {
+      val upper_bits = data_buffer.read(shift_index + UInt(1))
+      val lower_bits = data_buffer.read(shift_index)
+      val upper_shifted = upper_bits << rev_align
+      val lower_shifted = lower_bits >> bit_align
+      put_data := upper_shifted | lower_shifted
+    }
+  }
+
+  val put_acquire = PutBlock(
+    client_xact_id = UInt(2),
+    addr_block = dst_block,
+    addr_beat = put_beat,
+    data = put_data,
+    wmask = put_mask)
+
+  val get_acquire = GetBlock(
+    client_xact_id = get_half,
+    addr_block = src_block,
+    alloc = Bool(false))
+
+  val prefetch_acquire = Mux(prefetch_put,
+    PutPrefetch(client_xact_id = prefetch_id, addr_block = dst_block),
+    GetPrefetch(client_xact_id = prefetch_id, addr_block = dst_block))
+
+  val resp_id = Reg(UInt(width = dmaClientXactIdBits))
+
+  io.mem.acquire.valid := (state === s_get) ||
+                          (state === s_put && get_done) ||
+                          (state === s_prefetch && !prefetch_busy(prefetch_id))
+  io.mem.acquire.bits := MuxBundle(
+    state, prefetch_acquire, Seq(
+      s_get -> get_acquire,
+      s_put -> put_acquire))
+  io.mem.grant.ready := Bool(true)
+  io.dma.req.ready := state === s_idle
+  io.dma.resp.valid := state === s_resp
+  io.dma.resp.bits.client_xact_id := resp_id
+  io.dma.resp.bits.status := UInt(0)
+
+  when (io.dma.req.fire()) {
+    val src_off = io.dma.req.bits.source(blockOffset - 1, 0)
+    val dst_off = io.dma.req.bits.dest(blockOffset - 1, 0)
+    val direction = src_off < dst_off
+
+    resp_id := io.dma.req.bits.client_xact_id
+    src_block := io.dma.req.bits.source(addrBits - 1, blockOffset)
+    dst_block := io.dma.req.bits.dest(addrBits - 1, blockOffset)
+    alignment := Mux(direction, dst_off - src_off, src_off - dst_off)
+    shift_dir := direction
+    offset := dst_off
+    bytes_left := io.dma.req.bits.length + dst_off
+    get_inflight := UInt(0)
+    put_inflight := Bool(false)
+    get_half := UInt(0)
+    put_half := UInt(0)
+
+    when (io.dma.req.bits.cmd === DMA_CMD_COPY) {
+      state := s_get
+    } .otherwise {
+      prefetch_put := io.dma.req.bits.cmd(0)
+      state := s_prefetch
+    }
+  }
+
+  when (state === s_get && io.mem.acquire.ready) {
+    val bytes_in_buffer = UInt(blockBytes) - alignment
+    val extra_read = alignment > UInt(0) && !shift_dir && // dst_off < src_off
+                     get_half === UInt(0) && // this is the first block
+                     bytes_in_buffer < bytes_left // there is still more data left to fetch
+    get_inflight := get_inflight | FillInterleaved(tlDataBeats, UIntToOH(get_half))
+    get_half := get_half + UInt(1)
+    src_block := src_block + UInt(1)
+    when (!extra_read) {
+      state := s_put
+    }
+  }
+
+  when (prefetch_sent) {
+    prefetch_busy := prefetch_busy | UIntToOH(prefetch_id)
+    when (bytes_left < UInt(blockBytes)) {
+      bytes_left := UInt(0)
+      state := s_resp
+    } .otherwise {
+      bytes_left := bytes_left - UInt(blockBytes)
+      dst_block := dst_block + UInt(1)
+    }
+  }
+
+  when (io.mem.grant.fire()) {
+    when (gnt.g_type === Grant.prefetchAckType) {
+      prefetch_busy := prefetch_busy & ~UIntToOH(gnt.client_xact_id)
+    } .elsewhen (gnt.hasData()) {
+      val write_half = gnt.client_xact_id(0)
+      val write_idx = Cat(write_half, gnt.addr_beat)
+      get_inflight := get_inflight & ~UIntToOH(write_idx)
+      data_buffer.write(write_idx, gnt.data)
+    } .otherwise {
+      put_inflight := Bool(false)
+    }
+  }
+
+  when (put_done) { // state === s_put
+    put_half := put_half + UInt(1)
+    offset := UInt(0)
+    when (bytes_left < UInt(blockBytes)) {
+      bytes_left := UInt(0)
+    } .otherwise {
+      bytes_left := bytes_left - UInt(blockBytes)
+    }
+    put_inflight := Bool(true)
+    dst_block := dst_block + UInt(1)
+    state := s_wait
+  }
+
+  when (state === s_wait && get_done && !put_inflight) {
+    state := Mux(bytes_left === UInt(0), s_resp, s_get)
+  }
+
+  when (io.dma.resp.fire()) { state := s_idle }
+}
+
+class DmaArbiter(arbN: Int)(implicit p: Parameters) extends DmaModule()(p) {
+  val io = new Bundle {
+    val in = Vec(arbN, new DmaIO).flip
+    val out = new DmaIO
+  }
+
+  if (arbN > 1) {
+    val idBits = log2Up(arbN)
+    val req_arb = Module(new RRArbiter(new DmaRequest, arbN))
+    val out_resp_client_id = io.out.resp.bits.client_xact_id(idBits - 1, 0)
+
+    for (i <- 0 until arbN) {
+      req_arb.io.in(i) <> io.in(i).req
+      req_arb.io.in(i).bits.client_xact_id := Cat(
+        io.in(i).req.bits.client_xact_id,
+        UInt(i, idBits))
+
+      io.in(i).resp.valid := io.out.resp.valid && out_resp_client_id === UInt(i)
+      io.in(i).resp.bits := io.out.resp.bits
+    }
+
+    val respReadys = Vec(io.in.map(_.resp.ready))
+
+    io.out.req <> req_arb.io.out
+    io.out.resp.ready := respReadys(out_resp_client_id)
+  } else {
+    io.out <> io.in.head
+  }
+}
diff --git a/uncore/src/main/scala/util.scala b/uncore/src/main/scala/util.scala
index b0036b37..db1dd6f4 100644
--- a/uncore/src/main/scala/util.scala
+++ b/uncore/src/main/scala/util.scala
@@ -17,6 +17,10 @@ object MuxBundle {
   def apply[T <: Data] (default: T, mapping: Seq[(Bool, T)]): T = {
     mapping.reverse.foldLeft(default)((b, a) => Mux(a._1, a._2, b))
   }
+
+  def apply[S <: Data, T <: Data] (key: S, default: T, mapping: Seq[(S, T)]): T = {
+    apply(default, mapping.map{ case (a, b) => (a === key, b) })
+  }
 }
 
 // Produces 0-width value when counting to 1