From 88bf8a4f23948f43326c88a5c7440deaa50e5790 Mon Sep 17 00:00:00 2001
From: Andrew Waterman <waterman@eecs.berkeley.edu>
Date: Sun, 25 Mar 2012 17:03:58 -0700
Subject: [PATCH] add mem serdes unit

---
 rocket/src/main/scala/memserdes.scala | 89 +++++++++++++++++++++++++++
 1 file changed, 89 insertions(+)
 create mode 100644 rocket/src/main/scala/memserdes.scala

diff --git a/rocket/src/main/scala/memserdes.scala b/rocket/src/main/scala/memserdes.scala
new file mode 100644
index 00000000..2305ed69
--- /dev/null
+++ b/rocket/src/main/scala/memserdes.scala
@@ -0,0 +1,89 @@
+package rocket
+
+import Chisel._
+import Node._
+import Constants._
+import scala.math._
+
+class ioMemSerialized(w: Int) extends Bundle
+{
+  val req = (new ioDecoupled) { Bits(width = w) }
+  val resp = (new ioPipe) { Bits(width = w) }.flip
+}
+
+class MemSerdes(w: Int) extends Component
+{
+  val io = new Bundle {
+    val wide = new ioMem().flip
+    val narrow = new ioMemSerialized(w)
+  }
+  val abits = io.wide.req_cmd.bits.toBits.getWidth
+  val dbits = io.wide.req_data.bits.toBits.getWidth
+  val rbits = io.wide.resp.bits.getWidth
+
+  val out_buf = Reg() { Bits() }
+  val in_buf = Reg() { Bits() }
+
+  val s_idle :: s_read_addr :: s_write_addr :: s_write_idle :: s_write_data :: Nil = Enum(5) { UFix() }
+  val state = Reg(resetVal = s_idle)
+  val send_cnt = Reg(resetVal = UFix(0, log2up(max(abits, dbits))))
+  val data_send_cnt = Reg(resetVal = UFix(0, log2up(MEM_DATA_BITS)))
+  val adone = io.narrow.req.ready && send_cnt === UFix((abits-1)/w)
+  val ddone = io.narrow.req.ready && send_cnt === UFix((dbits-1)/w)
+
+  when (state === s_idle) {
+    when (io.wide.req_cmd.valid) {
+      state := Mux(io.wide.req_cmd.bits.rw, s_write_addr, s_read_addr)
+    }
+  }
+  when (state === s_read_addr && adone) {
+    state := s_idle
+    send_cnt := UFix(0)
+  }
+  when (state === s_write_addr && adone) {
+    state := s_write_idle
+    send_cnt := UFix(0)
+  }
+  when (state === s_write_idle && io.wide.req_data.valid) {
+    state := s_write_data
+  }
+  when (state === s_write_data && ddone) {
+    data_send_cnt := data_send_cnt + UFix(1)
+    state := Mux(data_send_cnt === UFix(REFILL_CYCLES-1), s_idle, s_write_idle)
+  }
+
+  when (io.narrow.req.valid && io.narrow.req.ready) {
+    send_cnt := Mux(adone, UFix(0), send_cnt + UFix(1))
+    out_buf := out_buf >> UFix(w)
+  }
+  when (io.wide.req_cmd.valid && io.wide.req_cmd.ready) {
+    out_buf := io.wide.req_cmd.bits.toBits
+  }
+  when (io.wide.req_data.valid && io.wide.req_data.ready) {
+    out_buf := io.wide.req_data.bits.toBits
+  }
+
+  io.wide.req_cmd.ready := state === s_idle
+  io.wide.req_data.ready := state === s_write_idle
+  io.narrow.req.valid := state === s_read_addr || state === s_write_addr || state === s_write_data
+  io.narrow.req.bits := out_buf
+
+  val recv_cnt = Reg() { UFix(width = log2up(rbits)) }
+  val data_recv_cnt = Reg(resetVal = UFix(0, log2up(MEM_DATA_BITS)))
+  val resp_val = Reg(resetVal = Bool(false))
+
+  resp_val := Bool(false)
+  when (io.narrow.resp.valid) {
+    recv_cnt := recv_cnt + UFix(1)
+    when (recv_cnt === UFix((rbits-1)/w)) {
+      recv_cnt := UFix(0)
+      data_recv_cnt := data_recv_cnt + UFix(1)
+      resp_val := Bool(true)
+    }
+    in_buf := Cat(io.narrow.resp.bits, in_buf(rbits-1,w))
+  }
+
+  io.wide.resp.valid := resp_val
+  io.wide.resp.bits.tag := in_buf(io.wide.resp.bits.tag.width-1,0)
+  io.wide.resp.bits.data := in_buf >> UFix(io.wide.resp.bits.tag.width)
+}