Merge pull request #37 from ucb-bar/utilsplit

Break out Utils.scala into smaller portions

1 files changed, 143 insertions, 0 deletions

diff --git a/src/main/scala/Chisel/util/Decoupled.scala b/src/main/scala/Chisel/util/Decoupled.scala
new file mode 100644
index 00000000..b1505887
--- /dev/null
+++ b/src/main/scala/Chisel/util/Decoupled.scala
@@ -0,0 +1,143 @@
+// See LICENSE for license details.
+
+/** Wrappers for ready-valid (Decoupled) interfaces and associated circuit generators using them.
+  */
+
+package Chisel
+
+/** An I/O Bundle with simple handshaking using valid and ready signals for data 'bits'*/
+class DecoupledIO[+T <: Data](gen: T) extends Bundle
+{
+  val ready = Bool(INPUT)
+  val valid = Bool(OUTPUT)
+  val bits  = gen.cloneType.asOutput
+  def fire(dummy: Int = 0): Bool = ready && valid
+  override def cloneType: this.type = new DecoupledIO(gen).asInstanceOf[this.type]
+}
+
+/** Adds a ready-valid handshaking protocol to any interface.
+  * The standard used is that the consumer uses the flipped interface.
+  */
+object Decoupled {
+  def apply[T <: Data](gen: T): DecoupledIO[T] = new DecoupledIO(gen)
+}
+
+/** An I/O bundle for enqueuing data with valid/ready handshaking */
+class EnqIO[T <: Data](gen: T) extends DecoupledIO(gen)
+{
+  def enq(dat: T): T = { valid := Bool(true); bits := dat; dat }
+  valid := Bool(false)
+  for (io <- bits.flatten)
+    io := UInt(0)
+  override def cloneType: this.type = { new EnqIO(gen).asInstanceOf[this.type]; }
+}
+
+/** An I/O bundle for dequeuing data with valid/ready handshaking */
+class DeqIO[T <: Data](gen: T) extends DecoupledIO(gen)
+{
+  flip()
+  ready := Bool(false)
+  def deq(b: Boolean = false): T = { ready := Bool(true); bits }
+  override def cloneType: this.type = { new DeqIO(gen).asInstanceOf[this.type]; }
+}
+
+/** An I/O bundle for dequeuing data with valid/ready handshaking */
+class DecoupledIOC[+T <: Data](gen: T) extends Bundle
+{
+  val ready = Bool(INPUT)
+  val valid = Bool(OUTPUT)
+  val bits  = gen.cloneType.asOutput
+}
+
+/** An I/O Bundle for Queues
+  * @param gen The type of data to queue
+  * @param entries The max number of entries in the queue */
+class QueueIO[T <: Data](gen: T, entries: Int) extends Bundle
+{
+  /** I/O to enqueue data, is [[Chisel.DecoupledIO]] flipped */
+  val enq   = Decoupled(gen.cloneType).flip
+  /** I/O to enqueue data, is [[Chisel.DecoupledIO]]*/
+  val deq   = Decoupled(gen.cloneType)
+  /** The current amount of data in the queue */
+  val count = UInt(OUTPUT, log2Up(entries + 1))
+}
+
+/** A hardware module implementing a Queue
+  * @param gen The type of data to queue
+  * @param entries The max number of entries in the queue
+  * @param pipe True if a single entry queue can run at full throughput (like a pipeline). The ''ready'' signals are
+  * combinationally coupled.
+  * @param flow True if the inputs can be consumed on the same cycle (the inputs "flow" through the queue immediately).
+  * The ''valid'' signals are coupled.
+  *
+  * Example usage:
+  *    {{{ val q = new Queue(UInt(), 16)
+  *    q.io.enq <> producer.io.out
+  *    consumer.io.in <> q.io.deq }}}
+  */
+class Queue[T <: Data](gen: T, val entries: Int,
+                       pipe: Boolean = false,
+                       flow: Boolean = false,
+                       _reset: Bool = null) extends Module(_reset=_reset)
+{
+  val io = new QueueIO(gen, entries)
+
+  val ram = Mem(gen, entries)
+  val enq_ptr = Counter(entries)
+  val deq_ptr = Counter(entries)
+  val maybe_full = Reg(init=Bool(false))
+
+  val ptr_match = enq_ptr.value === deq_ptr.value
+  val empty = ptr_match && !maybe_full
+  val full = ptr_match && maybe_full
+  val maybe_flow = Bool(flow) && empty
+  val do_flow = maybe_flow && io.deq.ready
+
+  val do_enq = io.enq.ready && io.enq.valid && !do_flow
+  val do_deq = io.deq.ready && io.deq.valid && !do_flow
+  when (do_enq) {
+    ram(enq_ptr.value) := io.enq.bits
+    enq_ptr.inc()
+  }
+  when (do_deq) {
+    deq_ptr.inc()
+  }
+  when (do_enq != do_deq) {
+    maybe_full := do_enq
+  }
+
+  io.deq.valid := !empty || Bool(flow) && io.enq.valid
+  io.enq.ready := !full || Bool(pipe) && io.deq.ready
+  io.deq.bits := Mux(maybe_flow, io.enq.bits, ram(deq_ptr.value))
+
+  val ptr_diff = enq_ptr.value - deq_ptr.value
+  if (isPow2(entries)) {
+    io.count := Cat(maybe_full && ptr_match, ptr_diff)
+  } else {
+    io.count := Mux(ptr_match,
+                    Mux(maybe_full,
+                      UInt(entries), UInt(0)),
+                    Mux(deq_ptr.value > enq_ptr.value,
+                      UInt(entries) + ptr_diff, ptr_diff))
+  }
+}
+
+/** Generic hardware queue. Required parameter entries controls
+  the depth of the queues. The width of the queue is determined
+  from the inputs.
+
+  Example usage:
+     {{{ val q = Queue(Decoupled(UInt()), 16)
+     q.io.enq <> producer.io.out
+     consumer.io.in <> q.io.deq }}}
+  */
+object Queue
+{
+  def apply[T <: Data](enq: DecoupledIO[T], entries: Int = 2, pipe: Boolean = false): DecoupledIO[T]  = {
+    val q = Module(new Queue(enq.bits.cloneType, entries, pipe))
+    q.io.enq.valid := enq.valid // not using <> so that override is allowed
+    q.io.enq.bits := enq.bits
+    enq.ready := q.io.enq.ready
+    q.io.deq
+  }
+}