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add HellaQueue, an SRAM-based queue

This commit is contained in:
Andrew Waterman 2013-01-28 20:54:25 -08:00
parent 37c67f1d87
commit 45d8066f45

View File

@ -73,3 +73,55 @@ case class WideCounter(width: Int, inc: Bool = Bool(true))
if (isWide) large := (if (w < smallWidth) UFix(0) else x(w.min(width)-1,smallWidth))
}
}
class HellaFlowQueue[T <: Data](val entries: Int)(data: => T) extends Component
{
val io = new ioQueue(entries)(data)
require(isPow2(entries) && entries > 1)
val do_flow = Bool()
val do_enq = io.enq.fire() && !do_flow
val do_deq = io.deq.fire() && !do_flow
val maybe_full = Reg(resetVal = Bool(false))
val enq_ptr = Counter(do_enq, entries)._1
val deq_ptr = Counter(do_deq, entries)._1
when (do_enq != do_deq) { maybe_full := do_enq }
val ptr_match = enq_ptr === deq_ptr
val empty = ptr_match && !maybe_full
val full = ptr_match && maybe_full
do_flow := empty && io.deq.ready
val ram = Mem(entries, seqRead = true){data}
val ram_out = Reg{data}
val ram_out_valid = Reg(io.deq.ready)
when (io.deq.ready && !empty) {
ram_out := ram(Mux(io.deq.valid, deq_ptr + UFix(1), deq_ptr))
}
when (do_enq) { ram(enq_ptr) := io.enq.bits }
io.deq.valid := Mux(empty, io.enq.valid, ram_out_valid)
io.enq.ready := !full
io.deq.bits := Mux(empty, io.enq.bits, ram_out)
}
class HellaQueue[T <: Data](val entries: Int)(data: => T) extends Component
{
val io = new ioQueue(entries)(data)
val fq = new HellaFlowQueue(entries)(data)
io.enq <> fq.io.enq
io.deq <> Queue(fq.io.deq, 1, pipe = true)
}
object HellaQueue
{
def apply[T <: Data](enq: FIFOIO[T], entries: Int) = {
val q = (new HellaQueue(entries)) { enq.bits.clone }
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
}
}