riscv/rocket-chip
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add flow queues and skid buffers

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hopefully they work
This commit is contained in:
Andrew Waterman 2012-07-30 18:45:13 -07:00
parent be4fa936dd
commit 80c243469e
1 changed files with 41 additions and 23 deletions
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64
rocket/src/main/scala/queues.scala
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@ -11,31 +11,21 @@ class ioQueue[T <: Data](entries: Int, flushable: Boolean)(data: => T) extends B
val count = UFix(OUTPUT, log2Up(entries+1))
}
class queue[T <: Data](val entries: Int, pipe: Boolean = false, flushable: Boolean = false)(data: => T) extends Component
class queue[T <: Data](val entries: Int, pipe: Boolean = false, flow: Boolean = false, flushable: Boolean = false)(data: => T) extends Component
{
val io = new ioQueue(entries, flushable)(data)
val do_enq = io.enq.ready && io.enq.valid
val do_deq = io.deq.ready && io.deq.valid
val do_flow = Bool()
val do_enq = io.enq.ready && io.enq.valid && !do_flow
val do_deq = io.deq.ready && io.deq.valid && !do_flow
var enq_ptr = UFix(0)
var deq_ptr = UFix(0)
val pow2 = (entries & (entries-1)) == 0
if (entries > 1)
{
enq_ptr = Reg(resetVal = UFix(0, log2Up(entries)))
deq_ptr = Reg(resetVal = UFix(0, log2Up(entries)))
var enq_next = enq_ptr + UFix(1)
var deq_next = deq_ptr + UFix(1)
if (!pow2) {
enq_next = Mux(enq_ptr === UFix(entries-1), UFix(0), enq_next)
deq_next = Mux(deq_ptr === UFix(entries-1), UFix(0), deq_next)
}
when (do_deq) { deq_ptr := deq_next }
when (do_enq) { enq_ptr := enq_next }
enq_ptr = Counter(do_enq, entries)._1
deq_ptr = Counter(do_deq, entries)._1
if (flushable) {
when (io.flush) {
deq_ptr := UFix(0)
@ -58,12 +48,16 @@ class queue[T <: Data](val entries: Int, pipe: Boolean = false, flushable: Boole
when (do_enq) { ram(enq_ptr) := io.enq.bits }
val ptr_match = enq_ptr === deq_ptr
io.deq.valid := maybe_full || !ptr_match
io.enq.ready := !maybe_full || !ptr_match || (if (pipe) io.deq.ready else Bool(false))
io.deq.bits <> ram(deq_ptr)
val empty = ptr_match && !maybe_full
val full = ptr_match && maybe_full
val maybe_flow = Bool(flow) && empty
do_flow := maybe_flow && io.deq.ready
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))
val ptr_diff = enq_ptr - deq_ptr
if (pow2)
if (isPow2(entries))
io.count := Cat(maybe_full && ptr_match, ptr_diff).toUFix
else
io.count := Mux(ptr_match, Mux(maybe_full, UFix(entries), UFix(0)), Mux(deq_ptr > enq_ptr, UFix(entries) + ptr_diff, ptr_diff))
@ -92,11 +86,11 @@ class pipereg[T <: Data]()(data: => T) extends Component
// bits := io.enq.bits
//}
val reg = Reg() { io.enq.bits.clone }
when (io.enq.valid) { reg := io.enq.bits }
val r = Reg() { io.enq.bits.clone }
when (io.enq.valid) { r := io.enq.bits }
io.deq.valid := Reg(io.enq.valid, resetVal = Bool(false))
io.deq.bits <> reg
io.deq.bits <> r
}
object Pipe
@ -112,3 +106,27 @@ object Pipe
q.io.deq
}
}
class SkidBuffer[T <: Data]()(data: => T) extends Component
{
val io = new Bundle {
val enq = new FIFOIO()(data).flip
val deq = new FIFOIO()(data)
}
val fq = new queue(1, flow = true)(data)
val pq = new queue(1, pipe = true)(data)
fq.io.enq <> io.enq
pq.io.enq <> fq.io.deq
io.deq <> pq.io.deq
}
object SkidBuffer
{
def apply[T <: Data](enq: FIFOIO[T]): FIFOIO[T] = {
val s = new SkidBuffer()(enq.bits.clone)
s.io.enq <> enq
s.io.deq
}
}