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axi4: the last missing piece for safe FIFO ordering

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This commit is contained in:
Wesley W. Terpstra 2017-04-27 17:55:51 -07:00
parent b0b5601e8d
commit 58a4529cc5
1 changed files with 33 additions and 5 deletions
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38
src/main/scala/uncore/tilelink2/ToAXI4.scala
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@ -60,9 +60,12 @@ class TLToAXI4(beatBytes: Int, combinational: Boolean = true)(implicit p: Parame
// Construct the source=>ID mapping table
val idTable = Wire(Vec(edgeIn.client.endSourceId, out.aw.bits.id))
var idCount = Array.fill(edgeOut.master.endId) { 0 }
(edgeIn.client.clients zip edgeOut.master.masters) foreach { case (c, m) =>
for (i <- 0 until c.sourceId.size) {
idTable(c.sourceId.start + i) := UInt(m.id.start + (if (c.requestFifo) 0 else i))
val id = m.id.start + (if (c.requestFifo) 0 else i)
idTable(c.sourceId.start + i) := UInt(id)
idCount(id) = idCount(id) + 1
}
}
@ -139,11 +142,11 @@ class TLToAXI4(beatBytes: Int, combinational: Boolean = true)(implicit p: Parame
arw.qos := UInt(0) // no QoS
arw.user.foreach { _ := a_state }
// !!! Mix R-W stall here
in.a.ready := Mux(a_isPut, (doneAW || out_arw.ready) && out_w.ready, out_arw.ready)
out_arw.valid := in.a.valid && Mux(a_isPut, !doneAW && out_w.ready, Bool(true))
val stall = Wire(Bool())
in.a.ready := !stall && Mux(a_isPut, (doneAW || out_arw.ready) && out_w.ready, out_arw.ready)
out_arw.valid := !stall && in.a.valid && Mux(a_isPut, !doneAW && out_w.ready, Bool(true))
out_w.valid := in.a.valid && a_isPut && (doneAW || out_arw.ready)
out_w.valid := !stall && in.a.valid && a_isPut && (doneAW || out_arw.ready)
out_w.bits.data := in.a.bits.data
out_w.bits.strb := in.a.bits.mask
out_w.bits.last := a_last
@ -167,6 +170,31 @@ class TLToAXI4(beatBytes: Int, combinational: Boolean = true)(implicit p: Parame
in.d.bits := Mux(r_wins, r_d, b_d)
in.d.bits.data := out.r.bits.data // avoid a costly Mux
// We need to track if any reads or writes are inflight for a given ID.
// If the opposite type arrives, we must stall until it completes.
val a_sel = UIntToOH(arw.id, edgeOut.master.endId).toBools
val d_sel = UIntToOH(Mux(r_wins, out.r.bits.id, out.b.bits.id), edgeOut.master.endId).toBools
val d_last = Mux(r_wins, out.r.bits.last, Bool(true))
val d_first = RegInit(Bool(true))
when (in.d.fire()) { d_first := d_last }
val stalls = ((a_sel zip d_sel) zip idCount) filter { case (_, n) => n > 1 } map { case ((as, ds), n) =>
val count = RegInit(UInt(0, width = log2Ceil(n + 1)))
val write = Reg(Bool())
val idle = count === UInt(0)
// Once we start getting the response, it's safe to already switch R/W
val inc = as && out_arw.fire()
val dec = ds && d_first && in.d.fire()
count := count + inc.asUInt - dec.asUInt
assert (!dec || count =/= UInt(0)) // underflow
assert (!inc || count =/= UInt(n)) // overflow
when (inc) { write := arw.wen }
!idle && write =/= arw.wen
}
stall := stalls.foldLeft(Bool(false))(_||_)
// Tie off unused channels
in.b.valid := Bool(false)
in.c.ready := Bool(true)