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allow host to read how much data/space is available in FIFOs

This commit is contained in:
Howard Mao 2016-10-03 17:03:38 -07:00
parent 8a18edde38
commit d392485525
1 changed files with 15 additions and 3 deletions
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18
common/src/main/scala/Top.scala
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@ -57,10 +57,21 @@ class NastiFIFO(implicit p: Parameters) extends NastiModule()(p) {
io.nasti.w.ready := inq.io.enq.ready && writing
inq.io.enq.bits := io.nasti.w.bits.data
io.nasti.r.valid := outq.io.deq.valid && reading
outq.io.deq.ready := io.nasti.r.ready && reading
val nRegisters = 3
val addrLSB = log2Up(w / 8)
val addrMSB = addrLSB + log2Up(nRegisters) - 1
val araddr = io.nasti.ar.bits.addr(addrMSB, addrLSB)
val awaddr = io.nasti.aw.bits.addr(addrMSB, addrLSB)
val raddr = Reg(araddr)
io.nasti.r.valid := reading && (raddr =/= UInt(0) || outq.io.deq.valid)
outq.io.deq.ready := reading && (raddr =/= UInt(0) || io.nasti.r.ready)
io.nasti.r.bits := NastiReadDataChannel(
id = rid, data = outq.io.deq.bits)
id = rid,
data = MuxLookup(raddr, UInt(0), Seq(
UInt(0) -> outq.io.deq.bits,
UInt(1) -> outq.io.count, // available output FIFO data
UInt(2) -> (UInt(depth) - inq.io.count)))) // free input FIFO space
io.nasti.aw.ready := !writing && !responding
io.nasti.ar.ready := !reading
@ -79,6 +90,7 @@ class NastiFIFO(implicit p: Parameters) extends NastiModule()(p) {
when (io.nasti.ar.fire()) {
len := io.nasti.ar.bits.len
rid := io.nasti.ar.bits.id
raddr := araddr
reading := Bool(true)
}
when (io.nasti.r.fire() && io.nasti.r.bits.last) { reading := Bool(false) }