Expose WFI signal from Rocket tile (#2315)

src/main/resources/vsrc/RoccBlackBox.v

@@ -29,6 +29,7 @@ module RoccBlackBox
     input [xLen-1:0] rocc_cmd_bits_rs2,
     input rocc_cmd_bits_status_debug,
     input rocc_cmd_bits_status_cease,
+    input rocc_cmd_bits_status_wfi,
     input [31:0] rocc_cmd_bits_status_isa,
     input [PRV_SZ-1:0] rocc_cmd_bits_status_dprv,
     input [PRV_SZ-1:0] rocc_cmd_bits_status_prv,

src/main/scala/rocket/CSR.scala

@@ -17,6 +17,7 @@ class MStatus extends Bundle {
   // not truly part of mstatus, but convenient
   val debug = Bool()
   val cease = Bool()
+  val wfi = Bool()
   val isa = UInt(width = 32)
 
   val dprv = UInt(width = PRV.SZ) // effective privilege for data accesses
@@ -741,6 +742,7 @@ class CSRFile(
   io.time := reg_cycle
   io.csr_stall := reg_wfi || io.status.cease
   io.status.cease := RegEnable(true.B, false.B, insn_cease)
+  io.status.wfi := reg_wfi
 
   for ((io, reg) <- io.customCSRs zip reg_custom) {
     io.wen := false

src/main/scala/rocket/RocketCore.scala

@@ -846,6 +846,7 @@ class Rocket(tile: RocketTile)(implicit p: Parameters) extends CoreModule()(p)
   val unpause = csr.io.time(rocketParams.lgPauseCycles-1, 0) === 0 || io.dmem.perf.release || take_pc
   when (unpause) { id_reg_pause := false }
   io.cease := csr.io.status.cease && !clock_en_reg
+  io.wfi := csr.io.status.wfi
   if (rocketParams.clockGate) {
     long_latency_stall := csr.io.csr_stall || io.dmem.perf.blocked || id_reg_pause && !unpause
     clock_en := clock_en_reg || ex_pc_valid || (!long_latency_stall && io.imem.resp.valid)

src/main/scala/tile/Core.scala

@@ -127,6 +127,7 @@ trait HasCoreIO extends HasTileParameters {
     val trace = Vec(coreParams.retireWidth, new TracedInstruction).asOutput
     val bpwatch = Vec(coreParams.nBreakpoints, new BPWatch(coreParams.retireWidth)).asOutput
     val cease = Bool().asOutput
+    val wfi = Bool().asOutput
     val traceStall = Bool().asInput
   }
 }

src/main/scala/tile/RocketTile.scala

@@ -135,7 +135,7 @@ class RocketTileModuleImp(outer: RocketTile) extends BaseTileModuleImp(outer)
     !ptw.io.dpath.clock_enabled &&
     core.io.cease))
 
-  outer.reportWFI(None) // TODO: actually report this?
+  outer.reportWFI(Some(core.io.wfi))
 
   outer.decodeCoreInterrupts(core.io.interrupts) // Decode the interrupt vector