From 4aef567a80b04afee5b81bb8383f0ccd4866869a Mon Sep 17 00:00:00 2001
From: Andrew Waterman <waterman@cs.berkeley.edu>
Date: Fri, 13 May 2016 17:54:23 -0700
Subject: [PATCH] Fix MMIO bug: replay_next wasn't set

---
 rocket/src/main/scala/arbiter.scala  |  4 +---
 rocket/src/main/scala/nbdcache.scala | 10 +++++++---
 rocket/src/main/scala/rocket.scala   |  2 +-
 3 files changed, 9 insertions(+), 7 deletions(-)

diff --git a/rocket/src/main/scala/arbiter.scala b/rocket/src/main/scala/arbiter.scala
index 8a207f2e..79cf6a36 100644
--- a/rocket/src/main/scala/arbiter.scala
+++ b/rocket/src/main/scala/arbiter.scala
@@ -55,9 +55,7 @@ class HellaCacheArbiter(n: Int)(implicit p: Parameters) extends Module
     resp.bits := io.mem.resp.bits
     resp.bits.tag := io.mem.resp.bits.tag >> log2Up(n)
 
-    io.requestor(i).replay_next.valid := io.mem.replay_next.valid &&
-      io.mem.replay_next.bits(log2Up(n)-1,0) === UInt(i)
-    io.requestor(i).replay_next.bits := io.mem.replay_next.bits >> log2Up(n)
+    io.requestor(i).replay_next := io.mem.replay_next
   }
 }
 
diff --git a/rocket/src/main/scala/nbdcache.scala b/rocket/src/main/scala/nbdcache.scala
index c9c108f1..2181b96e 100644
--- a/rocket/src/main/scala/nbdcache.scala
+++ b/rocket/src/main/scala/nbdcache.scala
@@ -100,7 +100,7 @@ class HellaCacheIO(implicit p: Parameters) extends CoreBundle()(p) {
   val s2_nack = Bool(INPUT) // req from two cycles ago is rejected
 
   val resp = Valid(new HellaCacheResp).flip
-  val replay_next = Valid(Bits(width = coreDCacheReqTagBits)).flip
+  val replay_next = Bool(INPUT)
   val xcpt = (new HellaCacheExceptions).asInput
   val invalidate_lr = Bool(OUTPUT)
   val ordered = Bool(INPUT)
@@ -157,6 +157,7 @@ class IOMSHR(id: Int)(implicit p: Parameters) extends L1HellaCacheModule()(p) {
     val grant = Valid(new GrantFromSrc).flip
     val finish = Decoupled(new FinishToDst)
     val resp = Decoupled(new HellaCacheResp)
+    val replay_next = Bool(OUTPUT)
   }
 
   def wordFromBeat(addr: UInt, dat: UInt) = {
@@ -210,6 +211,7 @@ class IOMSHR(id: Int)(implicit p: Parameters) extends L1HellaCacheModule()(p) {
   io.acquire.valid := (state === s_acquire)
   io.acquire.bits := Mux(isRead(req.cmd), get_acquire, put_acquire)
 
+  io.replay_next := (state === s_grant) || io.resp.valid && !io.resp.ready
   io.resp.valid := (state === s_resp)
   io.resp.bits := req
   io.resp.bits.has_data := isRead(req.cmd)
@@ -418,6 +420,7 @@ class MSHRFile(implicit p: Parameters) extends L1HellaCacheModule()(p) {
 
     val probe_rdy = Bool(OUTPUT)
     val fence_rdy = Bool(OUTPUT)
+    val replay_next = Bool(OUTPUT)
   }
 
   // determine if the request is cacheable or not
@@ -501,6 +504,7 @@ class MSHRFile(implicit p: Parameters) extends L1HellaCacheModule()(p) {
   val resp_arb = Module(new Arbiter(new HellaCacheResp, nIOMSHRs))
 
   var mmio_rdy = Bool(false)
+  io.replay_next := Bool(false)
 
   for (i <- 0 until nIOMSHRs) {
     val id = nMSHRs + i
@@ -522,6 +526,7 @@ class MSHRFile(implicit p: Parameters) extends L1HellaCacheModule()(p) {
     resp_arb.io.in(i) <> mshr.io.resp
 
     when (!mshr.io.req.ready) { io.fence_rdy := Bool(false) }
+    when (mshr.io.replay_next) { io.replay_next := Bool(true) }
   }
 
   mmio_alloc_arb.io.out.ready := io.req.valid && !cacheable
@@ -1086,8 +1091,7 @@ class HellaCache(implicit p: Parameters) extends L1HellaCacheModule()(p) {
   io.cpu.resp := Mux(mshrs.io.resp.ready, uncache_resp, cache_resp)
   io.cpu.resp.bits.data_word_bypass := loadgen.wordData
   io.cpu.ordered := mshrs.io.fence_rdy && !s1_valid && !s2_valid
-  io.cpu.replay_next.valid := s1_replay && s1_read
-  io.cpu.replay_next.bits := s1_req.tag
+  io.cpu.replay_next := (s1_replay && s1_read) || mshrs.io.replay_next
 }
 
 // exposes a sane decoupled request interface
diff --git a/rocket/src/main/scala/rocket.scala b/rocket/src/main/scala/rocket.scala
index 757e870d..879f0f08 100644
--- a/rocket/src/main/scala/rocket.scala
+++ b/rocket/src/main/scala/rocket.scala
@@ -352,7 +352,7 @@ class Rocket(implicit p: Parameters) extends CoreModule()(p) {
     (mem_reg_valid && mem_ctrl.mem && io.dmem.xcpt.pf.st, UInt(Causes.fault_store)),
     (mem_reg_valid && mem_ctrl.mem && io.dmem.xcpt.pf.ld, UInt(Causes.fault_load))))
 
-  val dcache_kill_mem = mem_reg_valid && mem_ctrl.wxd && io.dmem.replay_next.valid // structural hazard on writeback port
+  val dcache_kill_mem = mem_reg_valid && mem_ctrl.wxd && io.dmem.replay_next // structural hazard on writeback port
   val fpu_kill_mem = mem_reg_valid && mem_ctrl.fp && io.fpu.nack_mem
   val replay_mem  = dcache_kill_mem || mem_reg_replay || fpu_kill_mem
   val killm_common = dcache_kill_mem || take_pc_wb || mem_reg_xcpt || !mem_reg_valid