RequestArb: restrict concurrent number of Acquires with same set

Consider a deadlock situation: given 4 ways in each slice, MSHR 0~3 are
accessing separate ways, which makes all the ways occupied. At the same
time, MSHR 4 already got CompData from HN, and is waiting for a free way
to replace and to echo data through channel D to L1. Therefore MSHR 4
selects replacement way but fails repeatedly. If there is an incoming
snoop that has the same address with MSHR 4, the snoop will be blocked
because Grant message of MSHR 4 is blocked. Then CompData(s)
corresponding to MSHR 0~3 could not be returned due to the blocked
snoop. There goes the deadlock.

Author: linjuanZ

src/main/scala/coupledL2/Common.scala

@@ -173,7 +173,7 @@ class MSHRRequest(implicit p: Parameters) extends L2Bundle {
 }
 
 // MSHR info to ReqBuf and SinkB
-class MSHRInfo(implicit p: Parameters) extends L2Bundle {
+class MSHRInfo(implicit p: Parameters) extends L2Bundle with HasTLChannelBits {
   val set = UInt(setBits.W)
   val way = UInt(wayBits.W)
   val reqTag = UInt(tagBits.W)

src/main/scala/coupledL2/RequestArb.scala

@@ -70,6 +70,9 @@ class RequestArb(implicit p: Parameters) extends L2Module {
     val fromTXDAT = if (enableCHI) Some(Input(new TXDATBlockBundle)) else None
     val fromTXRSP = if (enableCHI) Some(Input(new TXRSPBlockBundle)) else None
     val fromTXREQ = if (enableCHI) Some(Input(new TXBlockBundle)) else None
+
+    /* MSHR Status */
+    val msInfo = Vec(mshrsAll, Flipped(ValidIO(new MSHRInfo())))
   })
 
   /* ======== Reset ======== */
@@ -137,7 +140,9 @@ class RequestArb(implicit p: Parameters) extends L2Module {
 
   val sink_ready_basic = io.dirRead_s1.ready && resetFinish && !mshr_task_s1.valid && s2_ready
 
-  io.sinkA.ready := sink_ready_basic && !block_A && !sinkValids(1) && !sinkValids(0) // SinkC prior to SinkA & SinkB
+  val noFreeWay = Wire(Bool())
+
+  io.sinkA.ready := sink_ready_basic && !block_A && !sinkValids(1) && !sinkValids(0) && !noFreeWay // SinkC prior to SinkA & SinkB
   io.sinkB.ready := sink_ready_basic && !block_B && !sinkValids(0) // SinkB prior to SinkA
   io.sinkC.ready := sink_ready_basic && !block_C
 
@@ -189,6 +194,13 @@ class RequestArb(implicit p: Parameters) extends L2Module {
   task_s2.valid := s1_fire
   when(s1_fire) { task_s2.bits := task_s1.bits }
 
+  val sameSet_s2 = task_s2.valid && task_s2.bits.fromA && !task_s2.bits.mshrTask && task_s2.bits.set === A_task.set
+  val sameSet_s3 = RegNext(task_s2.valid && task_s2.bits.fromA && !task_s2.bits.mshrTask) &&
+    RegEnable(task_s2.bits.set, task_s2.valid) === A_task.set
+  val sameSetCnt = PopCount(VecInit(io.msInfo.map(s => s.valid && s.bits.set === A_task.set && s.bits.fromA) :+
+    sameSet_s2 :+ sameSet_s3).asUInt)
+  noFreeWay := sameSetCnt >= cacheParams.ways.U
+
   io.taskToPipe_s2 := task_s2
 
   // MSHR task

src/main/scala/coupledL2/tl2chi/MSHR.scala

@@ -958,6 +958,7 @@ class MSHR(implicit p: Parameters) extends TL2CHIL2Module {
   io.msInfo.bits.w_replResp := state.w_replResp
   io.msInfo.bits.w_rprobeacklast := state.w_rprobeacklast
   io.msInfo.bits.replaceData := isT(meta.state) && meta.dirty || probeDirty
+  io.msInfo.bits.channel := req.channel
 
   assert(!(c_resp.valid && !io.status.bits.w_c_resp))
   assert(!(rxrsp.valid && !io.status.bits.w_d_resp))

src/main/scala/coupledL2/tl2chi/Slice.scala

@@ -102,6 +102,7 @@ class Slice()(implicit p: Parameters) extends TL2CHIL2Module {
   reqArb.io.fromTXDAT.foreach(_ := txdat.io.toReqArb)
   reqArb.io.fromTXRSP.foreach(_ := txrsp.io.toReqArb)
   reqArb.io.fromTXREQ.foreach(_ := txreq.io.toReqArb)
+  reqArb.io.msInfo := mshrCtl.io.msInfo
 
   reqBuf.io.in <> sinkA.io.task
   reqBuf.io.mshrInfo := mshrCtl.io.msInfo

src/main/scala/coupledL2/tl2tl/MSHR.scala

@@ -553,6 +553,7 @@ class MSHR(implicit p: Parameters) extends L2Module {
   io.msInfo.bits.w_releaseack := state.w_releaseack
   io.msInfo.bits.w_replResp := state.w_replResp
   io.msInfo.bits.w_rprobeacklast := state.w_rprobeacklast
+  io.msInfo.bits.channel := req.channel
 
   assert(!(c_resp.valid && !io.status.bits.w_c_resp))
   assert(!(d_resp.valid && !io.status.bits.w_d_resp))

src/main/scala/coupledL2/tl2tl/Slice.scala

@@ -81,6 +81,7 @@ class Slice()(implicit p: Parameters) extends L2Module {
   reqArb.io.fromMainPipe := mainPipe.io.toReqArb
   reqArb.io.fromGrantBuffer := grantBuf.io.toReqArb
   reqArb.io.fromSourceC.foreach(_ := sourceC.io.toReqArb)
+  reqArb.io.msInfo := mshrCtl.io.msInfo
 
   mshrCtl.io.fromReqArb.status_s1 := reqArb.io.status_s1
   mshrCtl.io.resps.sinkC := sinkC.io.resp