riscv/rocket-chip
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[rocket] fix PTW critical path

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Pipeline the killing of a D$ request following a PTW cache hit.
This commit is contained in:
Andrew Waterman 2016-08-02 14:39:33 -07:00
parent 7e9d139e49
commit 2ce702dc0a
1 changed files with 8 additions and 10 deletions
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18
rocket/src/main/scala/ptw.scala
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@ -76,6 +76,7 @@ class PTW(n: Int)(implicit p: Parameters) extends CoreModule()(p) {
val s_ready :: s_req :: s_wait :: s_set_dirty :: s_wait_dirty :: s_done :: Nil = Enum(UInt(), 6)
val state = Reg(init=s_ready)
val count = Reg(UInt(width = log2Up(pgLevels)))
val s1_kill = Reg(next = Bool(false))
val r_req = Reg(new PTWReq)
val r_req_dest = Reg(Bits())
@ -121,12 +122,7 @@ class PTW(n: Int)(implicit p: Parameters) extends CoreModule()(p) {
when (hit && state === s_req) { plru.access(OHToUInt(hits)) }
when (io.dpath.invalidate) { valid := 0 }
(hit, Mux1H(hits, data))
}
val set_dirty_bit = pte.access_ok(r_req) && (!pte.a || (r_req.store && !pte.d))
when (io.mem.resp.valid && state === s_wait && !set_dirty_bit) {
r_pte := pte
(hit && count < pgLevels-1, Mux1H(hits, data))
}
val pte_wdata = Wire(init=new PTE().fromBits(0))
@ -139,7 +135,7 @@ class PTW(n: Int)(implicit p: Parameters) extends CoreModule()(p) {
io.mem.req.bits.typ := MT_D
io.mem.req.bits.addr := pte_addr
io.mem.s1_data := pte_wdata.asUInt
io.mem.s1_kill := Bool(false)
io.mem.s1_kill := s1_kill
io.mem.invalidate_lr := Bool(false)
val resp_ppns = (0 until pgLevels-1).map(i => Cat(pte_addr >> (pgIdxBits + pgLevelBits*(pgLevels-i-1)), r_req.addr(pgLevelBits*(pgLevels-i-1)-1,0))) :+ (pte_addr >> pgIdxBits)
@ -161,8 +157,8 @@ class PTW(n: Int)(implicit p: Parameters) extends CoreModule()(p) {
count := UInt(0)
}
is (s_req) {
when (pte_cache_hit && count < pgLevels-1) {
io.mem.req.valid := false
when (pte_cache_hit) {
s1_kill := true
state := s_req
count := count + 1
r_pte.ppn := pte_cache_data
@ -176,8 +172,10 @@ class PTW(n: Int)(implicit p: Parameters) extends CoreModule()(p) {
}
when (io.mem.resp.valid) {
state := s_done
when (set_dirty_bit) {
when (pte.access_ok(r_req) && (!pte.a || (r_req.store && !pte.d))) {
state := s_set_dirty
}.otherwise {
r_pte := pte
}
when (pte.table() && count < pgLevels-1) {
state := s_req