riscv/rocket-chip
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There's no structural hazard on MMIO store responses

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So don't stall as though there were.
This commit is contained in:
Andrew Waterman 2017-03-21 13:52:06 -07:00
parent 5eae7e1da4
commit 3609254e4a
1 changed files with 10 additions and 7 deletions
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7
src/main/scala/rocket/DCache.scala
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@ -297,6 +297,7 @@ class DCacheModule(outer: DCache) extends HellaCacheModule(outer) {
val (d_first, d_last, d_done, d_address_inc) = edge.addr_inc(tl_out.d)
val grantIsCached = tl_out.d.bits.opcode.isOneOf(Grant, GrantData)
val grantIsUncached = tl_out.d.bits.opcode.isOneOf(AccessAck, AccessAckData, HintAck)
val grantIsUncachedData = tl_out.d.bits.opcode === AccessAckData
val grantIsVoluntary = tl_out.d.bits.opcode === ReleaseAck // Clears a different pending bit
val grantIsRefill = tl_out.d.bits.opcode === GrantData // Writes the data array
tl_out.d.ready := true
@ -313,11 +314,13 @@ class DCacheModule(outer: DCache) extends HellaCacheModule(outer) {
f := false
}
}
when (grantIsUncachedData) {
s2_data := tl_out.d.bits.data
s2_req.cmd := req.cmd
s2_req.typ := req.typ
s2_req.tag := req.tag
s2_req.addr := Cat(s1_paddr >> beatOffBits /* don't-care */, req.addr(beatOffBits-1, 0))
}
} .elsewhen (grantIsVoluntary) {
assert(release_ack_wait, "A ReleaseAck was unexpected by the dcache.") // TODO should handle Ack coming back on same cycle!
release_ack_wait := false
@ -343,7 +346,7 @@ class DCacheModule(outer: DCache) extends HellaCacheModule(outer) {
// don't accept uncached grants if there's a structural hazard on s2_data...
val blockUncachedGrant = Reg(Bool())
blockUncachedGrant := dataArb.io.out.valid
when (grantIsUncached) {
when (grantIsUncachedData) {
tl_out.d.ready := !(blockUncachedGrant || s1_valid)
// ...but insert bubble to guarantee grant's eventual forward progress
when (tl_out.d.valid && !tl_out.d.ready) {
@ -458,7 +461,7 @@ class DCacheModule(outer: DCache) extends HellaCacheModule(outer) {
io.cpu.ordered := !(s1_valid || s2_valid || cached_grant_wait || uncachedInFlight.asUInt.orR)
// uncached response
io.cpu.replay_next := tl_out.d.fire() && grantIsUncached
io.cpu.replay_next := tl_out.d.fire() && grantIsUncachedData
val doUncachedResp = Reg(next = io.cpu.replay_next)
when (doUncachedResp) {
assert(!s2_valid_hit)