systemc: Send response to TLM side if a packet does not need response

A completed TLM transaction includes request and response parts.
Currently, if a gem5 packet does not need a reponse, the bridge would not
send BEGIN_RESP to its upstream. It causes stuck on TLM side.

To fix this problem, the bridge should send BEGIN_RESP by itself in this
case.

Change-Id: I318dec21bc3f291693715c0d70bc624addf05076
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/32735
Reviewed-by: Gabe Black <gabeblack@google.com>
Tested-by: kokoro <noreply+kokoro@google.com>
Maintainer: Gabe Black <gabeblack@google.com>

diff --git a/src/systemc/tlm_bridge/tlm_to_gem5.cc b/src/systemc/tlm_bridge/tlm_to_gem5.cc
index e6cb48332046b6608d936cb60bd42a644220f2ab..2bfbcc495573a5b64acfbb5e5e6abbe6ea4b2e16 100644 (file)
--- a/src/systemc/tlm_bridge/tlm_to_gem5.cc
+++ b/src/systemc/tlm_bridge/tlm_to_gem5.cc
@@ -162,8 +162,15 @@ TlmToGem5Bridge<BITWIDTH>::handleBeginReq(tlm::tlm_generic_payload &trans)
     auto tlmSenderState = new TlmSenderState(trans);
     pkt->pushSenderState(tlmSenderState);
 
+    // If the packet doesn't need a response, we should send BEGIN_RESP by
+    // ourselves.
+    bool needsResponse = pkt->needsResponse();
     if (bmp.sendTimingReq(pkt)) { // port is free -> send END_REQ immediately
         sendEndReq(trans);
+        if (!needsResponse) {
+            auto delay = sc_core::SC_ZERO_TIME;
+            sendBeginResp(trans, delay);
+        }
         trans.release();
     } else { // port is blocked -> wait for retry before sending END_REQ
         waitForRetry = true;
@@ -429,12 +436,19 @@ TlmToGem5Bridge<BITWIDTH>::recvReqRetry()
     sc_assert(pendingRequest != nullptr);
     sc_assert(pendingPacket != nullptr);
 
+    // If the packet doesn't need a response, we should send BEGIN_RESP by
+    // ourselves.
+    bool needsResponse = pendingPacket->needsResponse();
     if (bmp.sendTimingReq(pendingPacket)) {
         waitForRetry = false;
         pendingPacket = nullptr;
 
         auto &trans = *pendingRequest;
         sendEndReq(trans);
+        if (!needsResponse) {
+            auto delay = sc_core::SC_ZERO_TIME;
+            sendBeginResp(trans, delay);
+        }
         trans.release();
 
         pendingRequest = nullptr;