mem: Clarification of packet crossbar timings

This patch clarifies the packet timings annotated
when going through a crossbar.

The old 'firstWordDelay' is replaced by 'headerDelay' that represents
the delay associated to the delivery of the header of the packet.

The old 'lastWordDelay' is replaced by 'payloadDelay' that represents
the delay needed to processing the payload of the packet.

For now the uses and values remain identical. However, going forward
the payloadDelay will be additive, and not include the
headerDelay. Follow-on patches will make the headerDelay capture the
pipeline latency incurred in the crossbar, whereas the payloadDelay
will capture the additional serialisation delay.

1 files changed, 4 insertions, 4 deletions

diff --git a/src/mem/noncoherent_xbar.cc b/src/mem/noncoherent_xbar.cc
index e93446b47..0cf656f80 100644
--- a/src/mem/noncoherent_xbar.cc
+++ b/src/mem/noncoherent_xbar.cc
@@ -128,7 +128,7 @@ NoncoherentXBar::recvTimingReq(PacketPtr pkt, PortID slave_port_id)
     unsigned int pkt_cmd = pkt->cmdToIndex();
 
     calcPacketTiming(pkt);
-    Tick packetFinishTime = pkt->lastWordDelay + curTick();
+    Tick packetFinishTime = curTick() + pkt->payloadDelay;
 
     // before forwarding the packet (and possibly altering it),
     // remember if we are expecting a response
@@ -146,7 +146,7 @@ NoncoherentXBar::recvTimingReq(PacketPtr pkt, PortID slave_port_id)
                 src_port->name(), pkt->cmdString(), pkt->getAddr());
 
         // undo the calculation so we can check for 0 again
-        pkt->firstWordDelay = pkt->lastWordDelay = 0;
+        pkt->headerDelay = pkt->payloadDelay = 0;
 
         // occupy until the header is sent
         reqLayers[master_port_id]->failedTiming(src_port,
@@ -201,7 +201,7 @@ NoncoherentXBar::recvTimingResp(PacketPtr pkt, PortID master_port_id)
     unsigned int pkt_cmd = pkt->cmdToIndex();
 
     calcPacketTiming(pkt);
-    Tick packetFinishTime = pkt->lastWordDelay + curTick();
+    Tick packetFinishTime = curTick() + pkt->payloadDelay;
 
     // send the packet through the destination slave port
     bool success M5_VAR_USED = slavePorts[slave_port_id]->sendTimingResp(pkt);
@@ -265,7 +265,7 @@ NoncoherentXBar::recvAtomic(PacketPtr pkt, PortID slave_port_id)
     }
 
     // @todo: Not setting first-word time
-    pkt->lastWordDelay = response_latency;
+    pkt->payloadDelay = response_latency;
     return response_latency;
 }