A little more cleanup & refactoring of SimpleTimingPort.

Make it a better base class for cache ports.

--HG--
extra : convert_revision : 37d6de11545a68c1a7d11ce33fe5971c51434ee4

2 files changed, 63 insertions, 46 deletions

diff --git a/src/mem/tport.cc b/src/mem/tport.cc
index 8797cf6e6..7b1c14467 100644
--- a/src/mem/tport.cc
+++ b/src/mem/tport.cc
@@ -36,7 +36,7 @@ SimpleTimingPort::checkFunctional(PacketPtr pkt)
     DeferredPacketIterator i = transmitList.begin();
     DeferredPacketIterator end = transmitList.end();
 
-    while (i != end) {
+    for (; i != end; ++i) {
         PacketPtr target = i->pkt;
         // If the target contains data, and it overlaps the
         // probed request, need to update data
@@ -46,8 +46,6 @@ SimpleTimingPort::checkFunctional(PacketPtr pkt)
                 return;
             }
         }
-
-        i++;
     }
 }
 
@@ -74,7 +72,7 @@ SimpleTimingPort::recvTiming(PacketPtr pkt)
     // turn packet around to go back to requester if response expected
     if (pkt->needsResponse()) {
         pkt->makeTimingResponse();
-        sendTiming(pkt, latency);
+        schedSendTiming(pkt, latency);
     }
     else if (pkt->cmd != MemCmd::UpgradeReq) {
         delete pkt->req;
@@ -83,81 +81,85 @@ SimpleTimingPort::recvTiming(PacketPtr pkt)
     return true;
 }
 
-void
-SimpleTimingPort::recvRetry()
-{
-    assert(!transmitList.empty());
-    if (Port::sendTiming(transmitList.front().pkt)) {
-        transmitList.pop_front();
-        DPRINTF(Bus, "No Longer waiting on retry\n");
-        if (!transmitList.empty()) {
-            Tick time = transmitList.front().tick;
-            sendEvent->schedule(time <= curTick ? curTick+1 : time);
-        }
-    }
-
-    if (transmitList.empty() && drainEvent) {
-        drainEvent->process();
-        drainEvent = NULL;
-    }
-}
 
 void
-SimpleTimingPort::sendTiming(PacketPtr pkt, Tick time)
+SimpleTimingPort::schedSendTiming(PacketPtr pkt, Tick when)
 {
+    assert(when > curTick);
+
     // Nothing is on the list: add it and schedule an event
     if (transmitList.empty()) {
         assert(!sendEvent->scheduled());
-        sendEvent->schedule(curTick+time);
-        transmitList.push_back(DeferredPacket(time+curTick, pkt));
+        sendEvent->schedule(when);
+        transmitList.push_back(DeferredPacket(when, pkt));
         return;
     }
 
     // something is on the list and this belongs at the end
-    if (time+curTick >= transmitList.back().tick) {
-        transmitList.push_back(DeferredPacket(time+curTick, pkt));
+    if (when >= transmitList.back().tick) {
+        transmitList.push_back(DeferredPacket(when, pkt));
         return;
     }
     // Something is on the list and this belongs somewhere else
     DeferredPacketIterator i = transmitList.begin();
     DeferredPacketIterator end = transmitList.end();
-    bool done = false;
 
-    while (i != end && !done) {
-        if (time+curTick < i->tick) {
+    for (; i != end; ++i) {
+        if (when < i->tick) {
             if (i == transmitList.begin()) {
                 //Inserting at begining, reschedule
-                sendEvent->reschedule(time+curTick);
+                sendEvent->reschedule(when);
             }
-            transmitList.insert(i, DeferredPacket(time+curTick, pkt));
-            done = true;
+            transmitList.insert(i, DeferredPacket(when, pkt));
+            return;
         }
-        i++;
     }
-    assert(done);
+    assert(false); // should never get here
 }
 
+
 void
-SimpleTimingPort::processSendEvent()
+SimpleTimingPort::sendDeferredPacket()
 {
-    assert(transmitList.size());
-    assert(transmitList.front().tick <= curTick);
-    if (Port::sendTiming(transmitList.front().pkt)) {
+    assert(deferredPacketReady());
+    bool success = sendTiming(transmitList.front().pkt);
+
+    if (success) {
         //send successful, remove packet
         transmitList.pop_front();
         if (!transmitList.empty()) {
             Tick time = transmitList.front().tick;
             sendEvent->schedule(time <= curTick ? curTick+1 : time);
         }
+
         if (transmitList.empty() && drainEvent) {
             drainEvent->process();
             drainEvent = NULL;
         }
-        return;
     }
-    // send unsuccessful (due to flow control).  Will get retry
-    // callback later; save for then if not already
-    DPRINTF(Bus, "Waiting on retry\n");
+
+    waitingOnRetry = !success;
+
+    if (waitingOnRetry) {
+        DPRINTF(Bus, "Send failed, waiting on retry\n");
+    }
+}
+
+
+void
+SimpleTimingPort::recvRetry()
+{
+    DPRINTF(Bus, "Received retry\n");
+    assert(waitingOnRetry);
+    sendDeferredPacket();
+}
+
+
+void
+SimpleTimingPort::processSendEvent()
+{
+    assert(!waitingOnRetry);
+    sendDeferredPacket();
 }
 
 
diff --git a/src/mem/tport.hh b/src/mem/tport.hh
index 9e8a01786..ea0f05ed1 100644
--- a/src/mem/tport.hh
+++ b/src/mem/tport.hh
@@ -94,15 +94,29 @@ class SimpleTimingPort : public Port
      * here.*/
     Event *drainEvent;
 
+    /** Remember whether we're awaiting a retry from the bus. */
+    bool waitingOnRetry;
+
     /** Check the list of buffered packets against the supplied
      * functional request. */
     void checkFunctional(PacketPtr funcPkt);
 
+    /** Check whether we have a packet ready to go on the transmit list. */
+    bool deferredPacketReady()
+    { return !transmitList.empty() && transmitList.front().tick <= curTick; }
+
     /** Schedule a sendTiming() event to be called in the future.
      * @param pkt packet to send
-     * @param time increment from now (in ticks) to send packet
+     * @param absolute time (in ticks) to send packet
+     */
+    void schedSendTiming(PacketPtr pkt, Tick when);
+
+    /** Attempt to send the packet at the head of the deferred packet
+     * list.  Caller must guarantee that the deferred packet list is
+     * non-empty and that the head packet is scheduled for curTick (or
+     * earlier).
      */
-    void sendTiming(PacketPtr pkt, Tick time);
+    void sendDeferredPacket();
 
     /** This function is notification that the device should attempt to send a
      * packet again. */
@@ -126,7 +140,8 @@ class SimpleTimingPort : public Port
     SimpleTimingPort(std::string pname, MemObject *_owner = NULL)
         : Port(pname, _owner),
           sendEvent(new SendEvent(this)),
-          drainEvent(NULL)
+          drainEvent(NULL),
+          waitingOnRetry(false)
     {}
 
     ~SimpleTimingPort() { delete sendEvent; }