Move more common functionality into SimpleTimingPort,

allowing derived classes to be simplified.

--HG--
extra : convert_revision : c980d3aec5e6c044d8f41e96252726fe9a256605

src/mem/physical.cc

@@ -182,7 +182,8 @@ PhysicalMemory::getAddressRanges(AddrRangeList &resp, AddrRangeList &snoop)
 {
     snoop.clear();
     resp.clear();
-    resp.push_back(RangeSize(params()->addrRange.start, params()->addrRange.size()));
+    resp.push_back(RangeSize(params()->addrRange.start,
+                             params()->addrRange.size()));
 }
 
 int
@@ -191,21 +192,6 @@ PhysicalMemory::MemoryPort::deviceBlockSize()
     return memory->deviceBlockSize();
 }
 
-bool
-PhysicalMemory::MemoryPort::recvTiming(Packet *pkt)
-{
-    assert(pkt->result != Packet::Nacked);
-
-    Tick latency = memory->calculateLatency(pkt);
-
-    memory->doFunctionalAccess(pkt);
-
-    pkt->makeTimingResponse();
-    sendTiming(pkt, latency);
-
-    return true;
-}
-
 Tick
 PhysicalMemory::MemoryPort::recvAtomic(Packet *pkt)
 {
@@ -216,6 +202,9 @@ PhysicalMemory::MemoryPort::recvAtomic(Packet *pkt)
 void
 PhysicalMemory::MemoryPort::recvFunctional(Packet *pkt)
 {
+    // Default implementation of SimpleTimingPort::recvFunctional()
+    // calls recvAtomic() and throws away the latency; we can save a
+    // little here by just not calculating the latency.
     memory->doFunctionalAccess(pkt);
 }
 

src/mem/physical.hh

@@ -57,8 +57,6 @@ class PhysicalMemory : public MemObject
 
       protected:
 
-        virtual bool recvTiming(Packet *pkt);
-
         virtual Tick recvAtomic(Packet *pkt);
 
         virtual void recvFunctional(Packet *pkt);

src/mem/port.hh

@@ -252,11 +252,13 @@ class FunctionalPort : public Port
         : Port(_name)
     {}
 
+  protected:
     virtual bool recvTiming(Packet *pkt) { panic("FuncPort is UniDir"); }
     virtual Tick recvAtomic(Packet *pkt) { panic("FuncPort is UniDir"); }
     virtual void recvFunctional(Packet *pkt) { panic("FuncPort is UniDir"); }
     virtual void recvStatusChange(Status status) {}
 
+  public:
     /** a write function that also does an endian conversion. */
     template <typename T>
     inline void writeHtoG(Addr addr, T d);

src/mem/tport.cc

@@ -30,19 +30,42 @@
 
 #include "mem/tport.hh"
 
+void
+SimpleTimingPort::recvFunctional(Packet *pkt)
+{
+    // just do an atomic access and throw away the returned latency
+    recvAtomic(pkt);
+}
+
+bool
+SimpleTimingPort::recvTiming(Packet *pkt)
+{
+    // If the device is only a slave, it should only be sending
+    // responses, which should never get nacked.  There used to be
+    // code to hanldle nacks here, but I'm pretty sure it didn't work
+    // correctly with the drain code, so that would need to be fixed
+    // if we ever added it back.
+    assert(pkt->result != Packet::Nacked);
+    Tick latency = recvAtomic(pkt);
+    // turn packet around to go back to requester
+    pkt->makeTimingResponse();
+    sendTimingLater(pkt, latency);
+    return true;
+}
+
 void
 SimpleTimingPort::recvRetry()
 {
     bool result = true;
     while (result && transmitList.size()) {
-        result = Port::sendTiming(transmitList.front());
+        result = sendTiming(transmitList.front());
         if (result)
             transmitList.pop_front();
     }
-   if (transmitList.size() == 0 && drainEvent) {
-       drainEvent->process();
-       drainEvent = NULL;
-   }
+    if (transmitList.size() == 0 && drainEvent) {
+        drainEvent->process();
+        drainEvent = NULL;
+    }
 }
 
 void
@@ -50,26 +73,18 @@ SimpleTimingPort::SendEvent::process()
 {
     port->outTiming--;
     assert(port->outTiming >= 0);
-    if (port->Port::sendTiming(packet))
-       if (port->transmitList.size() == 0 && port->drainEvent) {
-           port->drainEvent->process();
-           port->drainEvent = NULL;
-       }
-       return;
-
-    port->transmitList.push_back(packet);
-}
-
-void
-SimpleTimingPort::resendNacked(Packet *pkt) {
-    pkt->reinitNacked();
-    if (transmitList.size()) {
-         transmitList.push_front(pkt);
+    if (port->sendTiming(packet)) {
+        // send successfule
+        if (port->transmitList.size() == 0 && port->drainEvent) {
+            port->drainEvent->process();
+            port->drainEvent = NULL;
+        }
     } else {
-        if (!Port::sendTiming(pkt))
-            transmitList.push_front(pkt);
+        // send unsuccessful (due to flow control).  Will get retry
+        // callback later; save for then.
+        port->transmitList.push_back(packet);
     }
-};
+}
 
 
 unsigned int

src/mem/tport.hh

@@ -28,57 +28,40 @@
  * Authors: Ali Saidi
  */
 
-/**
- * @file
- * Implement a port which adds simple support of a sendTiming() function that
- * takes a delay. In this way the * device can immediatly call
- * sendTiming(pkt, time) after processing a request and the request will be
- * handled by the port even if the port bus the device connects to is blocked.
- */
-
-/** recvTiming and drain should be implemented something like this when this
- * class is used.
-
-bool
-PioPort::recvTiming(Packet *pkt)
-{
-    if (pkt->result == Packet::Nacked) {
-        resendNacked(pkt);
-    } else {
-        Tick latency = device->recvAtomic(pkt);
-        // turn packet around to go back to requester
-        pkt->makeTimingResponse();
-        sendTiming(pkt, latency);
-    }
-    return true;
-}
-
-PioDevice::drain(Event *de)
-{
-    unsigned int count;
-    count = SimpleTimingPort->drain(de);
-    if (count)
-        changeState(Draining);
-    else
-        changeState(Drained);
-    return count;
-}
-*/
-
 #ifndef __MEM_TPORT_HH__
 #define __MEM_TPORT_HH__
 
+/**
+ * @file
+ *
+ * Declaration of SimpleTimingPort.
+ */
+
 #include "mem/port.hh"
 #include "sim/eventq.hh"
 #include <list>
 #include <string>
 
+/**
+ * A simple port for interfacing objects that basically have only
+ * functional memory behavior (e.g. I/O devices) to the memory system.
+ * Both timing and functional accesses are implemented in terms of
+ * atomic accesses.  A derived port class thus only needs to provide
+ * recvAtomic() to support all memory access modes.
+ *
+ * The tricky part is handling recvTiming(), where the response must
+ * be scheduled separately via a later call to sendTiming().  This
+ * feature is handled by scheduling an internal event that calls
+ * sendTiming() after a delay, and optionally rescheduling the
+ * response if it is nacked.
+ */
 class SimpleTimingPort : public Port
 {
   protected:
     /** A list of outgoing timing response packets that haven't been
      * serviced yet. */
     std::list<Packet*> transmitList;
+
     /**
      * This class is used to implemented sendTiming() with a delay. When
      * a delay is requested a new event is created. When the event time
@@ -112,20 +95,48 @@ class SimpleTimingPort : public Port
     Event *drainEvent;
 
     /** Schedule a sendTiming() event to be called in the future. */
-    void sendTiming(Packet *pkt, Tick time)
-    { outTiming++; new SimpleTimingPort::SendEvent(this, pkt, time); }
+    void sendTimingLater(Packet *pkt, Tick time)
+    { outTiming++; new SendEvent(this, pkt, time); }
 
     /** This function is notification that the device should attempt to send a
      * packet again. */
     virtual void recvRetry();
 
-    void resendNacked(Packet *pkt);
+    /** Implemented using recvAtomic(). */
+    void recvFunctional(Packet *pkt);
+
+    /** Implemented using recvAtomic(). */
+    bool recvTiming(Packet *pkt);
+
+    /**
+     * Simple ports generally don't care about any status
+     * changes... can always override this in cases where that's not
+     * true. */
+    virtual void recvStatusChange(Status status) { }
+
+
   public:
 
     SimpleTimingPort(std::string pname)
         : Port(pname), outTiming(0), drainEvent(NULL)
     {}
 
+    /** Hook for draining timing accesses from the system.  The
+     * associated SimObject's drain() functions should be implemented
+     * something like this when this class is used:
+     \code
+          PioDevice::drain(Event *de)
+          {
+              unsigned int count;
+              count = SimpleTimingPort->drain(de);
+              if (count)
+                  changeState(Draining);
+              else
+                  changeState(Drained);
+              return count;
+          }
+     \endcode
+    */
     unsigned int drain(Event *de);
 };