From f9ae0dcf1065454ca3d08512cd36a2dad9f08b2d Mon Sep 17 00:00:00 2001
From: Steve Reinhardt <stever@eecs.umich.edu>
Date: Wed, 30 Aug 2006 16:24:26 -0700
Subject: Move more common functionality into SimpleTimingPort, allowing
 derived classes to be simplified.

--HG--
extra : convert_revision : c980d3aec5e6c044d8f41e96252726fe9a256605
---
 src/mem/tport.hh | 89 +++++++++++++++++++++++++++++++-------------------------
 1 file changed, 50 insertions(+), 39 deletions(-)

(limited to 'src/mem/tport.hh')

diff --git a/src/mem/tport.hh b/src/mem/tport.hh
index 4d5c4599d..df6d48196 100644
--- a/src/mem/tport.hh
+++ b/src/mem/tport.hh
@@ -28,57 +28,40 @@
  * Authors: Ali Saidi
  */
 
+#ifndef __MEM_TPORT_HH__
+#define __MEM_TPORT_HH__
+
 /**
  * @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.
+ *
+ * Declaration of SimpleTimingPort.
  */
 
-/** 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__
-
 #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);
 };
 
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