Minor further cleanup & commenting of Packet class.

src/cpu/simple/atomic.cc:
    Make common ifetch setup based on Request rather than Packet.
    Packet::reset() no longer a separate function.
    sendAtomic() returns latency, not absolute tick.
src/cpu/simple/atomic.hh:
    sendAtomic returns latency, not absolute tick.
src/cpu/simple/base.cc:
src/cpu/simple/base.hh:
src/cpu/simple/timing.cc:
    Make common ifetch setup based on Request rather than Packet.
src/dev/alpha_console.cc:
src/dev/ide_ctrl.cc:
src/dev/io_device.cc:
src/dev/isa_fake.cc:
src/dev/ns_gige.cc:
src/dev/pciconfigall.cc:
src/dev/sinic.cc:
src/dev/tsunami_cchip.cc:
src/dev/tsunami_io.cc:
src/dev/tsunami_pchip.cc:
src/dev/uart8250.cc:
src/mem/physical.cc:
    Get rid of redundant Packet time field.
src/mem/packet.cc:
    Eliminate reset() method.
src/mem/packet.hh:
    Fold reset() function into reinitFromRequest()... it was
    only ever called together with that function.
    Get rid of redundant time field.
    Cleanup/add comments.
src/mem/port.hh:
    Document in comment that sendAtomic returns latency, not absolute tick.

--HG--
extra : convert_revision : 0252f1a294043ca3ed58f437232ad24fc0733e0c

4 files changed, 101 insertions, 81 deletions

diff --git a/src/mem/packet.cc b/src/mem/packet.cc
index 3b415d77f..4cda657f5 100644
--- a/src/mem/packet.cc
+++ b/src/mem/packet.cc
@@ -97,20 +97,6 @@ Packet::intersect(Packet *p)
     return false;
 }
 
-/** Minimally reset a packet so something like simple cpu can reuse it. */
-void
-Packet::reset()
-{
-    result = Unknown;
-    if (dynamicData) {
-       deleteData();
-       dynamicData = false;
-       arrayData = false;
-       time = curTick;
-    }
-}
-
-
 bool
 fixPacket(Packet *func, Packet *timing)
 {
diff --git a/src/mem/packet.hh b/src/mem/packet.hh
index 83f52ede5..e09ef4b85 100644
--- a/src/mem/packet.hh
+++ b/src/mem/packet.hh
@@ -28,8 +28,7 @@
 
 /**
  * @file
- * Declaration of the Packet Class, a packet is a transaction occuring
- * between a single level of the memory heirarchy (ie L1->L2).
+ * Declaration of the Packet class.
  */
 
 #ifndef __MEM_PACKET_HH__
@@ -44,81 +43,98 @@ typedef Packet* PacketPtr;
 typedef uint8_t* PacketDataPtr;
 
 /**
- * A Packet is the structure to handle requests between two levels
- * of the memory system.  The Request is a global object that trancends
- * all of the memory heirarchy, but at each levels interface a packet
- * is created to transfer data/requests.  For example, a request would
- * be used to initiate a request to go to memory/IOdevices, as the request
- * passes through the memory system several packets will be created.  One
- * will be created to go between the L1 and L2 caches and another to go to
- * the next level and so forth.
- *
- * Packets are assumed to be returned in the case of a single response.  If
- * the transaction has no response, then the consumer will delete the packet.
+ * A Packet is used to encapsulate a transfer between two objects in
+ * the memory system (e.g., the L1 and L2 cache).  (In contrast, a
+ * single Request travels all the way from the requester to the
+ * ultimate destination and back, possibly being conveyed by several
+ * different Packets along the way.)
  */
 class Packet
 {
   private:
-   /** A pointer to the data being transfered.  It can be differnt sizes
-        at each level of the heirarchy so it belongs in the packet,
-        not request. This may or may not be populated when a responder recieves
-        the packet. If not populated it memory should be allocated.
+   /** A pointer to the data being transfered.  It can be differnt
+    *    sizes at each level of the heirarchy so it belongs in the
+    *    packet, not request. This may or may not be populated when a
+    *    responder recieves the packet. If not populated it memory
+    *    should be allocated.
     */
     PacketDataPtr data;
 
-    /** Is the data pointer set to a value that shouldn't be freed when the
-     * packet is destroyed? */
+    /** Is the data pointer set to a value that shouldn't be freed
+     *   when the packet is destroyed? */
     bool staticData;
-    /** The data pointer points to a value that should be freed when the packet
-     * is destroyed. */
+    /** The data pointer points to a value that should be freed when
+     *   the packet is destroyed. */
     bool dynamicData;
-    /** the data pointer points to an array (thus delete [] ) needs to be called
-     * on it rather than simply delete.*/
+    /** the data pointer points to an array (thus delete [] ) needs to
+     *   be called on it rather than simply delete.*/
     bool arrayData;
 
 
-    /** The address of the request, could be virtual or physical (depending on
-        cache configurations). */
+    /** The address of the request.  This address could be virtual or
+     *   physical, depending on the system configuration. */
     Addr addr;
 
-     /** Indicates the size of the request. */
+     /** The size of the request or transfer. */
     int size;
 
-    /** A index of the source of the transaction. */
+    /** Device address (e.g., bus ID) of the source of the
+     *   transaction. The source is not responsible for setting this
+     *   field; it is set implicitly by the interconnect when the
+     *   packet * is first sent.  */
     short src;
 
-    /** A index to the destination of the transaction. */
+    /** Device address (e.g., bus ID) of the destination of the
+     *   transaction. The special value Broadcast indicates that the
+     *   packet should be routed based on its address. This field is
+     *   initialized in the constructor and is thus always valid
+     *   (unlike * addr, size, and src). */
     short dest;
 
+    /** Is the 'addr' field valid? */
     bool addrValid;
+    /** Is the 'size' field valid? */
     bool sizeValid;
+    /** Is the 'src' field valid? */
     bool srcValid;
 
   public:
 
+    /** The special destination address indicating that the packet
+     *   should be routed based on its address. */
     static const short Broadcast = -1;
 
-    /** A pointer to the overall request. */
+    /** A pointer to the original request. */
     RequestPtr req;
 
+    /** A virtual base opaque structure used to hold coherence-related
+     *    state.  A specific subclass would be derived from this to
+     *    carry state specific to a particular coherence protocol.  */
     class CoherenceState {
       public:
         virtual ~CoherenceState() {}
     };
 
-    /** A virtual base opaque structure used to hold
-        coherence status messages. */
-    CoherenceState *coherence;  // virtual base opaque,
-                           // assert(dynamic_cast<Foo>) etc.
-
+    /** This packet's coherence state.  Caches should use
+     *   dynamic_cast<> to cast to the state appropriate for the
+     *   system's coherence protocol.  */
+    CoherenceState *coherence;
+
+    /** A virtual base opaque structure used to hold state associated
+     *    with the packet but specific to the sending device (e.g., an
+     *    MSHR).  A pointer to this state is returned in the packet's
+     *    response so that the sender can quickly look up the state
+     *    needed to process it.  A specific subclass would be derived
+     *    from this to carry state specific to a particular sending
+     *    device.  */
     class SenderState {
       public:
         virtual ~SenderState() {}
     };
 
-    /** A virtual base opaque structure used to hold the senders state. */
-    SenderState *senderState; // virtual base opaque,
-    // assert(dynamic_cast<Foo>) etc.
+    /** This packet's sender state.  Devices should use dynamic_cast<>
+     *   to cast to the state appropriate to the sender. */
+    SenderState *senderState;
 
   private:
     /** List of command attributes. */
@@ -144,9 +160,11 @@ class Packet
         WriteResp	= IsWrite | IsResponse
     };
 
+    /** Return the string name of the cmd field (for debugging and
+     *   tracing). */
     const std::string &cmdString() const;
 
-    /** The command of the transaction. */
+    /** The command field of the packet. */
     Command cmd;
 
     bool isRead() 	 { return (cmd & IsRead)  != 0; }
@@ -154,20 +172,7 @@ class Packet
     bool isResponse()	 { return (cmd & IsResponse) != 0; }
     bool needsResponse() { return (cmd & NeedsResponse) != 0; }
 
-    void makeTimingResponse() {
-        assert(needsResponse());
-        int icmd = (int)cmd;
-        icmd &= ~(IsRequest | NeedsResponse);
-        icmd |= IsResponse;
-        cmd = (Command)icmd;
-        dest = src;
-        srcValid = false;
-    }
-
-    /** The time this request was responded to. Used to calculate latencies. */
-    Tick time;
-
-    /** The result of a particular packets request. */
+    /** Possible results of a packet's request. */
     enum Result
     {
         Success,
@@ -175,7 +180,7 @@ class Packet
         Unknown
     };
 
-    /** The result of the packet transaction. */
+    /** The result of this packet's request. */
     Result result;
 
     /** Accessor function that returns the source index of the packet. */
@@ -193,27 +198,56 @@ class Packet
     int getSize() const { assert(sizeValid); return size; }
     void setSize(int _size) { size = _size; sizeValid = true; }
 
-
+    /** Constructor.  Note that a Request object must be constructed
+     *   first, but the Requests's physical address and size fields
+     *   need not be valid. The command and destination addresses
+     *   must be supplied.  */
     Packet(Request *_req, Command _cmd, short _dest)
         :  data(NULL), staticData(false), dynamicData(false), arrayData(false),
            addr(_req->paddr), size(_req->size), dest(_dest),
            addrValid(_req->validPaddr), sizeValid(_req->validSize),
            srcValid(false),
            req(_req), coherence(NULL), senderState(NULL), cmd(_cmd),
-           time(curTick), result(Unknown)
+           result(Unknown)
     {
     }
 
+    /** Destructor. */
     ~Packet()
     { deleteData(); }
 
-
-    /** Minimally reset a packet so something like simple cpu can reuse it. */
-    void reset();
-
+    /** Reinitialize packet address and size from the associated
+     *   Request object, and reset other fields that may have been
+     *   modified by a previous transaction.  Typically called when a
+     *   statically allocated Request/Packet pair is reused for
+     *   multiple transactions. */
     void reinitFromRequest() {
-        if (req->validPaddr) setAddr(req->paddr);
-        if (req->validSize)  setSize(req->size);
+        assert(req->validPaddr);
+        setAddr(req->paddr);
+        assert(req->validSize);
+        setSize(req->size);
+        result = Unknown;
+        if (dynamicData) {
+            deleteData();
+            dynamicData = false;
+            arrayData = false;
+        }
+    }
+
+    /** Take a request packet and modify it in place to be suitable
+     *   for returning as a response to that request.  Used for timing
+     *   accesses only.  For atomic and functional accesses, the
+     *   request packet is always implicitly passed back *without*
+     *   modifying the command or destination fields, so this function
+     *   should not be called. */
+    void makeTimingResponse() {
+        assert(needsResponse());
+        int icmd = (int)cmd;
+        icmd &= ~(IsRequest | NeedsResponse);
+        icmd |= IsResponse;
+        cmd = (Command)icmd;
+        dest = src;
+        srcValid = false;
     }
 
     /** Set the data pointer to the following value that should not be freed. */
diff --git a/src/mem/physical.cc b/src/mem/physical.cc
index 26dbef0cd..fa7eb803e 100644
--- a/src/mem/physical.cc
+++ b/src/mem/physical.cc
@@ -139,8 +139,7 @@ Tick
 PhysicalMemory::doAtomicAccess(Packet *pkt)
 {
     doFunctionalAccess(pkt);
-    pkt->time = curTick + lat;
-    return curTick + lat;
+    return lat;
 }
 
 void
diff --git a/src/mem/port.hh b/src/mem/port.hh
index d0fa5ae8d..80ae035b1 100644
--- a/src/mem/port.hh
+++ b/src/mem/port.hh
@@ -165,10 +165,11 @@ class Port
     */
     bool sendTiming(Packet *pkt) { return peer->recvTiming(pkt); }
 
-    /** Function called by the associated device to send an atomic access,
-        an access in which the data is moved and the state is updated in one
-        cycle, without interleaving with other memory accesses.
-    */
+    /** Function called by the associated device to send an atomic
+     *   access, an access in which the data is moved and the state is
+     *   updated in one cycle, without interleaving with other memory
+     *   accesses.  Returns estimated latency of access.
+     */
     Tick sendAtomic(Packet *pkt)
         { return peer->recvAtomic(pkt); }