MEM: Separate requests and responses for timing accesses

This patch moves send/recvTiming and send/recvTimingSnoop from the
Port base class to the MasterPort and SlavePort, and also splits them
into separate member functions for requests and responses:
send/recvTimingReq, send/recvTimingResp, and send/recvTimingSnoopReq,
send/recvTimingSnoopResp. A master port sends requests and receives
responses, and also receives snoop requests and sends snoop
responses. A slave port has the reciprocal behaviour as it receives
requests and sends responses, and sends snoop requests and receives
snoop responses.

For all MemObjects that have only master ports or slave ports (but not
both), e.g. a CPU, or a PIO device, this patch merely adds more
clarity to what kind of access is taking place. For example, a CPU
port used to call sendTiming, and will now call
sendTimingReq. Similarly, a response previously came back through
recvTiming, which is now recvTimingResp. For the modules that have
both master and slave ports, e.g. the bus, the behaviour was
previously relying on branches based on pkt->isRequest(), and this is
now replaced with a direct call to the apprioriate member function
depending on the type of access. Please note that send/recvRetry is
still shared by all the timing accessors and remains in the Port base
class for now (to maintain the current bus functionality and avoid
changing the statistics of all regressions).

The packet queue is split into a MasterPort and SlavePort version to
facilitate the use of the new timing accessors. All uses of the
PacketQueue are updated accordingly.

With this patch, the type of packet (request or response) is now well
defined for each type of access, and asserts on pkt->isRequest() and
pkt->isResponse() are now moved to the appropriate send member
functions. It is also worth noting that sendTimingSnoopReq no longer
returns a boolean, as the semantics do not alow snoop requests to be
rejected or stalled. All these assumptions are now excplicitly part of
the port interface itself.

1 files changed, 73 insertions, 15 deletions

diff --git a/src/mem/packet_queue.hh b/src/mem/packet_queue.hh
index fbcd7d449..0171eb9a3 100644
--- a/src/mem/packet_queue.hh
+++ b/src/mem/packet_queue.hh
@@ -86,9 +86,6 @@ class PacketQueue
     /** The manager which is used for the event queue */
     EventManager& em;
 
-    /** Label to use for print request packets label stack. */
-    const std::string label;
-
     /** This function attempts to send deferred packets.  Scheduled to
      * be called in the future via SendEvent. */
     void processSendEvent();
@@ -104,8 +101,8 @@ class PacketQueue
 
   protected:
 
-    /** The port used to send the packets. */
-    Port& port;
+    /** Label to use for print request packets label stack. */
+    const std::string label;
 
     /** Remember whether we're awaiting a retry from the bus. */
     bool waitingOnRetry;
@@ -135,6 +132,11 @@ class PacketQueue
     void trySendTiming();
 
     /**
+     *
+     */
+    virtual bool sendTiming(PacketPtr pkt, bool send_as_snoop) = 0;
+
+    /**
      * Based on the transmit list, or the provided time, schedule a
      * send event if there are packets to send. If we are idle and
      * asked to drain then do so.
@@ -152,31 +154,28 @@ class PacketQueue
      */
     virtual void recvRangeChange() { }
 
-  public:
-
     /**
-     * Create a packet queue, linked to an event manager, a port used
-     * to send the packets, and potentially give it a label that will
-     * be used for functional print request packets.
+     * Create a packet queue, linked to an event manager, and a label
+     * that will be used for functional print request packets.
      *
      * @param _em Event manager used for scheduling this queue
-     * @param _port Port used to send the packets
      * @param _label Label to push on the label stack for print request packets
      */
-    PacketQueue(EventManager& _em, Port& _port,
-                const std::string _label = "PacketQueue");
+    PacketQueue(EventManager& _em, const std::string& _label);
 
     /**
      * Virtual desctructor since the class may be used as a base class.
      */
     virtual ~PacketQueue();
 
+  public:
+
     /**
-     * Provide a name to simplify debugging. Base it on the port.
+     * Provide a name to simplify debugging.
      *
      * @return A complete name, appended to module and port
      */
-    const std::string name() const { return port.name() + "-queue"; }
+    virtual const std::string name() const = 0;
 
     /** Check the list of buffered packets against the supplied
      * functional request. */
@@ -217,4 +216,63 @@ class PacketQueue
     unsigned int drain(Event *de);
 };
 
+class MasterPacketQueue : public PacketQueue
+{
+
+  protected:
+
+    MasterPort& masterPort;
+
+  public:
+
+    /**
+     * Create a master packet queue, linked to an event manager, a
+     * master port, and a label that will be used for functional print
+     * request packets.
+     *
+     * @param _em Event manager used for scheduling this queue
+     * @param _masterPort Master port used to send the packets
+     * @param _label Label to push on the label stack for print request packets
+     */
+    MasterPacketQueue(EventManager& _em, MasterPort& _masterPort,
+                      const std::string _label = "MasterPacketQueue");
+
+    virtual ~MasterPacketQueue() { }
+
+    const std::string name() const
+    { return masterPort.name() + "-" + label; }
+
+    bool sendTiming(PacketPtr pkt, bool send_as_snoop);
+};
+
+class SlavePacketQueue : public PacketQueue
+{
+
+  protected:
+
+    SlavePort& slavePort;
+
+  public:
+
+    /**
+     * Create a slave packet queue, linked to an event manager, a
+     * slave port, and a label that will be used for functional print
+     * request packets.
+     *
+     * @param _em Event manager used for scheduling this queue
+     * @param _slavePort Slave port used to send the packets
+     * @param _label Label to push on the label stack for print request packets
+     */
+    SlavePacketQueue(EventManager& _em, SlavePort& _slavePort,
+                     const std::string _label = "SlavePacketQueue");
+
+    virtual ~SlavePacketQueue() { }
+
+    const std::string name() const
+    { return slavePort.name() + "-" + label; }
+
+    bool sendTiming(PacketPtr pkt, bool send_as_snoop);
+
+};
+
 #endif // __MEM_PACKET_QUEUE_HH__