MEM: Split SimpleTimingPort into PacketQueue and ports

This patch decouples the queueing and the port interactions to
simplify the introduction of the master and slave ports. By separating
the queueing functionality from the port itself, it becomes much
easier to distinguish between master and slave ports, and still retain
the queueing ability for both (without code duplication).

As part of the split into a PacketQueue and a port, there is now also
a hierarchy of two port classes, QueuedPort and SimpleTimingPort. The
QueuedPort is useful for ports that want to leave the packet
transmission of outgoing packets to the queue and is used by both
master and slave ports. The SimpleTimingPort inherits from the
QueuedPort and adds the implemention of recvTiming and recvFunctional
through recvAtomic.

The PioPort and MessagePort are cleaned up as part of the changes.

--HG--
rename : src/mem/tport.cc => src/mem/packet_queue.cc
rename : src/mem/tport.hh => src/mem/packet_queue.hh

1 files changed, 218 insertions, 0 deletions

diff --git a/src/mem/packet_queue.hh b/src/mem/packet_queue.hh
new file mode 100644
index 000000000..ac868802b
--- /dev/null
+++ b/src/mem/packet_queue.hh
@@ -0,0 +1,218 @@
+/*
+ * Copyright (c) 2012 ARM Limited
+ * All rights reserved.
+ *
+ * The license below extends only to copyright in the software and shall
+ * not be construed as granting a license to any other intellectual
+ * property including but not limited to intellectual property relating
+ * to a hardware implementation of the functionality of the software
+ * licensed hereunder.  You may use the software subject to the license
+ * terms below provided that you ensure that this notice is replicated
+ * unmodified and in its entirety in all distributions of the software,
+ * modified or unmodified, in source code or in binary form.
+ *
+ * Copyright (c) 2006 The Regents of The University of Michigan
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met: redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer;
+ * redistributions in binary form must reproduce the above copyright
+ * notice, this list of conditions and the following disclaimer in the
+ * documentation and/or other materials provided with the distribution;
+ * neither the name of the copyright holders nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ * Authors: Ali Saidi
+ *          Andreas Hansson
+ */
+
+#ifndef __MEM_PACKET_QUEUE_HH__
+#define __MEM_PACKET_QUEUE_HH__
+
+/**
+ * @file
+ * Declaration of a simple PacketQueue that is associated with
+ * a port on which it attempts to send packets according to the time
+ * stamp given to them at insertion. The packet queue is responsible
+ * for the flow control of the port, but relies on the module
+ * notifying the queue when a transfer ends.
+ */
+
+#include <list>
+
+#include "mem/port.hh"
+#include "sim/eventq.hh"
+
+/**
+ * A packet queue is a class that holds deferred packets and later
+ * sends them using the associated slave port or master port.
+ */
+class PacketQueue
+{
+  private:
+    /** A deferred packet, buffered to transmit later. */
+    class DeferredPacket {
+      public:
+        Tick tick;      ///< The tick when the packet is ready to transmit
+        PacketPtr pkt;  ///< Pointer to the packet to transmit
+        DeferredPacket(Tick t, PacketPtr p)
+            : tick(t), pkt(p)
+        {}
+    };
+
+    typedef std::list<DeferredPacket> DeferredPacketList;
+    typedef std::list<DeferredPacket>::iterator DeferredPacketIterator;
+
+    /** A list of outgoing timing response packets that haven't been
+     * serviced yet. */
+    DeferredPacketList transmitList;
+
+    /** 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();
+
+    /**
+     * Event used to call processSendEvent.
+     **/
+    EventWrapper<PacketQueue, &PacketQueue::processSendEvent> sendEvent;
+
+    /** If we need to drain, keep the drain event around until we're done
+     * here.*/
+    Event *drainEvent;
+
+  protected:
+
+    /** The port used to send the packets. */
+    Port& port;
+
+    /** Remember whether we're awaiting a retry from the bus. */
+    bool waitingOnRetry;
+
+    /** Check whether we have a packet ready to go on the transmit list. */
+    bool deferredPacketReady()
+    { return !transmitList.empty() && transmitList.front().tick <= curTick(); }
+
+    Tick deferredPacketReadyTime()
+    { return transmitList.empty() ? MaxTick : transmitList.front().tick; }
+
+    /**
+     * Attempt to send the packet at the head of the transmit
+     * list. Caller must guarantee that the list is non-empty and that
+     * the head packet is scheduled for curTick() (or earlier). Note
+     * that a subclass of the PacketQueue can override this method and
+     * thus change the behaviour (as done by the cache).
+     */
+    virtual void sendDeferredPacket();
+
+    /**
+     * Attempt to send the packet at the front of the transmit list,
+     * and set waitingOnRetry accordingly. The packet is temporarily
+     * taken off the list, but put back at the front if not
+     * successfully sent.
+     */
+    void trySendTiming();
+
+    /**
+     * 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.
+     *
+     * @param time an alternative time for the next send event
+     */
+    void scheduleSend(Tick time = MaxTick);
+
+    /**
+     * Simple ports are generally used as slave ports (i.e. the
+     * respond to requests) and thus do not expect to receive any
+     * range changes (as the neighbouring port has a master role and
+     * do not have any address ranges. A subclass can override the
+     * default behaviuor if needed.
+     */
+    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.
+     *
+     * @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");
+
+    /**
+     * Virtual desctructor since the class may be used as a base class.
+     */
+    virtual ~PacketQueue();
+
+    /**
+     * Provide a name to simplify debugging. Base it on the port.
+     *
+     * @return A complete name, appended to module and port
+     */
+    const std::string name() const { return port.name() + "-queue"; }
+
+    /** Check the list of buffered packets against the supplied
+     * functional request. */
+    bool checkFunctional(PacketPtr pkt);
+
+    /**
+     * Schedule a send even if not already waiting for a retry. If the
+     * requested time is before an already scheduled send event it
+     * will be rescheduled.
+     *
+     * @param when
+     */
+    void schedSendEvent(Tick when);
+
+    /**
+     * Add a packet to the transmit list, and ensure that a
+     * processSendEvent is called in the future.
+     *
+     * @param pkt Packet to send
+     * @param when Absolute time (in ticks) to send packet
+     */
+    void schedSendTiming(PacketPtr pkt, Tick when);
+
+    /**
+     * Used by a port to notify the queue that a retry was received
+     * and that the queue can proceed and retry sending the packet
+     * that caused the wait.
+     */
+    void retry();
+
+    /**
+     * Hook for draining the packet queue.
+     *
+     * @param de An event which is used to signal back to the caller
+     * @return A number indicating how many times process will be called
+     */
+    unsigned int drain(Event *de);
+};
+
+#endif // __MEM_TPORT_HH__