packet_queue.hh revision 3403 
1/*
2 * Copyright (c) 2006 The Regents of The University of Michigan
3 * All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions are
7 * met: redistributions of source code must retain the above copyright
8 * notice, this list of conditions and the following disclaimer;
9 * redistributions in binary form must reproduce the above copyright
10 * notice, this list of conditions and the following disclaimer in the
11 * documentation and/or other materials provided with the distribution;
12 * neither the name of the copyright holders nor the names of its
13 * contributors may be used to endorse or promote products derived from
14 * this software without specific prior written permission.
15 *
16 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
17 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
18 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
19 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
20 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
21 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
22 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
23 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
24 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
25 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
26 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
27 *
28 * Authors: Ali Saidi
29 */
30
31#ifndef __MEM_TPORT_HH__
32#define __MEM_TPORT_HH__
33
34/**
35 * @file
36 *
37 * Declaration of SimpleTimingPort.
38 */
39
40#include "mem/port.hh"
41#include "sim/eventq.hh"
42#include <list>
43#include <string>
44
45/**
46 * A simple port for interfacing objects that basically have only
47 * functional memory behavior (e.g. I/O devices) to the memory system.
48 * Both timing and functional accesses are implemented in terms of
49 * atomic accesses.  A derived port class thus only needs to provide
50 * recvAtomic() to support all memory access modes.
51 *
52 * The tricky part is handling recvTiming(), where the response must
53 * be scheduled separately via a later call to sendTiming().  This
54 * feature is handled by scheduling an internal event that calls
55 * sendTiming() after a delay, and optionally rescheduling the
56 * response if it is nacked.
57 */
58class SimpleTimingPort : public Port
59{
60  protected:
61    /** A list of outgoing timing response packets that haven't been
62     * serviced yet. */
63    std::list<std::pair<Tick,PacketPtr> > transmitList;
64
65    /**
66     * This class is used to implemented sendTiming() with a delay. When
67     * a delay is requested a the event is scheduled if it isn't already.
68     * When the event time expires it attempts to send the packet.
69     * If it cannot, the packet sent when recvRetry() is called.
70     **/
71    class SendEvent : public Event
72    {
73        SimpleTimingPort *port;
74
75      public:
76        SendEvent(SimpleTimingPort *p)
77            : Event(&mainEventQueue), port(p)
78        { }
79
80        virtual void process();
81
82        virtual const char *description()
83        { return "Future scheduled sendTiming event"; }
84    };
85
86    SendEvent sendEvent;
87
88    /** If we need to drain, keep the drain event around until we're done
89     * here.*/
90    Event *drainEvent;
91
92    /** Schedule a sendTiming() event to be called in the future.
93     * @param pkt packet to send
94     * @param time increment from now (in ticks) to send packet
95     */
96    void sendTiming(PacketPtr pkt, Tick time);
97
98    /** This function is notification that the device should attempt to send a
99     * packet again. */
100    virtual void recvRetry();
101
102    /** Implemented using recvAtomic(). */
103    void recvFunctional(PacketPtr pkt);
104
105    /** Implemented using recvAtomic(). */
106    bool recvTiming(PacketPtr pkt);
107
108    /**
109     * Simple ports generally don't care about any status
110     * changes... can always override this in cases where that's not
111     * true. */
112    virtual void recvStatusChange(Status status) { }
113
114
115  public:
116
117    SimpleTimingPort(std::string pname)
118        : Port(pname), sendEvent(this), drainEvent(NULL)
119    {}
120
121    /** Hook for draining timing accesses from the system.  The
122     * associated SimObject's drain() functions should be implemented
123     * something like this when this class is used:
124     \code
125          PioDevice::drain(Event *de)
126          {
127              unsigned int count;
128              count = SimpleTimingPort->drain(de);
129              if (count)
130                  changeState(Draining);
131              else
132                  changeState(Drained);
133              return count;
134          }
135     \endcode
136    */
137    unsigned int drain(Event *de);
138};
139
140#endif // __MEM_TPORT_HH__
141