tport.hh revision 3091:dba513d68c16 
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<Packet*> transmitList;
64
65    /**
66     * This class is used to implemented sendTiming() with a delay. When
67     * a delay is requested a new event is created. When the event time
68     * expires it attempts to send the packet. If it cannot, the packet
69     * is pushed onto the transmit list to be sent when recvRetry() is
70     * called. */
71    class SendEvent : public Event
72    {
73        SimpleTimingPort *port;
74        Packet *packet;
75
76      public:
77        SendEvent(SimpleTimingPort *p, Packet *pkt, Tick t)
78            : Event(&mainEventQueue), port(p), packet(pkt)
79        { setFlags(AutoDelete); schedule(curTick + t); }
80
81        virtual void process();
82
83        virtual const char *description()
84        { return "Future scheduled sendTiming event"; }
85    };
86
87
88    /** Number of timing requests that are emulating the device timing before
89     * attempting to end up on the bus.
90     */
91    int outTiming;
92
93    /** If we need to drain, keep the drain event around until we're done
94     * here.*/
95    Event *drainEvent;
96
97    /** Schedule a sendTiming() event to be called in the future. */
98    void sendTimingLater(Packet *pkt, Tick time)
99    { outTiming++; new SendEvent(this, pkt, time); }
100
101    /** This function is notification that the device should attempt to send a
102     * packet again. */
103    virtual void recvRetry();
104
105    /** Implemented using recvAtomic(). */
106    void recvFunctional(Packet *pkt);
107
108    /** Implemented using recvAtomic(). */
109    bool recvTiming(Packet *pkt);
110
111    /**
112     * Simple ports generally don't care about any status
113     * changes... can always override this in cases where that's not
114     * true. */
115    virtual void recvStatusChange(Status status) { }
116
117
118  public:
119
120    SimpleTimingPort(std::string pname)
121        : Port(pname), outTiming(0), drainEvent(NULL)
122    {}
123
124    /** Hook for draining timing accesses from the system.  The
125     * associated SimObject's drain() functions should be implemented
126     * something like this when this class is used:
127     \code
128          PioDevice::drain(Event *de)
129          {
130              unsigned int count;
131              count = SimpleTimingPort->drain(de);
132              if (count)
133                  changeState(Draining);
134              else
135                  changeState(Drained);
136              return count;
137          }
138     \endcode
139    */
140    unsigned int drain(Event *de);
141};
142
143#endif // __MEM_TPORT_HH__
144