packet_queue.hh revision 8229 
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 <list>
41#include <string>
42
43#include "mem/port.hh"
44#include "sim/eventq.hh"
45
46/**
47 * A simple port for interfacing objects that basically have only
48 * functional memory behavior (e.g. I/O devices) to the memory system.
49 * Both timing and functional accesses are implemented in terms of
50 * atomic accesses.  A derived port class thus only needs to provide
51 * recvAtomic() to support all memory access modes.
52 *
53 * The tricky part is handling recvTiming(), where the response must
54 * be scheduled separately via a later call to sendTiming().  This
55 * feature is handled by scheduling an internal event that calls
56 * sendTiming() after a delay, and optionally rescheduling the
57 * response if it is nacked.
58 */
59class SimpleTimingPort : public Port
60{
61  protected:
62    /** A deferred packet, buffered to transmit later. */
63    class DeferredPacket {
64      public:
65        Tick tick;      ///< The tick when the packet is ready to transmit
66        PacketPtr pkt;  ///< Pointer to the packet to transmit
67        DeferredPacket(Tick t, PacketPtr p)
68            : tick(t), pkt(p)
69        {}
70    };
71
72    typedef std::list<DeferredPacket> DeferredPacketList;
73    typedef std::list<DeferredPacket>::iterator DeferredPacketIterator;
74
75    /** A list of outgoing timing response packets that haven't been
76     * serviced yet. */
77    DeferredPacketList transmitList;
78
79    /** This function attempts to send deferred packets.  Scheduled to
80     * be called in the future via SendEvent. */
81    void processSendEvent();
82
83    /**
84     * This class is used to implemented sendTiming() with a delay. When
85     * a delay is requested a the event is scheduled if it isn't already.
86     * When the event time expires it attempts to send the packet.
87     * If it cannot, the packet sent when recvRetry() is called.
88     **/
89    Event *sendEvent;
90
91    /** If we need to drain, keep the drain event around until we're done
92     * here.*/
93    Event *drainEvent;
94
95    /** Remember whether we're awaiting a retry from the bus. */
96    bool waitingOnRetry;
97
98    /** Check the list of buffered packets against the supplied
99     * functional request. */
100    bool checkFunctional(PacketPtr funcPkt);
101
102    /** Check whether we have a packet ready to go on the transmit list. */
103    bool deferredPacketReady()
104    { return !transmitList.empty() && transmitList.front().tick <= curTick(); }
105
106    Tick deferredPacketReadyTime()
107    { return transmitList.empty() ? MaxTick : transmitList.front().tick; }
108
109    void
110    schedSendEvent(Tick when)
111    {
112        if (waitingOnRetry) {
113            assert(!sendEvent->scheduled());
114            return;
115        }
116
117        if (!sendEvent->scheduled()) {
118            schedule(sendEvent, when);
119        } else if (sendEvent->when() > when) {
120            reschedule(sendEvent, when);
121        }
122    }
123
124
125    /** Schedule a sendTiming() event to be called in the future.
126     * @param pkt packet to send
127     * @param absolute time (in ticks) to send packet
128     */
129    void schedSendTiming(PacketPtr pkt, Tick when);
130
131    /** Attempt to send the packet at the head of the deferred packet
132     * list.  Caller must guarantee that the deferred packet list is
133     * non-empty and that the head packet is scheduled for curTick() (or
134     * earlier).
135     */
136    void sendDeferredPacket();
137
138    /** This function is notification that the device should attempt to send a
139     * packet again. */
140    virtual void recvRetry();
141
142    /** Implemented using recvAtomic(). */
143    void recvFunctional(PacketPtr pkt);
144
145    /** Implemented using recvAtomic(). */
146    bool recvTiming(PacketPtr pkt);
147
148    /**
149     * Simple ports generally don't care about any status
150     * changes... can always override this in cases where that's not
151     * true. */
152    virtual void recvStatusChange(Status status) { }
153
154
155  public:
156    SimpleTimingPort(std::string pname, MemObject *_owner);
157    ~SimpleTimingPort();
158
159    /** Hook for draining timing accesses from the system.  The
160     * associated SimObject's drain() functions should be implemented
161     * something like this when this class is used:
162     \code
163          PioDevice::drain(Event *de)
164          {
165              unsigned int count;
166              count = SimpleTimingPort->drain(de);
167              if (count)
168                  changeState(Draining);
169              else
170                  changeState(Drained);
171              return count;
172          }
173     \endcode
174    */
175    unsigned int drain(Event *de);
176};
177
178#endif // __MEM_TPORT_HH__
179