tport.hh revision 4666:5d110d024fcf 
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 deferred packet, buffered to transmit later. */
62    class DeferredPacket {
63      public:
64        Tick tick;      ///< The tick when the packet is ready to transmit
65        PacketPtr pkt;  ///< Pointer to the packet to transmit
66        DeferredPacket(Tick t, PacketPtr p)
67            : tick(t), pkt(p)
68        {}
69    };
70
71    typedef std::list<DeferredPacket> DeferredPacketList;
72    typedef std::list<DeferredPacket>::iterator DeferredPacketIterator;
73
74    /** A list of outgoing timing response packets that haven't been
75     * serviced yet. */
76    DeferredPacketList transmitList;
77
78    /** This function attempts to send deferred packets.  Scheduled to
79     * be called in the future via SendEvent. */
80    void processSendEvent();
81
82    /**
83     * This class is used to implemented sendTiming() with a delay. When
84     * a delay is requested a the event is scheduled if it isn't already.
85     * When the event time expires it attempts to send the packet.
86     * If it cannot, the packet sent when recvRetry() is called.
87     **/
88    typedef EventWrapper<SimpleTimingPort, &SimpleTimingPort::processSendEvent>
89            SendEvent;
90
91    Event *sendEvent;
92
93    /** If we need to drain, keep the drain event around until we're done
94     * here.*/
95    Event *drainEvent;
96
97    /** Remember whether we're awaiting a retry from the bus. */
98    bool waitingOnRetry;
99
100    /** Check the list of buffered packets against the supplied
101     * functional request. */
102    void checkFunctional(PacketPtr funcPkt);
103
104    /** Check whether we have a packet ready to go on the transmit list. */
105    bool deferredPacketReady()
106    { return !transmitList.empty() && transmitList.front().tick <= curTick; }
107
108    Tick deferredPacketReadyTick()
109    { return transmitList.empty() ? MaxTick : transmitList.front().tick; }
110
111    void schedSendEvent(Tick when)
112    {
113        if (waitingOnRetry) {
114            assert(!sendEvent->scheduled());
115            return;
116        }
117
118        if (!sendEvent->scheduled()) {
119            sendEvent->schedule(when);
120        } else if (sendEvent->when() > when) {
121            sendEvent->reschedule(when);
122        }
123    }
124
125
126    /** Schedule a sendTiming() event to be called in the future.
127     * @param pkt packet to send
128     * @param absolute time (in ticks) to send packet
129     */
130    void schedSendTiming(PacketPtr pkt, Tick when);
131
132    /** Attempt to send the packet at the head of the deferred packet
133     * list.  Caller must guarantee that the deferred packet list is
134     * non-empty and that the head packet is scheduled for curTick (or
135     * earlier).
136     */
137    void sendDeferredPacket();
138
139    /** This function is notification that the device should attempt to send a
140     * packet again. */
141    virtual void recvRetry();
142
143    /** Implemented using recvAtomic(). */
144    void recvFunctional(PacketPtr pkt);
145
146    /** Implemented using recvAtomic(). */
147    bool recvTiming(PacketPtr pkt);
148
149    /**
150     * Simple ports generally don't care about any status
151     * changes... can always override this in cases where that's not
152     * true. */
153    virtual void recvStatusChange(Status status) { }
154
155
156  public:
157
158    SimpleTimingPort(std::string pname, MemObject *_owner = NULL)
159        : Port(pname, _owner),
160          sendEvent(new SendEvent(this)),
161          drainEvent(NULL),
162          waitingOnRetry(false)
163    {}
164
165    ~SimpleTimingPort() { delete sendEvent; }
166
167    /** Hook for draining timing accesses from the system.  The
168     * associated SimObject's drain() functions should be implemented
169     * something like this when this class is used:
170     \code
171          PioDevice::drain(Event *de)
172          {
173              unsigned int count;
174              count = SimpleTimingPort->drain(de);
175              if (count)
176                  changeState(Draining);
177              else
178                  changeState(Drained);
179              return count;
180          }
181     \endcode
182    */
183    unsigned int drain(Event *de);
184};
185
186#endif // __MEM_TPORT_HH__
187