clocked_object.hh revision 9180:ee8d7a51651d 
1/*
2 * Copyright (c) 2012 ARM Limited
3 * All rights reserved
4 *
5 * The license below extends only to copyright in the software and shall
6 * not be construed as granting a license to any other intellectual
7 * property including but not limited to intellectual property relating
8 * to a hardware implementation of the functionality of the software
9 * licensed hereunder.  You may use the software subject to the license
10 * terms below provided that you ensure that this notice is replicated
11 * unmodified and in its entirety in all distributions of the software,
12 * modified or unmodified, in source code or in binary form.
13 *
14 * Redistribution and use in source and binary forms, with or without
15 * modification, are permitted provided that the following conditions are
16 * met: redistributions of source code must retain the above copyright
17 * notice, this list of conditions and the following disclaimer;
18 * redistributions in binary form must reproduce the above copyright
19 * notice, this list of conditions and the following disclaimer in the
20 * documentation and/or other materials provided with the distribution;
21 * neither the name of the copyright holders nor the names of its
22 * contributors may be used to endorse or promote products derived from
23 * this software without specific prior written permission.
24 *
25 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
26 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
27 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
28 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
29 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
30 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
31 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
32 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
33 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
34 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
35 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
36 *
37 * Authors: Andreas Hansson
38 */
39
40/**
41 * @file
42 * ClockedObject declaration and implementation.
43 */
44
45#ifndef __SIM_CLOCKED_OBJECT_HH__
46#define __SIM_CLOCKED_OBJECT_HH__
47
48#include "base/intmath.hh"
49#include "params/ClockedObject.hh"
50#include "sim/sim_object.hh"
51
52/**
53 * The ClockedObject class extends the SimObject with a clock and
54 * accessor functions to relate ticks to the cycles of the object.
55 */
56class ClockedObject : public SimObject
57{
58
59  private:
60
61    // the tick value of the next clock edge (>= curTick()) at the
62    // time of the last call to update()
63    mutable Tick tick;
64
65    // The cycle counter value corresponding to the current value of
66    // 'tick'
67    mutable Cycles cycle;
68
69    /**
70     * Prevent inadvertent use of the copy constructor and assignment
71     * operator by making them private.
72     */
73    ClockedObject(ClockedObject&);
74    ClockedObject& operator=(ClockedObject&);
75
76    /**
77     *  Align cycle and tick to the next clock edge if not already done.
78     */
79    void update() const
80    {
81        // both tick and cycle are up-to-date and we are done, note
82        // that the >= is important as it captures cases where tick
83        // has already passed curTick()
84        if (tick >= curTick())
85            return;
86
87        // optimise for the common case and see if the tick should be
88        // advanced by a single clock period
89        tick += clock;
90        ++cycle;
91
92        // see if we are done at this point
93        if (tick >= curTick())
94            return;
95
96        // if not, we have to recalculate the cycle and tick, we
97        // perform the calculations in terms of relative cycles to
98        // allow changes to the clock period in the future
99        Cycles elapsedCycles(divCeil(curTick() - tick, clock));
100        cycle += elapsedCycles;
101        tick += elapsedCycles * clock;
102    }
103
104  protected:
105
106    // Clock period in ticks
107    Tick clock;
108
109    /**
110     * Create a clocked object and set the clock based on the
111     * parameters.
112     */
113    ClockedObject(const ClockedObjectParams* p) :
114        SimObject(p), tick(0), cycle(0), clock(p->clock)
115    { }
116
117    /**
118     * Virtual destructor due to inheritance.
119     */
120    virtual ~ClockedObject() { }
121
122  public:
123
124    /**
125     * Determine the tick when a cycle begins, by default the current
126     * one, but the argument also enables the caller to determine a
127     * future cycle.
128     *
129     * @param cycles The number of cycles into the future
130     *
131     * @return The tick when the clock edge occurs
132     */
133    inline Tick clockEdge(Cycles cycles = Cycles(0)) const
134    {
135        // align tick to the next clock edge
136        update();
137
138        // figure out when this future cycle is
139        return tick + clock * cycles;
140    }
141
142    /**
143     * Determine the current cycle, corresponding to a tick aligned to
144     * a clock edge.
145     *
146     * @return The current cycle count
147     */
148    inline Cycles curCycle() const
149    {
150        // align cycle to the next clock edge.
151        update();
152
153        return cycle;
154    }
155
156    /**
157     * Based on the clock of the object, determine the tick when the
158     * next cycle begins, in other words, return the next clock edge.
159     *
160     * @return The tick when the next cycle starts
161     */
162    Tick nextCycle() const
163    { return clockEdge(); }
164
165    inline uint64_t frequency() const { return SimClock::Frequency / clock; }
166
167    inline Tick clockPeriod() const { return clock; }
168
169    inline Cycles ticksToCycles(Tick tick) const
170    { return Cycles(tick / clock); }
171
172};
173
174#endif //__SIM_CLOCKED_OBJECT_HH__
175