clocked_object.hh revision 9648 
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 "base/misc.hh"
50#include "params/ClockedObject.hh"
51#include "sim/core.hh"
52#include "sim/sim_object.hh"
53
54/**
55 * The ClockedObject class extends the SimObject with a clock and
56 * accessor functions to relate ticks to the cycles of the object.
57 */
58class ClockedObject : public SimObject
59{
60
61  private:
62
63    // the tick value of the next clock edge (>= curTick()) at the
64    // time of the last call to update()
65    mutable Tick tick;
66
67    // The cycle counter value corresponding to the current value of
68    // 'tick'
69    mutable Cycles cycle;
70
71    /**
72     * Prevent inadvertent use of the copy constructor and assignment
73     * operator by making them private.
74     */
75    ClockedObject(ClockedObject&);
76    ClockedObject& operator=(ClockedObject&);
77
78    /**
79     *  Align cycle and tick to the next clock edge if not already done.
80     */
81    void update() const
82    {
83        // both tick and cycle are up-to-date and we are done, note
84        // that the >= is important as it captures cases where tick
85        // has already passed curTick()
86        if (tick >= curTick())
87            return;
88
89        // optimise for the common case and see if the tick should be
90        // advanced by a single clock period
91        tick += clock;
92        ++cycle;
93
94        // see if we are done at this point
95        if (tick >= curTick())
96            return;
97
98        // if not, we have to recalculate the cycle and tick, we
99        // perform the calculations in terms of relative cycles to
100        // allow changes to the clock period in the future
101        Cycles elapsedCycles(divCeil(curTick() - tick, clock));
102        cycle += elapsedCycles;
103        tick += elapsedCycles * clock;
104    }
105
106    // Clock period in ticks
107    Tick clock;
108
109  protected:
110
111    /**
112     * Create a clocked object and set the clock based on the
113     * parameters.
114     */
115    ClockedObject(const ClockedObjectParams* p) :
116        SimObject(p), tick(0), cycle(0), clock(p->clock)
117    {
118        if (clock == 0) {
119            fatal("%s has a clock period of zero\n", name());
120        }
121    }
122
123    /**
124     * Virtual destructor due to inheritance.
125     */
126    virtual ~ClockedObject() { }
127
128    /**
129     * Reset the object's clock using the current global tick value. Likely
130     * to be used only when the global clock is reset. Currently, this done
131     * only when Ruby is done warming up the memory system.
132     */
133    void resetClock() const
134    {
135        Cycles elapsedCycles(divCeil(curTick(), clock));
136        cycle = elapsedCycles;
137        tick = elapsedCycles * clock;
138    }
139
140  public:
141
142    /**
143     * Determine the tick when a cycle begins, by default the current
144     * one, but the argument also enables the caller to determine a
145     * future cycle.
146     *
147     * @param cycles The number of cycles into the future
148     *
149     * @return The tick when the clock edge occurs
150     */
151    inline Tick clockEdge(Cycles cycles = Cycles(0)) const
152    {
153        // align tick to the next clock edge
154        update();
155
156        // figure out when this future cycle is
157        return tick + clock * cycles;
158    }
159
160    /**
161     * Determine the current cycle, corresponding to a tick aligned to
162     * a clock edge.
163     *
164     * @return The current cycle count
165     */
166    inline Cycles curCycle() const
167    {
168        // align cycle to the next clock edge.
169        update();
170
171        return cycle;
172    }
173
174    /**
175     * Based on the clock of the object, determine the tick when the next
176     * cycle begins, in other words, return the next clock edge.
177     * (This can never be the current tick.)
178     *
179     * @return The tick when the next cycle starts
180     */
181    Tick nextCycle() const
182    { return clockEdge(Cycles(1)); }
183
184    inline uint64_t frequency() const { return SimClock::Frequency / clock; }
185
186    inline Tick clockPeriod() const { return clock; }
187
188    inline Cycles ticksToCycles(Tick t) const
189    { return Cycles(t / clock); }
190
191};
192
193#endif //__SIM_CLOCKED_OBJECT_HH__
194