clocked_object.hh revision 9987 
1/*
2 * Copyright (c) 2012-2013 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/clock_domain.hh"
53#include "sim/sim_object.hh"
54
55/**
56 * The ClockedObject class extends the SimObject with a clock and
57 * accessor functions to relate ticks to the cycles of the object.
58 */
59class ClockedObject : public SimObject
60{
61
62  private:
63
64    // the tick value of the next clock edge (>= curTick()) at the
65    // time of the last call to update()
66    mutable Tick tick;
67
68    // The cycle counter value corresponding to the current value of
69    // 'tick'
70    mutable Cycles cycle;
71
72    /**
73     * Prevent inadvertent use of the copy constructor and assignment
74     * operator by making them private.
75     */
76    ClockedObject(ClockedObject&);
77    ClockedObject& operator=(ClockedObject&);
78
79    /**
80     *  Align cycle and tick to the next clock edge if not already done.
81     */
82    void update() const
83    {
84        // both tick and cycle are up-to-date and we are done, note
85        // that the >= is important as it captures cases where tick
86        // has already passed curTick()
87        if (tick >= curTick())
88            return;
89
90        // optimise for the common case and see if the tick should be
91        // advanced by a single clock period
92        tick += clockPeriod();
93        ++cycle;
94
95        // see if we are done at this point
96        if (tick >= curTick())
97            return;
98
99        // if not, we have to recalculate the cycle and tick, we
100        // perform the calculations in terms of relative cycles to
101        // allow changes to the clock period in the future
102        Cycles elapsedCycles(divCeil(curTick() - tick, clockPeriod()));
103        cycle += elapsedCycles;
104        tick += elapsedCycles * clockPeriod();
105    }
106
107    /**
108     * The clock domain this clocked object belongs to
109     */
110    ClockDomain &clockDomain;
111
112  protected:
113
114    /**
115     * Create a clocked object and set the clock domain based on the
116     * parameters.
117     */
118    ClockedObject(const ClockedObjectParams* p) :
119        SimObject(p), tick(0), cycle(0), clockDomain(*p->clk_domain)
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(), clockPeriod()));
136        cycle = elapsedCycles;
137        tick = elapsedCycles * clockPeriod();
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 + clockPeriod() * 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
185    {
186        return SimClock::Frequency / clockPeriod();
187    }
188
189    inline Tick clockPeriod() const
190    {
191        return clockDomain.clockPeriod();
192    }
193
194    inline Cycles ticksToCycles(Tick t) const
195    { return Cycles(divCeil(t, clockPeriod())); }
196
197};
198
199#endif //__SIM_CLOCKED_OBJECT_HH__
200