clocked_object.hh revision 10236:79af6cc0384d 
1/*
2 * Copyright (c) 2012-2013 ARM Limited
3 * Copyright (c) 2013 Cornell University
4 * All rights reserved
5 *
6 * The license below extends only to copyright in the software and shall
7 * not be construed as granting a license to any other intellectual
8 * property including but not limited to intellectual property relating
9 * to a hardware implementation of the functionality of the software
10 * licensed hereunder.  You may use the software subject to the license
11 * terms below provided that you ensure that this notice is replicated
12 * unmodified and in its entirety in all distributions of the software,
13 * modified or unmodified, in source code or in binary form.
14 *
15 * Redistribution and use in source and binary forms, with or without
16 * modification, are permitted provided that the following conditions are
17 * met: redistributions of source code must retain the above copyright
18 * notice, this list of conditions and the following disclaimer;
19 * redistributions in binary form must reproduce the above copyright
20 * notice, this list of conditions and the following disclaimer in the
21 * documentation and/or other materials provided with the distribution;
22 * neither the name of the copyright holders nor the names of its
23 * contributors may be used to endorse or promote products derived from
24 * this software without specific prior written permission.
25 *
26 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
27 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
28 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
29 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
30 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
31 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
32 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
33 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
34 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
35 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
36 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
37 *
38 * Authors: Andreas Hansson
39 *          Christopher Torng
40 */
41
42/**
43 * @file
44 * ClockedObject declaration and implementation.
45 */
46
47#ifndef __SIM_CLOCKED_OBJECT_HH__
48#define __SIM_CLOCKED_OBJECT_HH__
49
50#include "base/intmath.hh"
51#include "base/misc.hh"
52#include "params/ClockedObject.hh"
53#include "sim/core.hh"
54#include "sim/clock_domain.hh"
55#include "sim/sim_object.hh"
56
57/**
58 * The ClockedObject class extends the SimObject with a clock and
59 * accessor functions to relate ticks to the cycles of the object.
60 */
61class ClockedObject : public SimObject
62{
63
64  private:
65
66    // the tick value of the next clock edge (>= curTick()) at the
67    // time of the last call to update()
68    mutable Tick tick;
69
70    // The cycle counter value corresponding to the current value of
71    // 'tick'
72    mutable Cycles cycle;
73
74    /**
75     * Prevent inadvertent use of the copy constructor and assignment
76     * operator by making them private.
77     */
78    ClockedObject(ClockedObject&);
79    ClockedObject& operator=(ClockedObject&);
80
81    /**
82     *  Align cycle and tick to the next clock edge if not already done. When
83     *  complete, tick must be at least curTick().
84     */
85    void update() const
86    {
87        // both tick and cycle are up-to-date and we are done, note
88        // that the >= is important as it captures cases where tick
89        // has already passed curTick()
90        if (tick >= curTick())
91            return;
92
93        // optimise for the common case and see if the tick should be
94        // advanced by a single clock period
95        tick += clockPeriod();
96        ++cycle;
97
98        // see if we are done at this point
99        if (tick >= curTick())
100            return;
101
102        // if not, we have to recalculate the cycle and tick, we
103        // perform the calculations in terms of relative cycles to
104        // allow changes to the clock period in the future
105        Cycles elapsedCycles(divCeil(curTick() - tick, clockPeriod()));
106        cycle += elapsedCycles;
107        tick += elapsedCycles * clockPeriod();
108    }
109
110    /**
111     * The clock domain this clocked object belongs to
112     */
113    ClockDomain &clockDomain;
114
115  protected:
116
117    /**
118     * Create a clocked object and set the clock domain based on the
119     * parameters.
120     */
121    ClockedObject(const ClockedObjectParams* p) :
122        SimObject(p), tick(0), cycle(0), clockDomain(*p->clk_domain)
123    {
124        // Register with the clock domain, so that if the clock domain
125        // frequency changes, we can update this object's tick.
126        clockDomain.registerWithClockDomain(this);
127    }
128
129    /**
130     * Virtual destructor due to inheritance.
131     */
132    virtual ~ClockedObject() { }
133
134    /**
135     * Reset the object's clock using the current global tick value. Likely
136     * to be used only when the global clock is reset. Currently, this done
137     * only when Ruby is done warming up the memory system.
138     */
139    void resetClock() const
140    {
141        Cycles elapsedCycles(divCeil(curTick(), clockPeriod()));
142        cycle = elapsedCycles;
143        tick = elapsedCycles * clockPeriod();
144    }
145
146  public:
147
148    /**
149     * Update the tick to the current tick.
150     *
151     */
152    inline void updateClockPeriod() const
153    {
154        update();
155    }
156
157    /**
158     * Determine the tick when a cycle begins, by default the current one, but
159     * the argument also enables the caller to determine a future cycle. When
160     * curTick() is on a clock edge, the number of cycles in the parameter is
161     * added to curTick() to be returned. When curTick() is not aligned to a
162     * clock edge, the number of cycles in the parameter is added to the next
163     * clock edge.
164     *
165     * @param cycles The number of cycles into the future
166     *
167     * @return The start tick when the requested clock edge occurs. Precisely,
168     * this tick can be
169     *     curTick() + [0, clockPeriod()) + clockPeriod() * cycles
170     */
171    inline Tick clockEdge(Cycles cycles = Cycles(0)) const
172    {
173        // align tick to the next clock edge
174        update();
175
176        // figure out when this future cycle is
177        return tick + clockPeriod() * cycles;
178    }
179
180    /**
181     * Determine the current cycle, corresponding to a tick aligned to
182     * a clock edge.
183     *
184     * @return When curTick() is on a clock edge, return the Cycle corresponding
185     * to that clock edge. When curTick() is not on a clock edge, return the
186     * Cycle corresponding to the next clock edge.
187     */
188    inline Cycles curCycle() const
189    {
190        // align cycle to the next clock edge.
191        update();
192
193        return cycle;
194    }
195
196    /**
197     * Based on the clock of the object, determine the start tick of the first
198     * cycle that is at least one cycle in the future. When curTick() is at the
199     * current cycle edge, this returns the next clock edge. When calling this
200     * during the middle of a cycle, this returns 2 clock edges in the future.
201     *
202     * @return The start tick of the first cycle that is at least one cycle in
203     * the future. Precisely, the returned tick can be in the range
204     *     curTick() + [clockPeriod(), 2 * clockPeriod())
205     */
206    Tick nextCycle() const
207    { return clockEdge(Cycles(1)); }
208
209    inline uint64_t frequency() const
210    {
211        return SimClock::Frequency / clockPeriod();
212    }
213
214    inline Tick clockPeriod() const
215    {
216        return clockDomain.clockPeriod();
217    }
218
219    inline Cycles ticksToCycles(Tick t) const
220    { return Cycles(divCeil(t, clockPeriod())); }
221
222};
223
224#endif //__SIM_CLOCKED_OBJECT_HH__
225