clocked_object.hh revision 11009:32e374b7cbdb 
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 * Helper class for objects that need to be clocked. Clocked objects
59 * typically inherit from this class. Objects that need SimObject
60 * functionality as well should inherit from ClockedObject.
61 */
62class Clocked
63{
64
65  private:
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     *  Align cycle and tick to the next clock edge if not already done. When
76     *  complete, tick must be at least curTick().
77     */
78    void update() const
79    {
80        // both tick and cycle are up-to-date and we are done, note
81        // that the >= is important as it captures cases where tick
82        // has already passed curTick()
83        if (tick >= curTick())
84            return;
85
86        // optimise for the common case and see if the tick should be
87        // advanced by a single clock period
88        tick += clockPeriod();
89        ++cycle;
90
91        // see if we are done at this point
92        if (tick >= curTick())
93            return;
94
95        // if not, we have to recalculate the cycle and tick, we
96        // perform the calculations in terms of relative cycles to
97        // allow changes to the clock period in the future
98        Cycles elapsedCycles(divCeil(curTick() - tick, clockPeriod()));
99        cycle += elapsedCycles;
100        tick += elapsedCycles * clockPeriod();
101    }
102
103    /**
104     * The clock domain this clocked object belongs to
105     */
106    ClockDomain &clockDomain;
107
108  protected:
109
110    /**
111     * Create a clocked object and set the clock domain based on the
112     * parameters.
113     */
114    Clocked(ClockDomain &clk_domain)
115        : tick(0), cycle(0), clockDomain(clk_domain)
116    {
117        // Register with the clock domain, so that if the clock domain
118        // frequency changes, we can update this object's tick.
119        clockDomain.registerWithClockDomain(this);
120    }
121
122    Clocked(Clocked &) = delete;
123    Clocked &operator=(Clocked &) = delete;
124
125    /**
126     * Virtual destructor due to inheritance.
127     */
128    virtual ~Clocked() { }
129
130    /**
131     * Reset the object's clock using the current global tick value. Likely
132     * to be used only when the global clock is reset. Currently, this done
133     * only when Ruby is done warming up the memory system.
134     */
135    void resetClock() const
136    {
137        Cycles elapsedCycles(divCeil(curTick(), clockPeriod()));
138        cycle = elapsedCycles;
139        tick = elapsedCycles * clockPeriod();
140    }
141
142  public:
143
144    /**
145     * Update the tick to the current tick.
146     *
147     */
148    inline void updateClockPeriod() const
149    {
150        update();
151    }
152
153    /**
154     * Determine the tick when a cycle begins, by default the current one, but
155     * the argument also enables the caller to determine a future cycle. When
156     * curTick() is on a clock edge, the number of cycles in the parameter is
157     * added to curTick() to be returned. When curTick() is not aligned to a
158     * clock edge, the number of cycles in the parameter is added to the next
159     * clock edge.
160     *
161     * @param cycles The number of cycles into the future
162     *
163     * @return The start tick when the requested clock edge occurs. Precisely,
164     * this tick can be
165     *     curTick() + [0, clockPeriod()) + clockPeriod() * cycles
166     */
167    inline Tick clockEdge(Cycles cycles = Cycles(0)) const
168    {
169        // align tick to the next clock edge
170        update();
171
172        // figure out when this future cycle is
173        return tick + clockPeriod() * cycles;
174    }
175
176    /**
177     * Determine the current cycle, corresponding to a tick aligned to
178     * a clock edge.
179     *
180     * @return When curTick() is on a clock edge, return the Cycle corresponding
181     * to that clock edge. When curTick() is not on a clock edge, return the
182     * Cycle corresponding to the next clock edge.
183     */
184    inline Cycles curCycle() const
185    {
186        // align cycle to the next clock edge.
187        update();
188
189        return cycle;
190    }
191
192    /**
193     * Based on the clock of the object, determine the start tick of the first
194     * cycle that is at least one cycle in the future. When curTick() is at the
195     * current cycle edge, this returns the next clock edge. When calling this
196     * during the middle of a cycle, this returns 2 clock edges in the future.
197     *
198     * @return The start tick of the first cycle that is at least one cycle in
199     * the future. Precisely, the returned tick can be in the range
200     *     curTick() + [clockPeriod(), 2 * clockPeriod())
201     */
202    Tick nextCycle() const
203    { return clockEdge(Cycles(1)); }
204
205    inline uint64_t frequency() const
206    {
207        return SimClock::Frequency / clockPeriod();
208    }
209
210    inline Tick clockPeriod() const
211    {
212        return clockDomain.clockPeriod();
213    }
214
215    inline Cycles ticksToCycles(Tick t) const
216    { return Cycles(divCeil(t, clockPeriod())); }
217
218};
219
220/**
221 * The ClockedObject class extends the SimObject with a clock and
222 * accessor functions to relate ticks to the cycles of the object.
223 */
224class ClockedObject
225    : public SimObject, public Clocked
226{
227  public:
228    ClockedObject(const ClockedObjectParams *p)
229        : SimObject(p), Clocked(*p->clk_domain) { }
230};
231
232#endif //__SIM_CLOCKED_OBJECT_HH__
233