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.
83 */
84 void update() const
85 {
86 // both tick and cycle are up-to-date and we are done, note
87 // that the >= is important as it captures cases where tick
88 // has already passed curTick()
89 if (tick >= curTick())
90 return;
91
92 // optimise for the common case and see if the tick should be
93 // advanced by a single clock period
94 tick += clockPeriod();
95 ++cycle;
96
97 // see if we are done at this point
98 if (tick >= curTick())
99 return;
100
101 // if not, we have to recalculate the cycle and tick, we
102 // perform the calculations in terms of relative cycles to
103 // allow changes to the clock period in the future
104 Cycles elapsedCycles(divCeil(curTick() - tick, clockPeriod()));
105 cycle += elapsedCycles;
106 tick += elapsedCycles * clockPeriod();
107 }
108
109 /**
110 * The clock domain this clocked object belongs to
111 */
112 ClockDomain &clockDomain;
113
114 protected:
115
116 /**
117 * Create a clocked object and set the clock domain based on the
118 * parameters.
119 */
120 ClockedObject(const ClockedObjectParams* p) :
121 SimObject(p), tick(0), cycle(0), clockDomain(*p->clk_domain)
122 {
123 // Register with the clock domain, so that if the clock domain
124 // frequency changes, we can update this object's tick.
125 clockDomain.registerWithClockDomain(this);
126 }
127
128 /**
129 * Virtual destructor due to inheritance.
130 */
131 virtual ~ClockedObject() { }
132
133 /**
134 * Reset the object's clock using the current global tick value. Likely
135 * to be used only when the global clock is reset. Currently, this done
136 * only when Ruby is done warming up the memory system.
137 */
138 void resetClock() const
139 {
140 Cycles elapsedCycles(divCeil(curTick(), clockPeriod()));
141 cycle = elapsedCycles;
142 tick = elapsedCycles * clockPeriod();
143 }
144
145 public:
146
147 /**
148 * Update the tick to the current tick.
149 *
150 */
151 inline void updateClockPeriod() const
152 {
153 update();
154 }
155
156 /**
157 * Determine the tick when a cycle begins, by default the current
158 * one, but the argument also enables the caller to determine a
159 * future cycle.
160 *
161 * @param cycles The number of cycles into the future
162 *
163 * @return The tick when the clock edge occurs
164 */
165 inline Tick clockEdge(Cycles cycles = Cycles(0)) const
166 {
167 // align tick to the next clock edge
168 update();
169
170 // figure out when this future cycle is
171 return tick + clockPeriod() * cycles;
172 }
173
174 /**
175 * Determine the current cycle, corresponding to a tick aligned to
176 * a clock edge.
177 *
178 * @return The current cycle count
179 */
180 inline Cycles curCycle() const
181 {
182 // align cycle to the next clock edge.
183 update();
184
185 return cycle;
186 }
187
188 /**
189 * Based on the clock of the object, determine the tick when the next
190 * cycle begins, in other words, return the next clock edge.
191 * (This can never be the current tick.)
192 *
193 * @return The tick when the next cycle starts
194 */
195 Tick nextCycle() const
196 { return clockEdge(Cycles(1)); }
197
198 inline uint64_t frequency() const
199 {
200 return SimClock::Frequency / clockPeriod();
201 }
202
203 inline Tick clockPeriod() const
204 {
205 return clockDomain.clockPeriod();
206 }
207
208 inline Cycles ticksToCycles(Tick t) const
209 { return Cycles(divCeil(t, clockPeriod())); }
210
211};
212
213#endif //__SIM_CLOCKED_OBJECT_HH__