clocked_object.hh revision 9296
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 "params/ClockedObject.hh" 50#include "sim/sim_object.hh" 51 52/** 53 * The ClockedObject class extends the SimObject with a clock and 54 * accessor functions to relate ticks to the cycles of the object. 55 */ 56class ClockedObject : public SimObject 57{ 58 59 private: 60 61 // the tick value of the next clock edge (>= curTick()) at the 62 // time of the last call to update() 63 mutable Tick tick; 64 65 // The cycle counter value corresponding to the current value of 66 // 'tick' 67 mutable Cycles cycle; 68 69 /** 70 * Prevent inadvertent use of the copy constructor and assignment 71 * operator by making them private. 72 */ 73 ClockedObject(ClockedObject&); 74 ClockedObject& operator=(ClockedObject&); 75 76 /** 77 * Align cycle and tick to the next clock edge if not already done. 78 */ 79 void update() const 80 { 81 // both tick and cycle are up-to-date and we are done, note 82 // that the >= is important as it captures cases where tick 83 // has already passed curTick() 84 if (tick >= curTick()) 85 return; 86 87 // optimise for the common case and see if the tick should be 88 // advanced by a single clock period 89 tick += clock; 90 ++cycle; 91 92 // see if we are done at this point 93 if (tick >= curTick()) 94 return; 95 96 // if not, we have to recalculate the cycle and tick, we 97 // perform the calculations in terms of relative cycles to 98 // allow changes to the clock period in the future 99 Cycles elapsedCycles(divCeil(curTick() - tick, clock)); 100 cycle += elapsedCycles; 101 tick += elapsedCycles * clock; 102 } 103 104 protected: 105 106 // Clock period in ticks 107 Tick clock; 108 109 /** 110 * Create a clocked object and set the clock based on the 111 * parameters. 112 */ 113 ClockedObject(const ClockedObjectParams* p) : 114 SimObject(p), tick(0), cycle(0), clock(p->clock) 115 { } 116 117 /** 118 * Virtual destructor due to inheritance. 119 */ 120 virtual ~ClockedObject() { } 121 122 /** 123 * Reset the object's clock using the current global tick value. Likely 124 * to be used only when the global clock is reset. Currently, this done 125 * only when Ruby is done warming up the memory system. 126 */ 127 void resetClock() const 128 { 129 Cycles elapsedCycles(divCeil(curTick(), clock)); 130 cycle = elapsedCycles; 131 tick = elapsedCycles * clock; 132 } 133 134 public: 135 136 /** 137 * Determine the tick when a cycle begins, by default the current 138 * one, but the argument also enables the caller to determine a 139 * future cycle. 140 * 141 * @param cycles The number of cycles into the future 142 * 143 * @return The tick when the clock edge occurs 144 */ 145 inline Tick clockEdge(Cycles cycles = Cycles(0)) const 146 { 147 // align tick to the next clock edge 148 update(); 149 150 // figure out when this future cycle is 151 return tick + clock * cycles; 152 } 153 154 /** 155 * Determine the current cycle, corresponding to a tick aligned to 156 * a clock edge. 157 * 158 * @return The current cycle count 159 */ 160 inline Cycles curCycle() const 161 { 162 // align cycle to the next clock edge. 163 update(); 164 165 return cycle; 166 } 167 168 /** 169 * Based on the clock of the object, determine the tick when the 170 * next cycle begins, in other words, return the next clock edge. 171 * 172 * @return The tick when the next cycle starts 173 */ 174 Tick nextCycle() const 175 { return clockEdge(); } 176 177 inline uint64_t frequency() const { return SimClock::Frequency / clock; } 178 179 inline Tick clockPeriod() const { return clock; } 180 181 inline Cycles ticksToCycles(Tick tick) const 182 { return Cycles(tick / clock); } 183 184}; 185 186#endif //__SIM_CLOCKED_OBJECT_HH__ 187