clocked_object.hh revision 9356
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/core.hh" 51#include "sim/sim_object.hh" 52 53/** 54 * The ClockedObject class extends the SimObject with a clock and 55 * accessor functions to relate ticks to the cycles of the object. 56 */ 57class ClockedObject : public SimObject 58{ 59 60 private: 61 62 // the tick value of the next clock edge (>= curTick()) at the 63 // time of the last call to update() 64 mutable Tick tick; 65 66 // The cycle counter value corresponding to the current value of 67 // 'tick' 68 mutable Cycles cycle; 69 70 /** 71 * Prevent inadvertent use of the copy constructor and assignment 72 * operator by making them private. 73 */ 74 ClockedObject(ClockedObject&); 75 ClockedObject& operator=(ClockedObject&); 76 77 /** 78 * Align cycle and tick to the next clock edge if not already done. 79 */ 80 void update() const 81 { 82 // both tick and cycle are up-to-date and we are done, note 83 // that the >= is important as it captures cases where tick 84 // has already passed curTick() 85 if (tick >= curTick()) 86 return; 87 88 // optimise for the common case and see if the tick should be 89 // advanced by a single clock period 90 tick += clock; 91 ++cycle; 92 93 // see if we are done at this point 94 if (tick >= curTick()) 95 return; 96 97 // if not, we have to recalculate the cycle and tick, we 98 // perform the calculations in terms of relative cycles to 99 // allow changes to the clock period in the future 100 Cycles elapsedCycles(divCeil(curTick() - tick, clock)); 101 cycle += elapsedCycles; 102 tick += elapsedCycles * clock; 103 } 104 105 protected: 106 107 // Clock period in ticks 108 Tick clock; 109 110 /** 111 * Create a clocked object and set the clock based on the 112 * parameters. 113 */ 114 ClockedObject(const ClockedObjectParams* p) : 115 SimObject(p), tick(0), cycle(0), clock(p->clock) 116 { } 117 118 /** 119 * Virtual destructor due to inheritance. 120 */ 121 virtual ~ClockedObject() { } 122 123 /** 124 * Reset the object's clock using the current global tick value. Likely 125 * to be used only when the global clock is reset. Currently, this done 126 * only when Ruby is done warming up the memory system. 127 */ 128 void resetClock() const 129 { 130 Cycles elapsedCycles(divCeil(curTick(), clock)); 131 cycle = elapsedCycles; 132 tick = elapsedCycles * clock; 133 } 134 135 public: 136 137 /** 138 * Determine the tick when a cycle begins, by default the current 139 * one, but the argument also enables the caller to determine a 140 * future cycle. 141 * 142 * @param cycles The number of cycles into the future 143 * 144 * @return The tick when the clock edge occurs 145 */ 146 inline Tick clockEdge(Cycles cycles = Cycles(0)) const 147 { 148 // align tick to the next clock edge 149 update(); 150 151 // figure out when this future cycle is 152 return tick + clock * cycles; 153 } 154 155 /** 156 * Determine the current cycle, corresponding to a tick aligned to 157 * a clock edge. 158 * 159 * @return The current cycle count 160 */ 161 inline Cycles curCycle() const 162 { 163 // align cycle to the next clock edge. 164 update(); 165 166 return cycle; 167 } 168 169 /** 170 * Based on the clock of the object, determine the tick when the 171 * next cycle begins, in other words, return the next clock edge. 172 * 173 * @return The tick when the next cycle starts 174 */ 175 Tick nextCycle() const 176 { return clockEdge(); } 177 178 inline uint64_t frequency() const { return SimClock::Frequency / clock; } 179 180 inline Tick clockPeriod() const { return clock; } 181 182 inline Cycles ticksToCycles(Tick tick) const 183 { return Cycles(tick / clock); } 184 185}; 186 187#endif //__SIM_CLOCKED_OBJECT_HH__ 188