src/sim/clocked_object.hh

   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  */
  62 class 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 double voltage() const
 216     {
 217         return clockDomain.voltage();
 218     }
 219
 220     inline Cycles ticksToCycles(Tick t) const
 221     { return Cycles(divCeil(t, clockPeriod())); }
 222
 223     inline Tick cyclesToTicks(Cycles c) const
 224     { return clockPeriod() * c; }
 225 };
 226
 227 /**
 228  * The ClockedObject class extends the SimObject with a clock and
 229  * accessor functions to relate ticks to the cycles of the object.
 230  */
 231 class ClockedObject
 232     : public SimObject, public Clocked
 233 {
 234   public:
 235     ClockedObject(const ClockedObjectParams *p)
 236         : SimObject(p), Clocked(*p->clk_domain) { }
 237 };
 238
 239 #endif //__SIM_CLOCKED_OBJECT_HH__