gem5/src/mem/dram_ctrl.hh

/*
 * Copyright (c) 2012-2020 ARM Limited
 * All rights reserved
 *
 * The license below extends only to copyright in the software and shall
 * not be construed as granting a license to any other intellectual
 * property including but not limited to intellectual property relating
 * to a hardware implementation of the functionality of the software
 * licensed hereunder.  You may use the software subject to the license
 * terms below provided that you ensure that this notice is replicated
 * unmodified and in its entirety in all distributions of the software,
 * modified or unmodified, in source code or in binary form.
 *
 * Copyright (c) 2013 Amin Farmahini-Farahani
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are
 * met: redistributions of source code must retain the above copyright
 * notice, this list of conditions and the following disclaimer;
 * redistributions in binary form must reproduce the above copyright
 * notice, this list of conditions and the following disclaimer in the
 * documentation and/or other materials provided with the distribution;
 * neither the name of the copyright holders nor the names of its
 * contributors may be used to endorse or promote products derived from
 * this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

/**
 * @file
 * DRAMCtrl declaration
 */

#ifndef __MEM_DRAM_CTRL_HH__
#define __MEM_DRAM_CTRL_HH__

#include <deque>
#include <string>
#include <unordered_set>
#include <vector>

#include "base/statistics.hh"
#include "enums/AddrMap.hh"
#include "enums/MemSched.hh"
#include "enums/PageManage.hh"
#include "mem/abstract_mem.hh"
#include "mem/drampower.hh"
#include "mem/qos/mem_ctrl.hh"
#include "mem/qport.hh"
#include "params/DRAMCtrl.hh"
#include "sim/eventq.hh"

class DRAMInterfaceParams;

/**
 * A basic class to track the bank state, i.e. what row is
 * currently open (if any), when is the bank free to accept a new
 * column (read/write) command, when can it be precharged, and
 * when can it be activated.
 *
 * The bank also keeps track of how many bytes have been accessed
 * in the open row since it was opened.
 */
class Bank
{

  public:

    static const uint32_t NO_ROW = -1;

    uint32_t openRow;
    uint8_t bank;
    uint8_t bankgr;

    Tick rdAllowedAt;
    Tick wrAllowedAt;
    Tick preAllowedAt;
    Tick actAllowedAt;

    uint32_t rowAccesses;
    uint32_t bytesAccessed;

    Bank() :
        openRow(NO_ROW), bank(0), bankgr(0),
        rdAllowedAt(0), wrAllowedAt(0), preAllowedAt(0), actAllowedAt(0),
        rowAccesses(0), bytesAccessed(0)
    { }
};

/**
 * A burst helper helps organize and manage a packet that is larger than
 * the DRAM burst size. A system packet that is larger than the burst size
 * is split into multiple DRAM packets and all those DRAM packets point to
 * a single burst helper such that we know when the whole packet is served.
 */
class BurstHelper
{
  public:

    /** Number of DRAM bursts requred for a system packet **/
    const unsigned int burstCount;

    /** Number of DRAM bursts serviced so far for a system packet **/
    unsigned int burstsServiced;

    BurstHelper(unsigned int _burstCount)
        : burstCount(_burstCount), burstsServiced(0)
    { }
};

/**
 * A DRAM packet stores packets along with the timestamp of when
 * the packet entered the queue, and also the decoded address.
 */
class DRAMPacket
{
  public:

    /** When did request enter the controller */
    const Tick entryTime;

    /** When will request leave the controller */
    Tick readyTime;

    /** This comes from the outside world */
    const PacketPtr pkt;

    /** MasterID associated with the packet */
    const MasterID _masterId;

    const bool read;

    /** Will be populated by address decoder */
    const uint8_t rank;
    const uint8_t bank;
    const uint32_t row;

    /**
     * Bank id is calculated considering banks in all the ranks
     * eg: 2 ranks each with 8 banks, then bankId = 0 --> rank0, bank0 and
     * bankId = 8 --> rank1, bank0
     */
    const uint16_t bankId;

    /**
     * The starting address of the DRAM packet.
     * This address could be unaligned to burst size boundaries. The
     * reason is to keep the address offset so we can accurately check
     * incoming read packets with packets in the write queue.
     */
    Addr addr;

    /**
     * The size of this dram packet in bytes
     * It is always equal or smaller than DRAM burst size
     */
    unsigned int size;

    /**
     * A pointer to the BurstHelper if this DRAMPacket is a split packet
     * If not a split packet (common case), this is set to NULL
     */
    BurstHelper* burstHelper;
    Bank& bankRef;

    /**
     * QoS value of the encapsulated packet read at queuing time
     */
    uint8_t _qosValue;

    /**
     * Set the packet QoS value
     * (interface compatibility with Packet)
     */
    inline void qosValue(const uint8_t qv) { _qosValue = qv; }

    /**
     * Get the packet QoS value
     * (interface compatibility with Packet)
     */
    inline uint8_t qosValue() const { return _qosValue; }

    /**
     * Get the packet MasterID
     * (interface compatibility with Packet)
     */
    inline MasterID masterId() const { return _masterId; }

    /**
     * Get the packet size
     * (interface compatibility with Packet)
     */
    inline unsigned int getSize() const { return size; }

    /**
     * Get the packet address
     * (interface compatibility with Packet)
     */
    inline Addr getAddr() const { return addr; }

    /**
     * Return true if its a read packet
     * (interface compatibility with Packet)
     */
    inline bool isRead() const { return read; }

    /**
     * Return true if its a write packet
     * (interface compatibility with Packet)
     */
    inline bool isWrite() const { return !read; }


    DRAMPacket(PacketPtr _pkt, bool is_read, uint8_t _rank, uint8_t _bank,
               uint32_t _row, uint16_t bank_id, Addr _addr,
               unsigned int _size, Bank& bank_ref)
        : entryTime(curTick()), readyTime(curTick()), pkt(_pkt),
          _masterId(pkt->masterId()),
          read(is_read), rank(_rank), bank(_bank), row(_row),
          bankId(bank_id), addr(_addr), size(_size), burstHelper(NULL),
          bankRef(bank_ref), _qosValue(_pkt->qosValue())
    { }

};

// The DRAM packets are store in a multiple dequeue structure,
// based on their QoS priority
typedef std::deque<DRAMPacket*> DRAMPacketQueue;

/**
 * Interface to DRAM devices with media specific parameters,
 * statistics, and functions.
 * The DRAMInterface includes a class for individual ranks
 * and per rank functions.
 */
class DRAMInterface : public AbstractMemory
{
  private:
    /**
     * Simple structure to hold the values needed to keep track of
     * commands for DRAMPower
     */
    struct Command
    {
       Data::MemCommand::cmds type;
       uint8_t bank;
       Tick timeStamp;

       constexpr Command(Data::MemCommand::cmds _type, uint8_t _bank,
                         Tick time_stamp)
            : type(_type), bank(_bank), timeStamp(time_stamp)
        { }
    };

    /**
     * The power state captures the different operational states of
     * the DRAM and interacts with the bus read/write state machine,
     * and the refresh state machine.
     *
     * PWR_IDLE      : The idle state in which all banks are closed
     *                 From here can transition to:  PWR_REF, PWR_ACT,
     *                 PWR_PRE_PDN
     *
     * PWR_REF       : Auto-refresh state.  Will transition when refresh is
     *                 complete based on power state prior to PWR_REF
     *                 From here can transition to:  PWR_IDLE, PWR_PRE_PDN,
     *                 PWR_SREF
     *
     * PWR_SREF      : Self-refresh state.  Entered after refresh if
     *                 previous state was PWR_PRE_PDN
     *                 From here can transition to:  PWR_IDLE
     *
     * PWR_PRE_PDN   : Precharge power down state
     *                 From here can transition to:  PWR_REF, PWR_IDLE
     *
     * PWR_ACT       : Activate state in which one or more banks are open
     *                 From here can transition to:  PWR_IDLE, PWR_ACT_PDN
     *
     * PWR_ACT_PDN   : Activate power down state
     *                 From here can transition to:  PWR_ACT
     */
    enum PowerState
    {
        PWR_IDLE = 0,
        PWR_REF,
        PWR_SREF,
        PWR_PRE_PDN,
        PWR_ACT,
        PWR_ACT_PDN
    };

    /**
     * The refresh state is used to control the progress of the
     * refresh scheduling. When normal operation is in progress the
     * refresh state is idle. Once tREFI has elasped, a refresh event
     * is triggered to start the following STM transitions which are
     * used to issue a refresh and return back to normal operation
     *
     * REF_IDLE      : IDLE state used during normal operation
     *                 From here can transition to:  REF_DRAIN
     *
     * REF_SREF_EXIT : Exiting a self-refresh; refresh event scheduled
     *                 after self-refresh exit completes
     *                 From here can transition to:  REF_DRAIN
     *
     * REF_DRAIN     : Drain state in which on going accesses complete.
     *                 From here can transition to:  REF_PD_EXIT
     *
     * REF_PD_EXIT   : Evaluate pwrState and issue wakeup if needed
     *                 Next state dependent on whether banks are open
     *                 From here can transition to:  REF_PRE, REF_START
     *
     * REF_PRE       : Close (precharge) all open banks
     *                 From here can transition to:  REF_START
     *
     * REF_START     : Issue refresh command and update DRAMPower stats
     *                 From here can transition to:  REF_RUN
     *
     * REF_RUN       : Refresh running, waiting for tRFC to expire
     *                 From here can transition to:  REF_IDLE, REF_SREF_EXIT
     */
    enum RefreshState
    {
        REF_IDLE = 0,
        REF_DRAIN,
        REF_PD_EXIT,
        REF_SREF_EXIT,
        REF_PRE,
        REF_START,
        REF_RUN
    };

    class Rank;
    struct RankStats : public Stats::Group
    {
        RankStats(DRAMInterface &dram, Rank &rank);

        void regStats() override;
        void resetStats() override;
        void preDumpStats() override;

        Rank &rank;

        /*
         * Command energies
         */
        Stats::Scalar actEnergy;
        Stats::Scalar preEnergy;
        Stats::Scalar readEnergy;
        Stats::Scalar writeEnergy;
        Stats::Scalar refreshEnergy;

        /*
         * Active Background Energy
         */
        Stats::Scalar actBackEnergy;

        /*
         * Precharge Background Energy
         */
        Stats::Scalar preBackEnergy;

        /*
         * Active Power-Down Energy
         */
        Stats::Scalar actPowerDownEnergy;

        /*
         * Precharge Power-Down Energy
         */
        Stats::Scalar prePowerDownEnergy;

        /*
         * self Refresh Energy
         */
        Stats::Scalar selfRefreshEnergy;

        Stats::Scalar totalEnergy;
        Stats::Scalar averagePower;

        /**
         * Stat to track total DRAM idle time
         *
         */
        Stats::Scalar totalIdleTime;

        /**
         * Track time spent in each power state.
         */
        Stats::Vector pwrStateTime;
    };

    /**
     * Rank class includes a vector of banks. Refresh and Power state
     * machines are defined per rank. Events required to change the
     * state of the refresh and power state machine are scheduled per
     * rank. This class allows the implementation of rank-wise refresh
     * and rank-wise power-down.
     */
    class Rank : public EventManager
    {
      private:

        /**
         * A reference to the parent DRAMInterface instance
         */
        DRAMInterface& dram;

        /**
         * Since we are taking decisions out of order, we need to keep
         * track of what power transition is happening at what time
         */
        PowerState pwrStateTrans;

        /**
         * Previous low-power state, which will be re-entered after refresh.
         */
        PowerState pwrStatePostRefresh;

        /**
         * Track when we transitioned to the current power state
         */
        Tick pwrStateTick;

        /**
         * Keep track of when a refresh is due.
         */
        Tick refreshDueAt;

        /**
         * Function to update Power Stats
         */
        void updatePowerStats();

        /**
         * Schedule a power state transition in the future, and
         * potentially override an already scheduled transition.
         *
         * @param pwr_state Power state to transition to
         * @param tick Tick when transition should take place
         */
        void schedulePowerEvent(PowerState pwr_state, Tick tick);

      public:

        /**
         * Current power state.
         */
        PowerState pwrState;

       /**
         * current refresh state
         */
        RefreshState refreshState;

        /**
         * rank is in or transitioning to power-down or self-refresh
         */
        bool inLowPowerState;

        /**
         * Current Rank index
         */
        uint8_t rank;

       /**
         * Track number of packets in read queue going to this rank
         */
        uint32_t readEntries;

       /**
         * Track number of packets in write queue going to this rank
         */
        uint32_t writeEntries;

        /**
         * Number of ACT, RD, and WR events currently scheduled
         * Incremented when a refresh event is started as well
         * Used to determine when a low-power state can be entered
         */
        uint8_t outstandingEvents;

        /**
         * delay low-power exit until this requirement is met
         */
        Tick wakeUpAllowedAt;

        /**
         * One DRAMPower instance per rank
         */
        DRAMPower power;

        /**
         * List of commands issued, to be sent to DRAMPpower at refresh
         * and stats dump.  Keep commands here since commands to different
         * banks are added out of order.  Will only pass commands up to
         * curTick() to DRAMPower after sorting.
         */
        std::vector<Command> cmdList;

        /**
         * Vector of Banks. Each rank is made of several devices which in
         * term are made from several banks.
         */
        std::vector<Bank> banks;

        /**
         *  To track number of banks which are currently active for
         *  this rank.
         */
        unsigned int numBanksActive;

        /** List to keep track of activate ticks */
        std::deque<Tick> actTicks;

        /**
         * Track when we issued the last read/write burst
         */
        Tick lastBurstTick;

        Rank(const DRAMInterfaceParams* _p, int _rank,
             DRAMInterface& _dram);

        const std::string name() const { return csprintf("%d", rank); }

        /**
         * Kick off accounting for power and refresh states and
         * schedule initial refresh.
         *
         * @param ref_tick Tick for first refresh
         */
        void startup(Tick ref_tick);

        /**
         * Stop the refresh events.
         */
        void suspend();

        /**
         * Check if there is no refresh and no preparation of refresh ongoing
         * i.e. the refresh state machine is in idle
         *
         * @param Return true if the rank is idle from a refresh point of view
         */
        bool inRefIdleState() const { return refreshState == REF_IDLE; }

        /**
         * Check if the current rank has all banks closed and is not
         * in a low power state
         *
         * @param Return true if the rank is idle from a bank
         *        and power point of view
         */
        bool inPwrIdleState() const { return pwrState == PWR_IDLE; }

        /**
         * Trigger a self-refresh exit if there are entries enqueued
         * Exit if there are any read entries regardless of the bus state.
         * If we are currently issuing write commands, exit if we have any
         * write commands enqueued as well.
         * Could expand this in the future to analyze state of entire queue
         * if needed.
         *
         * @return boolean indicating self-refresh exit should be scheduled
         */
        bool forceSelfRefreshExit() const;

        /**
         * Check if the command queue of current rank is idle
         *
         * @param Return true if the there are no commands in Q.
         *                    Bus direction determines queue checked.
         */
        bool isQueueEmpty() const;

        /**
         * Let the rank check if it was waiting for requests to drain
         * to allow it to transition states.
         */
        void checkDrainDone();

        /**
         * Push command out of cmdList queue that are scheduled at
         * or before curTick() to DRAMPower library
         * All commands before curTick are guaranteed to be complete
         * and can safely be flushed.
         */
        void flushCmdList();

        /**
         * Computes stats just prior to dump event
         */
        void computeStats();

        /**
         * Reset stats on a stats event
         */
        void resetStats();

        /**
         * Schedule a transition to power-down (sleep)
         *
         * @param pwr_state Power state to transition to
         * @param tick Absolute tick when transition should take place
         */
        void powerDownSleep(PowerState pwr_state, Tick tick);

       /**
         * schedule and event to wake-up from power-down or self-refresh
         * and update bank timing parameters
         *
         * @param exit_delay Relative tick defining the delay required between
         *                   low-power exit and the next command
         */
        void scheduleWakeUpEvent(Tick exit_delay);

        void processWriteDoneEvent();
        EventFunctionWrapper writeDoneEvent;

        void processActivateEvent();
        EventFunctionWrapper activateEvent;

        void processPrechargeEvent();
        EventFunctionWrapper prechargeEvent;

        void processRefreshEvent();
        EventFunctionWrapper refreshEvent;

        void processPowerEvent();
        EventFunctionWrapper powerEvent;

        void processWakeUpEvent();
        EventFunctionWrapper wakeUpEvent;

      protected:
        RankStats stats;
    };

    /**
     * Function for sorting Command structures based on timeStamp
     *
     * @param a Memory Command
     * @param next Memory Command
     * @return true if timeStamp of Command 1 < timeStamp of Command 2
     */
    static bool
    sortTime(const Command& cmd, const Command& cmd_next)
    {
        return cmd.timeStamp < cmd_next.timeStamp;
    }

    /**
     * A pointer to the parent DRAMCtrl instance
     */
    DRAMCtrl* ctrl;

    /**
     * Memory controller configuration initialized based on parameter
     * values.
     */
    Enums::AddrMap addrMapping;


    /**
     * DRAM device and channel characteristics
     * The rowsPerBank is determined based on the capacity, number of
     * ranks and banks, the burst size, and the row buffer size.
     */
    const uint32_t burstSize;
    const uint32_t deviceSize;
    const uint32_t deviceRowBufferSize;
    const uint32_t devicesPerRank;
    const uint32_t rowBufferSize;
    const uint32_t columnsPerRowBuffer;
    const uint32_t columnsPerStripe;
    const uint32_t ranksPerChannel;
    const uint32_t bankGroupsPerRank;
    const bool bankGroupArch;
    const uint32_t banksPerRank;
    uint32_t rowsPerBank;

    /**
     * DRAM timing requirements
     */
    const Tick M5_CLASS_VAR_USED tCK;
    const Tick tCS;
    const Tick tCL;
    const Tick tBURST;
    const Tick tBURST_MIN;
    const Tick tBURST_MAX;
    const Tick tRTW;
    const Tick tCCD_L_WR;
    const Tick tCCD_L;
    const Tick tRCD;
    const Tick tRP;
    const Tick tRAS;
    const Tick tWR;
    const Tick tRTP;
    const Tick tRFC;
    const Tick tREFI;
    const Tick tRRD;
    const Tick tRRD_L;
    const Tick tPPD;
    const Tick tAAD;
    const Tick tXAW;
    const Tick tXP;
    const Tick tXS;
    const Tick clkResyncDelay;
    unsigned int maxCommandsPerBurst;
    const bool dataClockSync;
    const bool burstInterleave;
    const uint8_t twoCycleActivate;
    const uint32_t activationLimit;
    const Tick wrToRdDly;
    const Tick rdToWrDly;
    const Tick wrToRdDlySameBG;
    const Tick rdToWrDlySameBG;
    const Tick rankToRankDly;

    Enums::PageManage pageMgmt;
    /**
     * Max column accesses (read and write) per row, before forefully
     * closing it.
     */
    const uint32_t maxAccessesPerRow;

    // timestamp offset
    uint64_t timeStampOffset;

    // Holds the value of the DRAM rank of burst issued
    uint8_t activeRank;

    /** Enable or disable DRAM powerdown states. */
    bool enableDRAMPowerdown;

    /** The time when stats were last reset used to calculate average power */
    Tick lastStatsResetTick;

    /**
     * Keep track of when row activations happen, in order to enforce
     * the maximum number of activations in the activation window. The
     * method updates the time that the banks become available based
     * on the current limits.
     *
     * @param rank_ref Reference to the rank
     * @param bank_ref Reference to the bank
     * @param act_tick Time when the activation takes place
     * @param row Index of the row
     */
    void activateBank(Rank& rank_ref, Bank& bank_ref, Tick act_tick,
                      uint32_t row);

    /**
     * Precharge a given bank and also update when the precharge is
     * done. This will also deal with any stats related to the
     * accesses to the open page.
     *
     * @param rank_ref The rank to precharge
     * @param bank_ref The bank to precharge
     * @param pre_tick Time when the precharge takes place
     * @param auto_or_preall Is this an auto-precharge or precharge all command
     * @param trace Is this an auto precharge then do not add to trace
     */
    void prechargeBank(Rank& rank_ref, Bank& bank_ref,
                       Tick pre_tick, bool auto_or_preall = false,
                       bool trace = true);

    struct DRAMStats : public Stats::Group
    {
        DRAMStats(DRAMInterface &dram);

        void regStats() override;
        void resetStats() override;

        DRAMInterface &dram;

        /** total number of DRAM bursts serviced */
        Stats::Scalar readBursts;
        Stats::Scalar writeBursts;

        /** DRAM per bank stats */
        Stats::Vector perBankRdBursts;
        Stats::Vector perBankWrBursts;

        // Latencies summed over all requests
        Stats::Scalar totQLat;
        Stats::Scalar totBusLat;
        Stats::Scalar totMemAccLat;

        // Average latencies per request
        Stats::Formula avgQLat;
        Stats::Formula avgBusLat;
        Stats::Formula avgMemAccLat;

        // Row hit count and rate
        Stats::Scalar readRowHits;
        Stats::Scalar writeRowHits;
        Stats::Formula readRowHitRate;
        Stats::Formula writeRowHitRate;
        Stats::Histogram bytesPerActivate;
        // Number of bytes transferred to/from DRAM
        Stats::Scalar bytesRead;
        Stats::Scalar bytesWritten;

        // Average bandwidth
        Stats::Formula avgRdBW;
        Stats::Formula avgWrBW;
        Stats::Formula peakBW;
        // bus utilization
        Stats::Formula busUtil;
        Stats::Formula busUtilRead;
        Stats::Formula busUtilWrite;
        Stats::Formula pageHitRate;
    };

    DRAMStats stats;

    /**
      * Vector of dram ranks
      */
    std::vector<Rank*> ranks;

  public:

    /**
      * Buffer sizes for read and write queues in the controller
      * These are passed to the controller on instantiation
      * Defining them here allows for buffers to be resized based
      * on memory type / configuration.
      */
    const uint32_t readBufferSize;
    const uint32_t writeBufferSize;

    /** Setting a pointer to the controller */
    void setCtrl(DRAMCtrl* _ctrl) { ctrl = _ctrl; }

    /**
     * Initialize the DRAM interface and verify parameters
     */
    void init() override;

    /**
     * Iterate through dram ranks and instantiate per rank startup routine
     */
    void startup() override;

    /**
     * Iterate through dram ranks to exit self-refresh in order to drain
     */
    void drainRanks();

    /**
     * Return true once refresh is complete for all ranks and there are no
     * additional commands enqueued.  (only evaluated when draining)
     * This will ensure that all banks are closed, power state is IDLE, and
     * power stats have been updated
     *
     * @return true if all ranks have refreshed, with no commands enqueued
     *
     */
    bool allRanksDrained() const;

    /**
     * Iterate through DRAM ranks and suspend them
     */
    void suspend();

    /**
     * Get an address in a dense range which starts from 0. The input
     * address is the physical address of the request in an address
     * space that contains other SimObjects apart from this
     * controller.
     *
     * @param addr The intput address which should be in the addrRange
     * @return An address in the continues range [0, max)
     */
    Addr getCtrlAddr(Addr addr) { return range.getOffset(addr); }

    /**
     * @return number of bytes in a burst for this interface
     */
    uint32_t bytesPerBurst() const { return burstSize; }

    /**
     *
     * @return number of ranks per channel for this interface
     */
    uint32_t numRanks() const { return ranksPerChannel; }

    /*
     * @return time to send a burst of data
     */
    Tick burstDelay() const { return tBURST; }

    /*
     * @return time to send a burst of data without gaps
     */
    Tick
    burstDataDelay() const
    {
        return (burstInterleave ? tBURST_MAX / 2 : tBURST);
    }

    /*
     * @return Maximum number of commands that can issue per burst
     */
    Tick maxCmdsPerBst() const { return maxCommandsPerBurst; }

    /**
     *
     * @return additional bus turnaround required for read-to-write
     */
    Tick minRdToWr() const { return tRTW; }

    /**
     * Determine the required delay for an access to a different rank
     *
     * @return required rank to rank delay
     */
    Tick rankDelay() const { return tCS; }

    /*
     * Function to calulate RAS cycle time for use within and
     * outside of this class
     */
    Tick tRC() const { return (tRP + tRCD); }

    /*
     * Function to calulate unloaded, closed bank access latency
     */
    Tick accessLatency() const { return (tRP + tRCD + tCL); }

    /**
     * Address decoder to figure out physical mapping onto ranks,
     * banks, and rows. This function is called multiple times on the same
     * system packet if the pakcet is larger than burst of the memory. The
     * dramPktAddr is used for the offset within the packet.
     *
     * @param pkt The packet from the outside world
     * @param dramPktAddr The starting address of the DRAM packet
     * @param size The size of the DRAM packet in bytes
     * @param isRead Is the request for a read or a write to DRAM
     * @return A DRAMPacket pointer with the decoded information
     */
    DRAMPacket* decodePacket(const PacketPtr pkt, Addr dramPktAddr,
                           unsigned int size, bool isRead) const;

    /**
     * Actually do the burst - figure out the latency it
     * will take to service the req based on bank state, channel state etc
     * and then update those states to account for this request. Based
     * on this, update the packet's "readyTime" and move it to the
     * response q from where it will eventually go back to the outside
     * world.
     *
     * @param dram_pkt The DRAM packet created from the outside world pkt
     * @param next_burst_at Minimum bus timing requirement from controller
     * @param queue Reference to the read or write queue with the packet
     * @return tick when burst is issued
     */
    Tick doBurstAccess(DRAMPacket* dram_pkt, Tick next_burst_at,
                             const std::vector<DRAMPacketQueue>& queue);

    /**
     * Find which are the earliest banks ready to issue an activate
     * for the enqueued requests. Assumes maximum of 32 banks per rank
     * Also checks if the bank is already prepped.
     *
     * @param queue Queued requests to consider
     * @param min_col_at time of seamless burst command
     * @return One-hot encoded mask of bank indices
     * @return boolean indicating burst can issue seamlessly, with no gaps
     */
    std::pair<std::vector<uint32_t>, bool>
    minBankPrep(const DRAMPacketQueue& queue, Tick min_col_at) const;

    /**
     * Check if a burst operation can be issued to the DRAM
     *
     * @param Return true if RD/WR can issue
     *                    This requires the DRAM to be in the
     *                    REF IDLE state
     */
    bool
    burstReady(uint8_t rank) const
    {
        return ranks[rank]->inRefIdleState();
    }

    /**
     * This function checks if ranks are actively refreshing and
     * therefore busy. The function also checks if ranks are in
     * the self-refresh state, in which case, a self-refresh exit
     * is initiated.
     *
     * return boolean if all ranks are in refresh and therefore busy
     */
    bool isBusy();

    /**
     * Complete response process for DRAM when read burst is complete
     * This will update the counters and check if a power down state
     * can be entered.
     *
     * @param rank Specifies rank associated with read burst
     */
    void respondEvent(uint8_t rank);

    /**
     * Check the refresh state to determine if refresh needs
     * to be kicked back into action after a read response
     *
     * @param rank Specifies rank associated with read burst
     */
    void checkRefreshState(uint8_t rank);

    DRAMInterface(const DRAMInterfaceParams* _p);
};

/**
 * The DRAM controller is a single-channel memory controller capturing
 * the most important timing constraints associated with a
 * contemporary DRAM. For multi-channel memory systems, the controller
 * is combined with a crossbar model, with the channel address
 * interleaving taking part in the crossbar.
 *
 * As a basic design principle, this controller
 * model is not cycle callable, but instead uses events to: 1) decide
 * when new decisions can be made, 2) when resources become available,
 * 3) when things are to be considered done, and 4) when to send
 * things back. Through these simple principles, the model delivers
 * high performance, and lots of flexibility, allowing users to
 * evaluate the system impact of a wide range of memory technologies,
 * such as DDR3/4, LPDDR2/3/4, WideIO1/2, HBM and HMC.
 *
 * For more details, please see Hansson et al, "Simulating DRAM
 * controllers for future system architecture exploration",
 * Proc. ISPASS, 2014. If you use this model as part of your research
 * please cite the paper.
 *
 * The low-power functionality implements a staggered powerdown
 * similar to that described in "Optimized Active and Power-Down Mode
 * Refresh Control in 3D-DRAMs" by Jung et al, VLSI-SoC, 2014.
 */
class DRAMCtrl : public QoS::MemCtrl
{

  private:

    // For now, make use of a queued slave port to avoid dealing with
    // flow control for the responses being sent back
    class MemoryPort : public QueuedSlavePort
    {

        RespPacketQueue queue;
        DRAMCtrl& ctrl;

      public:

        MemoryPort(const std::string& name, DRAMCtrl& _ctrl);

      protected:

        Tick recvAtomic(PacketPtr pkt);

        void recvFunctional(PacketPtr pkt);

        bool recvTimingReq(PacketPtr);

        virtual AddrRangeList getAddrRanges() const;

    };

    /**
     * Our incoming port, for a multi-ported controller add a crossbar
     * in front of it
     */
    MemoryPort port;

    /**
     * Remember if the memory system is in timing mode
     */
    bool isTimingMode;

    /**
     * Remember if we have to retry a request when available.
     */
    bool retryRdReq;
    bool retryWrReq;

    /**
     * Bunch of things requires to setup "events" in gem5
     * When event "respondEvent" occurs for example, the method
     * processRespondEvent is called; no parameters are allowed
     * in these methods
     */
    void processNextReqEvent();
    EventFunctionWrapper nextReqEvent;

    void processRespondEvent();
    EventFunctionWrapper respondEvent;

    /**
     * Check if the read queue has room for more entries
     *
     * @param pktCount The number of entries needed in the read queue
     * @return true if read queue is full, false otherwise
     */
    bool readQueueFull(unsigned int pktCount) const;

    /**
     * Check if the write queue has room for more entries
     *
     * @param pktCount The number of entries needed in the write queue
     * @return true if write queue is full, false otherwise
     */
    bool writeQueueFull(unsigned int pktCount) const;

    /**
     * When a new read comes in, first check if the write q has a
     * pending request to the same address.\ If not, decode the
     * address to populate rank/bank/row, create one or mutliple
     * "dram_pkt", and push them to the back of the read queue.\
     * If this is the only
     * read request in the system, schedule an event to start
     * servicing it.
     *
     * @param pkt The request packet from the outside world
     * @param pktCount The number of DRAM bursts the pkt
     * translate to. If pkt size is larger then one full burst,
     * then pktCount is greater than one.
     */
    void addToReadQueue(PacketPtr pkt, unsigned int pktCount);

    /**
     * Decode the incoming pkt, create a dram_pkt and push to the
     * back of the write queue. \If the write q length is more than
     * the threshold specified by the user, ie the queue is beginning
     * to get full, stop reads, and start draining writes.
     *
     * @param pkt The request packet from the outside world
     * @param pktCount The number of DRAM bursts the pkt
     * translate to. If pkt size is larger then one full burst,
     * then pktCount is greater than one.
     */
    void addToWriteQueue(PacketPtr pkt, unsigned int pktCount);

    /**
     * Actually do the burst based on media specific access function.
     * Update bus statistics when complete.
     *
     * @param pkt The DRAM packet created from the outside world pkt
     */
    void doBurstAccess(DRAMPacket* dram_pkt);

    /**
     * When a packet reaches its "readyTime" in the response Q,
     * use the "access()" method in AbstractMemory to actually
     * create the response packet, and send it back to the outside
     * world requestor.
     *
     * @param pkt The packet from the outside world
     * @param static_latency Static latency to add before sending the packet
     */
    void accessAndRespond(PacketPtr pkt, Tick static_latency);

    /**
     * The memory schduler/arbiter - picks which request needs to
     * go next, based on the specified policy such as FCFS or FR-FCFS
     * and moves it to the head of the queue.
     * Prioritizes accesses to the same rank as previous burst unless
     * controller is switching command type.
     *
     * @param queue Queued requests to consider
     * @param extra_col_delay Any extra delay due to a read/write switch
     * @return an iterator to the selected packet, else queue.end()
     */
    DRAMPacketQueue::iterator chooseNext(DRAMPacketQueue& queue,
        Tick extra_col_delay);

    /**
     * For FR-FCFS policy reorder the read/write queue depending on row buffer
     * hits and earliest bursts available in DRAM
     *
     * @param queue Queued requests to consider
     * @param extra_col_delay Any extra delay due to a read/write switch
     * @return an iterator to the selected packet, else queue.end()
     */
    DRAMPacketQueue::iterator chooseNextFRFCFS(DRAMPacketQueue& queue,
            Tick extra_col_delay);

    /**
     * Calculate burst window aligned tick
     *
     * @param cmd_tick Initial tick of command
     * @return burst window aligned tick
     */
    Tick getBurstWindow(Tick cmd_tick);

    /**
     * Used for debugging to observe the contents of the queues.
     */
    void printQs() const;

    /**
     * Burst-align an address.
     *
     * @param addr The potentially unaligned address
     *
     * @return An address aligned to a DRAM burst
     */
    Addr burstAlign(Addr addr) const
    {
        return (addr & ~(Addr(dram->bytesPerBurst() - 1)));
    }

    /**
     * The controller's main read and write queues, with support for QoS reordering
     */
    std::vector<DRAMPacketQueue> readQueue;
    std::vector<DRAMPacketQueue> writeQueue;

    /**
     * To avoid iterating over the write queue to check for
     * overlapping transactions, maintain a set of burst addresses
     * that are currently queued. Since we merge writes to the same
     * location we never have more than one address to the same burst
     * address.
     */
    std::unordered_set<Addr> isInWriteQueue;

    /**
     * Response queue where read packets wait after we're done working
     * with them, but it's not time to send the response yet. The
     * responses are stored separately mostly to keep the code clean
     * and help with events scheduling. For all logical purposes such
     * as sizing the read queue, this and the main read queue need to
     * be added together.
     */
    std::deque<DRAMPacket*> respQueue;

    /**
     * Holds count of commands issued in burst window starting at
     * defined Tick. This is used to ensure that the command bandwidth
     * does not exceed the allowable media constraints.
     */
    std::unordered_multiset<Tick> burstTicks;

    /**
     * Create pointer to interface of the actual dram media
     */
    DRAMInterface* const dram;

    /**
     * The following are basic design parameters of the memory
     * controller, and are initialized based on parameter values.
     * The rowsPerBank is determined based on the capacity, number of
     * ranks and banks, the burst size, and the row buffer size.
     */
    const uint32_t readBufferSize;
    const uint32_t writeBufferSize;
    const uint32_t writeHighThreshold;
    const uint32_t writeLowThreshold;
    const uint32_t minWritesPerSwitch;
    uint32_t writesThisTime;
    uint32_t readsThisTime;

    /**
     * Memory controller configuration initialized based on parameter
     * values.
     */
    Enums::MemSched memSchedPolicy;

    /**
     * Pipeline latency of the controller frontend. The frontend
     * contribution is added to writes (that complete when they are in
     * the write buffer) and reads that are serviced the write buffer.
     */
    const Tick frontendLatency;

    /**
     * Pipeline latency of the backend and PHY. Along with the
     * frontend contribution, this latency is added to reads serviced
     * by the DRAM.
     */
    const Tick backendLatency;

    /**
     * Till when must we wait before issuing next RD/WR burst?
     */
    Tick nextBurstAt;

    Tick prevArrival;

    /**
     * The soonest you have to start thinking about the next request
     * is the longest access time that can occur before
     * nextBurstAt. Assuming you need to precharge, open a new row,
     * and access, it is tRP + tRCD + tCL.
     */
    Tick nextReqTime;

    struct CtrlStats : public Stats::Group
    {
        CtrlStats(DRAMCtrl &ctrl);

        void regStats() override;

        DRAMCtrl &ctrl;

        // All statistics that the model needs to capture
        Stats::Scalar readReqs;
        Stats::Scalar writeReqs;
        Stats::Scalar readBursts;
        Stats::Scalar writeBursts;
        Stats::Scalar servicedByWrQ;
        Stats::Scalar mergedWrBursts;
        Stats::Scalar neitherReadNorWriteReqs;
        // Average queue lengths
        Stats::Average avgRdQLen;
        Stats::Average avgWrQLen;

        Stats::Scalar numRdRetry;
        Stats::Scalar numWrRetry;
        Stats::Vector readPktSize;
        Stats::Vector writePktSize;
        Stats::Vector rdQLenPdf;
        Stats::Vector wrQLenPdf;
        Stats::Histogram rdPerTurnAround;
        Stats::Histogram wrPerTurnAround;

        Stats::Scalar bytesReadWrQ;
        Stats::Scalar bytesReadSys;
        Stats::Scalar bytesWrittenSys;
        // Average bandwidth
        Stats::Formula avgRdBWSys;
        Stats::Formula avgWrBWSys;

        Stats::Scalar totGap;
        Stats::Formula avgGap;

        // per-master bytes read and written to memory
        Stats::Vector masterReadBytes;
        Stats::Vector masterWriteBytes;

        // per-master bytes read and written to memory rate
        Stats::Formula masterReadRate;
        Stats::Formula masterWriteRate;

        // per-master read and write serviced memory accesses
        Stats::Vector masterReadAccesses;
        Stats::Vector masterWriteAccesses;

        // per-master read and write total memory access latency
        Stats::Vector masterReadTotalLat;
        Stats::Vector masterWriteTotalLat;

        // per-master raed and write average memory access latency
        Stats::Formula masterReadAvgLat;
        Stats::Formula masterWriteAvgLat;
    };

    CtrlStats stats;

    /**
     * Upstream caches need this packet until true is returned, so
     * hold it for deletion until a subsequent call
     */
    std::unique_ptr<Packet> pendingDelete;

    /**
     * Select either the read or write queue
     *
     * @param is_read The current burst is a read, select read queue
     * @return a reference to the appropriate queue
     */
    std::vector<DRAMPacketQueue>& selQueue(bool is_read)
    {
        return (is_read ? readQueue : writeQueue);
    };

    /**
     * Remove commands that have already issued from burstTicks
     */
    void pruneBurstTick();

  public:
    DRAMCtrl(const DRAMCtrlParams* p);

    DrainState drain() override;

    /**
     * Check for command bus contention for single cycle command.
     * If there is contention, shift command to next burst.
     * Check verifies that the commands issued per burst is less
     * than a defined max number, maxCommandsPerBurst.
     * Therefore, contention per cycle is not verified and instead
     * is done based on a burst window.
     *
     * @param cmd_tick Initial tick of command, to be verified
     * @return tick for command issue without contention
     */
    Tick verifySingleCmd(Tick cmd_tick);

    /**
     * Check for command bus contention for multi-cycle (2 currently)
     * command. If there is contention, shift command(s) to next burst.
     * Check verifies that the commands issued per burst is less
     * than a defined max number, maxCommandsPerBurst.
     * Therefore, contention per cycle is not verified and instead
     * is done based on a burst window.
     *
     * @param cmd_tick Initial tick of command, to be verified
     * @param max_multi_cmd_split Maximum delay between commands
     * @return tick for command issue without contention
     */
    Tick verifyMultiCmd(Tick cmd_tick, Tick max_multi_cmd_split = 0);

    /**
     * Is there a respondEvent scheduled?
     *
     * @return true if event is scheduled
     */
    bool respondEventScheduled() const { return respondEvent.scheduled(); }

    /**
     * Is there a read/write burst Event scheduled?
     *
     * @return true if event is scheduled
     */
    bool requestEventScheduled() const { return nextReqEvent.scheduled(); }

    /**
     * restart the controller
     * This can be used by interfaces to restart the
     * scheduler after maintainence commands complete
     *
     * @param Tick to schedule next event
     */
    void restartScheduler(Tick tick) { schedule(nextReqEvent, tick); }

    /**
     * Check the current direction of the memory channel
     *
     * @param next_state Check either the current or next bus state
     * @return True when bus is currently in a read state
     */
    bool inReadBusState(bool next_state) const;

    /**
     * Check the current direction of the memory channel
     *
     * @param next_state Check either the current or next bus state
     * @return True when bus is currently in a write state
     */
    bool inWriteBusState(bool next_state) const;

    Port &getPort(const std::string &if_name,
                  PortID idx=InvalidPortID) override;

    virtual void init() override;
    virtual void startup() override;
    virtual void drainResume() override;

  protected:

    Tick recvAtomic(PacketPtr pkt);
    void recvFunctional(PacketPtr pkt);
    bool recvTimingReq(PacketPtr pkt);

};

#endif //__MEM_DRAM_CTRL_HH__