gem5/src/mem/bus.hh

/*
 * Copyright (c) 2011-2012 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) 2002-2005 The Regents of The University of Michigan
 * 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.
 *
 * Authors: Ron Dreslinski
 *          Ali Saidi
 *          Andreas Hansson
 *          William Wang
 */

/**
 * @file
 * Declaration of a bus object.
 */

#ifndef __MEM_BUS_HH__
#define __MEM_BUS_HH__

#include <list>
#include <set>
#include <string>

#include "base/range.hh"
#include "base/range_map.hh"
#include "base/types.hh"
#include "mem/mem_object.hh"
#include "mem/packet.hh"
#include "mem/port.hh"
#include "params/Bus.hh"
#include "sim/eventq.hh"

class Bus : public MemObject
{

    /**
     * Declaration of the bus slave port type, one will be
     * instantiated for each of the master interfaces connecting to
     * the bus.
     */
    class BusSlavePort : public SlavePort
    {
      private:
        /** A pointer to the bus to which this port belongs. */
        Bus *bus;

      public:

        /** Constructor for the BusSlavePort.*/
        BusSlavePort(const std::string &_name, Bus *_bus, PortID _id)
            : SlavePort(_name, _bus, _id), bus(_bus)
        { }

      protected:

        /**
         * When receiving a timing request, pass it to the bus.
         */
        virtual bool recvTimingReq(PacketPtr pkt)
        { return bus->recvTimingReq(pkt, id); }

        /**
         * When receiving a timing snoop response, pass it to the bus.
         */
        virtual bool recvTimingSnoopResp(PacketPtr pkt)
        { return bus->recvTimingSnoopResp(pkt, id); }

        /**
         * When receiving an atomic request, pass it to the bus.
         */
        virtual Tick recvAtomic(PacketPtr pkt)
        { return bus->recvAtomic(pkt, id); }

        /**
         * When receiving a functional request, pass it to the bus.
         */
        virtual void recvFunctional(PacketPtr pkt)
        { bus->recvFunctional(pkt, id); }

        /**
         * When receiving a retry, pass it to the bus.
         */
        virtual void recvRetry()
        { panic("Bus slave ports always succeed and should never retry.\n"); }

        // This should return all the 'owned' addresses that are
        // downstream from this bus, yes?  That is, the union of all
        // the 'owned' address ranges of all the other interfaces on
        // this bus...
        virtual AddrRangeList getAddrRanges()
        { return bus->getAddrRanges(); }

        // Ask the bus to ask everyone on the bus what their block size is and
        // take the max of it. This might need to be changed a bit if we ever
        // support multiple block sizes.
        virtual unsigned deviceBlockSize() const
        { return bus->findBlockSize(); }

    };

    /**
     * Declaration of the bus master port type, one will be
     * instantiated for each of the slave interfaces connecting to the
     * bus.
     */
    class BusMasterPort : public MasterPort
    {
      private:
        /** A pointer to the bus to which this port belongs. */
        Bus *bus;

      public:

        /** Constructor for the BusMasterPort.*/
        BusMasterPort(const std::string &_name, Bus *_bus, PortID _id)
            : MasterPort(_name, _bus, _id), bus(_bus)
        { }

        /**
         * Determine if this port should be considered a snooper. This
         * is determined by the bus.
         *
         * @return a boolean that is true if this port is snooping
         */
        virtual bool isSnooping() const
        { return bus->isSnooping(); }

      protected:

        /**
         * When receiving a timing response, pass it to the bus.
         */
        virtual bool recvTimingResp(PacketPtr pkt)
        { return bus->recvTimingResp(pkt, id); }

        /**
         * When receiving a timing snoop request, pass it to the bus.
         */
        virtual void recvTimingSnoopReq(PacketPtr pkt)
        { return bus->recvTimingSnoopReq(pkt, id); }

        /**
         * When receiving an atomic snoop request, pass it to the bus.
         */
        virtual Tick recvAtomicSnoop(PacketPtr pkt)
        { return bus->recvAtomicSnoop(pkt, id); }

        /**
         * When receiving a functional snoop request, pass it to the bus.
         */
        virtual void recvFunctionalSnoop(PacketPtr pkt)
        { bus->recvFunctionalSnoop(pkt, id); }

        /** When reciving a range change from the peer port (at id),
            pass it to the bus. */
        virtual void recvRangeChange()
        { bus->recvRangeChange(id); }

        /** When reciving a retry from the peer port (at id),
            pass it to the bus. */
        virtual void recvRetry()
        { bus->recvRetry(); }

        // Ask the bus to ask everyone on the bus what their block size is and
        // take the max of it. This might need to be changed a bit if we ever
        // support multiple block sizes.
        virtual unsigned deviceBlockSize() const
        { return bus->findBlockSize(); }

    };

    /** the clock speed for the bus */
    int clock;
    /** cycles of overhead per transaction */
    int headerCycles;
    /** the width of the bus in bytes */
    int width;
    /** the next tick at which the bus will be idle */
    Tick tickNextIdle;

    Event * drainEvent;

    typedef range_map<Addr, PortID>::iterator PortIter;
    range_map<Addr, PortID> portMap;

    AddrRangeList defaultRange;

    std::vector<SlavePort*> snoopPorts;

    /**
     * Store the outstanding requests so we can determine which ones
     * we generated and which ones were merely forwarded. This is used
     * in the coherent bus when coherency responses come back.
     */
    std::set<RequestPtr> outstandingReq;

    /** Function called by the port when the bus is recieving a Timing
      request packet.*/
    bool recvTimingReq(PacketPtr pkt, PortID slave_port_id);

    /** Function called by the port when the bus is recieving a Timing
      response packet.*/
    bool recvTimingResp(PacketPtr pkt, PortID master_port_id);

    /** Function called by the port when the bus is recieving a timing
        snoop request.*/
    void recvTimingSnoopReq(PacketPtr pkt, PortID master_port_id);

    /** Function called by the port when the bus is recieving a timing
        snoop response.*/
    bool recvTimingSnoopResp(PacketPtr pkt, PortID slave_port_id);

    /**
     * Forward a timing packet to our snoopers, potentially excluding
     * one of the connected coherent masters to avoid sending a packet
     * back to where it came from.
     *
     * @param pkt Packet to forward
     * @param exclude_slave_port_id Id of slave port to exclude
     */
    void forwardTiming(PacketPtr pkt, PortID exclude_slave_port_id);

    /**
     * Determine if the bus is to be considered occupied when being
     * presented with a packet from a specific port. If so, the port
     * in question is also added to the retry list.
     *
     * @param port Source port on the bus presenting the packet
     *
     * @return True if the bus is to be considered occupied
     */
    bool isOccupied(Port* port);

    /**
     * Deal with a destination port accepting a packet by potentially
     * removing the source port from the retry list (if retrying) and
     * occupying the bus accordingly.
     *
     * @param busy_time Time to spend as a result of a successful send
     */
    void succeededTiming(Tick busy_time);

    /** Function called by the port when the bus is recieving a Atomic
      transaction.*/
    Tick recvAtomic(PacketPtr pkt, PortID slave_port_id);

    /** Function called by the port when the bus is recieving an
        atomic snoop transaction.*/
    Tick recvAtomicSnoop(PacketPtr pkt, PortID master_port_id);

    /**
     * Forward an atomic packet to our snoopers, potentially excluding
     * one of the connected coherent masters to avoid sending a packet
     * back to where it came from.
     *
     * @param pkt Packet to forward
     * @param exclude_slave_port_id Id of slave port to exclude
     *
     * @return a pair containing the snoop response and snoop latency
     */
    std::pair<MemCmd, Tick> forwardAtomic(PacketPtr pkt,
                                          PortID exclude_slave_port_id);

    /** Function called by the port when the bus is recieving a Functional
        transaction.*/
    void recvFunctional(PacketPtr pkt, PortID slave_port_id);

    /** Function called by the port when the bus is recieving a functional
        snoop transaction.*/
    void recvFunctionalSnoop(PacketPtr pkt, PortID master_port_id);

    /**
     * Forward a functional packet to our snoopers, potentially
     * excluding one of the connected coherent masters to avoid
     * sending a packet back to where it came from.
     *
     * @param pkt Packet to forward
     * @param exclude_slave_port_id Id of slave port to exclude
     */
    void forwardFunctional(PacketPtr pkt, PortID exclude_slave_port_id);

    /** Timing function called by port when it is once again able to process
     * requests. */
    void recvRetry();

    /**
     * Function called by the port when the bus is recieving a range change.
     *
     * @param master_port_id id of the port that received the change
     */
    void recvRangeChange(PortID master_port_id);

    /** Find which port connected to this bus (if any) should be given a packet
     * with this address.
     * @param addr Address to find port for.
     * @return id of port that the packet should be sent out of.
     */
    PortID findPort(Addr addr);

    // Cache for the findPort function storing recently used ports from portMap
    struct PortCache {
        bool valid;
        PortID id;
        Addr start;
        Addr end;
    };

    PortCache portCache[3];

    // Checks the cache and returns the id of the port that has the requested
    // address within its range
    inline PortID checkPortCache(Addr addr) {
        if (portCache[0].valid && addr >= portCache[0].start &&
            addr < portCache[0].end) {
            return portCache[0].id;
        }
        if (portCache[1].valid && addr >= portCache[1].start &&
                   addr < portCache[1].end) {
            return portCache[1].id;
        }
        if (portCache[2].valid && addr >= portCache[2].start &&
            addr < portCache[2].end) {
            return portCache[2].id;
        }

        return InvalidPortID;
    }

    // Clears the earliest entry of the cache and inserts a new port entry
    inline void updatePortCache(short id, Addr start, Addr end) {
        portCache[2].valid = portCache[1].valid;
        portCache[2].id    = portCache[1].id;
        portCache[2].start = portCache[1].start;
        portCache[2].end   = portCache[1].end;

        portCache[1].valid = portCache[0].valid;
        portCache[1].id    = portCache[0].id;
        portCache[1].start = portCache[0].start;
        portCache[1].end   = portCache[0].end;

        portCache[0].valid = true;
        portCache[0].id    = id;
        portCache[0].start = start;
        portCache[0].end   = end;
    }

    // Clears the cache. Needs to be called in constructor.
    inline void clearPortCache() {
        portCache[2].valid = false;
        portCache[1].valid = false;
        portCache[0].valid = false;
    }

    /**
     * Return the address ranges the bus is responsible for.
     *
     * @return a list of non-overlapping address ranges
     */
    AddrRangeList getAddrRanges();

    /**
     * Determine if the bus port is snooping or not.
     *
     * @return a boolean indicating if this port is snooping or not
     */
    bool isSnooping() const;

    /** Calculate the timing parameters for the packet.  Updates the
     * firstWordTime and finishTime fields of the packet object.
     * Returns the tick at which the packet header is completed (which
     * will be all that is sent if the target rejects the packet).
     */
    Tick calcPacketTiming(PacketPtr pkt);

    /** Occupy the bus until until */
    void occupyBus(Tick until);

    /**
     * Release the bus after being occupied and return to an idle
     * state where we proceed to send a retry to any potential waiting
     * port, or drain if asked to do so.
     */
    void releaseBus();

    /**
     * Send a retry to the port at the head of the retryList. The
     * caller must ensure that the list is not empty.
     */
    void retryWaiting();

    /**
     * Ask everyone on the bus what their size is
     *
     * @return the max of all the sizes
     */
    unsigned findBlockSize();

    // event used to schedule a release of the bus
    EventWrapper<Bus, &Bus::releaseBus> busIdleEvent;

    bool inRetry;
    std::set<PortID> inRecvRangeChange;

    /** The master and slave ports of the bus */
    std::vector<SlavePort*> slavePorts;
    std::vector<MasterPort*> masterPorts;

    typedef std::vector<SlavePort*>::iterator SlavePortIter;
    typedef std::vector<SlavePort*>::const_iterator SlavePortConstIter;

    /** An array of pointers to ports that retry should be called on because the
     * original send failed for whatever reason.*/
    std::list<Port*> retryList;

    void addToRetryList(Port* port)
    {
        if (!inRetry) {
            // The device wasn't retrying a packet, or wasn't at an
            // appropriate time.
            retryList.push_back(port);
        } else {
            if (!retryList.empty() && port == retryList.front()) {
                // The device was retrying a packet. It didn't work,
                // so we'll leave it at the head of the retry list.
                inRetry = false;
            } else {
                // We are in retry, but not for this port, put it at
                // the end.
                retryList.push_back(port);
            }
        }
    }

    /** Port that handles requests that don't match any of the interfaces.*/
    PortID defaultPortID;

    /** If true, use address range provided by default device.  Any
       address not handled by another port and not in default device's
       range will cause a fatal error.  If false, just send all
       addresses not handled by another port to default device. */
    bool useDefaultRange;

    unsigned defaultBlockSize;
    unsigned cachedBlockSize;
    bool cachedBlockSizeValid;

  public:

    /** A function used to return the port associated with this bus object. */
    virtual MasterPort& getMasterPort(const std::string& if_name, int idx = -1);
    virtual SlavePort& getSlavePort(const std::string& if_name, int idx = -1);

    virtual void init();
    virtual void startup();

    unsigned int drain(Event *de);

    Bus(const BusParams *p);
};

#endif //__MEM_BUS_HH__