gem5/mem/port.hh

/*
 * 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
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/**
 * @file
 * Port Object Decleration. Ports are used to interface memory objects to
 * each other.  They will always come in pairs, and we refer to the other
 * port object as the peer.  These are used to make the design more
 * modular so that a specific interface between every type of objcet doesn't
 * have to be created.
 */

#ifndef __MEM_PORT_HH__
#define __MEM_PORT_HH__

#include <string>
#include <list>
#include <inttypes.h>

#include "base/range.hh"
#include "mem/packet.hh"
#include "mem/request.hh"

/**
 * Ports are used to interface memory objects to
 * each other.  They will always come in pairs, and we refer to the other
 * port object as the peer.  These are used to make the design more
 * modular so that a specific interface between every type of objcet doesn't
 * have to be created.
 *
 * Recv accesor functions are being called from the peer interface.
 * Send accessor functions are being called from the device the port is
 * associated with, and it will call the peer recv. accessor function.
 */
class Port
{
  public:

    // mey be better to use subclasses & RTTI?
    /** Holds the ports status.  Keeps track if it is blocked, or has
        calculated a range change. */
    enum Status {
        Blocked,
        Unblocked,
        RangeChange
    };

  private:

    /** A pointer to the peer port.  Ports always come in pairs, that way they
        can use a standardized interface to communicate between different
        memory objects. */
    Port *peer;

  public:

    /** Function to set the pointer for the peer port.
        @todo should be called by the configuration stuff (python).
    */
    void setPeer(Port *port) { peer = port; }

  protected:

    /** Called to recive a timing call from the peer port. */
    virtual SendResult recvTiming(Packet &pkt) = 0;

    /** Virtual function that can be used to handle scheduling an event
        to send the recvTiming at a given time.  This is for direct
        connection without a interconnect.  The bus will override
        this in it's port class because the bus does the timing.
        This is used to insert timing when an interconnect doesn't
        have it's own event queue.
    */
    virtual SendResult recvTiming(Packet &pkt, Tick t)
    {
        // schedule event to call recvTiming(pkt) @ tick t
    }

    /** Called to recive a atomic call from the peer port. */
    virtual SendResult recvAtomic(Packet &pkt) = 0;

    /** Called to recive a functional call from the peer port. */
    virtual SendResult recvFunctional(Packet &pkt) = 0;

    /** Called to recieve a status change from the peer port. */
    virtual void recvStatusChange(Status status) = 0;

    /** Called by a peer port if the send was unsuccesful, and had to
        wait.  This shouldn't be valid for response paths (IO Devices).
        so it is set to panic if it isn't already defined.
    */
    virtual Packet *recvRetry() { panic("??"); }

    /** Called by a peer port in order to determine the block size of the
        device connected to this port.  It sometimes doesn't make sense for
        this function to be called, a DMA interface doesn't really have a
        block size, so it is defaulted to a panic.
    */
    virtual int recvBlockSizeQuery() { panic("??"); }

    /** The peer port is requesting us to reply with a list of the ranges we
        are responsible for.
        @param owner is an output param that, if set, indicates that the
        port is the owner of the specified ranges (i.e., slave, default
        responder, etc.).  If 'owner' is false, the interface is
        interested in the specified ranges for snooping purposes.  If
        an object wants to own some ranges and snoop on others, it will
        need to use two different ports.
    */
    virtual void recvAddressRangeQuery(std::list<Range<Addr> > &range_list,
                                       bool &owner) = 0;

  public:

    /** Function called by associated memory device (cache, memory, iodevice)
        in order to send a timing request to the port.  Simply calls the peer
        port receive function.
        @return This function returns if the send was succesful in it's
        recieve. If it was a failure, then the port will wait for a recvRetry
        at which point it can issue a successful sendTiming.  This is used in
        case a cache has a higher priority request come in while waiting for
        the bus to arbitrate.
    */
    SendResult sendTiming(Packet &pkt) { return peer->recvTiming(pkt); }

    /** This function is identical to the sendTiming function, accept it
        provides a time when the recvTiming should be called.  The
        peer->recvTimimng will schedule the event, if it's device handles the
        timing (bus) it will be overloaded by the bus type port to handle it
        properly.
    */
    SendResult sendTiming(Packet &pkt, Tick t) { return peer->recvTiming(pkt, t); }

    /** Function called by the associated device to send an atomic access,
        an access in which the data is moved and the state is updated in one
        cycle, without interleaving with other memory accesses.
    */
    SendResult sendAtomic(Packet &pkt)
        { return peer->recvAtomic(pkt); }

    /** Function called by the associated device to send a functional access,
        an access in which the data is instantly updated everywhere in the
        memory system, without affecting the current state of any block
        or moving the block.
    */
    SendResult sendFunctional(Packet &pkt)
        { return peer->recvFunctional(pkt); }

    /** Called by the associated device to send a status change to the device
        connected to the peer interface.
    */
    void sendStatusChange(Status status) {peer->recvStatusChange(status); }

    /** When a timing access doesn't return a success, some time later the
        Retry will be sent.
    */
    Packet *sendRetry() { return peer->recvRetry(); }

    /** Called by the associated device if it wishes to find out the blocksize
        of the device on attached to the peer port.
    */
    int sendBlockSizeQuery() { return peer->recvBlockSizeQuery(); }

    /** Called by the associated device if it wishes to find out the address
        ranges connected to the peer ports devices.
    */
    void sendAddressRangesQuery(std::list<Range<Addr> > &range_list,
                                bool &owner)
    { peer->recvAddressRangesQuery(range_list, owner); }

    // For the read/write blob functional
    // This should be sufficient for everything except ProxyMemory
    // which needs to slip a translation step in as well.  (Unless it
    // does the translation underneath sendFunctional(), in which case
    // maybe this doesn't need to be virtual at all.)  Do we need
    // similar wrappers for sendAtomic()?  If not, should we drop the
    // "Functional" from the names?

    /** This function is a wrapper around sendFunctional()
        that breaks a larger, arbitrarily aligned access into
        appropriate chunks.  The default implementation can use
        getBlockSize() to determine the block size and go from there.
    */
    virtual void readBlobFunctional(Addr addr, uint8_t *p, int size);

    /** This function is a wrapper around sendFunctional()
        that breaks a larger, arbitrarily aligned access into
        appropriate chunks.  The default implementation can use
        getBlockSize() to determine the block size and go from there.
    */
    virtual void writeBlobFunctional(Addr addr, const uint8_t *p, int size);

    /** Fill size bytes starting at addr with byte value val.  This
        should not need to be virtual, since it can be implemented in
        terms of writeBlobFunctional().  However, it shouldn't be
        performance-critical either, so it could be if we wanted to.
        Not even sure if this is actually needed anywhere (there's a
        prot_memset on the old functional memory that's never used),
        but Nate claims it is.
    */
    void memsetBlobFunctional(Addr addr, uint8_t val, int size);

    // I believe these two string functions can be defined once and
    // for all at the top level by implementing them in terms of
    // readBlob and writeBlob.

    /** Write null-terminated string 'str' into memory at 'addr'. */
    void writeStringFunctional(Addr addr, const char *str);

    /** Read null-terminated string from 'addr' into 'str'. */
    void readStringFunctional(std::string &str, Addr addr);
};

#endif //__MEM_PORT_HH__