xref: /gem5/src/cpu/simple/atomic.hh

/*
 * Copyright (c) 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: Steve Reinhardt
 */

#ifndef __CPU_SIMPLE_ATOMIC_HH__
#define __CPU_SIMPLE_ATOMIC_HH__

#include "cpu/simple/base.hh"
#include "params/AtomicSimpleCPU.hh"

class AtomicSimpleCPU : public BaseSimpleCPU
{
  public:

    AtomicSimpleCPU(AtomicSimpleCPUParams *params);
    virtual ~AtomicSimpleCPU();

    virtual void init();

  private:

    struct TickEvent : public Event
    {
        AtomicSimpleCPU *cpu;

        TickEvent(AtomicSimpleCPU *c);
        void process();
        const char *description() const;
    };

    TickEvent tickEvent;

    const int width;
    bool locked;
    const bool simulate_data_stalls;
    const bool simulate_inst_stalls;

    /**
     * Drain manager to use when signaling drain completion
     *
     * This pointer is non-NULL when draining and NULL otherwise.
     */
    DrainManager *drain_manager;

    // main simulation loop (one cycle)
    void tick();

    /**
     * Check if a system is in a drained state.
     *
     * We need to drain if:
     * <ul>
     * <li>We are in the middle of a microcode sequence as some CPUs
     *     (e.g., HW accelerated CPUs) can't be started in the middle
     *     of a gem5 microcode sequence.
     *
     * <li>The CPU is in a LLSC region. This shouldn't normally happen
     *     as these are executed atomically within a single tick()
     *     call. The only way this can happen at the moment is if
     *     there is an event in the PC event queue that affects the
     *     CPU state while it is in an LLSC region.
     *
     * <li>Stay at PC is true.
     * </ul>
     */
    bool isDrained() {
        return microPC() == 0 &&
            !locked &&
            !stayAtPC;
    }

    /**
     * Try to complete a drain request.
     *
     * @returns true if the CPU is drained, false otherwise.
     */
    bool tryCompleteDrain();

    /**
     * An AtomicCPUPort overrides the default behaviour of the
     * recvAtomic and ignores the packet instead of panicking.
     */
    class AtomicCPUPort : public CpuPort
    {

      public:

        AtomicCPUPort(const std::string &_name, BaseCPU* _cpu)
            : CpuPort(_name, _cpu)
        { }

      protected:

        virtual Tick recvAtomicSnoop(PacketPtr pkt)
        {
            // Snooping a coherence request, just return
            return 0;
        }

    };

    AtomicCPUPort icachePort;
    AtomicCPUPort dcachePort;

    bool fastmem;
    Request ifetch_req;
    Request data_read_req;
    Request data_write_req;

    bool dcache_access;
    Tick dcache_latency;

  protected:

    /** Return a reference to the data port. */
    virtual CpuPort &getDataPort() { return dcachePort; }

    /** Return a reference to the instruction port. */
    virtual CpuPort &getInstPort() { return icachePort; }

  public:

    unsigned int drain(DrainManager *drain_manager);
    void drainResume();

    void switchOut();
    void takeOverFrom(BaseCPU *oldCPU);

    virtual void activateContext(ThreadID thread_num, Cycles delay);
    virtual void suspendContext(ThreadID thread_num);

    Fault readMem(Addr addr, uint8_t *data, unsigned size, unsigned flags);

    Fault writeMem(uint8_t *data, unsigned size,
                   Addr addr, unsigned flags, uint64_t *res);

    /**
     * Print state of address in memory system via PrintReq (for
     * debugging).
     */
    void printAddr(Addr a);
};

#endif // __CPU_SIMPLE_ATOMIC_HH__