xref: /gem5/src/mem/hmc_controller.hh

/*
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 * licensed hereunder.  You may use the software subject to the license
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 * modified or unmodified, in source code or in binary form.
 *
 * Copyright (c) 2015 The University of Bologna
 * All rights reserved.
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 * modification, are permitted provided that the following conditions are
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 * this software without specific prior written permission.
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 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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 * Authors: Erfan Azarkhish
 */


/**
 * @file
 * HMCController declaration
 */

#ifndef __MEM_HMC_CONTROLLER_HH__
#define __MEM_HMC_CONTROLLER_HH__

#include "mem/noncoherent_xbar.hh"
#include "mem/port.hh"
#include "params/HMCController.hh"

/**
 * HMC Controller, in general, is responsible for translating the host
 * protocol (AXI for example) to serial links protocol. Plus, it should have
 * large internal buffers to hide the access latency of the cube. It is also
 * inferred from the standard [1] and the literature [2] that serial links
 * share the same address range and packets can travel over any of them, so a
 * load distribution mechanism is required.
 * This model simply queues the incoming transactions (using a Bridge) and
 * schedules them to the serial links using a simple round robin mechanism to
 * balance the load among them. More advanced global scheduling policies and
 * reordering and steering of transactions can be added to this model if
 * required [3].
 * [1] http://www.hybridmemorycube.org/specification-download/
 * [2] Low-Power Hybrid Memory Cubes With Link Power Manageme and Two-Level
 * Prefetching (J. Ahn et. al)
 * [3] The Open-Silicon HMC Controller IP
 * http://www.open-silicon.com/open-silicon-ips/hmc/
 */

class HMCController : public NoncoherentXBar
{
public:

    HMCController(const HMCControllerParams *p);

private:

    // Receive range change only on one of the ports (because they all have
    //  the same range)
    virtual void recvRangeChange(PortID master_port_id);

    // Receive a request and distribute it among slave ports
    //  Simply forwards the packet to the next serial link based on a
    //  Round-robin counter
    virtual bool recvTimingReq(PacketPtr pkt, PortID slave_port_id);

    int n_master_ports;

    // The round-robin counter
    int rr_counter;
    /**
     * Function for rotating the round robin counter
     * @return the next value of the counter
     */
    int rotate_counter();
};

#endif //__MEM_HMC_CONTROLLER_HH__