src/mem/noncoherent_xbar.hh

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/**
 * @file
 * Declaration of a non-coherent crossbar.
 */

#ifndef __MEM_NONCOHERENT_XBAR_HH__
#define __MEM_NONCOHERENT_XBAR_HH__

#include "mem/xbar.hh"
#include "params/NoncoherentXBar.hh"

namespace gem5
{

/**
 * A non-coherent crossbar connects a number of non-snooping memory-side ports
 * and cpu_sides, and routes the request and response packets based on
 * the address. The request packets issued by the memory-side port connected to
 * a non-coherent crossbar could still snoop in caches attached to a
 * coherent crossbar, as is the case with the I/O bus and memory bus
 * in most system configurations. No snoops will, however, reach any
 * memory-side port on the non-coherent crossbar itself.
 *
 * The non-coherent crossbar can be used as a template for modelling
 * PCIe, and non-coherent AMBA and OCP buses, and is typically used
 * for the I/O buses.
 */
class NoncoherentXBar : public BaseXBar
{

  protected:

    /**
     * Declare the layers of this crossbar, one vector for requests
     * and one for responses.
     */
    std::vector<ReqLayer*> reqLayers;
    std::vector<RespLayer*> respLayers;

    /**
     * Declaration of the non-coherent crossbar CPU-side port type, one
     * will be instantiated for each of the memory-side ports connecting to
     * the crossbar.
     */
    class NoncoherentXBarResponsePort : public QueuedResponsePort
    {
      private:

        /** A reference to the crossbar to which this port belongs. */
        NoncoherentXBar &xbar;

        /** A normal packet queue used to store responses. */
        RespPacketQueue queue;

      public:

        NoncoherentXBarResponsePort(const std::string &_name,
                                NoncoherentXBar &_xbar, PortID _id)
            : QueuedResponsePort(_name, &_xbar, queue, _id), xbar(_xbar),
              queue(_xbar, *this)
        { }

      protected:

        bool
        recvTimingReq(PacketPtr pkt) override
        {
            return xbar.recvTimingReq(pkt, id);
        }

        Tick
        recvAtomic(PacketPtr pkt) override
        {
            return xbar.recvAtomicBackdoor(pkt, id);
        }

        Tick
        recvAtomicBackdoor(PacketPtr pkt, MemBackdoorPtr &backdoor) override
        {
            return xbar.recvAtomicBackdoor(pkt, id, &backdoor);
        }

        void
        recvFunctional(PacketPtr pkt) override
        {
            xbar.recvFunctional(pkt, id);
        }

        AddrRangeList
        getAddrRanges() const override
        {
            return xbar.getAddrRanges();
        }
    };

    /**
     * Declaration of the crossbar memory-side port type, one will be
     * instantiated for each of the CPU-side ports connecting to the
     * crossbar.
     */
    class NoncoherentXBarRequestPort : public RequestPort
    {
      private:

        /** A reference to the crossbar to which this port belongs. */
        NoncoherentXBar &xbar;

      public:

        NoncoherentXBarRequestPort(const std::string &_name,
                                 NoncoherentXBar &_xbar, PortID _id)
            : RequestPort(_name, &_xbar, _id), xbar(_xbar)
        { }

      protected:

        bool
        recvTimingResp(PacketPtr pkt) override
        {
            return xbar.recvTimingResp(pkt, id);
        }

        void
        recvRangeChange() override
        {
            xbar.recvRangeChange(id);
        }

        void
        recvReqRetry() override
        {
            xbar.recvReqRetry(id);
        }
    };

    virtual bool recvTimingReq(PacketPtr pkt, PortID cpu_side_port_id);
    virtual bool recvTimingResp(PacketPtr pkt, PortID mem_side_port_id);
    void recvReqRetry(PortID mem_side_port_id);
    Tick recvAtomicBackdoor(PacketPtr pkt, PortID cpu_side_port_id,
                            MemBackdoorPtr *backdoor=nullptr);
    void recvFunctional(PacketPtr pkt, PortID cpu_side_port_id);

  public:

    NoncoherentXBar(const NoncoherentXBarParams &p);

    virtual ~NoncoherentXBar();
};

} // namespace gem5

#endif //__MEM_NONCOHERENT_XBAR_HH__