mem: Rename Bus to XBar to better reflect its behaviour

This patch changes the name of the Bus classes to XBar to better
reflect the actual timing behaviour. The actual instances in the
config scripts are not renamed, and remain as e.g. iobus or membus.

As part of this renaming, the code has also been clean up slightly,
making use of range-based for loops and tidying up some comments. The
only changes outside the bus/crossbar code is due to the delay
variables in the packet.

--HG--
rename : src/mem/Bus.py => src/mem/XBar.py
rename : src/mem/coherent_bus.cc => src/mem/coherent_xbar.cc
rename : src/mem/coherent_bus.hh => src/mem/coherent_xbar.hh
rename : src/mem/noncoherent_bus.cc => src/mem/noncoherent_xbar.cc
rename : src/mem/noncoherent_bus.hh => src/mem/noncoherent_xbar.hh
rename : src/mem/bus.cc => src/mem/xbar.cc
rename : src/mem/bus.hh => src/mem/xbar.hh

1 files changed, 397 insertions, 0 deletions

diff --git a/src/mem/coherent_xbar.hh b/src/mem/coherent_xbar.hh
new file mode 100644
index 000000000..fd4dd1cca
--- /dev/null
+++ b/src/mem/coherent_xbar.hh
@@ -0,0 +1,397 @@
+/*
+ * Copyright (c) 2011-2014 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 coherent crossbar.
+ */
+
+#ifndef __MEM_COHERENT_XBAR_HH__
+#define __MEM_COHERENT_XBAR_HH__
+
+#include "base/hashmap.hh"
+#include "mem/snoop_filter.hh"
+#include "mem/xbar.hh"
+#include "params/CoherentXBar.hh"
+
+/**
+ * A coherent crossbar connects a number of (potentially) snooping
+ * masters and slaves, and routes the request and response packets
+ * based on the address, and also forwards all requests to the
+ * snoopers and deals with the snoop responses.
+ *
+ * The coherent crossbar can be used as a template for modelling QPI,
+ * HyperTransport, ACE and coherent OCP buses, and is typically used
+ * for the L1-to-L2 buses and as the main system interconnect.  @sa
+ * \ref gem5MemorySystem "gem5 Memory System"
+ */
+class CoherentXBar : public BaseXBar
+{
+
+  protected:
+
+    /**
+     * Declare the layers of this crossbar, one vector for requests,
+     * one for responses, and one for snoop responses
+     */
+    typedef Layer<SlavePort,MasterPort> ReqLayer;
+    typedef Layer<MasterPort,SlavePort> RespLayer;
+    typedef Layer<SlavePort,MasterPort> SnoopLayer;
+    std::vector<ReqLayer*> reqLayers;
+    std::vector<RespLayer*> respLayers;
+    std::vector<SnoopLayer*> snoopLayers;
+
+    /**
+     * Declaration of the coherent crossbar slave port type, one will
+     * be instantiated for each of the master ports connecting to the
+     * crossbar.
+     */
+    class CoherentXBarSlavePort : public SlavePort
+    {
+
+      private:
+
+        /** A reference to the crossbar to which this port belongs. */
+        CoherentXBar &xbar;
+
+      public:
+
+        CoherentXBarSlavePort(const std::string &_name,
+                             CoherentXBar &_xbar, PortID _id)
+            : SlavePort(_name, &_xbar, _id), xbar(_xbar)
+        { }
+
+      protected:
+
+        /**
+         * When receiving a timing request, pass it to the crossbar.
+         */
+        virtual bool recvTimingReq(PacketPtr pkt)
+        { return xbar.recvTimingReq(pkt, id); }
+
+        /**
+         * When receiving a timing snoop response, pass it to the crossbar.
+         */
+        virtual bool recvTimingSnoopResp(PacketPtr pkt)
+        { return xbar.recvTimingSnoopResp(pkt, id); }
+
+        /**
+         * When receiving an atomic request, pass it to the crossbar.
+         */
+        virtual Tick recvAtomic(PacketPtr pkt)
+        { return xbar.recvAtomic(pkt, id); }
+
+        /**
+         * When receiving a functional request, pass it to the crossbar.
+         */
+        virtual void recvFunctional(PacketPtr pkt)
+        { xbar.recvFunctional(pkt, id); }
+
+        /**
+         * When receiving a retry, pass it to the crossbar.
+         */
+        virtual void recvRetry()
+        { panic("Crossbar slave ports should never retry.\n"); }
+
+        /**
+         * Return the union of all adress ranges seen by this crossbar.
+         */
+        virtual AddrRangeList getAddrRanges() const
+        { return xbar.getAddrRanges(); }
+
+    };
+
+    /**
+     * Declaration of the coherent crossbar master port type, one will be
+     * instantiated for each of the slave interfaces connecting to the
+     * crossbar.
+     */
+    class CoherentXBarMasterPort : public MasterPort
+    {
+      private:
+        /** A reference to the crossbar to which this port belongs. */
+        CoherentXBar &xbar;
+
+      public:
+
+        CoherentXBarMasterPort(const std::string &_name,
+                              CoherentXBar &_xbar, PortID _id)
+            : MasterPort(_name, &_xbar, _id), xbar(_xbar)
+        { }
+
+      protected:
+
+        /**
+         * Determine if this port should be considered a snooper. For
+         * a coherent crossbar master port this is always true.
+         *
+         * @return a boolean that is true if this port is snooping
+         */
+        virtual bool isSnooping() const
+        { return true; }
+
+        /**
+         * When receiving a timing response, pass it to the crossbar.
+         */
+        virtual bool recvTimingResp(PacketPtr pkt)
+        { return xbar.recvTimingResp(pkt, id); }
+
+        /**
+         * When receiving a timing snoop request, pass it to the crossbar.
+         */
+        virtual void recvTimingSnoopReq(PacketPtr pkt)
+        { return xbar.recvTimingSnoopReq(pkt, id); }
+
+        /**
+         * When receiving an atomic snoop request, pass it to the crossbar.
+         */
+        virtual Tick recvAtomicSnoop(PacketPtr pkt)
+        { return xbar.recvAtomicSnoop(pkt, id); }
+
+        /**
+         * When receiving a functional snoop request, pass it to the crossbar.
+         */
+        virtual void recvFunctionalSnoop(PacketPtr pkt)
+        { xbar.recvFunctionalSnoop(pkt, id); }
+
+        /** When reciving a range change from the peer port (at id),
+            pass it to the crossbar. */
+        virtual void recvRangeChange()
+        { xbar.recvRangeChange(id); }
+
+        /** When reciving a retry from the peer port (at id),
+            pass it to the crossbar. */
+        virtual void recvRetry()
+        { xbar.recvRetry(id); }
+
+    };
+
+    /**
+     * Internal class to bridge between an incoming snoop response
+     * from a slave port and forwarding it through an outgoing slave
+     * port. It is effectively a dangling master port.
+     */
+    class SnoopRespPort : public MasterPort
+    {
+
+      private:
+
+        /** The port which we mirror internally. */
+        SlavePort& slavePort;
+
+      public:
+
+        /**
+         * Create a snoop response port that mirrors a given slave port.
+         */
+        SnoopRespPort(SlavePort& slave_port, CoherentXBar& _xbar) :
+            MasterPort(slave_port.name() + ".snoopRespPort", &_xbar),
+            slavePort(slave_port) { }
+
+        /**
+         * Override the sending of retries and pass them on through
+         * the mirrored slave port.
+         */
+        void sendRetry() {
+            slavePort.sendRetry();
+        }
+
+        /**
+         * Provided as necessary.
+         */
+        void recvRetry() { panic("SnoopRespPort should never see retry\n"); }
+
+        /**
+         * Provided as necessary.
+         */
+        bool recvTimingResp(PacketPtr pkt)
+        {
+            panic("SnoopRespPort should never see timing response\n");
+            return false;
+        }
+
+    };
+
+    std::vector<SnoopRespPort*> snoopRespPorts;
+
+    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 crossbar when coherency responses come back.
+     */
+    m5::hash_set<RequestPtr> outstandingReq;
+
+    /**
+     * Keep a pointer to the system to be allow to querying memory system
+     * properties.
+     */
+    System *system;
+
+    /** A snoop filter that tracks cache line residency and can restrict the
+      * broadcast needed for probes.  NULL denotes an absent filter. */
+    SnoopFilter *snoopFilter;
+
+    /** Function called by the port when the crossbar is recieving a Timing
+      request packet.*/
+    bool recvTimingReq(PacketPtr pkt, PortID slave_port_id);
+
+    /** Function called by the port when the crossbar is recieving a Timing
+      response packet.*/
+    bool recvTimingResp(PacketPtr pkt, PortID master_port_id);
+
+    /** Function called by the port when the crossbar is recieving a timing
+        snoop request.*/
+    void recvTimingSnoopReq(PacketPtr pkt, PortID master_port_id);
+
+    /** Function called by the port when the crossbar is recieving a timing
+        snoop response.*/
+    bool recvTimingSnoopResp(PacketPtr pkt, PortID slave_port_id);
+
+    /** Timing function called by port when it is once again able to process
+     * requests. */
+    void recvRetry(PortID master_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) {
+        forwardTiming(pkt, exclude_slave_port_id, snoopPorts);
+    }
+
+    /**
+     * Forward a timing packet to a selected list of 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
+     * @param dests Vector of destination ports for the forwarded pkt
+     */
+    void forwardTiming(PacketPtr pkt, PortID exclude_slave_port_id,
+                       const std::vector<SlavePort*>& dests);
+
+    /** Function called by the port when the crossbar is recieving a Atomic
+      transaction.*/
+    Tick recvAtomic(PacketPtr pkt, PortID slave_port_id);
+
+    /** Function called by the port when the crossbar 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)
+    {
+        return forwardAtomic(pkt, exclude_slave_port_id, InvalidPortID, snoopPorts);
+    }
+
+    /**
+     * Forward an atomic packet to a selected list of 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
+     * @param source_master_port_id Id of the master port for snoops from below
+     * @param dests Vector of destination ports for the forwarded pkt
+     *
+     * @return a pair containing the snoop response and snoop latency
+     */
+    std::pair<MemCmd, Tick> forwardAtomic(PacketPtr pkt,
+                                          PortID exclude_slave_port_id,
+                                          PortID source_master_port_id,
+                                          const std::vector<SlavePort*>& dests);
+
+    /** Function called by the port when the crossbar is recieving a Functional
+        transaction.*/
+    void recvFunctional(PacketPtr pkt, PortID slave_port_id);
+
+    /** Function called by the port when the crossbar 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);
+
+    Stats::Scalar snoops;
+    Stats::Distribution snoopFanout;
+
+  public:
+
+    virtual void init();
+
+    CoherentXBar(const CoherentXBarParams *p);
+
+    virtual ~CoherentXBar();
+
+    unsigned int drain(DrainManager *dm);
+
+    virtual void regStats();
+};
+
+#endif //__MEM_COHERENT_XBAR_HH__