src/mem/xbar.hh

   1 /*
   2  * Copyright (c) 2011-2015 ARM Limited
   3  * All rights reserved
   4  *
   5  * The license below extends only to copyright in the software and shall
   6  * not be construed as granting a license to any other intellectual
   7  * property including but not limited to intellectual property relating
   8  * to a hardware implementation of the functionality of the software
   9  * licensed hereunder.  You may use the software subject to the license
  10  * terms below provided that you ensure that this notice is replicated
  11  * unmodified and in its entirety in all distributions of the software,
  12  * modified or unmodified, in source code or in binary form.
  13  *
  14  * Copyright (c) 2002-2005 The Regents of The University of Michigan
  15  * All rights reserved.
  16  *
  17  * Redistribution and use in source and binary forms, with or without
  18  * modification, are permitted provided that the following conditions are
  19  * met: redistributions of source code must retain the above copyright
  20  * notice, this list of conditions and the following disclaimer;
  21  * redistributions in binary form must reproduce the above copyright
  22  * notice, this list of conditions and the following disclaimer in the
  23  * documentation and/or other materials provided with the distribution;
  24  * neither the name of the copyright holders nor the names of its
  25  * contributors may be used to endorse or promote products derived from
  26  * this software without specific prior written permission.
  27  *
  28  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
  29  * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
  30  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
  31  * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
  32  * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
  33  * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
  34  * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  35  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  36  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  37  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  38  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  39  *
  40  * Authors: Ron Dreslinski
  41  *          Ali Saidi
  42  *          Andreas Hansson
  43  *          William Wang
  44  */
  45
  46 /**
  47  * @file
  48  * Declaration of an abstract crossbar base class.
  49  */
  50
  51 #ifndef __MEM_XBAR_HH__
  52 #define __MEM_XBAR_HH__
  53
  54 #include <deque>
  55 #include <unordered_map>
  56
  57 #include "base/addr_range_map.hh"
  58 #include "base/types.hh"
  59 #include "mem/mem_object.hh"
  60 #include "mem/qport.hh"
  61 #include "params/BaseXBar.hh"
  62 #include "sim/stats.hh"
  63
  64 /**
  65  * The base crossbar contains the common elements of the non-coherent
  66  * and coherent crossbar. It is an abstract class that does not have
  67  * any of the functionality relating to the actual reception and
  68  * transmission of packets, as this is left for the subclasses.
  69  *
  70  * The BaseXBar is responsible for the basic flow control (busy or
  71  * not), the administration of retries, and the address decoding.
  72  */
  73 class BaseXBar : public MemObject
  74 {
  75
  76   protected:
  77
  78     /**
  79      * A layer is an internal crossbar arbitration point with its own
  80      * flow control. Each layer is a converging multiplexer tree. By
  81      * instantiating one layer per destination port (and per packet
  82      * type, i.e. request, response, snoop request and snoop
  83      * response), we model full crossbar structures like AXI, ACE,
  84      * PCIe, etc.
  85      *
  86      * The template parameter, PortClass, indicates the destination
  87      * port type for the layer. The retry list holds either master
  88      * ports or slave ports, depending on the direction of the
  89      * layer. Thus, a request layer has a retry list containing slave
  90      * ports, whereas a response layer holds master ports.
  91      */
  92     template <typename SrcType, typename DstType>
  93     class Layer : public Drainable
  94     {
  95
  96       public:
  97
  98         /**
  99          * Create a layer and give it a name. The layer uses
 100          * the crossbar an event manager.
 101          *
 102          * @param _port destination port the layer converges at
 103          * @param _xbar the crossbar this layer belongs to
 104          * @param _name the layer's name
 105          */
 106         Layer(DstType& _port, BaseXBar& _xbar, const std::string& _name);
 107
 108         /**
 109          * Drain according to the normal semantics, so that the crossbar
 110          * can tell the layer to drain, and pass an event to signal
 111          * back when drained.
 112          *
 113          * @param de drain event to call once drained
 114          *
 115          * @return 1 if busy or waiting to retry, or 0 if idle
 116          */
 117         DrainState drain() override;
 118
 119         /**
 120          * Get the crossbar layer's name
 121          */
 122         const std::string name() const { return xbar.name() + _name; }
 123
 124
 125         /**
 126          * Determine if the layer accepts a packet from a specific
 127          * port. If not, the port in question is also added to the
 128          * retry list. In either case the state of the layer is
 129          * updated accordingly.
 130          *
 131          * @param port Source port presenting the packet
 132          *
 133          * @return True if the layer accepts the packet
 134          */
 135         bool tryTiming(SrcType* src_port);
 136
 137         /**
 138          * Deal with a destination port accepting a packet by potentially
 139          * removing the source port from the retry list (if retrying) and
 140          * occupying the layer accordingly.
 141          *
 142          * @param busy_time Time to spend as a result of a successful send
 143          */
 144         void succeededTiming(Tick busy_time);
 145
 146         /**
 147          * Deal with a destination port not accepting a packet by
 148          * potentially adding the source port to the retry list (if
 149          * not already at the front) and occupying the layer
 150          * accordingly.
 151          *
 152          * @param src_port Source port
 153          * @param busy_time Time to spend as a result of a failed send
 154          */
 155         void failedTiming(SrcType* src_port, Tick busy_time);
 156
 157         /** Occupy the layer until until */
 158         void occupyLayer(Tick until);
 159
 160         /**
 161          * Send a retry to the port at the head of waitingForLayer. The
 162          * caller must ensure that the list is not empty.
 163          */
 164         void retryWaiting();
 165
 166         /**
 167          * Handle a retry from a neighbouring module. This wraps
 168          * retryWaiting by verifying that there are ports waiting
 169          * before calling retryWaiting.
 170          */
 171         void recvRetry();
 172
 173         /**
 174          * Register stats for the layer
 175          */
 176         void regStats();
 177
 178       protected:
 179
 180         /**
 181          * Sending the actual retry, in a manner specific to the
 182          * individual layers. Note that for a MasterPort, there is
 183          * both a RequestLayer and a SnoopResponseLayer using the same
 184          * port, but using different functions for the flow control.
 185          */
 186         virtual void sendRetry(SrcType* retry_port) = 0;
 187
 188       private:
 189
 190         /** The destination port this layer converges at. */
 191         DstType& port;
 192
 193         /** The crossbar this layer is a part of. */
 194         BaseXBar& xbar;
 195
 196         /** A name for this layer. */
 197         std::string _name;
 198
 199         /**
 200          * We declare an enum to track the state of the layer. The
 201          * starting point is an idle state where the layer is waiting
 202          * for a packet to arrive. Upon arrival, the layer
 203          * transitions to the busy state, where it remains either
 204          * until the packet transfer is done, or the header time is
 205          * spent. Once the layer leaves the busy state, it can
 206          * either go back to idle, if no packets have arrived while it
 207          * was busy, or the layer goes on to retry the first port
 208          * in waitingForLayer. A similar transition takes place from
 209          * idle to retry if the layer receives a retry from one of
 210          * its connected ports. The retry state lasts until the port
 211          * in questions calls sendTiming and returns control to the
 212          * layer, or goes to a busy state if the port does not
 213          * immediately react to the retry by calling sendTiming.
 214          */
 215         enum State { IDLE, BUSY, RETRY };
 216
 217         /** track the state of the layer */
 218         State state;
 219
 220         /**
 221          * A deque of ports that retry should be called on because
 222          * the original send was delayed due to a busy layer.
 223          */
 224         std::deque<SrcType*> waitingForLayer;
 225
 226         /**
 227          * Track who is waiting for the retry when receiving it from a
 228          * peer. If no port is waiting NULL is stored.
 229          */
 230         SrcType* waitingForPeer;
 231
 232         /**
 233          * Release the layer after being occupied and return to an
 234          * idle state where we proceed to send a retry to any
 235          * potential waiting port, or drain if asked to do so.
 236          */
 237         void releaseLayer();
 238
 239         /** event used to schedule a release of the layer */
 240         EventFunctionWrapper releaseEvent;
 241
 242         /**
 243          * Stats for occupancy and utilization. These stats capture
 244          * the time the layer spends in the busy state and are thus only
 245          * relevant when the memory system is in timing mode.
 246          */
 247         Stats::Scalar occupancy;
 248         Stats::Formula utilization;
 249
 250     };
 251
 252     class ReqLayer : public Layer<SlavePort,MasterPort>
 253     {
 254       public:
 255         /**
 256          * Create a request layer and give it a name.
 257          *
 258          * @param _port destination port the layer converges at
 259          * @param _xbar the crossbar this layer belongs to
 260          * @param _name the layer's name
 261          */
 262         ReqLayer(MasterPort& _port, BaseXBar& _xbar, const std::string& _name) :
 263             Layer(_port, _xbar, _name) {}
 264
 265       protected:
 266
 267         void sendRetry(SlavePort* retry_port)
 268         { retry_port->sendRetryReq(); }
 269     };
 270
 271     class RespLayer : public Layer<MasterPort,SlavePort>
 272     {
 273       public:
 274         /**
 275          * Create a response layer and give it a name.
 276          *
 277          * @param _port destination port the layer converges at
 278          * @param _xbar the crossbar this layer belongs to
 279          * @param _name the layer's name
 280          */
 281         RespLayer(SlavePort& _port, BaseXBar& _xbar, const std::string& _name) :
 282             Layer(_port, _xbar, _name) {}
 283
 284       protected:
 285
 286         void sendRetry(MasterPort* retry_port)
 287         { retry_port->sendRetryResp(); }
 288     };
 289
 290     class SnoopRespLayer : public Layer<SlavePort,MasterPort>
 291     {
 292       public:
 293         /**
 294          * Create a snoop response layer and give it a name.
 295          *
 296          * @param _port destination port the layer converges at
 297          * @param _xbar the crossbar this layer belongs to
 298          * @param _name the layer's name
 299          */
 300         SnoopRespLayer(MasterPort& _port, BaseXBar& _xbar,
 301                        const std::string& _name) :
 302             Layer(_port, _xbar, _name) {}
 303
 304       protected:
 305
 306         void sendRetry(SlavePort* retry_port)
 307         { retry_port->sendRetrySnoopResp(); }
 308     };
 309
 310     /**
 311      * Cycles of front-end pipeline including the delay to accept the request
 312      * and to decode the address.
 313      */
 314     const Cycles frontendLatency;
 315     /** Cycles of forward latency */
 316     const Cycles forwardLatency;
 317     /** Cycles of response latency */
 318     const Cycles responseLatency;
 319     /** the width of the xbar in bytes */
 320     const uint32_t width;
 321
 322     AddrRangeMap<PortID, 3> portMap;
 323
 324     /**
 325      * Remember where request packets came from so that we can route
 326      * responses to the appropriate port. This relies on the fact that
 327      * the underlying Request pointer inside the Packet stays
 328      * constant.
 329      */
 330     std::unordered_map<RequestPtr, PortID> routeTo;
 331
 332     /** all contigous ranges seen by this crossbar */
 333     AddrRangeList xbarRanges;
 334
 335     AddrRange defaultRange;
 336
 337     /**
 338      * Function called by the port when the crossbar is recieving a
 339      * range change.
 340      *
 341      * @param master_port_id id of the port that received the change
 342      */
 343     virtual void recvRangeChange(PortID master_port_id);
 344
 345     /** Find which port connected to this crossbar (if any) should be
 346      * given a packet with this address.
 347      *
 348      * @param addr Address to find port for.
 349      * @return id of port that the packet should be sent out of.
 350      */
 351     PortID findPort(Addr addr);
 352
 353     /**
 354      * Return the address ranges the crossbar is responsible for.
 355      *
 356      * @return a list of non-overlapping address ranges
 357      */
 358     AddrRangeList getAddrRanges() const;
 359
 360     /**
 361      * Calculate the timing parameters for the packet. Updates the
 362      * headerDelay and payloadDelay fields of the packet
 363      * object with the relative number of ticks required to transmit
 364      * the header and the payload, respectively.
 365      *
 366      * @param pkt Packet to populate with timings
 367      * @param header_delay Header delay to be added
 368      */
 369     void calcPacketTiming(PacketPtr pkt, Tick header_delay);
 370
 371     /**
 372      * Remember for each of the master ports of the crossbar if we got
 373      * an address range from the connected slave. For convenience,
 374      * also keep track of if we got ranges from all the slave modules
 375      * or not.
 376      */
 377     std::vector<bool> gotAddrRanges;
 378     bool gotAllAddrRanges;
 379
 380     /** The master and slave ports of the crossbar */
 381     std::vector<QueuedSlavePort*> slavePorts;
 382     std::vector<MasterPort*> masterPorts;
 383
 384     /** Port that handles requests that don't match any of the interfaces.*/
 385     PortID defaultPortID;
 386
 387     /** If true, use address range provided by default device.  Any
 388        address not handled by another port and not in default device's
 389        range will cause a fatal error.  If false, just send all
 390        addresses not handled by another port to default device. */
 391     const bool useDefaultRange;
 392
 393     BaseXBar(const BaseXBarParams *p);
 394
 395     /**
 396      * Stats for transaction distribution and data passing through the
 397      * crossbar. The transaction distribution is globally counting
 398      * different types of commands. The packet count and total packet
 399      * size are two-dimensional vectors that are indexed by the
 400      * slave port and master port id (thus the neighbouring master and
 401      * neighbouring slave), summing up both directions (request and
 402      * response).
 403      */
 404     Stats::Vector transDist;
 405     Stats::Vector2d pktCount;
 406     Stats::Vector2d pktSize;
 407
 408   public:
 409
 410     virtual ~BaseXBar();
 411
 412     virtual void init();
 413
 414     /** A function used to return the port associated with this object. */
 415     BaseMasterPort& getMasterPort(const std::string& if_name,
 416                                   PortID idx = InvalidPortID);
 417     BaseSlavePort& getSlavePort(const std::string& if_name,
 418                                 PortID idx = InvalidPortID);
 419
 420     virtual void regStats();
 421
 422 };
 423
 424 #endif //__MEM_XBAR_HH__