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
  56 #include "base/addr_range_map.hh"
  57 #include "base/hashmap.hh"
  58 #include "base/types.hh"
  59 #include "mem/mem_object.hh"
  60 #include "params/BaseXBar.hh"
  61 #include "sim/stats.hh"
  62
  63 /**
  64  * The base crossbar contains the common elements of the non-coherent
  65  * and coherent crossbar. It is an abstract class that does not have
  66  * any of the functionality relating to the actual reception and
  67  * transmission of packets, as this is left for the subclasses.
  68  *
  69  * The BaseXBar is responsible for the basic flow control (busy or
  70  * not), the administration of retries, and the address decoding.
  71  */
  72 class BaseXBar : public MemObject
  73 {
  74
  75   protected:
  76
  77     /**
  78      * A layer is an internal crossbar arbitration point with its own
  79      * flow control. Each layer is a converging multiplexer tree. By
  80      * instantiating one layer per destination port (and per packet
  81      * type, i.e. request, response, snoop request and snoop
  82      * response), we model full crossbar structures like AXI, ACE,
  83      * PCIe, etc.
  84      *
  85      * The template parameter, PortClass, indicates the destination
  86      * port type for the layer. The retry list holds either master
  87      * ports or slave ports, depending on the direction of the
  88      * layer. Thus, a request layer has a retry list containing slave
  89      * ports, whereas a response layer holds master ports.
  90      */
  91     template <typename SrcType, typename DstType>
  92     class Layer : public Drainable
  93     {
  94
  95       public:
  96
  97         /**
  98          * Create a layer and give it a name. The layer uses
  99          * the crossbar an event manager.
 100          *
 101          * @param _port destination port the layer converges at
 102          * @param _xbar the crossbar this layer belongs to
 103          * @param _name the layer's name
 104          */
 105         Layer(DstType& _port, BaseXBar& _xbar, const std::string& _name);
 106
 107         /**
 108          * Drain according to the normal semantics, so that the crossbar
 109          * can tell the layer to drain, and pass an event to signal
 110          * back when drained.
 111          *
 112          * @param de drain event to call once drained
 113          *
 114          * @return 1 if busy or waiting to retry, or 0 if idle
 115          */
 116         unsigned int drain(DrainManager *dm);
 117
 118         /**
 119          * Get the crossbar layer's name
 120          */
 121         const std::string name() const { return xbar.name() + _name; }
 122
 123
 124         /**
 125          * Determine if the layer accepts a packet from a specific
 126          * port. If not, the port in question is also added to the
 127          * retry list. In either case the state of the layer is
 128          * updated accordingly.
 129          *
 130          * @param port Source port presenting the packet
 131          *
 132          * @return True if the layer accepts the packet
 133          */
 134         bool tryTiming(SrcType* src_port);
 135
 136         /**
 137          * Deal with a destination port accepting a packet by potentially
 138          * removing the source port from the retry list (if retrying) and
 139          * occupying the layer accordingly.
 140          *
 141          * @param busy_time Time to spend as a result of a successful send
 142          */
 143         void succeededTiming(Tick busy_time);
 144
 145         /**
 146          * Deal with a destination port not accepting a packet by
 147          * potentially adding the source port to the retry list (if
 148          * not already at the front) and occupying the layer
 149          * accordingly.
 150          *
 151          * @param src_port Source port
 152          * @param busy_time Time to spend as a result of a failed send
 153          */
 154         void failedTiming(SrcType* src_port, Tick busy_time);
 155
 156         /** Occupy the layer until until */
 157         void occupyLayer(Tick until);
 158
 159         /**
 160          * Send a retry to the port at the head of waitingForLayer. The
 161          * caller must ensure that the list is not empty.
 162          */
 163         void retryWaiting();
 164
 165         /**
 166          * Handle a retry from a neighbouring module. This wraps
 167          * retryWaiting by verifying that there are ports waiting
 168          * before calling retryWaiting.
 169          */
 170         void recvRetry();
 171
 172         /**
 173          * Register stats for the layer
 174          */
 175         void regStats();
 176
 177       protected:
 178
 179         /**
 180          * Sending the actual retry, in a manner specific to the
 181          * individual layers. Note that for a MasterPort, there is
 182          * both a RequestLayer and a SnoopResponseLayer using the same
 183          * port, but using different functions for the flow control.
 184          */
 185         virtual void sendRetry(SrcType* retry_port) = 0;
 186
 187       private:
 188
 189         /** The destination port this layer converges at. */
 190         DstType& port;
 191
 192         /** The crossbar this layer is a part of. */
 193         BaseXBar& xbar;
 194
 195         /** A name for this layer. */
 196         std::string _name;
 197
 198         /**
 199          * We declare an enum to track the state of the layer. The
 200          * starting point is an idle state where the layer is waiting
 201          * for a packet to arrive. Upon arrival, the layer
 202          * transitions to the busy state, where it remains either
 203          * until the packet transfer is done, or the header time is
 204          * spent. Once the layer leaves the busy state, it can
 205          * either go back to idle, if no packets have arrived while it
 206          * was busy, or the layer goes on to retry the first port
 207          * in waitingForLayer. A similar transition takes place from
 208          * idle to retry if the layer receives a retry from one of
 209          * its connected ports. The retry state lasts until the port
 210          * in questions calls sendTiming and returns control to the
 211          * layer, or goes to a busy state if the port does not
 212          * immediately react to the retry by calling sendTiming.
 213          */
 214         enum State { IDLE, BUSY, RETRY };
 215
 216         /** track the state of the layer */
 217         State state;
 218
 219         /** manager to signal when drained */
 220         DrainManager *drainManager;
 221
 222         /**
 223          * A deque of ports that retry should be called on because
 224          * the original send was delayed due to a busy layer.
 225          */
 226         std::deque<SrcType*> waitingForLayer;
 227
 228         /**
 229          * Track who is waiting for the retry when receiving it from a
 230          * peer. If no port is waiting NULL is stored.
 231          */
 232         SrcType* waitingForPeer;
 233
 234         /**
 235          * Release the layer after being occupied and return to an
 236          * idle state where we proceed to send a retry to any
 237          * potential waiting port, or drain if asked to do so.
 238          */
 239         void releaseLayer();
 240
 241         /** event used to schedule a release of the layer */
 242         EventWrapper<Layer, &Layer::releaseLayer> releaseEvent;
 243
 244         /**
 245          * Stats for occupancy and utilization. These stats capture
 246          * the time the layer spends in the busy state and are thus only
 247          * relevant when the memory system is in timing mode.
 248          */
 249         Stats::Scalar occupancy;
 250         Stats::Formula utilization;
 251
 252     };
 253
 254     class ReqLayer : public Layer<SlavePort,MasterPort>
 255     {
 256       public:
 257         /**
 258          * Create a request layer and give it a name.
 259          *
 260          * @param _port destination port the layer converges at
 261          * @param _xbar the crossbar this layer belongs to
 262          * @param _name the layer's name
 263          */
 264         ReqLayer(MasterPort& _port, BaseXBar& _xbar, const std::string& _name) :
 265             Layer(_port, _xbar, _name) {}
 266
 267       protected:
 268
 269         void sendRetry(SlavePort* retry_port)
 270         { retry_port->sendRetryReq(); }
 271     };
 272
 273     class RespLayer : public Layer<MasterPort,SlavePort>
 274     {
 275       public:
 276         /**
 277          * Create a response layer and give it a name.
 278          *
 279          * @param _port destination port the layer converges at
 280          * @param _xbar the crossbar this layer belongs to
 281          * @param _name the layer's name
 282          */
 283         RespLayer(SlavePort& _port, BaseXBar& _xbar, const std::string& _name) :
 284             Layer(_port, _xbar, _name) {}
 285
 286       protected:
 287
 288         void sendRetry(MasterPort* retry_port)
 289         { retry_port->sendRetryResp(); }
 290     };
 291
 292     class SnoopRespLayer : public Layer<SlavePort,MasterPort>
 293     {
 294       public:
 295         /**
 296          * Create a snoop response layer and give it a name.
 297          *
 298          * @param _port destination port the layer converges at
 299          * @param _xbar the crossbar this layer belongs to
 300          * @param _name the layer's name
 301          */
 302         SnoopRespLayer(MasterPort& _port, BaseXBar& _xbar,
 303                        const std::string& _name) :
 304             Layer(_port, _xbar, _name) {}
 305
 306       protected:
 307
 308         void sendRetry(SlavePort* retry_port)
 309         { retry_port->sendRetrySnoopResp(); }
 310     };
 311
 312     /**
 313      * Cycles of front-end pipeline including the delay to accept the request
 314      * and to decode the address.
 315      */
 316     const Cycles frontendLatency;
 317     /** Cycles of forward latency */
 318     const Cycles forwardLatency;
 319     /** Cycles of response latency */
 320     const Cycles responseLatency;
 321     /** the width of the xbar in bytes */
 322     const uint32_t width;
 323
 324     AddrRangeMap<PortID> portMap;
 325
 326     /**
 327      * Remember where request packets came from so that we can route
 328      * responses to the appropriate port. This relies on the fact that
 329      * the underlying Request pointer inside the Packet stays
 330      * constant.
 331      */
 332     m5::unordered_map<RequestPtr, PortID> routeTo;
 333
 334     /** all contigous ranges seen by this crossbar */
 335     AddrRangeList xbarRanges;
 336
 337     AddrRange defaultRange;
 338
 339     /**
 340      * Function called by the port when the crossbar is recieving a
 341      * range change.
 342      *
 343      * @param master_port_id id of the port that received the change
 344      */
 345     void recvRangeChange(PortID master_port_id);
 346
 347     /** Find which port connected to this crossbar (if any) should be
 348      * given a packet with this address.
 349      *
 350      * @param addr Address to find port for.
 351      * @return id of port that the packet should be sent out of.
 352      */
 353     PortID findPort(Addr addr);
 354
 355     // Cache for the findPort function storing recently used ports from portMap
 356     struct PortCache {
 357         bool valid;
 358         PortID id;
 359         AddrRange range;
 360     };
 361
 362     PortCache portCache[3];
 363
 364     // Checks the cache and returns the id of the port that has the requested
 365     // address within its range
 366     inline PortID checkPortCache(Addr addr) const {
 367         if (portCache[0].valid && portCache[0].range.contains(addr)) {
 368             return portCache[0].id;
 369         }
 370         if (portCache[1].valid && portCache[1].range.contains(addr)) {
 371             return portCache[1].id;
 372         }
 373         if (portCache[2].valid && portCache[2].range.contains(addr)) {
 374             return portCache[2].id;
 375         }
 376
 377         return InvalidPortID;
 378     }
 379
 380     // Clears the earliest entry of the cache and inserts a new port entry
 381     inline void updatePortCache(short id, const AddrRange& range) {
 382         portCache[2].valid = portCache[1].valid;
 383         portCache[2].id    = portCache[1].id;
 384         portCache[2].range = portCache[1].range;
 385
 386         portCache[1].valid = portCache[0].valid;
 387         portCache[1].id    = portCache[0].id;
 388         portCache[1].range = portCache[0].range;
 389
 390         portCache[0].valid = true;
 391         portCache[0].id    = id;
 392         portCache[0].range = range;
 393     }
 394
 395     // Clears the cache. Needs to be called in constructor.
 396     inline void clearPortCache() {
 397         portCache[2].valid = false;
 398         portCache[1].valid = false;
 399         portCache[0].valid = false;
 400     }
 401
 402     /**
 403      * Return the address ranges the crossbar is responsible for.
 404      *
 405      * @return a list of non-overlapping address ranges
 406      */
 407     AddrRangeList getAddrRanges() const;
 408
 409     /**
 410      * Calculate the timing parameters for the packet. Updates the
 411      * headerDelay and payloadDelay fields of the packet
 412      * object with the relative number of ticks required to transmit
 413      * the header and the payload, respectively.
 414      *
 415      * @param pkt Packet to populate with timings
 416      * @param header_delay Header delay to be added
 417      */
 418     void calcPacketTiming(PacketPtr pkt, Tick header_delay);
 419
 420     /**
 421      * Remember for each of the master ports of the crossbar if we got
 422      * an address range from the connected slave. For convenience,
 423      * also keep track of if we got ranges from all the slave modules
 424      * or not.
 425      */
 426     std::vector<bool> gotAddrRanges;
 427     bool gotAllAddrRanges;
 428
 429     /** The master and slave ports of the crossbar */
 430     std::vector<SlavePort*> slavePorts;
 431     std::vector<MasterPort*> masterPorts;
 432
 433     /** Port that handles requests that don't match any of the interfaces.*/
 434     PortID defaultPortID;
 435
 436     /** If true, use address range provided by default device.  Any
 437        address not handled by another port and not in default device's
 438        range will cause a fatal error.  If false, just send all
 439        addresses not handled by another port to default device. */
 440     const bool useDefaultRange;
 441
 442     BaseXBar(const BaseXBarParams *p);
 443
 444     virtual ~BaseXBar();
 445
 446     /**
 447      * Stats for transaction distribution and data passing through the
 448      * crossbar. The transaction distribution is globally counting
 449      * different types of commands. The packet count and total packet
 450      * size are two-dimensional vectors that are indexed by the
 451      * slave port and master port id (thus the neighbouring master and
 452      * neighbouring slave), summing up both directions (request and
 453      * response).
 454      */
 455     Stats::Vector transDist;
 456     Stats::Vector2d pktCount;
 457     Stats::Vector2d pktSize;
 458
 459   public:
 460
 461     virtual void init();
 462
 463     /** A function used to return the port associated with this object. */
 464     BaseMasterPort& getMasterPort(const std::string& if_name,
 465                                   PortID idx = InvalidPortID);
 466     BaseSlavePort& getSlavePort(const std::string& if_name,
 467                                 PortID idx = InvalidPortID);
 468
 469     virtual unsigned int drain(DrainManager *dm) = 0;
 470
 471     virtual void regStats();
 472
 473 };
 474
 475 #endif //__MEM_XBAR_HH__