src/mem/xbar.hh

   1 /*
   2  * Copyright (c) 2011-2014 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/types.hh"
  58 #include "mem/mem_object.hh"
  59 #include "params/BaseXBar.hh"
  60 #include "sim/stats.hh"
  61
  62 /**
  63  * The base crossbar contains the common elements of the non-coherent
  64  * and coherent crossbar. It is an abstract class that does not have
  65  * any of the functionality relating to the actual reception and
  66  * transmission of packets, as this is left for the subclasses.
  67  *
  68  * The BaseXBar is responsible for the basic flow control (busy or
  69  * not), the administration of retries, and the address decoding.
  70  */
  71 class BaseXBar : public MemObject
  72 {
  73
  74   protected:
  75
  76     /**
  77      * A layer is an internal crossbar arbitration point with its own
  78      * flow control. Each layer is a converging multiplexer tree. By
  79      * instantiating one layer per destination port (and per packet
  80      * type, i.e. request, response, snoop request and snoop
  81      * response), we model full crossbar structures like AXI, ACE,
  82      * PCIe, etc.
  83      *
  84      * The template parameter, PortClass, indicates the destination
  85      * port type for the layer. The retry list holds either master
  86      * ports or slave ports, depending on the direction of the
  87      * layer. Thus, a request layer has a retry list containing slave
  88      * ports, whereas a response layer holds master ports.
  89      */
  90     template <typename SrcType, typename DstType>
  91     class Layer : public Drainable
  92     {
  93
  94       public:
  95
  96         /**
  97          * Create a layer and give it a name. The layer uses
  98          * the crossbar an event manager.
  99          *
 100          * @param _port destination port the layer converges at
 101          * @param _xbar the crossbar this layer belongs to
 102          * @param _name the layer's name
 103          */
 104         Layer(DstType& _port, BaseXBar& _xbar, const std::string& _name);
 105
 106         /**
 107          * Drain according to the normal semantics, so that the crossbar
 108          * can tell the layer to drain, and pass an event to signal
 109          * back when drained.
 110          *
 111          * @param de drain event to call once drained
 112          *
 113          * @return 1 if busy or waiting to retry, or 0 if idle
 114          */
 115         unsigned int drain(DrainManager *dm);
 116
 117         /**
 118          * Get the crossbar layer's name
 119          */
 120         const std::string name() const { return xbar.name() + _name; }
 121
 122
 123         /**
 124          * Determine if the layer accepts a packet from a specific
 125          * port. If not, the port in question is also added to the
 126          * retry list. In either case the state of the layer is
 127          * updated accordingly.
 128          *
 129          * @param port Source port presenting the packet
 130          *
 131          * @return True if the layer accepts the packet
 132          */
 133         bool tryTiming(SrcType* src_port);
 134
 135         /**
 136          * Deal with a destination port accepting a packet by potentially
 137          * removing the source port from the retry list (if retrying) and
 138          * occupying the layer accordingly.
 139          *
 140          * @param busy_time Time to spend as a result of a successful send
 141          */
 142         void succeededTiming(Tick busy_time);
 143
 144         /**
 145          * Deal with a destination port not accepting a packet by
 146          * potentially adding the source port to the retry list (if
 147          * not already at the front) and occupying the layer
 148          * accordingly.
 149          *
 150          * @param src_port Source port
 151          * @param busy_time Time to spend as a result of a failed send
 152          */
 153         void failedTiming(SrcType* src_port, Tick busy_time);
 154
 155         /** Occupy the layer until until */
 156         void occupyLayer(Tick until);
 157
 158         /**
 159          * Send a retry to the port at the head of waitingForLayer. The
 160          * caller must ensure that the list is not empty.
 161          */
 162         void retryWaiting();
 163
 164         /**
 165          * Handle a retry from a neighbouring module. This wraps
 166          * retryWaiting by verifying that there are ports waiting
 167          * before calling retryWaiting.
 168          */
 169         void recvRetry();
 170
 171         /**
 172          * Register stats for the layer
 173          */
 174         void regStats();
 175
 176       private:
 177
 178         /** The destination port this layer converges at. */
 179         DstType& port;
 180
 181         /** The crossbar this layer is a part of. */
 182         BaseXBar& xbar;
 183
 184         /** A name for this layer. */
 185         std::string _name;
 186
 187         /**
 188          * We declare an enum to track the state of the layer. The
 189          * starting point is an idle state where the layer is waiting
 190          * for a packet to arrive. Upon arrival, the layer
 191          * transitions to the busy state, where it remains either
 192          * until the packet transfer is done, or the header time is
 193          * spent. Once the layer leaves the busy state, it can
 194          * either go back to idle, if no packets have arrived while it
 195          * was busy, or the layer goes on to retry the first port
 196          * in waitingForLayer. A similar transition takes place from
 197          * idle to retry if the layer receives a retry from one of
 198          * its connected ports. The retry state lasts until the port
 199          * in questions calls sendTiming and returns control to the
 200          * layer, or goes to a busy state if the port does not
 201          * immediately react to the retry by calling sendTiming.
 202          */
 203         enum State { IDLE, BUSY, RETRY };
 204
 205         /** track the state of the layer */
 206         State state;
 207
 208         /** manager to signal when drained */
 209         DrainManager *drainManager;
 210
 211         /**
 212          * A deque of ports that retry should be called on because
 213          * the original send was delayed due to a busy layer.
 214          */
 215         std::deque<SrcType*> waitingForLayer;
 216
 217         /**
 218          * Track who is waiting for the retry when receiving it from a
 219          * peer. If no port is waiting NULL is stored.
 220          */
 221         SrcType* waitingForPeer;
 222
 223         /**
 224          * Release the layer after being occupied and return to an
 225          * idle state where we proceed to send a retry to any
 226          * potential waiting port, or drain if asked to do so.
 227          */
 228         void releaseLayer();
 229
 230         /** event used to schedule a release of the layer */
 231         EventWrapper<Layer, &Layer::releaseLayer> releaseEvent;
 232
 233         /**
 234          * Stats for occupancy and utilization. These stats capture
 235          * the time the layer spends in the busy state and are thus only
 236          * relevant when the memory system is in timing mode.
 237          */
 238         Stats::Scalar occupancy;
 239         Stats::Formula utilization;
 240
 241     };
 242
 243     /** cycles of overhead per transaction */
 244     const Cycles headerCycles;
 245     /** the width of the xbar in bytes */
 246     const uint32_t width;
 247
 248     AddrRangeMap<PortID> portMap;
 249
 250     /** all contigous ranges seen by this crossbar */
 251     AddrRangeList xbarRanges;
 252
 253     AddrRange defaultRange;
 254
 255     /**
 256      * Function called by the port when the crossbar is recieving a
 257      * range change.
 258      *
 259      * @param master_port_id id of the port that received the change
 260      */
 261     void recvRangeChange(PortID master_port_id);
 262
 263     /** Find which port connected to this crossbar (if any) should be
 264      * given a packet with this address.
 265      *
 266      * @param addr Address to find port for.
 267      * @return id of port that the packet should be sent out of.
 268      */
 269     PortID findPort(Addr addr);
 270
 271     // Cache for the findPort function storing recently used ports from portMap
 272     struct PortCache {
 273         bool valid;
 274         PortID id;
 275         AddrRange range;
 276     };
 277
 278     PortCache portCache[3];
 279
 280     // Checks the cache and returns the id of the port that has the requested
 281     // address within its range
 282     inline PortID checkPortCache(Addr addr) const {
 283         if (portCache[0].valid && portCache[0].range.contains(addr)) {
 284             return portCache[0].id;
 285         }
 286         if (portCache[1].valid && portCache[1].range.contains(addr)) {
 287             return portCache[1].id;
 288         }
 289         if (portCache[2].valid && portCache[2].range.contains(addr)) {
 290             return portCache[2].id;
 291         }
 292
 293         return InvalidPortID;
 294     }
 295
 296     // Clears the earliest entry of the cache and inserts a new port entry
 297     inline void updatePortCache(short id, const AddrRange& range) {
 298         portCache[2].valid = portCache[1].valid;
 299         portCache[2].id    = portCache[1].id;
 300         portCache[2].range = portCache[1].range;
 301
 302         portCache[1].valid = portCache[0].valid;
 303         portCache[1].id    = portCache[0].id;
 304         portCache[1].range = portCache[0].range;
 305
 306         portCache[0].valid = true;
 307         portCache[0].id    = id;
 308         portCache[0].range = range;
 309     }
 310
 311     // Clears the cache. Needs to be called in constructor.
 312     inline void clearPortCache() {
 313         portCache[2].valid = false;
 314         portCache[1].valid = false;
 315         portCache[0].valid = false;
 316     }
 317
 318     /**
 319      * Return the address ranges the crossbar is responsible for.
 320      *
 321      * @return a list of non-overlapping address ranges
 322      */
 323     AddrRangeList getAddrRanges() const;
 324
 325     /**
 326      * Calculate the timing parameters for the packet. Updates the
 327      * firstWordDelay and lastWordDelay fields of the packet
 328      * object with the relative number of ticks required to transmit
 329      * the header and the first word, and the last word, respectively.
 330      */
 331     void calcPacketTiming(PacketPtr pkt);
 332
 333     /**
 334      * Remember for each of the master ports of the crossbar if we got
 335      * an address range from the connected slave. For convenience,
 336      * also keep track of if we got ranges from all the slave modules
 337      * or not.
 338      */
 339     std::vector<bool> gotAddrRanges;
 340     bool gotAllAddrRanges;
 341
 342     /** The master and slave ports of the crossbar */
 343     std::vector<SlavePort*> slavePorts;
 344     std::vector<MasterPort*> masterPorts;
 345
 346     /** Port that handles requests that don't match any of the interfaces.*/
 347     PortID defaultPortID;
 348
 349     /** If true, use address range provided by default device.  Any
 350        address not handled by another port and not in default device's
 351        range will cause a fatal error.  If false, just send all
 352        addresses not handled by another port to default device. */
 353     const bool useDefaultRange;
 354
 355     BaseXBar(const BaseXBarParams *p);
 356
 357     virtual ~BaseXBar();
 358
 359     /**
 360      * Stats for transaction distribution and data passing through the
 361      * crossbar. The transaction distribution is globally counting
 362      * different types of commands. The packet count and total packet
 363      * size are two-dimensional vectors that are indexed by the
 364      * slave port and master port id (thus the neighbouring master and
 365      * neighbouring slave), summing up both directions (request and
 366      * response).
 367      */
 368     Stats::Vector transDist;
 369     Stats::Vector2d pktCount;
 370     Stats::Vector2d pktSize;
 371
 372   public:
 373
 374     virtual void init();
 375
 376     /** A function used to return the port associated with this object. */
 377     BaseMasterPort& getMasterPort(const std::string& if_name,
 378                                   PortID idx = InvalidPortID);
 379     BaseSlavePort& getSlavePort(const std::string& if_name,
 380                                 PortID idx = InvalidPortID);
 381
 382     virtual unsigned int drain(DrainManager *dm) = 0;
 383
 384     virtual void regStats();
 385
 386 };
 387
 388 #endif //__MEM_XBAR_HH__