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/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       private:
 178
 179         /** The destination port this layer converges at. */
 180         DstType& port;
 181
 182         /** The crossbar this layer is a part of. */
 183         BaseXBar& xbar;
 184
 185         /** A name for this layer. */
 186         std::string _name;
 187
 188         /**
 189          * We declare an enum to track the state of the layer. The
 190          * starting point is an idle state where the layer is waiting
 191          * for a packet to arrive. Upon arrival, the layer
 192          * transitions to the busy state, where it remains either
 193          * until the packet transfer is done, or the header time is
 194          * spent. Once the layer leaves the busy state, it can
 195          * either go back to idle, if no packets have arrived while it
 196          * was busy, or the layer goes on to retry the first port
 197          * in waitingForLayer. A similar transition takes place from
 198          * idle to retry if the layer receives a retry from one of
 199          * its connected ports. The retry state lasts until the port
 200          * in questions calls sendTiming and returns control to the
 201          * layer, or goes to a busy state if the port does not
 202          * immediately react to the retry by calling sendTiming.
 203          */
 204         enum State { IDLE, BUSY, RETRY };
 205
 206         /** track the state of the layer */
 207         State state;
 208
 209         /** manager to signal when drained */
 210         DrainManager *drainManager;
 211
 212         /**
 213          * A deque of ports that retry should be called on because
 214          * the original send was delayed due to a busy layer.
 215          */
 216         std::deque<SrcType*> waitingForLayer;
 217
 218         /**
 219          * Track who is waiting for the retry when receiving it from a
 220          * peer. If no port is waiting NULL is stored.
 221          */
 222         SrcType* waitingForPeer;
 223
 224         /**
 225          * Release the layer after being occupied and return to an
 226          * idle state where we proceed to send a retry to any
 227          * potential waiting port, or drain if asked to do so.
 228          */
 229         void releaseLayer();
 230
 231         /** event used to schedule a release of the layer */
 232         EventWrapper<Layer, &Layer::releaseLayer> releaseEvent;
 233
 234         /**
 235          * Stats for occupancy and utilization. These stats capture
 236          * the time the layer spends in the busy state and are thus only
 237          * relevant when the memory system is in timing mode.
 238          */
 239         Stats::Scalar occupancy;
 240         Stats::Formula utilization;
 241
 242     };
 243
 244     /** cycles of overhead per transaction */
 245     const Cycles headerCycles;
 246     /** the width of the xbar in bytes */
 247     const uint32_t width;
 248
 249     AddrRangeMap<PortID> portMap;
 250
 251     /**
 252      * Remember where request packets came from so that we can route
 253      * responses to the appropriate port. This relies on the fact that
 254      * the underlying Request pointer inside the Packet stays
 255      * constant.
 256      */
 257     m5::unordered_map<RequestPtr, PortID> routeTo;
 258
 259     /** all contigous ranges seen by this crossbar */
 260     AddrRangeList xbarRanges;
 261
 262     AddrRange defaultRange;
 263
 264     /**
 265      * Function called by the port when the crossbar is recieving a
 266      * range change.
 267      *
 268      * @param master_port_id id of the port that received the change
 269      */
 270     void recvRangeChange(PortID master_port_id);
 271
 272     /** Find which port connected to this crossbar (if any) should be
 273      * given a packet with this address.
 274      *
 275      * @param addr Address to find port for.
 276      * @return id of port that the packet should be sent out of.
 277      */
 278     PortID findPort(Addr addr);
 279
 280     // Cache for the findPort function storing recently used ports from portMap
 281     struct PortCache {
 282         bool valid;
 283         PortID id;
 284         AddrRange range;
 285     };
 286
 287     PortCache portCache[3];
 288
 289     // Checks the cache and returns the id of the port that has the requested
 290     // address within its range
 291     inline PortID checkPortCache(Addr addr) const {
 292         if (portCache[0].valid && portCache[0].range.contains(addr)) {
 293             return portCache[0].id;
 294         }
 295         if (portCache[1].valid && portCache[1].range.contains(addr)) {
 296             return portCache[1].id;
 297         }
 298         if (portCache[2].valid && portCache[2].range.contains(addr)) {
 299             return portCache[2].id;
 300         }
 301
 302         return InvalidPortID;
 303     }
 304
 305     // Clears the earliest entry of the cache and inserts a new port entry
 306     inline void updatePortCache(short id, const AddrRange& range) {
 307         portCache[2].valid = portCache[1].valid;
 308         portCache[2].id    = portCache[1].id;
 309         portCache[2].range = portCache[1].range;
 310
 311         portCache[1].valid = portCache[0].valid;
 312         portCache[1].id    = portCache[0].id;
 313         portCache[1].range = portCache[0].range;
 314
 315         portCache[0].valid = true;
 316         portCache[0].id    = id;
 317         portCache[0].range = range;
 318     }
 319
 320     // Clears the cache. Needs to be called in constructor.
 321     inline void clearPortCache() {
 322         portCache[2].valid = false;
 323         portCache[1].valid = false;
 324         portCache[0].valid = false;
 325     }
 326
 327     /**
 328      * Return the address ranges the crossbar is responsible for.
 329      *
 330      * @return a list of non-overlapping address ranges
 331      */
 332     AddrRangeList getAddrRanges() const;
 333
 334     /**
 335      * Calculate the timing parameters for the packet. Updates the
 336      * headerDelay and payloadDelay fields of the packet
 337      * object with the relative number of ticks required to transmit
 338      * the header and the payload, respectively.
 339      */
 340     void calcPacketTiming(PacketPtr pkt);
 341
 342     /**
 343      * Remember for each of the master ports of the crossbar if we got
 344      * an address range from the connected slave. For convenience,
 345      * also keep track of if we got ranges from all the slave modules
 346      * or not.
 347      */
 348     std::vector<bool> gotAddrRanges;
 349     bool gotAllAddrRanges;
 350
 351     /** The master and slave ports of the crossbar */
 352     std::vector<SlavePort*> slavePorts;
 353     std::vector<MasterPort*> masterPorts;
 354
 355     /** Port that handles requests that don't match any of the interfaces.*/
 356     PortID defaultPortID;
 357
 358     /** If true, use address range provided by default device.  Any
 359        address not handled by another port and not in default device's
 360        range will cause a fatal error.  If false, just send all
 361        addresses not handled by another port to default device. */
 362     const bool useDefaultRange;
 363
 364     BaseXBar(const BaseXBarParams *p);
 365
 366     virtual ~BaseXBar();
 367
 368     /**
 369      * Stats for transaction distribution and data passing through the
 370      * crossbar. The transaction distribution is globally counting
 371      * different types of commands. The packet count and total packet
 372      * size are two-dimensional vectors that are indexed by the
 373      * slave port and master port id (thus the neighbouring master and
 374      * neighbouring slave), summing up both directions (request and
 375      * response).
 376      */
 377     Stats::Vector transDist;
 378     Stats::Vector2d pktCount;
 379     Stats::Vector2d pktSize;
 380
 381   public:
 382
 383     virtual void init();
 384
 385     /** A function used to return the port associated with this object. */
 386     BaseMasterPort& getMasterPort(const std::string& if_name,
 387                                   PortID idx = InvalidPortID);
 388     BaseSlavePort& getSlavePort(const std::string& if_name,
 389                                 PortID idx = InvalidPortID);
 390
 391     virtual unsigned int drain(DrainManager *dm) = 0;
 392
 393     virtual void regStats();
 394
 395 };
 396
 397 #endif //__MEM_XBAR_HH__