coherent_xbar.hh revision 11190:0964165d1857 
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 a coherent crossbar.
49 */
50
51#ifndef __MEM_COHERENT_XBAR_HH__
52#define __MEM_COHERENT_XBAR_HH__
53
54#include "mem/snoop_filter.hh"
55#include "mem/xbar.hh"
56#include "params/CoherentXBar.hh"
57
58/**
59 * A coherent crossbar connects a number of (potentially) snooping
60 * masters and slaves, and routes the request and response packets
61 * based on the address, and also forwards all requests to the
62 * snoopers and deals with the snoop responses.
63 *
64 * The coherent crossbar can be used as a template for modelling QPI,
65 * HyperTransport, ACE and coherent OCP buses, and is typically used
66 * for the L1-to-L2 buses and as the main system interconnect.  @sa
67 * \ref gem5MemorySystem "gem5 Memory System"
68 */
69class CoherentXBar : public BaseXBar
70{
71
72  protected:
73
74    /**
75     * Declare the layers of this crossbar, one vector for requests,
76     * one for responses, and one for snoop responses
77     */
78    std::vector<ReqLayer*> reqLayers;
79    std::vector<RespLayer*> respLayers;
80    std::vector<SnoopRespLayer*> snoopLayers;
81
82    /**
83     * Declaration of the coherent crossbar slave port type, one will
84     * be instantiated for each of the master ports connecting to the
85     * crossbar.
86     */
87    class CoherentXBarSlavePort : public QueuedSlavePort
88    {
89
90      private:
91
92        /** A reference to the crossbar to which this port belongs. */
93        CoherentXBar &xbar;
94
95        /** A normal packet queue used to store responses. */
96        RespPacketQueue queue;
97
98      public:
99
100        CoherentXBarSlavePort(const std::string &_name,
101                             CoherentXBar &_xbar, PortID _id)
102            : QueuedSlavePort(_name, &_xbar, queue, _id), xbar(_xbar),
103              queue(_xbar, *this)
104        { }
105
106      protected:
107
108        /**
109         * When receiving a timing request, pass it to the crossbar.
110         */
111        virtual bool recvTimingReq(PacketPtr pkt)
112        { return xbar.recvTimingReq(pkt, id); }
113
114        /**
115         * When receiving a timing snoop response, pass it to the crossbar.
116         */
117        virtual bool recvTimingSnoopResp(PacketPtr pkt)
118        { return xbar.recvTimingSnoopResp(pkt, id); }
119
120        /**
121         * When receiving an atomic request, pass it to the crossbar.
122         */
123        virtual Tick recvAtomic(PacketPtr pkt)
124        { return xbar.recvAtomic(pkt, id); }
125
126        /**
127         * When receiving a functional request, pass it to the crossbar.
128         */
129        virtual void recvFunctional(PacketPtr pkt)
130        { xbar.recvFunctional(pkt, id); }
131
132        /**
133         * Return the union of all adress ranges seen by this crossbar.
134         */
135        virtual AddrRangeList getAddrRanges() const
136        { return xbar.getAddrRanges(); }
137
138    };
139
140    /**
141     * Declaration of the coherent crossbar master port type, one will be
142     * instantiated for each of the slave interfaces connecting to the
143     * crossbar.
144     */
145    class CoherentXBarMasterPort : public MasterPort
146    {
147      private:
148        /** A reference to the crossbar to which this port belongs. */
149        CoherentXBar &xbar;
150
151      public:
152
153        CoherentXBarMasterPort(const std::string &_name,
154                              CoherentXBar &_xbar, PortID _id)
155            : MasterPort(_name, &_xbar, _id), xbar(_xbar)
156        { }
157
158      protected:
159
160        /**
161         * Determine if this port should be considered a snooper. For
162         * a coherent crossbar master port this is always true.
163         *
164         * @return a boolean that is true if this port is snooping
165         */
166        virtual bool isSnooping() const
167        { return true; }
168
169        /**
170         * When receiving a timing response, pass it to the crossbar.
171         */
172        virtual bool recvTimingResp(PacketPtr pkt)
173        { return xbar.recvTimingResp(pkt, id); }
174
175        /**
176         * When receiving a timing snoop request, pass it to the crossbar.
177         */
178        virtual void recvTimingSnoopReq(PacketPtr pkt)
179        { return xbar.recvTimingSnoopReq(pkt, id); }
180
181        /**
182         * When receiving an atomic snoop request, pass it to the crossbar.
183         */
184        virtual Tick recvAtomicSnoop(PacketPtr pkt)
185        { return xbar.recvAtomicSnoop(pkt, id); }
186
187        /**
188         * When receiving a functional snoop request, pass it to the crossbar.
189         */
190        virtual void recvFunctionalSnoop(PacketPtr pkt)
191        { xbar.recvFunctionalSnoop(pkt, id); }
192
193        /** When reciving a range change from the peer port (at id),
194            pass it to the crossbar. */
195        virtual void recvRangeChange()
196        { xbar.recvRangeChange(id); }
197
198        /** When reciving a retry from the peer port (at id),
199            pass it to the crossbar. */
200        virtual void recvReqRetry()
201        { xbar.recvReqRetry(id); }
202
203    };
204
205    /**
206     * Internal class to bridge between an incoming snoop response
207     * from a slave port and forwarding it through an outgoing slave
208     * port. It is effectively a dangling master port.
209     */
210    class SnoopRespPort : public MasterPort
211    {
212
213      private:
214
215        /** The port which we mirror internally. */
216        QueuedSlavePort& slavePort;
217
218      public:
219
220        /**
221         * Create a snoop response port that mirrors a given slave port.
222         */
223        SnoopRespPort(QueuedSlavePort& slave_port, CoherentXBar& _xbar) :
224            MasterPort(slave_port.name() + ".snoopRespPort", &_xbar),
225            slavePort(slave_port) { }
226
227        /**
228         * Override the sending of retries and pass them on through
229         * the mirrored slave port.
230         */
231        void sendRetryResp() {
232            // forward it as a snoop response retry
233            slavePort.sendRetrySnoopResp();
234        }
235
236        /**
237         * Provided as necessary.
238         */
239        void recvReqRetry() { panic("SnoopRespPort should never see retry\n"); }
240
241        /**
242         * Provided as necessary.
243         */
244        bool recvTimingResp(PacketPtr pkt)
245        {
246            panic("SnoopRespPort should never see timing response\n");
247            return false;
248        }
249
250    };
251
252    std::vector<SnoopRespPort*> snoopRespPorts;
253
254    std::vector<QueuedSlavePort*> snoopPorts;
255
256    /**
257     * Store the outstanding requests that we are expecting snoop
258     * responses from so we can determine which snoop responses we
259     * generated and which ones were merely forwarded.
260     */
261    std::unordered_set<RequestPtr> outstandingSnoop;
262
263    /**
264     * Keep a pointer to the system to be allow to querying memory system
265     * properties.
266     */
267    System *system;
268
269    /** A snoop filter that tracks cache line residency and can restrict the
270      * broadcast needed for probes.  NULL denotes an absent filter. */
271    SnoopFilter *snoopFilter;
272
273    /** Cycles of snoop response latency.*/
274    const Cycles snoopResponseLatency;
275
276    /**
277     * Upstream caches need this packet until true is returned, so
278     * hold it for deletion until a subsequent call
279     */
280    std::unique_ptr<Packet> pendingDelete;
281
282    /** Function called by the port when the crossbar is recieving a Timing
283      request packet.*/
284    bool recvTimingReq(PacketPtr pkt, PortID slave_port_id);
285
286    /** Function called by the port when the crossbar is recieving a Timing
287      response packet.*/
288    bool recvTimingResp(PacketPtr pkt, PortID master_port_id);
289
290    /** Function called by the port when the crossbar is recieving a timing
291        snoop request.*/
292    void recvTimingSnoopReq(PacketPtr pkt, PortID master_port_id);
293
294    /** Function called by the port when the crossbar is recieving a timing
295        snoop response.*/
296    bool recvTimingSnoopResp(PacketPtr pkt, PortID slave_port_id);
297
298    /** Timing function called by port when it is once again able to process
299     * requests. */
300    void recvReqRetry(PortID master_port_id);
301
302    /**
303     * Forward a timing packet to our snoopers, potentially excluding
304     * one of the connected coherent masters to avoid sending a packet
305     * back to where it came from.
306     *
307     * @param pkt Packet to forward
308     * @param exclude_slave_port_id Id of slave port to exclude
309     */
310    void forwardTiming(PacketPtr pkt, PortID exclude_slave_port_id) {
311        forwardTiming(pkt, exclude_slave_port_id, snoopPorts);
312    }
313
314    /**
315     * Forward a timing packet to a selected list of snoopers, potentially
316     * excluding one of the connected coherent masters to avoid sending a packet
317     * back to where it came from.
318     *
319     * @param pkt Packet to forward
320     * @param exclude_slave_port_id Id of slave port to exclude
321     * @param dests Vector of destination ports for the forwarded pkt
322     */
323    void forwardTiming(PacketPtr pkt, PortID exclude_slave_port_id,
324                       const std::vector<QueuedSlavePort*>& dests);
325
326    /** Function called by the port when the crossbar is recieving a Atomic
327      transaction.*/
328    Tick recvAtomic(PacketPtr pkt, PortID slave_port_id);
329
330    /** Function called by the port when the crossbar is recieving an
331        atomic snoop transaction.*/
332    Tick recvAtomicSnoop(PacketPtr pkt, PortID master_port_id);
333
334    /**
335     * Forward an atomic packet to our snoopers, potentially excluding
336     * one of the connected coherent masters to avoid sending a packet
337     * back to where it came from.
338     *
339     * @param pkt Packet to forward
340     * @param exclude_slave_port_id Id of slave port to exclude
341     *
342     * @return a pair containing the snoop response and snoop latency
343     */
344    std::pair<MemCmd, Tick> forwardAtomic(PacketPtr pkt,
345                                          PortID exclude_slave_port_id)
346    {
347        return forwardAtomic(pkt, exclude_slave_port_id, InvalidPortID,
348                             snoopPorts);
349    }
350
351    /**
352     * Forward an atomic packet to a selected list of snoopers, potentially
353     * excluding one of the connected coherent masters to avoid sending a packet
354     * back to where it came from.
355     *
356     * @param pkt Packet to forward
357     * @param exclude_slave_port_id Id of slave port to exclude
358     * @param source_master_port_id Id of the master port for snoops from below
359     * @param dests Vector of destination ports for the forwarded pkt
360     *
361     * @return a pair containing the snoop response and snoop latency
362     */
363    std::pair<MemCmd, Tick> forwardAtomic(PacketPtr pkt,
364                                          PortID exclude_slave_port_id,
365                                          PortID source_master_port_id,
366                                          const std::vector<QueuedSlavePort*>&
367                                          dests);
368
369    /** Function called by the port when the crossbar is recieving a Functional
370        transaction.*/
371    void recvFunctional(PacketPtr pkt, PortID slave_port_id);
372
373    /** Function called by the port when the crossbar is recieving a functional
374        snoop transaction.*/
375    void recvFunctionalSnoop(PacketPtr pkt, PortID master_port_id);
376
377    /**
378     * Forward a functional packet to our snoopers, potentially
379     * excluding one of the connected coherent masters to avoid
380     * sending a packet back to where it came from.
381     *
382     * @param pkt Packet to forward
383     * @param exclude_slave_port_id Id of slave port to exclude
384     */
385    void forwardFunctional(PacketPtr pkt, PortID exclude_slave_port_id);
386
387    Stats::Scalar snoops;
388    Stats::Distribution snoopFanout;
389
390  public:
391
392    virtual void init();
393
394    CoherentXBar(const CoherentXBarParams *p);
395
396    virtual ~CoherentXBar();
397
398    virtual void regStats();
399};
400
401#endif //__MEM_COHERENT_XBAR_HH__
402