coherent_xbar.hh revision 10656:bd376adfb7d4 
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 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    typedef Layer<SlavePort,MasterPort> ReqLayer;
79    typedef Layer<MasterPort,SlavePort> RespLayer;
80    typedef Layer<SlavePort,MasterPort> SnoopLayer;
81    std::vector<ReqLayer*> reqLayers;
82    std::vector<RespLayer*> respLayers;
83    std::vector<SnoopLayer*> snoopLayers;
84
85    /**
86     * Declaration of the coherent crossbar slave port type, one will
87     * be instantiated for each of the master ports connecting to the
88     * crossbar.
89     */
90    class CoherentXBarSlavePort : public SlavePort
91    {
92
93      private:
94
95        /** A reference to the crossbar to which this port belongs. */
96        CoherentXBar &xbar;
97
98      public:
99
100        CoherentXBarSlavePort(const std::string &_name,
101                             CoherentXBar &_xbar, PortID _id)
102            : SlavePort(_name, &_xbar, _id), xbar(_xbar)
103        { }
104
105      protected:
106
107        /**
108         * When receiving a timing request, pass it to the crossbar.
109         */
110        virtual bool recvTimingReq(PacketPtr pkt)
111        { return xbar.recvTimingReq(pkt, id); }
112
113        /**
114         * When receiving a timing snoop response, pass it to the crossbar.
115         */
116        virtual bool recvTimingSnoopResp(PacketPtr pkt)
117        { return xbar.recvTimingSnoopResp(pkt, id); }
118
119        /**
120         * When receiving an atomic request, pass it to the crossbar.
121         */
122        virtual Tick recvAtomic(PacketPtr pkt)
123        { return xbar.recvAtomic(pkt, id); }
124
125        /**
126         * When receiving a functional request, pass it to the crossbar.
127         */
128        virtual void recvFunctional(PacketPtr pkt)
129        { xbar.recvFunctional(pkt, id); }
130
131        /**
132         * When receiving a retry, pass it to the crossbar.
133         */
134        virtual void recvRetry()
135        { panic("Crossbar slave ports should never retry.\n"); }
136
137        /**
138         * Return the union of all adress ranges seen by this crossbar.
139         */
140        virtual AddrRangeList getAddrRanges() const
141        { return xbar.getAddrRanges(); }
142
143    };
144
145    /**
146     * Declaration of the coherent crossbar master port type, one will be
147     * instantiated for each of the slave interfaces connecting to the
148     * crossbar.
149     */
150    class CoherentXBarMasterPort : public MasterPort
151    {
152      private:
153        /** A reference to the crossbar to which this port belongs. */
154        CoherentXBar &xbar;
155
156      public:
157
158        CoherentXBarMasterPort(const std::string &_name,
159                              CoherentXBar &_xbar, PortID _id)
160            : MasterPort(_name, &_xbar, _id), xbar(_xbar)
161        { }
162
163      protected:
164
165        /**
166         * Determine if this port should be considered a snooper. For
167         * a coherent crossbar master port this is always true.
168         *
169         * @return a boolean that is true if this port is snooping
170         */
171        virtual bool isSnooping() const
172        { return true; }
173
174        /**
175         * When receiving a timing response, pass it to the crossbar.
176         */
177        virtual bool recvTimingResp(PacketPtr pkt)
178        { return xbar.recvTimingResp(pkt, id); }
179
180        /**
181         * When receiving a timing snoop request, pass it to the crossbar.
182         */
183        virtual void recvTimingSnoopReq(PacketPtr pkt)
184        { return xbar.recvTimingSnoopReq(pkt, id); }
185
186        /**
187         * When receiving an atomic snoop request, pass it to the crossbar.
188         */
189        virtual Tick recvAtomicSnoop(PacketPtr pkt)
190        { return xbar.recvAtomicSnoop(pkt, id); }
191
192        /**
193         * When receiving a functional snoop request, pass it to the crossbar.
194         */
195        virtual void recvFunctionalSnoop(PacketPtr pkt)
196        { xbar.recvFunctionalSnoop(pkt, id); }
197
198        /** When reciving a range change from the peer port (at id),
199            pass it to the crossbar. */
200        virtual void recvRangeChange()
201        { xbar.recvRangeChange(id); }
202
203        /** When reciving a retry from the peer port (at id),
204            pass it to the crossbar. */
205        virtual void recvRetry()
206        { xbar.recvRetry(id); }
207
208    };
209
210    /**
211     * Internal class to bridge between an incoming snoop response
212     * from a slave port and forwarding it through an outgoing slave
213     * port. It is effectively a dangling master port.
214     */
215    class SnoopRespPort : public MasterPort
216    {
217
218      private:
219
220        /** The port which we mirror internally. */
221        SlavePort& slavePort;
222
223      public:
224
225        /**
226         * Create a snoop response port that mirrors a given slave port.
227         */
228        SnoopRespPort(SlavePort& slave_port, CoherentXBar& _xbar) :
229            MasterPort(slave_port.name() + ".snoopRespPort", &_xbar),
230            slavePort(slave_port) { }
231
232        /**
233         * Override the sending of retries and pass them on through
234         * the mirrored slave port.
235         */
236        void sendRetry() {
237            slavePort.sendRetry();
238        }
239
240        /**
241         * Provided as necessary.
242         */
243        void recvRetry() { panic("SnoopRespPort should never see retry\n"); }
244
245        /**
246         * Provided as necessary.
247         */
248        bool recvTimingResp(PacketPtr pkt)
249        {
250            panic("SnoopRespPort should never see timing response\n");
251            return false;
252        }
253
254    };
255
256    std::vector<SnoopRespPort*> snoopRespPorts;
257
258    std::vector<SlavePort*> snoopPorts;
259
260    /**
261     * Store the outstanding requests that we are expecting snoop
262     * responses from so we can determine which snoop responses we
263     * generated and which ones were merely forwarded.
264     */
265    m5::hash_set<RequestPtr> outstandingSnoop;
266
267    /**
268     * Keep a pointer to the system to be allow to querying memory system
269     * properties.
270     */
271    System *system;
272
273    /** A snoop filter that tracks cache line residency and can restrict the
274      * broadcast needed for probes.  NULL denotes an absent filter. */
275    SnoopFilter *snoopFilter;
276
277    /** Function called by the port when the crossbar is recieving a Timing
278      request packet.*/
279    bool recvTimingReq(PacketPtr pkt, PortID slave_port_id);
280
281    /** Function called by the port when the crossbar is recieving a Timing
282      response packet.*/
283    bool recvTimingResp(PacketPtr pkt, PortID master_port_id);
284
285    /** Function called by the port when the crossbar is recieving a timing
286        snoop request.*/
287    void recvTimingSnoopReq(PacketPtr pkt, PortID master_port_id);
288
289    /** Function called by the port when the crossbar is recieving a timing
290        snoop response.*/
291    bool recvTimingSnoopResp(PacketPtr pkt, PortID slave_port_id);
292
293    /** Timing function called by port when it is once again able to process
294     * requests. */
295    void recvRetry(PortID master_port_id);
296
297    /**
298     * Forward a timing packet to our snoopers, potentially excluding
299     * one of the connected coherent masters to avoid sending a packet
300     * back to where it came from.
301     *
302     * @param pkt Packet to forward
303     * @param exclude_slave_port_id Id of slave port to exclude
304     */
305    void forwardTiming(PacketPtr pkt, PortID exclude_slave_port_id) {
306        forwardTiming(pkt, exclude_slave_port_id, snoopPorts);
307    }
308
309    /**
310     * Forward a timing packet to a selected list of snoopers, potentially
311     * excluding one of the connected coherent masters to avoid sending a packet
312     * back to where it came from.
313     *
314     * @param pkt Packet to forward
315     * @param exclude_slave_port_id Id of slave port to exclude
316     * @param dests Vector of destination ports for the forwarded pkt
317     */
318    void forwardTiming(PacketPtr pkt, PortID exclude_slave_port_id,
319                       const std::vector<SlavePort*>& dests);
320
321    /** Function called by the port when the crossbar is recieving a Atomic
322      transaction.*/
323    Tick recvAtomic(PacketPtr pkt, PortID slave_port_id);
324
325    /** Function called by the port when the crossbar is recieving an
326        atomic snoop transaction.*/
327    Tick recvAtomicSnoop(PacketPtr pkt, PortID master_port_id);
328
329    /**
330     * Forward an atomic packet to our snoopers, potentially excluding
331     * one of the connected coherent masters to avoid sending a packet
332     * back to where it came from.
333     *
334     * @param pkt Packet to forward
335     * @param exclude_slave_port_id Id of slave port to exclude
336     *
337     * @return a pair containing the snoop response and snoop latency
338     */
339    std::pair<MemCmd, Tick> forwardAtomic(PacketPtr pkt,
340                                          PortID exclude_slave_port_id)
341    {
342        return forwardAtomic(pkt, exclude_slave_port_id, InvalidPortID, snoopPorts);
343    }
344
345    /**
346     * Forward an atomic packet to a selected list of snoopers, potentially
347     * excluding one of the connected coherent masters to avoid sending a packet
348     * back to where it came from.
349     *
350     * @param pkt Packet to forward
351     * @param exclude_slave_port_id Id of slave port to exclude
352     * @param source_master_port_id Id of the master port for snoops from below
353     * @param dests Vector of destination ports for the forwarded pkt
354     *
355     * @return a pair containing the snoop response and snoop latency
356     */
357    std::pair<MemCmd, Tick> forwardAtomic(PacketPtr pkt,
358                                          PortID exclude_slave_port_id,
359                                          PortID source_master_port_id,
360                                          const std::vector<SlavePort*>& dests);
361
362    /** Function called by the port when the crossbar is recieving a Functional
363        transaction.*/
364    void recvFunctional(PacketPtr pkt, PortID slave_port_id);
365
366    /** Function called by the port when the crossbar is recieving a functional
367        snoop transaction.*/
368    void recvFunctionalSnoop(PacketPtr pkt, PortID master_port_id);
369
370    /**
371     * Forward a functional packet to our snoopers, potentially
372     * excluding one of the connected coherent masters to avoid
373     * sending a packet back to where it came from.
374     *
375     * @param pkt Packet to forward
376     * @param exclude_slave_port_id Id of slave port to exclude
377     */
378    void forwardFunctional(PacketPtr pkt, PortID exclude_slave_port_id);
379
380    Stats::Scalar snoops;
381    Stats::Distribution snoopFanout;
382
383  public:
384
385    virtual void init();
386
387    CoherentXBar(const CoherentXBarParams *p);
388
389    virtual ~CoherentXBar();
390
391    unsigned int drain(DrainManager *dm);
392
393    virtual void regStats();
394};
395
396#endif //__MEM_COHERENT_XBAR_HH__
397