xbar.hh revision 10656 
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 */
72class 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     * firstWordDelay and lastWordDelay fields of the packet
337     * object with the relative number of ticks required to transmit
338     * the header and the first word, and the last word, 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__
398