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40 * Authors: Ron Dreslinski
48 * Declaration of a coherent crossbar.
51 #ifndef __MEM_COHERENT_XBAR_HH__
52 #define __MEM_COHERENT_XBAR_HH__
54 #include "mem/snoop_filter.hh"
55 #include "mem/xbar.hh"
56 #include "params/CoherentXBar.hh"
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.
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"
69 class CoherentXBar : public BaseXBar
75 * Declare the layers of this crossbar, one vector for requests,
76 * one for responses, and one for snoop responses
78 std::vector<ReqLayer*> reqLayers;
79 std::vector<RespLayer*> respLayers;
80 std::vector<SnoopRespLayer*> snoopLayers;
83 * Declaration of the coherent crossbar slave port type, one will
84 * be instantiated for each of the master ports connecting to the
87 class CoherentXBarSlavePort : public QueuedSlavePort
92 /** A reference to the crossbar to which this port belongs. */
95 /** A normal packet queue used to store responses. */
96 RespPacketQueue queue;
100 CoherentXBarSlavePort(const std::string &_name,
101 CoherentXBar &_xbar, PortID _id)
102 : QueuedSlavePort(_name, &_xbar, queue, _id), xbar(_xbar),
109 * When receiving a timing request, pass it to the crossbar.
111 virtual bool recvTimingReq(PacketPtr pkt)
112 { return xbar.recvTimingReq(pkt, id); }
115 * When receiving a timing snoop response, pass it to the crossbar.
117 virtual bool recvTimingSnoopResp(PacketPtr pkt)
118 { return xbar.recvTimingSnoopResp(pkt, id); }
121 * When receiving an atomic request, pass it to the crossbar.
123 virtual Tick recvAtomic(PacketPtr pkt)
124 { return xbar.recvAtomic(pkt, id); }
127 * When receiving a functional request, pass it to the crossbar.
129 virtual void recvFunctional(PacketPtr pkt)
130 { xbar.recvFunctional(pkt, id); }
133 * Return the union of all adress ranges seen by this crossbar.
135 virtual AddrRangeList getAddrRanges() const
136 { return xbar.getAddrRanges(); }
141 * Declaration of the coherent crossbar master port type, one will be
142 * instantiated for each of the slave interfaces connecting to the
145 class CoherentXBarMasterPort : public MasterPort
148 /** A reference to the crossbar to which this port belongs. */
153 CoherentXBarMasterPort(const std::string &_name,
154 CoherentXBar &_xbar, PortID _id)
155 : MasterPort(_name, &_xbar, _id), xbar(_xbar)
161 * Determine if this port should be considered a snooper. For
162 * a coherent crossbar master port this is always true.
164 * @return a boolean that is true if this port is snooping
166 virtual bool isSnooping() const
170 * When receiving a timing response, pass it to the crossbar.
172 virtual bool recvTimingResp(PacketPtr pkt)
173 { return xbar.recvTimingResp(pkt, id); }
176 * When receiving a timing snoop request, pass it to the crossbar.
178 virtual void recvTimingSnoopReq(PacketPtr pkt)
179 { return xbar.recvTimingSnoopReq(pkt, id); }
182 * When receiving an atomic snoop request, pass it to the crossbar.
184 virtual Tick recvAtomicSnoop(PacketPtr pkt)
185 { return xbar.recvAtomicSnoop(pkt, id); }
188 * When receiving a functional snoop request, pass it to the crossbar.
190 virtual void recvFunctionalSnoop(PacketPtr pkt)
191 { xbar.recvFunctionalSnoop(pkt, id); }
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); }
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); }
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.
210 class SnoopRespPort : public MasterPort
215 /** The port which we mirror internally. */
216 QueuedSlavePort& slavePort;
221 * Create a snoop response port that mirrors a given slave port.
223 SnoopRespPort(QueuedSlavePort& slave_port, CoherentXBar& _xbar) :
224 MasterPort(slave_port.name() + ".snoopRespPort", &_xbar),
225 slavePort(slave_port) { }
228 * Override the sending of retries and pass them on through
229 * the mirrored slave port.
231 void sendRetryResp() {
232 // forward it as a snoop response retry
233 slavePort.sendRetrySnoopResp();
237 * Provided as necessary.
239 void recvReqRetry() { panic("SnoopRespPort should never see retry\n"); }
242 * Provided as necessary.
244 bool recvTimingResp(PacketPtr pkt)
246 panic("SnoopRespPort should never see timing response\n");
252 std::vector<SnoopRespPort*> snoopRespPorts;
254 std::vector<QueuedSlavePort*> snoopPorts;
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.
261 std::unordered_set<RequestPtr> outstandingSnoop;
264 * Keep a pointer to the system to be allow to querying memory system
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;
273 /** Cycles of snoop response latency.*/
274 const Cycles snoopResponseLatency;
277 * Upstream caches need this packet until true is returned, so
278 * hold it for deletion until a subsequent call
280 std::unique_ptr<Packet> pendingDelete;
282 /** Function called by the port when the crossbar is recieving a Timing
284 bool recvTimingReq(PacketPtr pkt, PortID slave_port_id);
286 /** Function called by the port when the crossbar is recieving a Timing
288 bool recvTimingResp(PacketPtr pkt, PortID master_port_id);
290 /** Function called by the port when the crossbar is recieving a timing
292 void recvTimingSnoopReq(PacketPtr pkt, PortID master_port_id);
294 /** Function called by the port when the crossbar is recieving a timing
296 bool recvTimingSnoopResp(PacketPtr pkt, PortID slave_port_id);
298 /** Timing function called by port when it is once again able to process
300 void recvReqRetry(PortID master_port_id);
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.
307 * @param pkt Packet to forward
308 * @param exclude_slave_port_id Id of slave port to exclude
310 void forwardTiming(PacketPtr pkt, PortID exclude_slave_port_id) {
311 forwardTiming(pkt, exclude_slave_port_id, snoopPorts);
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.
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
323 void forwardTiming(PacketPtr pkt, PortID exclude_slave_port_id,
324 const std::vector<QueuedSlavePort*>& dests);
326 /** Function called by the port when the crossbar is recieving a Atomic
328 Tick recvAtomic(PacketPtr pkt, PortID slave_port_id);
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);
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.
339 * @param pkt Packet to forward
340 * @param exclude_slave_port_id Id of slave port to exclude
342 * @return a pair containing the snoop response and snoop latency
344 std::pair<MemCmd, Tick> forwardAtomic(PacketPtr pkt,
345 PortID exclude_slave_port_id)
347 return forwardAtomic(pkt, exclude_slave_port_id, InvalidPortID,
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.
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
361 * @return a pair containing the snoop response and snoop latency
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*>&
369 /** Function called by the port when the crossbar is recieving a Functional
371 void recvFunctional(PacketPtr pkt, PortID slave_port_id);
373 /** Function called by the port when the crossbar is recieving a functional
375 void recvFunctionalSnoop(PacketPtr pkt, PortID master_port_id);
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.
382 * @param pkt Packet to forward
383 * @param exclude_slave_port_id Id of slave port to exclude
385 void forwardFunctional(PacketPtr pkt, PortID exclude_slave_port_id);
387 Stats::Scalar snoops;
388 Stats::Distribution snoopFanout;
394 CoherentXBar(const CoherentXBarParams *p);
396 virtual ~CoherentXBar();
398 virtual void regStats();
401 #endif //__MEM_COHERENT_XBAR_HH__