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47 * Declaration of a memory-mapped bus bridge that connects a master
48 * and a slave through a request and response queue.
51 #ifndef __MEM_BRIDGE_HH__
52 #define __MEM_BRIDGE_HH__
58 #include "base/fast_alloc.hh"
59 #include "base/types.hh"
60 #include "mem/mem_object.hh"
61 #include "mem/packet.hh"
62 #include "mem/port.hh"
63 #include "params/Bridge.hh"
64 #include "sim/eventq.hh"
67 * A bridge is used to interface two different busses (or in general a
68 * memory-mapped master and slave), with buffering for requests and
69 * responses. The bridge has a fixed delay for packets passing through
70 * it and responds to a fixed set of address ranges.
72 * The bridge comprises a slave port and a master port, that buffer
73 * outgoing responses and requests respectively. Buffer space is
74 * reserved when a request arrives, also reserving response space
75 * before forwarding the request. An incoming request is always
76 * accepted (recvTiming returns true), but is potentially NACKed if
77 * there is no request space or response space.
79 class Bridge : public MemObject
84 * A packet buffer stores packets along with their sender state
85 * and scheduled time for transmission.
87 class PacketBuffer : public Packet::SenderState, public FastAlloc {
93 Packet::SenderState *origSenderState;
97 PacketBuffer(PacketPtr _pkt, Tick t, bool nack = false)
98 : ready(t), pkt(_pkt), nackedHere(nack),
99 origSenderState(_pkt->senderState),
100 origSrc(nack ? _pkt->getDest() : _pkt->getSrc() ),
101 expectResponse(_pkt->needsResponse() && !nack)
104 if (!pkt->isResponse() && !nack)
105 pkt->senderState = this;
108 void fixResponse(PacketPtr pkt)
110 assert(pkt->senderState == this);
111 pkt->setDest(origSrc);
112 pkt->senderState = origSenderState;
116 // Forward declaration to allow the slave port to have a pointer
117 class BridgeMasterPort;
120 * The port on the side that receives requests and sends
121 * responses. The slave port has a set of address ranges that it
122 * is responsible for. The slave port also has a buffer for the
123 * responses not yet sent.
125 class BridgeSlavePort : public SlavePort
130 /** A pointer to the bridge to which this port belongs. */
134 * Master port on the other side of the bridge
135 * (connected to the other bus).
137 BridgeMasterPort& masterPort;
139 /** Minimum request delay though this bridge. */
142 /** Min delay to respond with a nack. */
145 /** Address ranges to pass through the bridge */
146 AddrRangeList ranges;
149 * Response packet queue. Response packets are held in this
150 * queue for a specified delay to model the processing delay
153 std::list<PacketBuffer*> responseQueue;
155 /** Counter to track the outstanding responses. */
156 unsigned int outstandingResponses;
158 /** If we're waiting for a retry to happen. */
161 /** Max queue size for reserved responses. */
162 unsigned int respQueueLimit;
165 * Is this side blocked from accepting new response packets.
167 * @return true if the reserved space has reached the set limit
169 bool respQueueFull();
172 * Turn the request packet into a NACK response and put it in
173 * the response queue and schedule its transmission.
175 * @param pkt the request packet to NACK
177 void nackRequest(PacketPtr pkt);
180 * Handle send event, scheduled when the packet at the head of
181 * the response queue is ready to transmit (for timing
187 * Private class for scheduling sending of responses from the
190 class SendEvent : public Event
192 BridgeSlavePort& port;
195 SendEvent(BridgeSlavePort& p) : port(p) {}
196 virtual void process() { port.trySend(); }
197 virtual const char *description() const { return "bridge send"; }
200 /** Send event for the response queue. */
206 * Constructor for the BridgeSlavePort.
208 * @param _name the port name including the owner
209 * @param _bridge the structural owner
210 * @param _masterPort the master port on the other side of the bridge
211 * @param _delay the delay from seeing a response to sending it
212 * @param _nack_delay the delay from a NACK to sending the response
213 * @param _resp_limit the size of the response queue
214 * @param _ranges a number of address ranges to forward
216 BridgeSlavePort(const std::string &_name, Bridge *_bridge,
217 BridgeMasterPort& _masterPort, int _delay,
218 int _nack_delay, int _resp_limit,
219 std::vector<Range<Addr> > _ranges);
222 * Queue a response packet to be sent out later and also schedule
223 * a send if necessary.
225 * @param pkt a response to send out after a delay
227 void queueForSendTiming(PacketPtr pkt);
231 /** When receiving a timing request from the peer port,
232 pass it to the bridge. */
233 virtual bool recvTiming(PacketPtr pkt);
235 /** When receiving a retry request from the peer port,
236 pass it to the bridge. */
237 virtual void recvRetry();
239 /** When receiving a Atomic requestfrom the peer port,
240 pass it to the bridge. */
241 virtual Tick recvAtomic(PacketPtr pkt);
243 /** When receiving a Functional request from the peer port,
244 pass it to the bridge. */
245 virtual void recvFunctional(PacketPtr pkt);
247 /** When receiving a address range request the peer port,
248 pass it to the bridge. */
249 virtual AddrRangeList getAddrRanges();
254 * Port on the side that forwards requests and receives
255 * responses. The master port has a buffer for the requests not
258 class BridgeMasterPort : public MasterPort
263 /** A pointer to the bridge to which this port belongs. */
267 * Pointer to the slave port on the other side of the bridge
268 * (connected to the other bus).
270 BridgeSlavePort& slavePort;
272 /** Minimum delay though this bridge. */
276 * Request packet queue. Request packets are held in this
277 * queue for a specified delay to model the processing delay
280 std::list<PacketBuffer*> requestQueue;
282 /** If we're waiting for a retry to happen. */
285 /** Max queue size for request packets */
286 unsigned int reqQueueLimit;
289 * Handle send event, scheduled when the packet at the head of
290 * the outbound queue is ready to transmit (for timing
296 * Private class for scheduling sending of requests from the
299 class SendEvent : public Event
301 BridgeMasterPort& port;
304 SendEvent(BridgeMasterPort& p) : port(p) {}
305 virtual void process() { port.trySend(); }
306 virtual const char *description() const { return "bridge send"; }
309 /** Send event for the request queue. */
315 * Constructor for the BridgeMasterPort.
317 * @param _name the port name including the owner
318 * @param _bridge the structural owner
319 * @param _slavePort the slave port on the other side of the bridge
320 * @param _delay the delay from seeing a request to sending it
321 * @param _req_limit the size of the request queue
323 BridgeMasterPort(const std::string &_name, Bridge *_bridge,
324 BridgeSlavePort& _slavePort, int _delay,
328 * Is this side blocked from accepting new request packets.
330 * @return true if the occupied space has reached the set limit
335 * Queue a request packet to be sent out later and also schedule
336 * a send if necessary.
338 * @param pkt a request to send out after a delay
340 void queueForSendTiming(PacketPtr pkt);
343 * Check a functional request against the packets in our
346 * @param pkt packet to check against
348 * @return true if we find a match
350 bool checkFunctional(PacketPtr pkt);
354 /** When receiving a timing request from the peer port,
355 pass it to the bridge. */
356 virtual bool recvTiming(PacketPtr pkt);
358 /** When receiving a retry request from the peer port,
359 pass it to the bridge. */
360 virtual void recvRetry();
363 /** Slave port of the bridge. */
364 BridgeSlavePort slavePort;
366 /** Master port of the bridge. */
367 BridgeMasterPort masterPort;
369 /** If this bridge should acknowledge writes. */
373 typedef BridgeParams Params;
379 const Params *params() const { return _params; }
381 virtual MasterPort& getMasterPort(const std::string& if_name,
383 virtual SlavePort& getSlavePort(const std::string& if_name, int idx = -1);
390 #endif //__MEM_BUS_HH__