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43 * Declaration of a memory-mapped bridge that connects a master
44 * and a slave through a request and response queue.
47 #ifndef __MEM_BRIDGE_HH__
48 #define __MEM_BRIDGE_HH__
52 #include "base/types.hh"
53 #include "mem/port.hh"
54 #include "params/Bridge.hh"
55 #include "sim/clocked_object.hh"
58 * A bridge is used to interface two different crossbars (or in general a
59 * memory-mapped master and slave), with buffering for requests and
60 * responses. The bridge has a fixed delay for packets passing through
61 * it and responds to a fixed set of address ranges.
63 * The bridge comprises a slave port and a master port, that buffer
64 * outgoing responses and requests respectively. Buffer space is
65 * reserved when a request arrives, also reserving response space
66 * before forwarding the request. If there is no space present, then
67 * the bridge will delay accepting the packet until space becomes
70 class Bridge : public ClockedObject
75 * A deferred packet stores a packet along with its scheduled
86 DeferredPacket(PacketPtr _pkt, Tick _tick) : tick(_tick), pkt(_pkt)
90 // Forward declaration to allow the slave port to have a pointer
91 class BridgeMasterPort;
94 * The port on the side that receives requests and sends
95 * responses. The slave port has a set of address ranges that it
96 * is responsible for. The slave port also has a buffer for the
97 * responses not yet sent.
99 class BridgeSlavePort : public SlavePort
104 /** The bridge to which this port belongs. */
108 * Master port on the other side of the bridge.
110 BridgeMasterPort& masterPort;
112 /** Minimum request delay though this bridge. */
115 /** Address ranges to pass through the bridge */
116 const AddrRangeList ranges;
119 * Response packet queue. Response packets are held in this
120 * queue for a specified delay to model the processing delay
121 * of the bridge. We use a deque as we need to iterate over
122 * the items for functional accesses.
124 std::deque<DeferredPacket> transmitList;
126 /** Counter to track the outstanding responses. */
127 unsigned int outstandingResponses;
129 /** If we should send a retry when space becomes available. */
132 /** Max queue size for reserved responses. */
133 unsigned int respQueueLimit;
136 * Upstream caches need this packet until true is returned, so
137 * hold it for deletion until a subsequent call
139 std::unique_ptr<Packet> pendingDelete;
142 * Is this side blocked from accepting new response packets.
144 * @return true if the reserved space has reached the set limit
146 bool respQueueFull() const;
149 * Handle send event, scheduled when the packet at the head of
150 * the response queue is ready to transmit (for timing
153 void trySendTiming();
155 /** Send event for the response queue. */
156 EventFunctionWrapper sendEvent;
161 * Constructor for the BridgeSlavePort.
163 * @param _name the port name including the owner
164 * @param _bridge the structural owner
165 * @param _masterPort the master port on the other side of the bridge
166 * @param _delay the delay in cycles from receiving to sending
167 * @param _resp_limit the size of the response queue
168 * @param _ranges a number of address ranges to forward
170 BridgeSlavePort(const std::string& _name, Bridge& _bridge,
171 BridgeMasterPort& _masterPort, Cycles _delay,
172 int _resp_limit, std::vector<AddrRange> _ranges);
175 * Queue a response packet to be sent out later and also schedule
176 * a send if necessary.
178 * @param pkt a response to send out after a delay
179 * @param when tick when response packet should be sent
181 void schedTimingResp(PacketPtr pkt, Tick when);
184 * Retry any stalled request that we have failed to accept at
185 * an earlier point in time. This call will do nothing if no
186 * request is waiting.
188 void retryStalledReq();
192 /** When receiving a timing request from the peer port,
193 pass it to the bridge. */
194 bool recvTimingReq(PacketPtr pkt);
196 /** When receiving a retry request from the peer port,
197 pass it to the bridge. */
198 void recvRespRetry();
200 /** When receiving a Atomic requestfrom the peer port,
201 pass it to the bridge. */
202 Tick recvAtomic(PacketPtr pkt);
204 /** When receiving a Functional request from the peer port,
205 pass it to the bridge. */
206 void recvFunctional(PacketPtr pkt);
208 /** When receiving a address range request the peer port,
209 pass it to the bridge. */
210 AddrRangeList getAddrRanges() const;
215 * Port on the side that forwards requests and receives
216 * responses. The master port has a buffer for the requests not
219 class BridgeMasterPort : public MasterPort
224 /** The bridge to which this port belongs. */
228 * The slave port on the other side of the bridge.
230 BridgeSlavePort& slavePort;
232 /** Minimum delay though this bridge. */
236 * Request packet queue. Request packets are held in this
237 * queue for a specified delay to model the processing delay
238 * of the bridge. We use a deque as we need to iterate over
239 * the items for functional accesses.
241 std::deque<DeferredPacket> transmitList;
243 /** Max queue size for request packets */
244 const unsigned int reqQueueLimit;
247 * Handle send event, scheduled when the packet at the head of
248 * the outbound queue is ready to transmit (for timing
251 void trySendTiming();
253 /** Send event for the request queue. */
254 EventFunctionWrapper sendEvent;
259 * Constructor for the BridgeMasterPort.
261 * @param _name the port name including the owner
262 * @param _bridge the structural owner
263 * @param _slavePort the slave port on the other side of the bridge
264 * @param _delay the delay in cycles from receiving to sending
265 * @param _req_limit the size of the request queue
267 BridgeMasterPort(const std::string& _name, Bridge& _bridge,
268 BridgeSlavePort& _slavePort, Cycles _delay,
272 * Is this side blocked from accepting new request packets.
274 * @return true if the occupied space has reached the set limit
276 bool reqQueueFull() const;
279 * Queue a request packet to be sent out later and also schedule
280 * a send if necessary.
282 * @param pkt a request to send out after a delay
283 * @param when tick when response packet should be sent
285 void schedTimingReq(PacketPtr pkt, Tick when);
288 * Check a functional request against the packets in our
291 * @param pkt packet to check against
293 * @return true if we find a match
295 bool trySatisfyFunctional(PacketPtr pkt);
299 /** When receiving a timing request from the peer port,
300 pass it to the bridge. */
301 bool recvTimingResp(PacketPtr pkt);
303 /** When receiving a retry request from the peer port,
304 pass it to the bridge. */
308 /** Slave port of the bridge. */
309 BridgeSlavePort slavePort;
311 /** Master port of the bridge. */
312 BridgeMasterPort masterPort;
316 Port &getPort(const std::string &if_name,
317 PortID idx=InvalidPortID) override;
319 void init() override;
321 typedef BridgeParams Params;
326 #endif //__MEM_BRIDGE_HH__