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43 * Declaration of a memory-mapped bridge that connects a requestor
44 * and a responder 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 requestor and responder), 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 response port and a request 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 response port to have a pointer
91 class BridgeRequestPort;
94 * The port on the side that receives requests and sends
95 * responses. The response port has a set of address ranges that it
96 * is responsible for. The response port also has a buffer for the
97 * responses not yet sent.
99 class BridgeResponsePort : public ResponsePort
104 /** The bridge to which this port belongs. */
108 * Request port on the other side of the bridge.
110 BridgeRequestPort& memSidePort;
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 BridgeResponsePort.
163 * @param _name the port name including the owner
164 * @param _bridge the structural owner
165 * @param _memSidePort the request port on the other
167 * @param _delay the delay in cycles from receiving to sending
168 * @param _resp_limit the size of the response queue
169 * @param _ranges a number of address ranges to forward
171 BridgeResponsePort(const std::string& _name, Bridge& _bridge,
172 BridgeRequestPort& _memSidePort, Cycles _delay,
173 int _resp_limit, std::vector<AddrRange> _ranges);
176 * Queue a response packet to be sent out later and also schedule
177 * a send if necessary.
179 * @param pkt a response to send out after a delay
180 * @param when tick when response packet should be sent
182 void schedTimingResp(PacketPtr pkt, Tick when);
185 * Retry any stalled request that we have failed to accept at
186 * an earlier point in time. This call will do nothing if no
187 * request is waiting.
189 void retryStalledReq();
193 /** When receiving a timing request from the peer port,
194 pass it to the bridge. */
195 bool recvTimingReq(PacketPtr pkt);
197 /** When receiving a retry request from the peer port,
198 pass it to the bridge. */
199 void recvRespRetry();
201 /** When receiving a Atomic requestfrom the peer port,
202 pass it to the bridge. */
203 Tick recvAtomic(PacketPtr pkt);
205 /** When receiving a Functional request from the peer port,
206 pass it to the bridge. */
207 void recvFunctional(PacketPtr pkt);
209 /** When receiving a address range request the peer port,
210 pass it to the bridge. */
211 AddrRangeList getAddrRanges() const;
216 * Port on the side that forwards requests and receives
217 * responses. The request port has a buffer for the requests not
220 class BridgeRequestPort : public RequestPort
225 /** The bridge to which this port belongs. */
229 * The response port on the other side of the bridge.
231 BridgeResponsePort& cpuSidePort;
233 /** Minimum delay though this bridge. */
237 * Request packet queue. Request packets are held in this
238 * queue for a specified delay to model the processing delay
239 * of the bridge. We use a deque as we need to iterate over
240 * the items for functional accesses.
242 std::deque<DeferredPacket> transmitList;
244 /** Max queue size for request packets */
245 const unsigned int reqQueueLimit;
248 * Handle send event, scheduled when the packet at the head of
249 * the outbound queue is ready to transmit (for timing
252 void trySendTiming();
254 /** Send event for the request queue. */
255 EventFunctionWrapper sendEvent;
260 * Constructor for the BridgeRequestPort.
262 * @param _name the port name including the owner
263 * @param _bridge the structural owner
264 * @param _cpuSidePort the response port on the other side of
266 * @param _delay the delay in cycles from receiving to sending
267 * @param _req_limit the size of the request queue
269 BridgeRequestPort(const std::string& _name, Bridge& _bridge,
270 BridgeResponsePort& _cpuSidePort, Cycles _delay,
274 * Is this side blocked from accepting new request packets.
276 * @return true if the occupied space has reached the set limit
278 bool reqQueueFull() const;
281 * Queue a request packet to be sent out later and also schedule
282 * a send if necessary.
284 * @param pkt a request to send out after a delay
285 * @param when tick when response packet should be sent
287 void schedTimingReq(PacketPtr pkt, Tick when);
290 * Check a functional request against the packets in our
293 * @param pkt packet to check against
295 * @return true if we find a match
297 bool trySatisfyFunctional(PacketPtr pkt);
301 /** When receiving a timing request from the peer port,
302 pass it to the bridge. */
303 bool recvTimingResp(PacketPtr pkt);
305 /** When receiving a retry request from the peer port,
306 pass it to the bridge. */
310 /** Response port of the bridge. */
311 BridgeResponsePort cpuSidePort;
313 /** Request port of the bridge. */
314 BridgeRequestPort memSidePort;
318 Port &getPort(const std::string &if_name,
319 PortID idx=InvalidPortID) override;
321 void init() override;
323 typedef BridgeParams Params;
325 Bridge(const Params &p);
328 #endif //__MEM_BRIDGE_HH__