-
/*
+ * Copyright (c) 2011-2013, 2015 ARM Limited
+ * All rights reserved
+ *
+ * The license below extends only to copyright in the software and shall
+ * not be construed as granting a license to any other intellectual
+ * property including but not limited to intellectual property relating
+ * to a hardware implementation of the functionality of the software
+ * licensed hereunder. You may use the software subject to the license
+ * terms below provided that you ensure that this notice is replicated
+ * unmodified and in its entirety in all distributions of the software,
+ * modified or unmodified, in source code or in binary form.
+ *
* Copyright (c) 2006 The Regents of The University of Michigan
* All rights reserved.
*
*
* Authors: Ali Saidi
* Steve Reinhardt
+ * Andreas Hansson
*/
/**
* @file
- * Definition of a simple bus bridge without buffering.
+ * Implementation of a memory-mapped bridge that connects a master
+ * and a slave through a request and response queue.
*/
-#include <algorithm>
-
-#include "base/range_ops.hh"
#include "base/trace.hh"
+#include "debug/Bridge.hh"
#include "mem/bridge.hh"
#include "params/Bridge.hh"
-Bridge::BridgePort::BridgePort(const std::string &_name,
- Bridge *_bridge, BridgePort *_otherPort,
- int _delay, int _nack_delay, int _req_limit,
- int _resp_limit,
- std::vector<Range<Addr> > filter_ranges)
- : Port(_name), bridge(_bridge), otherPort(_otherPort),
- delay(_delay), nackDelay(_nack_delay), filterRanges(filter_ranges),
- outstandingResponses(0), queuedRequests(0), inRetry(false),
- reqQueueLimit(_req_limit), respQueueLimit(_resp_limit), sendEvent(this)
+Bridge::BridgeSlavePort::BridgeSlavePort(const std::string& _name,
+ Bridge& _bridge,
+ BridgeMasterPort& _masterPort,
+ Cycles _delay, int _resp_limit,
+ std::vector<AddrRange> _ranges)
+ : SlavePort(_name, &_bridge), bridge(_bridge), masterPort(_masterPort),
+ delay(_delay), ranges(_ranges.begin(), _ranges.end()),
+ outstandingResponses(0), retryReq(false),
+ respQueueLimit(_resp_limit), sendEvent(*this)
+{
+}
+
+Bridge::BridgeMasterPort::BridgeMasterPort(const std::string& _name,
+ Bridge& _bridge,
+ BridgeSlavePort& _slavePort,
+ Cycles _delay, int _req_limit)
+ : MasterPort(_name, &_bridge), bridge(_bridge), slavePort(_slavePort),
+ delay(_delay), reqQueueLimit(_req_limit), sendEvent(*this)
{
}
Bridge::Bridge(Params *p)
: MemObject(p),
- portA(p->name + "-portA", this, &portB, p->delay, p->nack_delay,
- p->req_size_a, p->resp_size_a, p->filter_ranges_a),
- portB(p->name + "-portB", this, &portA, p->delay, p->nack_delay,
- p->req_size_b, p->resp_size_b, p->filter_ranges_b),
- ackWrites(p->write_ack), _params(p)
+ slavePort(p->name + ".slave", *this, masterPort,
+ ticksToCycles(p->delay), p->resp_size, p->ranges),
+ masterPort(p->name + ".master", *this, slavePort,
+ ticksToCycles(p->delay), p->req_size)
{
- if (ackWrites)
- panic("No support for acknowledging writes\n");
}
-Port *
-Bridge::getPort(const std::string &if_name, int idx)
+BaseMasterPort&
+Bridge::getMasterPort(const std::string &if_name, PortID idx)
{
- BridgePort *port;
-
- if (if_name == "side_a")
- port = &portA;
- else if (if_name == "side_b")
- port = &portB;
+ if (if_name == "master")
+ return masterPort;
else
- return NULL;
-
- if (port->getPeer() != NULL && !port->getPeer()->isDefaultPort())
- panic("bridge side %s already connected to %s.",
- if_name, port->getPeer()->name());
- return port;
+ // pass it along to our super class
+ return MemObject::getMasterPort(if_name, idx);
}
+BaseSlavePort&
+Bridge::getSlavePort(const std::string &if_name, PortID idx)
+{
+ if (if_name == "slave")
+ return slavePort;
+ else
+ // pass it along to our super class
+ return MemObject::getSlavePort(if_name, idx);
+}
void
Bridge::init()
{
- // Make sure that both sides are connected to.
- if (!portA.isConnected() || !portB.isConnected())
- fatal("Both ports of bus bridge are not connected to a bus.\n");
+ // make sure both sides are connected and have the same block size
+ if (!slavePort.isConnected() || !masterPort.isConnected())
+ fatal("Both ports of a bridge must be connected.\n");
- if (portA.peerBlockSize() != portB.peerBlockSize())
- fatal("Busses don't have the same block size... Not supported.\n");
+ // notify the master side of our address ranges
+ slavePort.sendRangeChange();
}
bool
-Bridge::BridgePort::respQueueFull()
+Bridge::BridgeSlavePort::respQueueFull() const
{
- assert(outstandingResponses >= 0 && outstandingResponses <= respQueueLimit);
- return outstandingResponses >= respQueueLimit;
+ return outstandingResponses == respQueueLimit;
}
bool
-Bridge::BridgePort::reqQueueFull()
+Bridge::BridgeMasterPort::reqQueueFull() const
{
- assert(queuedRequests >= 0 && queuedRequests <= reqQueueLimit);
- return queuedRequests >= reqQueueLimit;
+ return transmitList.size() == reqQueueLimit;
}
-/** Function called by the port when the bus is receiving a Timing
- * transaction.*/
bool
-Bridge::BridgePort::recvTiming(PacketPtr pkt)
+Bridge::BridgeMasterPort::recvTimingResp(PacketPtr pkt)
{
- DPRINTF(BusBridge, "recvTiming: src %d dest %d addr 0x%x\n",
- pkt->getSrc(), pkt->getDest(), pkt->getAddr());
-
- DPRINTF(BusBridge, "Local queue size: %d outreq: %d outresp: %d\n",
- sendQueue.size(), queuedRequests, outstandingResponses);
- DPRINTF(BusBridge, "Remote queue size: %d outreq: %d outresp: %d\n",
- otherPort->sendQueue.size(), otherPort->queuedRequests,
- otherPort->outstandingResponses);
-
- if (pkt->isRequest() && otherPort->reqQueueFull()) {
- DPRINTF(BusBridge, "Remote queue full, nacking\n");
- nackRequest(pkt);
- return true;
- }
+ // all checks are done when the request is accepted on the slave
+ // side, so we are guaranteed to have space for the response
+ DPRINTF(Bridge, "recvTimingResp: %s addr 0x%x\n",
+ pkt->cmdString(), pkt->getAddr());
- if (pkt->needsResponse())
- if (respQueueFull()) {
- DPRINTF(BusBridge, "Local queue full, no space for response, nacking\n");
- DPRINTF(BusBridge, "queue size: %d outreq: %d outstanding resp: %d\n",
- sendQueue.size(), queuedRequests, outstandingResponses);
- nackRequest(pkt);
- return true;
- } else {
- DPRINTF(BusBridge, "Request Needs response, reserving space\n");
- ++outstandingResponses;
- }
+ DPRINTF(Bridge, "Request queue size: %d\n", transmitList.size());
- otherPort->queueForSendTiming(pkt);
+ // technically the packet only reaches us after the header delay,
+ // and typically we also need to deserialise any payload (unless
+ // the two sides of the bridge are synchronous)
+ Tick receive_delay = pkt->headerDelay + pkt->payloadDelay;
+ pkt->headerDelay = pkt->payloadDelay = 0;
+
+ slavePort.schedTimingResp(pkt, bridge.clockEdge(delay) +
+ receive_delay);
return true;
}
-void
-Bridge::BridgePort::nackRequest(PacketPtr pkt)
+bool
+Bridge::BridgeSlavePort::recvTimingReq(PacketPtr pkt)
{
- // Nack the packet
- pkt->makeTimingResponse();
- pkt->setNacked();
-
- //put it on the list to send
- Tick readyTime = curTick + nackDelay;
- PacketBuffer *buf = new PacketBuffer(pkt, readyTime, true);
-
- // nothing on the list, add it and we're done
- if (sendQueue.empty()) {
- assert(!sendEvent.scheduled());
- sendEvent.schedule(readyTime);
- sendQueue.push_back(buf);
- return;
+ DPRINTF(Bridge, "recvTimingReq: %s addr 0x%x\n",
+ pkt->cmdString(), pkt->getAddr());
+
+ // if a cache is responding, sink the packet without further
+ // action, also discard any packet that is not a read or a write
+ if (pkt->cacheResponding() ||
+ !(pkt->isWrite() || pkt->isRead())) {
+ assert(!pkt->needsResponse());
+ pendingDelete.reset(pkt);
+ return true;
}
- assert(sendEvent.scheduled() || inRetry);
+ // we should not get a new request after committing to retry the
+ // current one, but unfortunately the CPU violates this rule, so
+ // simply ignore it for now
+ if (retryReq)
+ return false;
- // does it go at the end?
- if (readyTime >= sendQueue.back()->ready) {
- sendQueue.push_back(buf);
- return;
- }
+ DPRINTF(Bridge, "Response queue size: %d outresp: %d\n",
+ transmitList.size(), outstandingResponses);
- // ok, somewhere in the middle, fun
- std::list<PacketBuffer*>::iterator i = sendQueue.begin();
- std::list<PacketBuffer*>::iterator end = sendQueue.end();
- std::list<PacketBuffer*>::iterator begin = sendQueue.begin();
- bool done = false;
-
- while (i != end && !done) {
- if (readyTime < (*i)->ready) {
- if (i == begin)
- sendEvent.reschedule(readyTime);
- sendQueue.insert(i,buf);
- done = true;
+ // if the request queue is full then there is no hope
+ if (masterPort.reqQueueFull()) {
+ DPRINTF(Bridge, "Request queue full\n");
+ retryReq = true;
+ } else {
+ // look at the response queue if we expect to see a response
+ bool expects_response = pkt->needsResponse();
+ if (expects_response) {
+ if (respQueueFull()) {
+ DPRINTF(Bridge, "Response queue full\n");
+ retryReq = true;
+ } else {
+ // ok to send the request with space for the response
+ DPRINTF(Bridge, "Reserving space for response\n");
+ assert(outstandingResponses != respQueueLimit);
+ ++outstandingResponses;
+
+ // no need to set retryReq to false as this is already the
+ // case
+ }
+ }
+
+ if (!retryReq) {
+ // technically the packet only reaches us after the header
+ // delay, and typically we also need to deserialise any
+ // payload (unless the two sides of the bridge are
+ // synchronous)
+ Tick receive_delay = pkt->headerDelay + pkt->payloadDelay;
+ pkt->headerDelay = pkt->payloadDelay = 0;
+
+ masterPort.schedTimingReq(pkt, bridge.clockEdge(delay) +
+ receive_delay);
}
- i++;
}
- assert(done);
-}
+ // remember that we are now stalling a packet and that we have to
+ // tell the sending master to retry once space becomes available,
+ // we make no distinction whether the stalling is due to the
+ // request queue or response queue being full
+ return !retryReq;
+}
void
-Bridge::BridgePort::queueForSendTiming(PacketPtr pkt)
+Bridge::BridgeSlavePort::retryStalledReq()
{
- if (pkt->isResponse()) {
- // This is a response for a request we forwarded earlier. The
- // corresponding PacketBuffer should be stored in the packet's
- // senderState field.
-
- PacketBuffer *buf = dynamic_cast<PacketBuffer*>(pkt->senderState);
- assert(buf != NULL);
- // set up new packet dest & senderState based on values saved
- // from original request
- buf->fixResponse(pkt);
-
- DPRINTF(BusBridge, "response, new dest %d\n", pkt->getDest());
- delete buf;
+ if (retryReq) {
+ DPRINTF(Bridge, "Request waiting for retry, now retrying\n");
+ retryReq = false;
+ sendRetryReq();
}
+}
-
- if (pkt->isRequest()) {
- ++queuedRequests;
+void
+Bridge::BridgeMasterPort::schedTimingReq(PacketPtr pkt, Tick when)
+{
+ // If we're about to put this packet at the head of the queue, we
+ // need to schedule an event to do the transmit. Otherwise there
+ // should already be an event scheduled for sending the head
+ // packet.
+ if (transmitList.empty()) {
+ bridge.schedule(sendEvent, when);
}
+ assert(transmitList.size() != reqQueueLimit);
+ transmitList.emplace_back(pkt, when);
+}
- Tick readyTime = curTick + delay;
- PacketBuffer *buf = new PacketBuffer(pkt, readyTime);
+void
+Bridge::BridgeSlavePort::schedTimingResp(PacketPtr pkt, Tick when)
+{
// If we're about to put this packet at the head of the queue, we
// need to schedule an event to do the transmit. Otherwise there
// should already be an event scheduled for sending the head
// packet.
- if (sendQueue.empty()) {
- sendEvent.schedule(readyTime);
+ if (transmitList.empty()) {
+ bridge.schedule(sendEvent, when);
}
- sendQueue.push_back(buf);
+
+ transmitList.emplace_back(pkt, when);
}
void
-Bridge::BridgePort::trySend()
+Bridge::BridgeMasterPort::trySendTiming()
{
- assert(!sendQueue.empty());
+ assert(!transmitList.empty());
+
+ DeferredPacket req = transmitList.front();
+
+ assert(req.tick <= curTick());
+
+ PacketPtr pkt = req.pkt;
+
+ DPRINTF(Bridge, "trySend request addr 0x%x, queue size %d\n",
+ pkt->getAddr(), transmitList.size());
+
+ if (sendTimingReq(pkt)) {
+ // send successful
+ transmitList.pop_front();
+ DPRINTF(Bridge, "trySend request successful\n");
- PacketBuffer *buf = sendQueue.front();
+ // If there are more packets to send, schedule event to try again.
+ if (!transmitList.empty()) {
+ DeferredPacket next_req = transmitList.front();
+ DPRINTF(Bridge, "Scheduling next send\n");
+ bridge.schedule(sendEvent, std::max(next_req.tick,
+ bridge.clockEdge()));
+ }
- assert(buf->ready <= curTick);
+ // if we have stalled a request due to a full request queue,
+ // then send a retry at this point, also note that if the
+ // request we stalled was waiting for the response queue
+ // rather than the request queue we might stall it again
+ slavePort.retryStalledReq();
+ }
- PacketPtr pkt = buf->pkt;
+ // if the send failed, then we try again once we receive a retry,
+ // and therefore there is no need to take any action
+}
- DPRINTF(BusBridge, "trySend: origSrc %d dest %d addr 0x%x\n",
- buf->origSrc, pkt->getDest(), pkt->getAddr());
+void
+Bridge::BridgeSlavePort::trySendTiming()
+{
+ assert(!transmitList.empty());
+
+ DeferredPacket resp = transmitList.front();
- bool wasReq = pkt->isRequest();
- bool was_nacked_here = buf->nackedHere;
+ assert(resp.tick <= curTick());
- // If the send was successful, make sure sender state was set to NULL
- // otherwise we could get a NACK back of a packet that didn't expect a
- // response and we would try to use freed memory.
+ PacketPtr pkt = resp.pkt;
- Packet::SenderState *old_sender_state = pkt->senderState;
- if (pkt->isRequest() && !buf->expectResponse)
- pkt->senderState = NULL;
+ DPRINTF(Bridge, "trySend response addr 0x%x, outstanding %d\n",
+ pkt->getAddr(), outstandingResponses);
- if (sendTiming(pkt)) {
+ if (sendTimingResp(pkt)) {
// send successful
- sendQueue.pop_front();
- buf->pkt = NULL; // we no longer own packet, so it's not safe to look at it
-
- if (buf->expectResponse) {
- // Must wait for response
- DPRINTF(BusBridge, " successful: awaiting response (%d)\n",
- outstandingResponses);
- } else {
- // no response expected... deallocate packet buffer now.
- DPRINTF(BusBridge, " successful: no response expected\n");
- delete buf;
- }
+ transmitList.pop_front();
+ DPRINTF(Bridge, "trySend response successful\n");
- if (wasReq)
- --queuedRequests;
- else if (!was_nacked_here)
- --outstandingResponses;
+ assert(outstandingResponses != 0);
+ --outstandingResponses;
// If there are more packets to send, schedule event to try again.
- if (!sendQueue.empty()) {
- buf = sendQueue.front();
- DPRINTF(BusBridge, "Scheduling next send\n");
- sendEvent.schedule(std::max(buf->ready, curTick + 1));
+ if (!transmitList.empty()) {
+ DeferredPacket next_resp = transmitList.front();
+ DPRINTF(Bridge, "Scheduling next send\n");
+ bridge.schedule(sendEvent, std::max(next_resp.tick,
+ bridge.clockEdge()));
+ }
+
+ // if there is space in the request queue and we were stalling
+ // a request, it will definitely be possible to accept it now
+ // since there is guaranteed space in the response queue
+ if (!masterPort.reqQueueFull() && retryReq) {
+ DPRINTF(Bridge, "Request waiting for retry, now retrying\n");
+ retryReq = false;
+ sendRetryReq();
}
- } else {
- DPRINTF(BusBridge, " unsuccessful\n");
- pkt->senderState = old_sender_state;
- inRetry = true;
}
- DPRINTF(BusBridge, "trySend: queue size: %d outreq: %d outstanding resp: %d\n",
- sendQueue.size(), queuedRequests, outstandingResponses);
+ // if the send failed, then we try again once we receive a retry,
+ // and therefore there is no need to take any action
}
+void
+Bridge::BridgeMasterPort::recvReqRetry()
+{
+ trySendTiming();
+}
void
-Bridge::BridgePort::recvRetry()
+Bridge::BridgeSlavePort::recvRespRetry()
{
- inRetry = false;
- Tick nextReady = sendQueue.front()->ready;
- if (nextReady <= curTick)
- trySend();
- else
- sendEvent.schedule(nextReady);
+ trySendTiming();
}
-/** Function called by the port when the bus is receiving a Atomic
- * transaction.*/
Tick
-Bridge::BridgePort::recvAtomic(PacketPtr pkt)
+Bridge::BridgeSlavePort::recvAtomic(PacketPtr pkt)
{
- return delay + otherPort->sendAtomic(pkt);
+ return delay * bridge.clockPeriod() + masterPort.sendAtomic(pkt);
}
-/** Function called by the port when the bus is receiving a Functional
- * transaction.*/
void
-Bridge::BridgePort::recvFunctional(PacketPtr pkt)
+Bridge::BridgeSlavePort::recvFunctional(PacketPtr pkt)
{
- std::list<PacketBuffer*>::iterator i;
-
pkt->pushLabel(name());
- for (i = sendQueue.begin(); i != sendQueue.end(); ++i) {
- if (pkt->checkFunctional((*i)->pkt))
+ // check the response queue
+ for (auto i = transmitList.begin(); i != transmitList.end(); ++i) {
+ if (pkt->checkFunctional((*i).pkt)) {
+ pkt->makeResponse();
return;
+ }
+ }
+
+ // also check the master port's request queue
+ if (masterPort.checkFunctional(pkt)) {
+ return;
}
pkt->popLabel();
// fall through if pkt still not satisfied
- otherPort->sendFunctional(pkt);
+ masterPort.sendFunctional(pkt);
}
-/** Function called by the port when the bus is receiving a status change.*/
-void
-Bridge::BridgePort::recvStatusChange(Port::Status status)
+bool
+Bridge::BridgeMasterPort::checkFunctional(PacketPtr pkt)
{
- otherPort->sendStatusChange(status);
+ bool found = false;
+ auto i = transmitList.begin();
+
+ while (i != transmitList.end() && !found) {
+ if (pkt->checkFunctional((*i).pkt)) {
+ pkt->makeResponse();
+ found = true;
+ }
+ ++i;
+ }
+
+ return found;
}
-void
-Bridge::BridgePort::getDeviceAddressRanges(AddrRangeList &resp,
- bool &snoop)
+AddrRangeList
+Bridge::BridgeSlavePort::getAddrRanges() const
{
- otherPort->getPeerAddressRanges(resp, snoop);
- FilterRangeList(filterRanges, resp);
- // we don't allow snooping across bridges
- snoop = false;
+ return ranges;
}
Bridge *
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