-
/*
+ * 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.
*
* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
- *
- * Authors: Ali Saidi
- * Steve Reinhardt
*/
/**
* @file
- * Definition of a simple bus bridge without buffering.
+ * Implementation of a memory-mapped bridge that connects a requestor
+ * and a responder through a request and response queue.
*/
-#include <algorithm>
+#include "mem/bridge.hh"
#include "base/trace.hh"
-#include "mem/bridge.hh"
-#include "sim/builder.hh"
-
-Bridge::BridgePort::BridgePort(const std::string &_name,
- Bridge *_bridge, BridgePort *_otherPort,
- int _delay, int _nack_delay, int _req_limit,
- int _resp_limit, bool fix_partial_write)
- : Port(_name), bridge(_bridge), otherPort(_otherPort),
- delay(_delay), nackDelay(_nack_delay), fixPartialWrite(fix_partial_write),
- outstandingResponses(0), queuedRequests(0), inRetry(false),
- reqQueueLimit(_req_limit), respQueueLimit(_resp_limit), sendEvent(this)
+#include "debug/Bridge.hh"
+#include "params/Bridge.hh"
+
+Bridge::BridgeResponsePort::BridgeResponsePort(const std::string& _name,
+ Bridge& _bridge,
+ BridgeRequestPort& _memSidePort,
+ Cycles _delay, int _resp_limit,
+ std::vector<AddrRange> _ranges)
+ : ResponsePort(_name, &_bridge), bridge(_bridge),
+ memSidePort(_memSidePort), delay(_delay),
+ ranges(_ranges.begin(), _ranges.end()),
+ outstandingResponses(0), retryReq(false), respQueueLimit(_resp_limit),
+ sendEvent([this]{ trySendTiming(); }, _name)
{
}
-Bridge::Bridge(Params *p)
- : MemObject(p->name),
- portA(p->name + "-portA", this, &portB, p->delay, p->nack_delay,
- p->req_size_a, p->resp_size_a, p->fix_partial_write_a),
- portB(p->name + "-portB", this, &portA, p->delay, p->nack_delay,
- p->req_size_b, p->resp_size_b, p->fix_partial_write_b),
- ackWrites(p->write_ack), _params(p)
+Bridge::BridgeRequestPort::BridgeRequestPort(const std::string& _name,
+ Bridge& _bridge,
+ BridgeResponsePort& _cpuSidePort,
+ Cycles _delay, int _req_limit)
+ : RequestPort(_name, &_bridge), bridge(_bridge),
+ cpuSidePort(_cpuSidePort),
+ delay(_delay), reqQueueLimit(_req_limit),
+ sendEvent([this]{ trySendTiming(); }, _name)
{
- if (ackWrites)
- panic("No support for acknowledging writes\n");
}
-Port *
-Bridge::getPort(const std::string &if_name, int idx)
+Bridge::Bridge(const Params &p)
+ : ClockedObject(p),
+ cpuSidePort(p.name + ".cpu_side_port", *this, memSidePort,
+ ticksToCycles(p.delay), p.resp_size, p.ranges),
+ memSidePort(p.name + ".mem_side_port", *this, cpuSidePort,
+ ticksToCycles(p.delay), p.req_size)
{
- BridgePort *port;
+}
- if (if_name == "side_a")
- port = &portA;
- else if (if_name == "side_b")
- port = &portB;
+Port &
+Bridge::getPort(const std::string &if_name, PortID idx)
+{
+ if (if_name == "mem_side_port")
+ return memSidePort;
+ else if (if_name == "cpu_side_port")
+ return cpuSidePort;
else
- return NULL;
-
- if (port->getPeer() != NULL)
- panic("bridge side %s already connected to.", if_name);
- return port;
+ // pass it along to our super class
+ return ClockedObject::getPort(if_name, idx);
}
-
void
Bridge::init()
{
- // Make sure that both sides are connected to.
- if (portA.getPeer() == NULL || portB.getPeer() == NULL)
- 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 (!cpuSidePort.isConnected() || !memSidePort.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 request side of our address ranges
+ cpuSidePort.sendRangeChange();
}
bool
-Bridge::BridgePort::respQueueFull()
+Bridge::BridgeResponsePort::respQueueFull() const
{
- assert(outstandingResponses >= 0 && outstandingResponses <= respQueueLimit);
- return outstandingResponses >= respQueueLimit;
+ return outstandingResponses == respQueueLimit;
}
bool
-Bridge::BridgePort::reqQueueFull()
+Bridge::BridgeRequestPort::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::BridgeRequestPort::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, "Remove queue size: %d outreq: %d outresp: %d\n",
- otherPort->sendQueue.size(), otherPort->queuedRequests,
- otherPort->outstandingResponses);
-
- if (pkt->isRequest() && otherPort->reqQueueFull() && !pkt->wasNacked()) {
- DPRINTF(BusBridge, "Remote queue full, nacking\n");
- nackRequest(pkt);
- return true;
- }
+ // all checks are done when the request is accepted on the response
+ // 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() && !pkt->wasNacked())
- 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());
+
+ // 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;
- otherPort->queueForSendTiming(pkt);
+ cpuSidePort.schedTimingResp(pkt, bridge.clockEdge(delay) +
+ receive_delay);
return true;
}
-void
-Bridge::BridgePort::nackRequest(PacketPtr pkt)
+bool
+Bridge::BridgeResponsePort::recvTimingReq(PacketPtr pkt)
{
- // Nack the packet
- pkt->setNacked();
- pkt->setDest(pkt->getSrc());
-
- //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());
- assert(sendEvent.scheduled() || inRetry);
+ panic_if(pkt->cacheResponding(), "Should not see packets where cache "
+ "is responding");
- // does it go at the end?
- if (readyTime >= sendQueue.back()->ready) {
- sendQueue.push_back(buf);
- return;
- }
+ // 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;
+
+ 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 (memSidePort.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;
+
+ memSidePort.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 requestor 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::BridgeResponsePort::retryStalledReq()
{
- if (pkt->isResponse() || pkt->wasNacked()) {
- // 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);
-
- // Check if this packet was expecting a response and it's a nacked
- // packet, in which case we will never being seeing it
- if (buf->expectResponse && pkt->wasNacked())
- --outstandingResponses;
-
-
- DPRINTF(BusBridge, "restoring sender state: %#X, from packet buffer: %#X\n",
- pkt->senderState, buf);
- DPRINTF(BusBridge, " is 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() && !pkt->wasNacked()) {
- ++queuedRequests;
+void
+Bridge::BridgeRequestPort::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);
- DPRINTF(BusBridge, "old sender state: %#X, new sender state: %#X\n",
- buf->origSenderState, buf);
+void
+Bridge::BridgeResponsePort::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::BridgeRequestPort::trySendTiming()
{
- assert(!sendQueue.empty());
+ assert(!transmitList.empty());
- PacketBuffer *buf = sendQueue.front();
+ DeferredPacket req = transmitList.front();
- assert(buf->ready <= curTick);
+ assert(req.tick <= curTick());
- PacketPtr pkt = buf->pkt;
+ PacketPtr pkt = req.pkt;
- // Ugly! @todo When multilevel coherence works this will be removed
- if (pkt->cmd == MemCmd::WriteInvalidateReq && fixPartialWrite &&
- !pkt->wasNacked()) {
- PacketPtr funcPkt = new Packet(pkt->req, MemCmd::WriteReq,
- Packet::Broadcast);
- funcPkt->dataStatic(pkt->getPtr<uint8_t>());
- sendFunctional(funcPkt);
- pkt->cmd = MemCmd::WriteReq;
- delete funcPkt;
+ 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");
+
+ // 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()));
+ }
+
+ // 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
+ cpuSidePort.retryStalledReq();
}
- DPRINTF(BusBridge, "trySend: origSrc %d dest %d addr 0x%x\n",
- buf->origSrc, pkt->getDest(), pkt->getAddr());
+ // 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::BridgeResponsePort::trySendTiming()
+{
+ assert(!transmitList.empty());
+
+ DeferredPacket resp = transmitList.front();
- bool wasReq = pkt->isRequest();
- bool wasNacked = pkt->wasNacked();
+ assert(resp.tick <= curTick());
- if (sendTiming(pkt)) {
+ PacketPtr pkt = resp.pkt;
+
+ DPRINTF(Bridge, "trySend response addr 0x%x, outstanding %d\n",
+ pkt->getAddr(), outstandingResponses);
+
+ 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 (!wasNacked) {
- if (wasReq)
- --queuedRequests;
- else
- --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 (!memSidePort.reqQueueFull() && retryReq) {
+ DPRINTF(Bridge, "Request waiting for retry, now retrying\n");
+ retryReq = false;
+ sendRetryReq();
}
- } else {
- DPRINTF(BusBridge, " unsuccessful\n");
- 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::BridgeRequestPort::recvReqRetry()
+{
+ trySendTiming();
+}
void
-Bridge::BridgePort::recvRetry()
+Bridge::BridgeResponsePort::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::BridgeResponsePort::recvAtomic(PacketPtr pkt)
{
- // fix partial atomic writes... similar to the timing code that does the
- // same... will be removed once our code gets this right
- if (pkt->cmd == MemCmd::WriteInvalidateReq && fixPartialWrite) {
-
- PacketPtr funcPkt = new Packet(pkt->req, MemCmd::WriteReq,
- Packet::Broadcast);
- funcPkt->dataStatic(pkt->getPtr<uint8_t>());
- otherPort->sendFunctional(funcPkt);
- delete funcPkt;
- pkt->cmd = MemCmd::WriteReq;
- }
- return delay + otherPort->sendAtomic(pkt);
+ panic_if(pkt->cacheResponding(), "Should not see packets where cache "
+ "is responding");
+
+ return delay * bridge.clockPeriod() + memSidePort.sendAtomic(pkt);
}
-/** Function called by the port when the bus is receiving a Functional
- * transaction.*/
void
-Bridge::BridgePort::recvFunctional(PacketPtr pkt)
+Bridge::BridgeResponsePort::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->trySatisfyFunctional((*i).pkt)) {
+ pkt->makeResponse();
return;
+ }
}
- // fall through if pkt still not satisfied
- otherPort->sendFunctional(pkt);
-}
+ // also check the request port's request queue
+ if (memSidePort.trySatisfyFunctional(pkt)) {
+ return;
+ }
-/** Function called by the port when the bus is receiving a status change.*/
-void
-Bridge::BridgePort::recvStatusChange(Port::Status status)
-{
- otherPort->sendStatusChange(status);
-}
+ pkt->popLabel();
-void
-Bridge::BridgePort::getDeviceAddressRanges(AddrRangeList &resp,
- bool &snoop)
-{
- otherPort->getPeerAddressRanges(resp, snoop);
- // we don't allow snooping across bridges
- snoop = false;
+ // fall through if pkt still not satisfied
+ memSidePort.sendFunctional(pkt);
}
-BEGIN_DECLARE_SIM_OBJECT_PARAMS(Bridge)
-
- Param<int> req_size_a;
- Param<int> req_size_b;
- Param<int> resp_size_a;
- Param<int> resp_size_b;
- Param<Tick> delay;
- Param<Tick> nack_delay;
- Param<bool> write_ack;
- Param<bool> fix_partial_write_a;
- Param<bool> fix_partial_write_b;
-
-END_DECLARE_SIM_OBJECT_PARAMS(Bridge)
-
-BEGIN_INIT_SIM_OBJECT_PARAMS(Bridge)
+bool
+Bridge::BridgeRequestPort::trySatisfyFunctional(PacketPtr pkt)
+{
+ bool found = false;
+ auto i = transmitList.begin();
- INIT_PARAM(req_size_a, "The size of the queue for requests coming into side a"),
- INIT_PARAM(req_size_b, "The size of the queue for requests coming into side b"),
- INIT_PARAM(resp_size_a, "The size of the queue for responses coming into side a"),
- INIT_PARAM(resp_size_b, "The size of the queue for responses coming into side b"),
- INIT_PARAM(delay, "The miminum delay to cross this bridge"),
- INIT_PARAM(nack_delay, "The minimum delay to nack a packet"),
- INIT_PARAM(write_ack, "Acknowledge any writes that are received."),
- INIT_PARAM(fix_partial_write_a, "Fixup any partial block writes that are received"),
- INIT_PARAM(fix_partial_write_b, "Fixup any partial block writes that are received")
+ while (i != transmitList.end() && !found) {
+ if (pkt->trySatisfyFunctional((*i).pkt)) {
+ pkt->makeResponse();
+ found = true;
+ }
+ ++i;
+ }
-END_INIT_SIM_OBJECT_PARAMS(Bridge)
+ return found;
+}
-CREATE_SIM_OBJECT(Bridge)
+AddrRangeList
+Bridge::BridgeResponsePort::getAddrRanges() const
{
- Bridge::Params *p = new Bridge::Params;
- p->name = getInstanceName();
- p->req_size_a = req_size_a;
- p->req_size_b = req_size_b;
- p->resp_size_a = resp_size_a;
- p->resp_size_b = resp_size_b;
- p->delay = delay;
- p->nack_delay = nack_delay;
- p->write_ack = write_ack;
- p->fix_partial_write_a = fix_partial_write_a;
- p->fix_partial_write_b = fix_partial_write_b;
- return new Bridge(p);
+ return ranges;
}
-
-REGISTER_SIM_OBJECT("Bridge", Bridge)
-
-
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