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/*
* Copyright (c) 2011-2013, 2015 ARM Limited
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*
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*
* Copyright (c) 2006 The Regents of The University of Michigan
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*/
/**
* @file
* Implementation of a memory-mapped bridge that connects a requestor
* and a responder through a request and response queue.
*/
#include "mem/bridge.hh"
#include "base/trace.hh"
#include "debug/Bridge.hh"
#include "params/Bridge.hh"
namespace gem5
{
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::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)
{
}
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)
{
}
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
// pass it along to our super class
return ClockedObject::getPort(if_name, idx);
}
void
Bridge::init()
{
// 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");
// notify the request side of our address ranges
cpuSidePort.sendRangeChange();
}
bool
Bridge::BridgeResponsePort::respQueueFull() const
{
return outstandingResponses == respQueueLimit;
}
bool
Bridge::BridgeRequestPort::reqQueueFull() const
{
return transmitList.size() == reqQueueLimit;
}
bool
Bridge::BridgeRequestPort::recvTimingResp(PacketPtr pkt)
{
// 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());
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;
cpuSidePort.schedTimingResp(pkt, bridge.clockEdge(delay) +
receive_delay);
return true;
}
bool
Bridge::BridgeResponsePort::recvTimingReq(PacketPtr pkt)
{
DPRINTF(Bridge, "recvTimingReq: %s addr 0x%x\n",
pkt->cmdString(), pkt->getAddr());
panic_if(pkt->cacheResponding(), "Should not see packets where cache "
"is responding");
// 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);
// 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);
}
}
// 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::BridgeResponsePort::retryStalledReq()
{
if (retryReq) {
DPRINTF(Bridge, "Request waiting for retry, now retrying\n");
retryReq = false;
sendRetryReq();
}
}
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);
}
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 (transmitList.empty()) {
bridge.schedule(sendEvent, when);
}
transmitList.emplace_back(pkt, when);
}
void
Bridge::BridgeRequestPort::trySendTiming()
{
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");
// 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();
}
// 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();
assert(resp.tick <= curTick());
PacketPtr pkt = resp.pkt;
DPRINTF(Bridge, "trySend response addr 0x%x, outstanding %d\n",
pkt->getAddr(), outstandingResponses);
if (sendTimingResp(pkt)) {
// send successful
transmitList.pop_front();
DPRINTF(Bridge, "trySend response successful\n");
assert(outstandingResponses != 0);
--outstandingResponses;
// If there are more packets to send, schedule event to try again.
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();
}
}
// 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::BridgeResponsePort::recvRespRetry()
{
trySendTiming();
}
Tick
Bridge::BridgeResponsePort::recvAtomic(PacketPtr pkt)
{
panic_if(pkt->cacheResponding(), "Should not see packets where cache "
"is responding");
return delay * bridge.clockPeriod() + memSidePort.sendAtomic(pkt);
}
void
Bridge::BridgeResponsePort::recvFunctional(PacketPtr pkt)
{
pkt->pushLabel(name());
// check the response queue
for (auto i = transmitList.begin(); i != transmitList.end(); ++i) {
if (pkt->trySatisfyFunctional((*i).pkt)) {
pkt->makeResponse();
return;
}
}
// also check the request port's request queue
if (memSidePort.trySatisfyFunctional(pkt)) {
return;
}
pkt->popLabel();
// fall through if pkt still not satisfied
memSidePort.sendFunctional(pkt);
}
bool
Bridge::BridgeRequestPort::trySatisfyFunctional(PacketPtr pkt)
{
bool found = false;
auto i = transmitList.begin();
while (i != transmitList.end() && !found) {
if (pkt->trySatisfyFunctional((*i).pkt)) {
pkt->makeResponse();
found = true;
}
++i;
}
return found;
}
AddrRangeList
Bridge::BridgeResponsePort::getAddrRanges() const
{
return ranges;
}
} // namespace gem5