gem5/src/mem/serial_link.cc

440 lines
15 KiB
C++
Raw Normal View History

/*
* Copyright (c) 2011-2013 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
* Copyright (c) 2015 The University of Bologna
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are
* met: redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer;
* redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution;
* neither the name of the copyright holders nor the names of its
* contributors may be used to endorse or promote products derived from
* this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
* A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
* OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
* 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
* Andreas Hansson
* Erfan Azarkhish
*/
/**
* @file
* Implementation of the SerialLink Class, modeling Hybrid-Memory-Cube's
* serial interface.
*/
#include "mem/serial_link.hh"
#include "base/trace.hh"
#include "debug/SerialLink.hh"
#include "params/SerialLink.hh"
SerialLink::SerialLinkSlavePort::SerialLinkSlavePort(const std::string& _name,
SerialLink& _serial_link,
SerialLinkMasterPort& _masterPort,
Cycles _delay, int _resp_limit,
const std::vector<AddrRange>&
_ranges)
: SlavePort(_name, &_serial_link), serial_link(_serial_link),
masterPort(_masterPort), delay(_delay),
ranges(_ranges.begin(), _ranges.end()),
outstandingResponses(0), retryReq(false),
respQueueLimit(_resp_limit), sendEvent(*this)
{
}
SerialLink::SerialLinkMasterPort::SerialLinkMasterPort(const std::string&
_name, SerialLink& _serial_link,
SerialLinkSlavePort& _slavePort,
Cycles _delay, int _req_limit)
: MasterPort(_name, &_serial_link), serial_link(_serial_link),
slavePort(_slavePort), delay(_delay), reqQueueLimit(_req_limit),
sendEvent(*this)
{
}
SerialLink::SerialLink(SerialLinkParams *p)
: MemObject(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),
num_lanes(p->num_lanes),
link_speed(p->link_speed)
{
}
BaseMasterPort&
SerialLink::getMasterPort(const std::string &if_name, PortID idx)
{
if (if_name == "master")
return masterPort;
else
// pass it along to our super class
return MemObject::getMasterPort(if_name, idx);
}
BaseSlavePort&
SerialLink::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
SerialLink::init()
{
// make sure both sides are connected and have the same block size
if (!slavePort.isConnected() || !masterPort.isConnected())
fatal("Both ports of a serial_link must be connected.\n");
// notify the master side of our address ranges
slavePort.sendRangeChange();
}
bool
SerialLink::SerialLinkSlavePort::respQueueFull() const
{
return outstandingResponses == respQueueLimit;
}
bool
SerialLink::SerialLinkMasterPort::reqQueueFull() const
{
return transmitList.size() == reqQueueLimit;
}
bool
SerialLink::SerialLinkMasterPort::recvTimingResp(PacketPtr pkt)
{
// all checks are done when the request is accepted on the slave
// side, so we are guaranteed to have space for the response
DPRINTF(SerialLink, "recvTimingResp: %s addr 0x%x\n",
pkt->cmdString(), pkt->getAddr());
DPRINTF(SerialLink, "Request queue size: %d\n", transmitList.size());
// @todo: We need to pay for this and not just zero it out
pkt->headerDelay = pkt->payloadDelay = 0;
// This is similar to what happens for the request packets:
// The serializer will start serialization as soon as it receives the
// first flit, but the deserializer (at the host side in this case), will
// have to wait to receive the whole packet. So we only account for the
// deserialization latency.
Cycles cycles = delay;
cycles += Cycles(divCeil(pkt->getSize() * 8, serial_link.num_lanes
* serial_link.link_speed));
Tick t = serial_link.clockEdge(cycles);
//@todo: If the processor sends two uncached requests towards HMC and the
// second one is smaller than the first one. It may happen that the second
// one crosses this link faster than the first one (because the packet
// waits in the link based on its size). This can reorder the received
// response.
slavePort.schedTimingResp(pkt, t);
return true;
}
bool
SerialLink::SerialLinkSlavePort::recvTimingReq(PacketPtr pkt)
{
DPRINTF(SerialLink, "recvTimingReq: %s addr 0x%x\n",
pkt->cmdString(), pkt->getAddr());
// we should not see a timing request if we are already in a retry
assert(!retryReq);
DPRINTF(SerialLink, "Response queue size: %d outresp: %d\n",
transmitList.size(), outstandingResponses);
// if the request queue is full then there is no hope
if (masterPort.reqQueueFull()) {
DPRINTF(SerialLink, "Request queue full\n");
retryReq = true;
} else if ( !retryReq ) {
// look at the response queue if we expect to see a response
bool expects_response = pkt->needsResponse() &&
!pkt->cacheResponding();
if (expects_response) {
if (respQueueFull()) {
DPRINTF(SerialLink, "Response queue full\n");
retryReq = true;
} else {
// ok to send the request with space for the response
DPRINTF(SerialLink, "Reserving space for response\n");
assert(outstandingResponses != respQueueLimit);
++outstandingResponses;
// no need to set retryReq to false as this is already the
// case
}
}
if (!retryReq) {
// @todo: We need to pay for this and not just zero it out
pkt->headerDelay = pkt->payloadDelay = 0;
// We assume that the serializer component at the transmitter side
// does not need to receive the whole packet to start the
// serialization (this assumption is consistent with the HMC
// standard). But the deserializer waits for the complete packet
// to check its integrity first. So everytime a packet crosses a
// serial link, we should account for its deserialization latency
// only.
Cycles cycles = delay;
cycles += Cycles(divCeil(pkt->getSize() * 8,
serial_link.num_lanes * serial_link.link_speed));
Tick t = serial_link.clockEdge(cycles);
//@todo: If the processor sends two uncached requests towards HMC
// and the second one is smaller than the first one. It may happen
// that the second one crosses this link faster than the first one
// (because the packet waits in the link based on its size).
// This can reorder the received response.
masterPort.schedTimingReq(pkt, t);
}
}
// 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
SerialLink::SerialLinkSlavePort::retryStalledReq()
{
if (retryReq) {
DPRINTF(SerialLink, "Request waiting for retry, now retrying\n");
retryReq = false;
sendRetryReq();
}
}
void
SerialLink::SerialLinkMasterPort::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()) {
serial_link.schedule(sendEvent, when);
}
assert(transmitList.size() != reqQueueLimit);
transmitList.emplace_back(DeferredPacket(pkt, when));
}
void
SerialLink::SerialLinkSlavePort::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()) {
serial_link.schedule(sendEvent, when);
}
transmitList.emplace_back(DeferredPacket(pkt, when));
}
void
SerialLink::SerialLinkMasterPort::trySendTiming()
{
assert(!transmitList.empty());
DeferredPacket req = transmitList.front();
assert(req.tick <= curTick());
PacketPtr pkt = req.pkt;
DPRINTF(SerialLink, "trySend request addr 0x%x, queue size %d\n",
pkt->getAddr(), transmitList.size());
if (sendTimingReq(pkt)) {
// send successful
transmitList.pop_front();
DPRINTF(SerialLink, "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(SerialLink, "Scheduling next send\n");
// Make sure bandwidth limitation is met
Cycles cycles = Cycles(divCeil(pkt->getSize() * 8,
serial_link.num_lanes * serial_link.link_speed));
Tick t = serial_link.clockEdge(cycles);
serial_link.schedule(sendEvent, std::max(next_req.tick, t));
}
// 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();
}
// if the send failed, then we try again once we receive a retry,
// and therefore there is no need to take any action
}
void
SerialLink::SerialLinkSlavePort::trySendTiming()
{
assert(!transmitList.empty());
DeferredPacket resp = transmitList.front();
assert(resp.tick <= curTick());
PacketPtr pkt = resp.pkt;
DPRINTF(SerialLink, "trySend response addr 0x%x, outstanding %d\n",
pkt->getAddr(), outstandingResponses);
if (sendTimingResp(pkt)) {
// send successful
transmitList.pop_front();
DPRINTF(SerialLink, "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(SerialLink, "Scheduling next send\n");
// Make sure bandwidth limitation is met
Cycles cycles = Cycles(divCeil(pkt->getSize() * 8,
serial_link.num_lanes * serial_link.link_speed));
Tick t = serial_link.clockEdge(cycles);
serial_link.schedule(sendEvent, std::max(next_resp.tick, t));
}
// 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(SerialLink, "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
SerialLink::SerialLinkMasterPort::recvReqRetry()
{
trySendTiming();
}
void
SerialLink::SerialLinkSlavePort::recvRespRetry()
{
trySendTiming();
}
Tick
SerialLink::SerialLinkSlavePort::recvAtomic(PacketPtr pkt)
{
return delay * serial_link.clockPeriod() + masterPort.sendAtomic(pkt);
}
void
SerialLink::SerialLinkSlavePort::recvFunctional(PacketPtr pkt)
{
pkt->pushLabel(name());
// 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
masterPort.sendFunctional(pkt);
}
bool
SerialLink::SerialLinkMasterPort::checkFunctional(PacketPtr pkt)
{
bool found = false;
auto i = transmitList.begin();
while (i != transmitList.end() && !found) {
if (pkt->checkFunctional((*i).pkt)) {
pkt->makeResponse();
found = true;
}
++i;
}
return found;
}
AddrRangeList
SerialLink::SerialLinkSlavePort::getAddrRanges() const
{
return ranges;
}
SerialLink *
SerialLinkParams::create()
{
return new SerialLink(this);
}