mem: Add a memory delay simulator

Add a memory system component that delays traffic. The base
functionality to delay packets is implemented in the abstract MemDelay
class. This class exposes three methods that control packet delays:

  * delayReq(pkt)
  * delayResp(pkt)
  * delaySnoopResp(pkt)

These methods should be specialized to implement delays for specific
packet types.

The class SimpleMemDelay uses the MemDelay base class to implement
constant delays for read/write requests and responses.

The intention is that these classes can be used for rapid prototyping
of components that add a small fixed delay and the same throughput as
the interconnect. I.e., any buffering done in the base class will be
small and proportional to the introduced delay.

Change-Id: I158cb85f20e32bfdbcbfed66a785b4b2dd47b628
Signed-off-by: Andreas Sandberg <andreas.sandberg@arm.com>
Reviewed-by: Nicholas Lindsey <nicholas.lindsay@arm.com>
Reviewed-by: Nikos Nikoleris <nikos.nikoleris@arm.com>
Reviewed-on: https://gem5-review.googlesource.com/11521
Reviewed-by: Daniel Carvalho <odanrc@yahoo.com.br>
Reviewed-by: Jason Lowe-Power <jason@lowepower.com>
Maintainer: Nikos Nikoleris <nikos.nikoleris@arm.com>

1 files changed, 216 insertions, 0 deletions

diff --git a/src/mem/mem_delay.cc b/src/mem/mem_delay.cc
new file mode 100644
index 000000000..4a682f3bc
--- /dev/null
+++ b/src/mem/mem_delay.cc
@@ -0,0 +1,216 @@
+/*
+ * Copyright (c) 2018 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.
+ *
+ * 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: Andreas Sandberg
+ */
+
+#include "mem/mem_delay.hh"
+
+#include "params/MemDelay.hh"
+#include "params/SimpleMemDelay.hh"
+
+MemDelay::MemDelay(const MemDelayParams *p)
+    : MemObject(p),
+      masterPort(name() + "-master", *this),
+      slavePort(name() + "-slave", *this),
+      reqQueue(*this, masterPort),
+      respQueue(*this, slavePort),
+      snoopRespQueue(*this, masterPort)
+{
+}
+
+void
+MemDelay::init()
+{
+    if (!slavePort.isConnected() || !masterPort.isConnected())
+        fatal("Memory delay is not connected on both sides.\n");
+}
+
+
+BaseMasterPort&
+MemDelay::getMasterPort(const std::string& if_name, PortID idx)
+{
+    if (if_name == "master") {
+        return masterPort;
+    } else {
+        return MemObject::getMasterPort(if_name, idx);
+    }
+}
+
+BaseSlavePort&
+MemDelay::getSlavePort(const std::string& if_name, PortID idx)
+{
+    if (if_name == "slave") {
+        return slavePort;
+    } else {
+        return MemObject::getSlavePort(if_name, idx);
+    }
+}
+
+bool
+MemDelay::checkFunctional(PacketPtr pkt)
+{
+    return slavePort.checkFunctional(pkt) ||
+        masterPort.checkFunctional(pkt);
+}
+
+MemDelay::MasterPort::MasterPort(const std::string &_name, MemDelay &_parent)
+    : QueuedMasterPort(_name, &_parent,
+                       _parent.reqQueue, _parent.snoopRespQueue),
+      parent(_parent)
+{
+}
+
+bool
+MemDelay::MasterPort::recvTimingResp(PacketPtr pkt)
+{
+    const Tick when = curTick() + parent.delayResp(pkt);
+
+    parent.slavePort.schedTimingResp(pkt, when);
+
+    return true;
+}
+
+void
+MemDelay::MasterPort::recvFunctionalSnoop(PacketPtr pkt)
+{
+    if (parent.checkFunctional(pkt)) {
+        pkt->makeResponse();
+    } else {
+        parent.slavePort.sendFunctionalSnoop(pkt);
+    }
+}
+
+Tick
+MemDelay::MasterPort::recvAtomicSnoop(PacketPtr pkt)
+{
+    const Tick delay = parent.delaySnoopResp(pkt);
+
+    return delay + parent.slavePort.sendAtomicSnoop(pkt);
+}
+
+void
+MemDelay::MasterPort::recvTimingSnoopReq(PacketPtr pkt)
+{
+    parent.slavePort.sendTimingSnoopReq(pkt);
+}
+
+
+MemDelay::SlavePort::SlavePort(const std::string &_name, MemDelay &_parent)
+    : QueuedSlavePort(_name, &_parent, _parent.respQueue),
+      parent(_parent)
+{
+}
+
+Tick
+MemDelay::SlavePort::recvAtomic(PacketPtr pkt)
+{
+    const Tick delay = parent.delayReq(pkt) + parent.delayResp(pkt);
+
+    return delay + parent.masterPort.sendAtomic(pkt);
+}
+
+bool
+MemDelay::SlavePort::recvTimingReq(PacketPtr pkt)
+{
+    const Tick when = curTick() + parent.delayReq(pkt);
+
+    parent.masterPort.schedTimingReq(pkt, when);
+
+    return true;
+}
+
+void
+MemDelay::SlavePort::recvFunctional(PacketPtr pkt)
+{
+    if (parent.checkFunctional(pkt)) {
+        pkt->makeResponse();
+    } else {
+        parent.masterPort.sendFunctional(pkt);
+    }
+}
+
+bool
+MemDelay::SlavePort::recvTimingSnoopResp(PacketPtr pkt)
+{
+    const Tick when = curTick() + parent.delaySnoopResp(pkt);
+
+    parent.masterPort.schedTimingSnoopResp(pkt, when);
+
+    return true;
+}
+
+
+
+SimpleMemDelay::SimpleMemDelay(const SimpleMemDelayParams *p)
+    : MemDelay(p),
+      readReqDelay(p->read_req),
+      readRespDelay(p->read_resp),
+      writeReqDelay(p->write_req),
+      writeRespDelay(p->write_resp)
+{
+}
+
+Tick
+SimpleMemDelay::delayReq(PacketPtr pkt)
+{
+    if (pkt->isRead()) {
+        return readReqDelay;
+    } else if (pkt->isWrite()) {
+        return writeReqDelay;
+    } else {
+        return 0;
+    }
+}
+
+Tick
+SimpleMemDelay::delayResp(PacketPtr pkt)
+{
+    if (pkt->isRead()) {
+        return readRespDelay;
+    } else if (pkt->isWrite()) {
+        return writeRespDelay;
+    } else {
+        return 0;
+    }
+}
+
+
+SimpleMemDelay *
+SimpleMemDelayParams::create()
+{
+    return new SimpleMemDelay(this);
+}