sim: Adding thermal model support

This patch adds basic thermal support to gem5. It models energy dissipation
through a circuital equivalent, which allows us to use RC networks.
This lays down the basic infrastructure to do so, but it does not "work" due
to the lack of power models. For now some hardcoded number is used as a PoC.
The solver is embedded in the patch.

1 files changed, 319 insertions, 0 deletions

diff --git a/src/sim/power/thermal_model.cc b/src/sim/power/thermal_model.cc
new file mode 100644
index 000000000..13242f666
--- /dev/null
+++ b/src/sim/power/thermal_model.cc
@@ -0,0 +1,319 @@
+/*
+ * Copyright (c) 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.
+ *
+ * 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: David Guillen Fandos
+ */
+
+#include "sim/power/thermal_model.hh"
+
+#include "base/statistics.hh"
+#include "params/ThermalCapacitor.hh"
+#include "params/ThermalNode.hh"
+#include "params/ThermalReference.hh"
+#include "params/ThermalResistor.hh"
+#include "sim/clocked_object.hh"
+#include "sim/linear_solver.hh"
+#include "sim/power/thermal_domain.hh"
+#include "sim/sim_object.hh"
+
+/**
+ * ThermalNode
+ */
+ThermalNode::ThermalNode(const Params *p)
+    : SimObject(p), id(-1), isref(false), temp(0.0f)
+{
+}
+
+ThermalNode *
+ThermalNodeParams::create()
+{
+    return new ThermalNode(this);
+}
+
+/**
+ * ThermalReference
+ */
+ThermalReference::ThermalReference(const Params *p)
+    : SimObject(p), _temperature(p->temperature), node(NULL)
+{
+}
+
+ThermalReference *
+ThermalReferenceParams::create()
+{
+    return new ThermalReference(this);
+}
+
+void
+ThermalReference::serialize(CheckpointOut &cp) const
+{
+    SERIALIZE_SCALAR(_temperature);
+}
+
+void
+ThermalReference::unserialize(CheckpointIn &cp)
+{
+    UNSERIALIZE_SCALAR(_temperature);
+}
+
+LinearEquation
+ThermalReference::getEquation(ThermalNode * n, unsigned nnodes,
+                              double step) const {
+    // Just return an empty equation
+    return LinearEquation(nnodes);
+}
+
+/**
+ * ThermalResistor
+ */
+ThermalResistor::ThermalResistor(const Params *p)
+    : SimObject(p), _resistance(p->resistance), node1(NULL), node2(NULL)
+{
+}
+
+ThermalResistor *
+ThermalResistorParams::create()
+{
+    return new ThermalResistor(this);
+}
+
+void
+ThermalResistor::serialize(CheckpointOut &cp) const
+{
+    SERIALIZE_SCALAR(_resistance);
+}
+
+void
+ThermalResistor::unserialize(CheckpointIn &cp)
+{
+    UNSERIALIZE_SCALAR(_resistance);
+}
+
+LinearEquation
+ThermalResistor::getEquation(ThermalNode * n, unsigned nnodes,
+                             double step) const
+{
+    // i[n] = (Vn2 - Vn1)/R
+    LinearEquation eq(nnodes);
+
+    if (n != node1 && n != node2)
+        return eq;
+
+    if (node1->isref)
+        eq[eq.cnt()] += -node1->temp / _resistance;
+    else
+        eq[node1->id] += -1.0f / _resistance;
+
+    if (node2->isref)
+        eq[eq.cnt()] += node2->temp / _resistance;
+    else
+        eq[node2->id] += 1.0f / _resistance;
+
+    // We've assumed n was node1, reverse if necessary
+    if (n == node2)
+        eq *= -1.0f;
+
+    return eq;
+}
+
+/**
+ * ThermalCapacitor
+ */
+ThermalCapacitor::ThermalCapacitor(const Params *p)
+    : SimObject(p), _capacitance(p->capacitance), node1(NULL), node2(NULL)
+{
+}
+
+ThermalCapacitor *
+ThermalCapacitorParams::create()
+{
+    return new ThermalCapacitor(this);
+}
+
+void
+ThermalCapacitor::serialize(CheckpointOut &cp) const
+{
+    SERIALIZE_SCALAR(_capacitance);
+}
+
+void
+ThermalCapacitor::unserialize(CheckpointIn &cp)
+{
+    UNSERIALIZE_SCALAR(_capacitance);
+}
+
+LinearEquation
+ThermalCapacitor::getEquation(ThermalNode * n, unsigned nnodes,
+                              double step) const
+{
+    // i(t) = C * d(Vn2 - Vn1)/dt
+    // i[n] = C/step * (Vn2 - Vn1 - Vn2[n-1] + Vn1[n-1])
+    LinearEquation eq(nnodes);
+
+    if (n != node1 && n != node2)
+        return eq;
+
+    eq[eq.cnt()] += _capacitance / step * (node1->temp - node2->temp);
+
+    if (node1->isref)
+        eq[eq.cnt()] += _capacitance / step * (-node1->temp);
+    else
+        eq[node1->id] += -1.0f * _capacitance / step;
+
+    if (node2->isref)
+        eq[eq.cnt()] += _capacitance / step * (node2->temp);
+    else
+        eq[node2->id] += 1.0f * _capacitance / step;
+
+    // We've assumed n was node1, reverse if necessary
+    if (n == node2)
+        eq *= -1.0f;
+
+    return eq;
+}
+
+/**
+ * ThermalModel
+ */
+ThermalModel::ThermalModel(const Params *p)
+    : ClockedObject(p), stepEvent(this), _step(p->step)
+{
+}
+
+ThermalModel *
+ThermalModelParams::create()
+{
+    return new ThermalModel(this);
+}
+
+void
+ThermalModel::serialize(CheckpointOut &cp) const
+{
+    SERIALIZE_SCALAR(_step);
+}
+
+void
+ThermalModel::unserialize(CheckpointIn &cp)
+{
+    UNSERIALIZE_SCALAR(_step);
+}
+
+void
+ThermalModel::doStep()
+{
+    // Calculate new temperatures!
+    // For each node in the system, create the kirchhoff nodal equation
+    LinearSystem ls(eq_nodes.size());
+    for (unsigned i = 0; i < eq_nodes.size(); i++) {
+        auto n = eq_nodes[i];
+        LinearEquation node_equation (eq_nodes.size());
+        for (auto e : entities) {
+            LinearEquation eq = e->getEquation(n, eq_nodes.size(), _step);
+            node_equation = node_equation + eq;
+        }
+        ls[i] = node_equation;
+    }
+
+    // Get temperatures for this iteration
+    std::vector <double> temps = ls.solve();
+    for (unsigned i = 0; i < eq_nodes.size(); i++)
+        eq_nodes[i]->temp = temps[i];
+
+    // Schedule next computation
+    schedule(stepEvent, curTick() + SimClock::Int::s * _step);
+
+    // Notify everybody
+    for (auto dom : domains)
+        dom->emitUpdate();
+}
+
+void
+ThermalModel::startup()
+{
+    // Look for nodes connected to voltage references, these
+    // can be just set to the reference value (no nodal equation)
+    for (auto ref : references) {
+        ref->node->temp = ref->_temperature;
+        ref->node->isref = true;
+    }
+    // Setup the initial temperatures
+    for (auto dom : domains)
+        dom->getNode()->temp = dom->initialTemperature();
+
+    // Create a list of unknown temperature nodes
+    for (auto n : nodes) {
+        bool found = false;
+        for (auto ref : references)
+            if (ref->node == n) {
+                found = true;
+                break;
+            }
+        if (!found)
+            eq_nodes.push_back(n);
+    }
+
+    // Assign each node an ID
+    for (unsigned i = 0; i < eq_nodes.size(); i++)
+        eq_nodes[i]->id = i;
+
+    // Schedule first thermal update
+    schedule(stepEvent, curTick() + SimClock::Int::s * _step);
+}
+
+void ThermalModel::addDomain(ThermalDomain * d) {
+    domains.push_back(d);
+    entities.push_back(d);
+}
+void ThermalModel::addReference(ThermalReference * r) {
+    references.push_back(r);
+    entities.push_back(r);
+}
+void ThermalModel::addCapacitor(ThermalCapacitor * c) {
+    capacitors.push_back(c);
+    entities.push_back(c);
+}
+void ThermalModel::addResistor(ThermalResistor * r) {
+    resistors.push_back(r);
+    entities.push_back(r);
+}
+
+double ThermalModel::getTemp() const {
+    // Just pick the highest temperature
+    double temp = 0;
+    for (auto & n : eq_nodes)
+        temp = std::max(temp, n->temp);
+    return temp;
+}