Merge pull request #8981 from gadfort/psm-input-res

psm: add source resistance option to better model packaging effects

Author: maliberty

src/psm/README.md

@@ -145,6 +145,7 @@ set_pdnsim_source_settings
     [-bump_size size]
     [-bump_interval interval]
     [-strap_track_pitch pitch]
+    [-external_resistance resistance]
 ```
 
 #### Options
@@ -154,7 +155,8 @@ set_pdnsim_source_settings
 | `-bump_dx`,`-bump_dy` | Set the bump pitch to decide the voltage source location. The default bump pitch is 140um. |
 | `-bump_size` | Set the bump size. The default bump size is 70um. |
 | `-bump_interval` | Set the bump population interval, this is used to depopulate the bump grid to emulate signals and other power connections. The default bump pitch is 3. |
-| `-strap_track_pitch` | Sets the track pitck to use for moduling voltage sources as straps. The default is 10x. |
+| `-strap_track_pitch` | Sets the track pitch to use for modeling voltage sources as straps. The default is 10x. |
+| `-external_resistance` | Set to model the resistance of the package or power network outside the chip/block. The default value is 0.0. |
 
 ### Insert Decap Cells
 The `insert_decap` command inserts decap cells in the areas with the highest

src/psm/include/psm/pdnsim.h

@@ -56,6 +56,9 @@ class PDNSim : public odb::dbBlockCallBackObj
 
     // Straps
     int strap_track_pitch = 10;
+
+    // Source resistance
+    float resistance = 0.0;  // Ohms
   };
 
   using IRDropByPoint = std::map<odb::Point, double>;

src/psm/src/connection.cpp

@@ -204,15 +204,23 @@ TermConnection::TermConnection(Node* node0, Node* node1)
 {
 }
 
-Connection::Resistance TermConnection::getResistance(
-    const ResistanceMap& res_map) const
+std::string TermConnection::describe() const
 {
-  return kResistance;
+  return "Terminal Connection";
 }
 
-std::string TermConnection::describe() const
+/////////////////////////////
+
+FixedResistanceConnection::FixedResistanceConnection(Node* node0,
+                                                     Node* node1,
+                                                     Resistance resistance)
+    : Connection(node0, node1), res_(resistance)
 {
-  return "Terminal Connection";
+}
+
+std::string FixedResistanceConnection::describe() const
+{
+  return "Fixed Resistance Connection";
 }
 
 }  // namespace psm

src/psm/src/connection.h

@@ -131,7 +131,10 @@ class TermConnection : public Connection
  public:
   TermConnection(Node* node0, Node* node1);
 
-  Resistance getResistance(const ResistanceMap& res_map) const override;
+  Resistance getResistance(const ResistanceMap& res_map) const override
+  {
+    return kResistance;
+  }
   bool isValid() const override { return true; }
 
   void mergeWith(const Connection* other) override {}
@@ -142,4 +145,23 @@ class TermConnection : public Connection
   static constexpr Resistance kResistance = 0.001;
 };
 
+class FixedResistanceConnection : public Connection
+{
+ public:
+  FixedResistanceConnection(Node* node0, Node* node1, Resistance resistance);
+
+  Resistance getResistance(const ResistanceMap& res_map) const override
+  {
+    return res_;
+  };
+  bool isValid() const override { return true; }
+
+  void mergeWith(const Connection* other) override {}
+
+  std::string describe() const override;
+
+ private:
+  Resistance res_;
+};
+
 }  // namespace psm

src/psm/src/ir_solver.cpp

@@ -431,15 +431,17 @@ Connection::ResistanceMap IRSolver::getResistanceMap(sta::Corner* corner) const
 }
 
 Connection::ConnectionMap<Connection::Conductance>
-IRSolver::generateConductanceMap(sta::Corner* corner) const
+IRSolver::generateConductanceMap(
+    sta::Corner* corner,
+    const std::vector<std::unique_ptr<Connection>>& connections) const
 {
   const utl::DebugScopedTimer timer(
       logger_, utl::PSM, "timer", 1, "Generate conductance map: {}");
 
   const Connection::ResistanceMap resistance = getResistanceMap(corner);
 
   Connection::ConnectionMap<Connection::Conductance> conductance;
-  for (const auto& conn : network_->getConnections()) {
+  for (const auto& conn : connections) {
     const auto res = conn->getResistance(resistance);
     conductance[conn.get()] = 1.0 / res;
   }
@@ -985,7 +987,33 @@ void IRSolver::solve(sta::Corner* corner,
   voltages.clear();
   currents.clear();
 
-  const auto conductance = generateConductanceMap(corner);
+  // Build source map
+  std::vector<std::unique_ptr<SourceNode>> real_src_nodes;
+  Voltage src_voltage
+      = generateSourceNodes(source_type, source_file, corner, real_src_nodes);
+
+  std::vector<std::unique_ptr<SourceNode>> src_nodes;
+  std::vector<std::unique_ptr<Connection>> src_conns;
+  // If resistance is set, add connection from source nodes to new source and
+  // connect
+  if (generated_source_settings_.resistance > 0) {
+    src_nodes.reserve(real_src_nodes.size());
+    src_conns.reserve(real_src_nodes.size());
+    for (const auto& real_src_node : real_src_nodes) {
+      src_conns.push_back(std::make_unique<FixedResistanceConnection>(
+          real_src_node->getSource(),
+          real_src_node.get(),
+          generated_source_settings_.resistance));
+      src_nodes.push_back(std::make_unique<SourceNode>(real_src_node.get()));
+    }
+  } else {
+    src_nodes = std::move(real_src_nodes);
+    real_src_nodes.clear();
+  }
+
+  // Build conductance map
+  Connection::ConnectionMap<Connection::Conductance> conductance
+      = generateConductanceMap(corner, network_->getConnections());
   debugPrint(logger_,
              utl::PSM,
              "stats",
@@ -997,23 +1025,34 @@ void IRSolver::solve(sta::Corner* corner,
     dumpConductance(conductance, "cond");
   }
 
-  const auto node_connections = getNodeConnectionMap(conductance);
+  std::map<Node*, Connection::ConnectionSet> node_connections
+      = getNodeConnectionMap(conductance);
   Node::NodeSet all_nodes;
   for (const auto& [node, conns] : node_connections) {
     all_nodes.insert(node);
   }
 
-  const Power total_power = buildNodeCurrentMap(corner, currents);
+  // Add source conductance
+  if (!src_conns.empty()) {
+    const auto src_conductance = generateConductanceMap(corner, src_conns);
+    for (const auto& [conn, cond] : src_conductance) {
+      conductance[conn] = cond;
+    }
+    for (const auto& [node, conns] : getNodeConnectionMap(src_conductance)) {
+      node_connections[node].insert(conns.begin(), conns.end());
+    }
+  }
 
-  // Build source map
-  std::vector<std::unique_ptr<SourceNode>> src_nodes;
-  Voltage src_voltage
-      = generateSourceNodes(source_type, source_file, corner, src_nodes);
+  const Power total_power = buildNodeCurrentMap(corner, currents);
 
   // Solve
   // create vector of nodes
   std::map<Node*, std::size_t> node_index = assignNodeIDs(all_nodes);
   const std::map<Node*, std::size_t> real_node_index = node_index;
+  for (const auto& [node, id] :
+       assignNodeIDs(real_src_nodes, node_index.size())) {
+    node_index[node] = id;
+  }
   for (const auto& [node, id] : assignNodeIDs(src_nodes, node_index.size())) {
     node_index[node] = id;
   }
@@ -1052,6 +1091,7 @@ void IRSolver::solve(sta::Corner* corner,
     if (logger_->debugCheck(utl::PSM, "dump", 1)) {
       network_->dumpNodes(node_index);
       dumpMatrix(g_matrix, "G");
+      dumpVector(j_vector, "J");
     }
     logger_->error(
         utl::PSM,
@@ -1576,7 +1616,8 @@ Connection::ConnectionMap<IRSolver::Current> IRSolver::generateCurrentMap(
 {
   const auto& voltages = voltages_.at(corner);
   Connection::ConnectionMap<IRSolver::Current> currents;
-  for (const auto& [connection, cond] : generateConductanceMap(corner)) {
+  for (const auto& [connection, cond] :
+       generateConductanceMap(corner, network_->getConnections())) {
     if (connection->hasITermNode() || connection->hasBPinNode()) {
       continue;
     }

src/psm/src/ir_solver.h

@@ -143,7 +143,8 @@ class IRSolver
       sta::Corner* corner) const;
 
   Connection::ConnectionMap<Connection::Conductance> generateConductanceMap(
-      sta::Corner* corner) const;
+      sta::Corner* corner,
+      const std::vector<std::unique_ptr<Connection>>& connections) const;
   Voltage generateSourceNodes(
       GeneratedSourceType source_type,
       const std::string& source_file,

src/psm/src/pdnsim.cpp

@@ -205,6 +205,9 @@ void PDNSim::setGeneratedSourceSettings(const GeneratedSourceSettings& settings)
   if (settings.strap_track_pitch > 0) {
     generated_source_settings_.strap_track_pitch = settings.strap_track_pitch;
   }
+  if (settings.resistance > 0) {
+    generated_source_settings_.resistance = settings.resistance;
+  }
 }
 
 void PDNSim::clearSolvers()

src/psm/src/pdnsim.i

@@ -94,14 +94,15 @@ void clear_solvers()
   pdnsim->clearSolvers();
 }
 
-void set_source_settings(int bump_dx, int bump_dy, int bump_size, int bump_interval, int track_pitch)
+void set_source_settings(int bump_dx, int bump_dy, int bump_size, int bump_interval, int track_pitch, float resistance)
 {
   PDNSim::GeneratedSourceSettings settings;
   settings.bump_dx = bump_dx;
   settings.bump_dy = bump_dy;
   settings.bump_size = bump_size;
   settings.bump_interval = bump_interval;
   settings.strap_track_pitch = track_pitch;
+  settings.resistance = resistance;
 
   PDNSim* pdnsim = getPDNSim();
   pdnsim->setGeneratedSourceSettings(settings);

src/psm/src/pdnsim.tcl

@@ -227,11 +227,14 @@ sta::define_cmd_args "set_pdnsim_source_settings" {
   [-bump_dy pitch]
   [-bump_size size]
   [-bump_interval interval]
-  [-strap_track_pitch pitch]}
+  [-strap_track_pitch pitch]
+  [-external_resistance resistance]
+}
 
 proc set_pdnsim_source_settings { args } {
   sta::parse_key_args "set_pdnsim_source_settings" args \
-    keys {-bump_dx -bump_dy -bump_size -bump_interval -strap_track_pitch} flags {}
+    keys {-bump_dx -bump_dy -bump_size -bump_interval -strap_track_pitch -external_resistance} \
+    flags {}
 
   set dx 0
   if { [info exists keys(-bump_dx)] } {
@@ -255,7 +258,12 @@ proc set_pdnsim_source_settings { args } {
     set track_pitch $keys(-strap_track_pitch)
   }
 
-  psm::set_source_settings $dx $dy $size $interval $track_pitch
+  set resistance 0
+  if { [info exists keys(-external_resistance)] } {
+    set resistance $keys(-external_resistance)
+  }
+
+  psm::set_source_settings $dx $dy $size $interval $track_pitch $resistance
 }
 
 namespace eval psm {

src/psm/test/BUILD

@@ -7,6 +7,7 @@ package(features = ["layering_check"])
 # From CMakeLists.txt or_integration_tests(TESTS
 COMPULSORY_TESTS = [
     "aes_asap7_vdd",
+    "aes_test_bterms_source_resistance",
     "aes_test_bterms",
     "aes_test_multiple_bterms",
     "aes_test_multiple_bterms_skipped",
@@ -22,6 +23,7 @@ COMPULSORY_TESTS = [
     "check_power_grid_require_bterms_pass",
     "corners",
     "corners_assign_power",
+    "gcd_all_vss_source_res",
     "gcd_all_vss",
     "gcd_em_test_vdd",
     "gcd_no_vsrc",