gowin: Himbaechel. Extend clock router

Now the clock router can place a buffer into the specified network,
which divides the network into two parts: from the source to the buffer,
routing occurs through any available PIPs, and after the buffer to the
sink, only through a dedicated global clock network.

This is made specifically for the Tangnano20k where the external
oscillator is soldered to a regular non-clock pin. But it can be used
for other purposes, you just need to remember that the recipient must be
a CLK input or output pin.

The port/network to set the buffer to is specified in the .CST file:

CLOCK_LOC "name" BUFG;

Signed-off-by: YRabbit <rabbit@yrabbit.cyou>

himbaechel/uarch/gowin/constids.inc

@@ -1097,3 +1097,7 @@ X(HCLK_OUT1)
 X(HCLK_OUT2)
 X(HCLK_OUT3)
 
+// BUFG, clock buffers stuff
+X(BUFG)
+X(CLOCK)
+

himbaechel/uarch/gowin/cst.cc

@@ -129,8 +129,16 @@ struct GowinCstReader
  log_info("Can't use the long wires. The %s network will use normal routing.\n", net.c_str(ctx));
  //}
  } else {
- log_info("BUFG isn't supported\n");
- continue;
+ auto ni = ctx->nets.find(net);
+ if (ni == ctx->nets.end()) {
+ log_info("Net %s not found\n", net.c_str(ctx));
+ continue;
+ }
+ if (ctx->debug) {
+ log_info("Mark net '%s' as CLOCK\n", net.c_str(ctx));
+ }
+ // XXX YES for now. May be put the number here
+ ni->second->attrs[id_CLOCK] = Property(std::string("YES"));
  }
  } break;
  case ioloc: { // IO_LOC name pin

himbaechel/uarch/gowin/globals.cc

@@ -67,29 +67,14 @@ struct GowinGlobalRouter
 
  // Dedicated backwards BFS routing for global networks
  template <typename Tfilt>
- bool backwards_bfs_route(NetInfo *net, store_index<PortRef> user_idx, int iter_limit, bool strict, Tfilt pip_filter)
+ bool backwards_bfs_route(NetInfo *net, WireId src, WireId dst, int iter_limit, bool strict, Tfilt pip_filter)
  {
+ // log_info("%s:%s->%s\n", net->name.c_str(ctx), ctx->nameOfWire(src), ctx->nameOfWire(dst));
  // Queue of wires to visit
  std::queue<WireId> visit;
  // Wire -> upstream pip
  dict<WireId, PipId> backtrace;
 
- // Lookup source and destination wires
- WireId src = ctx->getNetinfoSourceWire(net);
- WireId dst = ctx->getNetinfoSinkWire(net, net->users.at(user_idx), 0);
-
- if (src == WireId())
- log_error("Net '%s' has an invalid source port %s.%s\n", ctx->nameOf(net), ctx->nameOf(net->driver.cell),
- ctx->nameOf(net->driver.port));
-
- if (dst == WireId())
- log_error("Net '%s' has an invalid sink port %s.%s\n", ctx->nameOf(net),
- ctx->nameOf(net->users.at(user_idx).cell), ctx->nameOf(net->users.at(user_idx).port));
-
- if (ctx->getBoundWireNet(src) != net) {
- ctx->bindWire(src, net, STRENGTH_LOCKED);
- }
-
  if (src == dst) {
  // Nothing more to do
  return true;
@@ -106,24 +91,29 @@ struct GowinGlobalRouter
  // Search uphill pips
  for (PipId pip : ctx->getPipsUphill(cursor)) {
  // Skip pip if unavailable, and not because it's already used for this net
- if (!ctx->checkPipAvail(pip) && ctx->getBoundPipNet(pip) != net)
+ if (!ctx->checkPipAvail(pip) && ctx->getBoundPipNet(pip) != net) {
  continue;
+ }
  WireId prev = ctx->getPipSrcWire(pip);
  // Ditto for the upstream wire
- if (!ctx->checkWireAvail(prev) && ctx->getBoundWireNet(prev) != net)
+ if (!ctx->checkWireAvail(prev) && ctx->getBoundWireNet(prev) != net) {
  continue;
+ }
  // Skip already visited wires
- if (backtrace.count(prev))
+ if (backtrace.count(prev)) {
  continue;
+ }
  // Apply our custom pip filter
- if (!pip_filter(pip))
+ if (!pip_filter(pip)) {
  continue;
+ }
  // Add to the queue
  visit.push(prev);
  backtrace[prev] = pip;
  // Check if we are done yet
- if (prev == src)
+ if (prev == src) {
  goto done;
+ }
  }
  if (false) {
  done:
@@ -137,18 +127,22 @@ struct GowinGlobalRouter
  // Create a list of pips on the routed path
  while (true) {
  PipId pip = backtrace.at(cursor);
- if (pip == PipId())
+ if (pip == PipId()) {
  break;
+ }
  pips.push_back(pip);
  cursor = ctx->getPipDstWire(pip);
+ // log_info(">> %s:%s\n", ctx->getPipName(pip).str(ctx).c_str(), ctx->nameOfWire(cursor));
  }
  // Reverse that list
  std::reverse(pips.begin(), pips.end());
  // Bind pips until we hit already-bound routing
  for (PipId pip : pips) {
  WireId dst = ctx->getPipDstWire(pip);
- if (ctx->getBoundWireNet(dst) == net)
+ // log_info("%s:%s\n", ctx->getPipName(pip).str(ctx).c_str(), ctx->nameOfWire(dst));
+ if (ctx->getBoundWireNet(dst) == net) {
  break;
+ }
  ctx->bindPip(pip, net, STRENGTH_LOCKED);
  }
  return true;
@@ -159,29 +153,90 @@ struct GowinGlobalRouter
  } else {
  log_warning("Failed to route net '%s' from %s to %s using dedicated routing.\n", ctx->nameOf(net),
  ctx->nameOfWire(src), ctx->nameOfWire(dst));
- ctx->unbindWire(src);
  return false;
  }
  }
  }
 
- void route_clk_net(NetInfo *net)
+ bool route_direct_net(NetInfo *net)
  {
+ // Lookup source and destination wires
+ WireId src = ctx->getNetinfoSourceWire(net);
+ if (src == WireId())
+ log_error("Net '%s' has an invalid source port %s.%s\n", ctx->nameOf(net), ctx->nameOf(net->driver.cell),
+ ctx->nameOf(net->driver.port));
+
+ if (ctx->getBoundWireNet(src) != net) {
+ ctx->bindWire(src, net, STRENGTH_LOCKED);
+ }
+
  bool routed = false;
  for (auto usr : net->users.enumerate()) {
- routed = backwards_bfs_route(net, usr.index, 1000000, false, [&](PipId pip) {
+ WireId dst = ctx->getNetinfoSinkWire(net, net->users.at(usr.index), 0);
+ if (dst == WireId()) {
+ log_error("Net '%s' has an invalid sink port %s.%s\n", ctx->nameOf(net),
+ ctx->nameOf(net->users.at(usr.index).cell), ctx->nameOf(net->users.at(usr.index).port));
+ }
+ routed = backwards_bfs_route(net, src, dst, 1000000, false, [&](PipId pip) {
  return (is_relaxed_sink(usr.value) || global_pip_filter(pip));
  });
  if (!routed) {
  break;
  }
  }
+ if (!routed) {
+ ctx->unbindWire(src);
+ }
+ return routed;
+ }
+
+ void route_buffered_net(NetInfo *net)
+ {
+ // a) route net after buf using the buf input as source
+ CellInfo *buf_ci = net->driver.cell;
+ WireId src = ctx->getBelPinWire(buf_ci->bel, id_I);
+
+ NetInfo *net_before_buf = buf_ci->getPort(id_I);
+ NPNR_ASSERT(net_before_buf != nullptr);
 
- if (routed) {
+ if (src == WireId()) {
+ log_error("Net '%s' has an invalid source port %s.%s\n", ctx->nameOf(net), ctx->nameOf(net->driver.cell),
+ ctx->nameOf(net->driver.port));
+ }
+ ctx->bindWire(src, net, STRENGTH_LOCKED);
+
+ for (auto usr : net->users.enumerate()) {
+ WireId dst = ctx->getNetinfoSinkWire(net, net->users.at(usr.index), 0);
+ if (dst == WireId()) {
+ log_error("Net '%s' has an invalid sink port %s.%s\n", ctx->nameOf(net),
+ ctx->nameOf(net->users.at(usr.index).cell), ctx->nameOf(net->users.at(usr.index).port));
+ }
+ // log_info(" usr wire: %s\n", ctx->nameOfWire(dst));
+ backwards_bfs_route(net, src, dst, 1000000, true,
+ [&](PipId pip) { return (is_relaxed_sink(usr.value) || global_pip_filter(pip)); });
+ }
+
+ // b) route net before buf from whatever to the buf input
+ WireId dst = src;
+ CellInfo *true_src_ci = net_before_buf->driver.cell;
+ src = ctx->getBelPinWire(true_src_ci->bel, net_before_buf->driver.port);
+ ctx->bindWire(src, net, STRENGTH_LOCKED);
+ ctx->unbindWire(dst);
+ backwards_bfs_route(net, src, dst, 1000000, false, [&](PipId pip) { return true; });
+ // remove net
+ buf_ci->movePortTo(id_O, true_src_ci, net_before_buf->driver.port);
+ net_before_buf->driver.cell = nullptr;
+ }
+
+ void route_clk_net(NetInfo *net)
+ {
+ if (route_direct_net(net)) {
  log_info(" routed net '%s' using global resources\n", ctx->nameOf(net));
  }
  }
 
+ bool driver_is_buf(const PortRef &driver) { return CellTypePort(driver) == CellTypePort(id_BUFG, id_O); }
+
  bool driver_is_clksrc(const PortRef &driver)
  {
  // dedicated pins
@@ -219,11 +274,27 @@ struct GowinGlobalRouter
  void run(void)
  {
  log_info("Routing globals...\n");
+ // buffered nets first
+ for (auto &net : ctx->nets) {
+ NetInfo *ni = net.second.get();
+ CellInfo *drv = ni->driver.cell;
+ if (drv == nullptr) {
+ continue;
+ }
+ if (driver_is_buf(ni->driver)) {
+ if (ctx->verbose) {
+ log_info("route buffered net '%s'\n", ctx->nameOf(ni));
+ }
+ route_buffered_net(ni);
+ continue;
+ }
+ }
  for (auto &net : ctx->nets) {
  NetInfo *ni = net.second.get();
  CellInfo *drv = ni->driver.cell;
- if (drv == nullptr)
+ if (drv == nullptr) {
  continue;
+ }
  if (driver_is_clksrc(ni->driver)) {
  route_clk_net(ni);
  continue;

himbaechel/uarch/gowin/gowin.h

@@ -88,6 +88,8 @@ enum
  IDES16_Z = 72,
  OSER16_Z = 73,
 
+ BUFG_Z = 74, // : 81 reserve just in case
+
  OSC_Z = 274,
  PLL_Z = 275,
  GSR_Z = 276,

himbaechel/uarch/gowin/gowin_arch_gen.py

@@ -32,6 +32,8 @@
 IDES16_Z = 72
 OSER16_Z = 73
 
+BUFG_Z = 74 # : 81 reserve just in case
+
 OSC_Z = 274
 PLL_Z = 275
 GSR_Z = 276
@@ -291,6 +293,18 @@ def create_extra_funcs(tt: TileType, db: chipdb, x: int, y: int):
  tt.add_bel_pin(bel, port, wire, PinType.OUTPUT)
  else:
  tt.add_bel_pin(bel, port, wire, PinType.INPUT)
+ if func == 'buf':
+ for buf_type, wires in desc.items():
+ for i, wire in enumerate(wires):
+ if not tt.has_wire(wire):
+ tt.create_wire(wire, "TILE_CLK")
+ wire_out = f'{buf_type}{i}_O'
+ tt.create_wire(wire_out, "TILE_CLK")
+ # XXX make Z from buf_type
+ bel = tt.create_bel(f'{buf_type}{i}', buf_type, z = BUFG_Z + i)
+ bel.flags = BEL_FLAG_GLOBAL
+ tt.add_bel_pin(bel, "I", wire, PinType.INPUT)
+ tt.add_bel_pin(bel, "O", wire_out, PinType.OUTPUT)
 
 def create_tiletype(create_func, chip: Chip, db: chipdb, x: int, y: int, ttyp: int):
  has_extra_func = (y, x) in db.extra_func

himbaechel/uarch/gowin/pack.cc

@@ -110,7 +110,7 @@ struct GowinPacker
  auto &ci = *cell.second;
  if (!ci.type.in(ctx->id("$nextpnr_ibuf"), ctx->id("$nextpnr_obuf"), ctx->id("$nextpnr_iobuf")))
  continue;
- NetInfo *i = ci.getPort(ctx->id("I"));
+ NetInfo *i = ci.getPort(id_I);
  if (i && i->driver.cell) {
  if (!top_ports.count(CellTypePort(i->driver)))
  log_error("Top-level port '%s' driven by illegal port %s.%s\n", ctx->nameOf(&ci),
@@ -119,7 +119,7 @@ struct GowinPacker
  i->driver.cell->attrs[attr.first] = attr.second;
  }
  }
- NetInfo *o = ci.getPort(ctx->id("O"));
+ NetInfo *o = ci.getPort(id_O);
  if (o) {
  for (auto &usr : o->users) {
  if (!top_ports.count(CellTypePort(usr)))
@@ -128,9 +128,21 @@ struct GowinPacker
  for (const auto &attr : ci.attrs) {
  usr.cell->attrs[attr.first] = attr.second;
  }
+ // network/port attributes that can be set in the
+ // restriction file and that need to be transferred to real
+ // networks before nextpnr buffers are removed.
+ NetInfo *dst_net = usr.cell->getPort(id_O);
+ if (dst_net != nullptr) {
+ for (const auto &attr : o->attrs) {
+ if (!attr.first.in(id_CLOCK)) {
+ continue;
+ }
+ dst_net->attrs[attr.first] = attr.second;
+ }
+ }
  }
  }
- NetInfo *io = ci.getPort(ctx->id("IO"));
+ NetInfo *io = ci.getPort(id_IO);
  if (io && io->driver.cell) {
  if (!top_ports.count(CellTypePort(io->driver)))
  log_error("Top-level port '%s' driven by illegal port %s.%s\n", ctx->nameOf(&ci),
@@ -139,9 +151,9 @@ struct GowinPacker
  io->driver.cell->attrs[attr.first] = attr.second;
  }
  }
- ci.disconnectPort(ctx->id("I"));
- ci.disconnectPort(ctx->id("O"));
- ci.disconnectPort(ctx->id("IO"));
+ ci.disconnectPort(id_I);
+ ci.disconnectPort(id_O);
+ ci.disconnectPort(id_IO);
  to_remove.push_back(ci.name);
  }
  for (IdString cell_name : to_remove)
@@ -1317,6 +1329,41 @@ struct GowinPacker
  }
  }
 
+ // =========================================
+ // Create entry points to the clock system
+ // =========================================
+ void pack_buffered_nets()
+ {
+ log_info("Pack buffered nets..\n");
+
+ for (auto &net : ctx->nets) {
+ auto &ni = *net.second;
+ if (ni.driver.cell == nullptr || ni.attrs.count(id_CLOCK) == 0 || ni.users.empty()) {
+ continue;
+ }
+
+ // make new BUF cell single user for the net driver
+ IdString buf_name = ctx->idf("%s_BUFG", net.first.c_str(ctx));
+ ctx->createCell(buf_name, id_BUFG);
+ CellInfo *buf_ci = ctx->cells.at(buf_name).get();
+ buf_ci->addInput(id_I);
+ auto s_net = std::make_unique<NetInfo>(ctx->idf("$PACKER_BUF_%s", net.first.c_str(ctx)));
+ NetInfo *buf_ni = s_net.get();
+ ctx->nets[s_net->name] = std::move(s_net);
+
+ if (ctx->verbose) {
+ log_info("Create buf '%s' with IN net '%s'\n", buf_name.c_str(ctx), buf_ni->name.c_str(ctx));
+ }
+ // move driver
+ CellInfo *driver_cell = ni.driver.cell;
+ IdString driver_port = ni.driver.port;
+
+ driver_cell->movePortTo(driver_port, buf_ci, id_O);
+ buf_ci->connectPort(id_I, buf_ni);
+ driver_cell->connectPort(driver_port, buf_ni);
+ }
+ }
+
  void run(void)
  {
  handle_constants();
@@ -1348,6 +1395,9 @@ struct GowinPacker
  ctx->check();
 
  pack_ram16sdp4();
+ ctx->check();
+
+ pack_buffered_nets();
 
  ctx->fixupHierarchy();
  ctx->check();