5 files changed, 96 insertions, 11 deletions
diff --git a/common/arch_pybindings_shared.h b/common/arch_pybindings_shared.h
index 46f1f9be..f44aa70e 100644
--- a/common/arch_pybindings_shared.h
+++ b/common/arch_pybindings_shared.h
@@ -27,6 +27,9 @@ fn_wrapper_2a_v<Context, decltype(&Context::addBelToRegion), &Context::addBelToR
 fn_wrapper_2a_v<Context, decltype(&Context::constrainCellToRegion), &Context::constrainCellToRegion,
                 conv_from_str<IdString>, conv_from_str<IdString>>::def_wrap(ctx_cls, "constrainCellToRegion");
 
+fn_wrapper_2a<Context, decltype(&Context::getNetinfoRouteDelay), &Context::getNetinfoRouteDelay, pass_through<delay_t>,
+              addr_and_unwrap<NetInfo>, unwrap_context<PortRef &>>::def_wrap(ctx_cls, "getNetinfoRouteDelay");
+
 fn_wrapper_1a<Context, decltype(&Context::createNet), &Context::createNet, deref_and_wrap<NetInfo>,
               conv_from_str<IdString>>::def_wrap(ctx_cls, "createNet");
 fn_wrapper_3a_v<Context, decltype(&Context::connectPort), &Context::connectPort, conv_from_str<IdString>,
diff --git a/common/pybindings.cc b/common/pybindings.cc
index 2f672a41..0e087e98 100644
--- a/common/pybindings.cc
+++ b/common/pybindings.cc
@@ -285,6 +285,8 @@ PYBIND11_EMBEDDED_MODULE(MODULE_NAME, m)
     WRAP_MAP(m, WireMap, wrap_context<PipMap &>, "WireMap");
     WRAP_MAP_UPTR(m, RegionMap, "RegionMap");
 
+    WRAP_VECTOR(m, PortRefVector, wrap_context<PortRef &>);
+
     typedef dict<IdString, ClockFmax> ClockFmaxMap;
     WRAP_MAP(m, ClockFmaxMap, pass_through<ClockFmax>, "ClockFmaxMap");
 
diff --git a/ecp5/pack.cc b/ecp5/pack.cc
index d0077375..3bc2dbb3 100644
--- a/ecp5/pack.cc
+++ b/ecp5/pack.cc
@@ -1766,6 +1766,26 @@ class Ecp5Packer
             if (ci->type == id_EXTREFB) {
                 const NetInfo *refo = net_or_nullptr(ci, id_REFCLKO);
                 CellInfo *dcu = nullptr;
+                std::string loc_bel = std::string("NONE");
+                std::string dcu_bel = std::string("NONE");
+                if (ci->attrs.count(ctx->id("LOC"))) {
+                    std::string loc = ci->attrs.at(ctx->id("LOC")).as_string();
+                    if (loc == "EXTREF0" &&
+                        (ctx->args.type == ArchArgs::LFE5UM_25F || ctx->args.type == ArchArgs::LFE5UM5G_25F))
+                        loc_bel = std::string("X42/Y50/EXTREF");
+                    else if (loc == "EXTREF0" &&
+                             (ctx->args.type == ArchArgs::LFE5UM_45F || ctx->args.type == ArchArgs::LFE5UM5G_45F))
+                        loc_bel = std::string("X42/Y71/EXTREF");
+                    else if (loc == "EXTREF1" &&
+                             (ctx->args.type == ArchArgs::LFE5UM_45F || ctx->args.type == ArchArgs::LFE5UM5G_45F))
+                        loc_bel = std::string("X69/Y71/EXTREF");
+                    else if (loc == "EXTREF0" &&
+                             (ctx->args.type == ArchArgs::LFE5UM_85F || ctx->args.type == ArchArgs::LFE5UM5G_85F))
+                        loc_bel = std::string("X46/Y95/EXTREF");
+                    else if (loc == "EXTREF1" &&
+                             (ctx->args.type == ArchArgs::LFE5UM_85F || ctx->args.type == ArchArgs::LFE5UM5G_85F))
+                        loc_bel = std::string("X71/Y95/EXTREF");
+                }
                 if (refo == nullptr)
                     log_error("EXTREFB REFCLKO must not be unconnected\n");
                 for (auto user : refo->users) {
@@ -1775,12 +1795,30 @@ class Ecp5Packer
                         log_error("EXTREFB REFCLKO must only drive a single DCUA\n");
                     dcu = user.cell;
                 }
-                if (!dcu->attrs.count(ctx->id("BEL")))
-                    log_error("DCU must be constrained to a Bel!\n");
-                std::string bel = dcu->attrs.at(ctx->id("BEL")).as_string();
-                NPNR_ASSERT(bel.substr(bel.length() - 3) == "DCU");
-                bel.replace(bel.length() - 3, 3, "EXTREF");
-                ci->attrs[ctx->id("BEL")] = bel;
+                if (dcu != nullptr) {
+                    if (!dcu->attrs.count(ctx->id("BEL")))
+                        log_error("DCU must be constrained to a Bel!\n");
+                    dcu_bel = dcu->attrs.at(ctx->id("BEL")).as_string();
+                    NPNR_ASSERT(dcu_bel.substr(dcu_bel.length() - 3) == "DCU");
+                    dcu_bel.replace(dcu_bel.length() - 3, 3, "EXTREF");
+                }
+                if (dcu_bel != loc_bel) {
+                    if (dcu_bel == "NONE" && loc_bel == "NONE") {
+                        log_error("EXTREFB has neither a LOC or a directly associated DCUA\n");
+                    } else if (dcu_bel == "NONE") {
+                        ci->attrs[ctx->id("BEL")] = loc_bel;
+                        dcu_bel = loc_bel;
+                    } else if (loc_bel == "NONE") {
+                        ci->attrs[ctx->id("BEL")] = dcu_bel;
+                    } else {
+                        log_error("EXTREFB has conflicting LOC '%s' and associated DCUA '%s'\n", loc_bel.c_str(),
+                                  dcu_bel.c_str());
+                    }
+                } else {
+                    if (dcu_bel == "NONE")
+                        log_error("EXTREFB has no LOC or associated DCUA\n");
+                    ci->attrs[ctx->id("BEL")] = dcu_bel;
+                }
             } else if (ci->type == id_PCSCLKDIV) {
                 const NetInfo *clki = net_or_nullptr(ci, id_CLKI);
                 if (clki != nullptr && clki->driver.cell != nullptr && clki->driver.cell->type == id_DCUA) {
diff --git a/gowin/arch.cc b/gowin/arch.cc
index 0bc0ef56..a4be92cd 100644
--- a/gowin/arch.cc
+++ b/gowin/arch.cc
@@ -482,14 +482,34 @@ DelayQuad Arch::getWireTypeDelay(IdString wire)
     }
 }
 
+static Loc getLoc(std::smatch match, int maxX, int maxY)
+{
+    int col = std::stoi(match[2]);
+    int row = 1; // Top
+    std::string side = match[1].str();
+    if (side == "R") {
+        row = col;
+        col = maxX;
+    } else if (side == "B") {
+        row = maxY;
+    } else if (side == "L") {
+        row = col;
+        col = 1;
+    }
+    int z = match[3].str()[0] - 'A';
+    return Loc(col - 1, row - 1, z);
+}
+
 void Arch::read_cst(std::istream &in)
 {
     std::regex iobre = std::regex("IO_LOC +\"([^\"]+)\" +([^ ;]+) *;.*");
     std::regex portre = std::regex("IO_PORT +\"([^\"]+)\" +([^;]+;).*");
     std::regex port_attrre = std::regex("([^ =;]+=[^ =;]+) *([^;]*;)");
-    std::smatch match, match_attr;
-    std::string line;
+    std::regex iobelre = std::regex("IO([TRBL])([0-9]+)([A-Z])");
+    std::smatch match, match_attr, match_pinloc;
+    std::string line, pinline;
     bool io_loc;
+
     while (!in.eof()) {
         std::getline(in, line);
         io_loc = true;
@@ -512,11 +532,23 @@ void Arch::read_cst(std::istream &in)
         }
         if (io_loc) { // IO_LOC name pin
             IdString pinname = id(match[2]);
+            pinline = match[2];
             const PairPOD *belname = pairLookup(package->pins.get(), package->num_pins, pinname.index);
-            if (belname == nullptr)
+            if (belname != nullptr) {
+                std::string bel = IdString(belname->src_id).str(this);
+                it->second->attrs[IdString(ID_BEL)] = bel;
+            } else if (std::regex_match(pinline, match_pinloc, iobelre)) {
+                // may be it's IOx#[AB] style?
+                Loc loc = getLoc(match_pinloc, getGridDimX(), getGridDimY());
+                BelId bel = getBelByLocation(loc);
+                if (bel == BelId()) {
+                    log_error("Pin %s not found\n", pinline.c_str());
+                }
+                std::string belname = getCtx()->nameOfBel(bel);
+                it->second->attrs[IdString(ID_BEL)] = belname;
+            } else {
                 log_error("Pin %s not found\n", pinname.c_str(this));
-            std::string bel = IdString(belname->src_id).str(this);
-            it->second->attrs[IdString(ID_BEL)] = bel;
+            }
         } else { // IO_PORT attr=value
             std::string attr_val = match[2];
             while (std::regex_match(attr_val, match_attr, port_attrre)) {
diff --git a/python/delay_vs_fanout.py b/python/delay_vs_fanout.py
new file mode 100644
index 00000000..c417ac78
--- /dev/null
+++ b/python/delay_vs_fanout.py
@@ -0,0 +1,10 @@
+with open("delay_vs_fanout.csv", "w") as f:
+    print("fanout,delay", file=f)
+    for net_name, net in ctx.nets:
+        if net.driver.cell is None:
+            continue
+        if net.driver.cell.type == "DCCA":
+            continue # ignore global clocks
+        for user in net.users:
+            print(f"{len(net.users)},{ctx.getNetinfoRouteDelay(net, user)}", file=f)
+