gowin: Add simplified IO cells processing

Some models have I/O cells that are IOBUFs, and other types (IBUFs and
OBUFs) are obtained by feeding 1 or 0 to the OEN input.  This is done
with general-purpose routing so it's best to do it here to avoid
conflicts.

For this purpose, in the new bases, these special cells are of type IOBS
(IOB Simplified).

The proposed changes are compatible with bases of previous versions of
Apycula and do not require changing .CST constraint files.

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

4 files changed, 77 insertions, 4 deletions

diff --git a/gowin/arch.cc b/gowin/arch.cc
index 801540cc..2f61685a 100644
--- a/gowin/arch.cc
+++ b/gowin/arch.cc
@@ -870,6 +870,39 @@ Arch::Arch(ArchArgs args) : args(args)
                 snprintf(buf, 32, "R%dC%d_%s", row + 1, col + 1, portname.c_str(this));
                 addBelInput(belname, id_OEN, id(buf));
                 break;
+                // Simplified IO
+            case ID_IOBJS:
+                z++; /* fall-through*/
+            case ID_IOBIS:
+                z++; /* fall-through*/
+            case ID_IOBHS:
+                z++; /* fall-through*/
+            case ID_IOBGS:
+                z++; /* fall-through*/
+            case ID_IOBFS:
+                z++; /* fall-through*/
+            case ID_IOBES:
+                z++; /* fall-through*/
+            case ID_IOBDS:
+                z++; /* fall-through*/
+            case ID_IOBCS:
+                z++; /* fall-through*/
+            case ID_IOBBS:
+                z++; /* fall-through*/
+            case ID_IOBAS:
+                snprintf(buf, 32, "R%dC%d_IOB%c", row + 1, col + 1, 'A' + z);
+                belname = id(buf);
+                addBel(belname, id_IOBS, Loc(col, row, z), false);
+                portname = IdString(pairLookup(bel->ports.get(), bel->num_ports, ID_O)->src_id);
+                snprintf(buf, 32, "R%dC%d_%s", row + 1, col + 1, portname.c_str(this));
+                addBelOutput(belname, id_O, id(buf));
+                portname = IdString(pairLookup(bel->ports.get(), bel->num_ports, ID_I)->src_id);
+                snprintf(buf, 32, "R%dC%d_%s", row + 1, col + 1, portname.c_str(this));
+                addBelInput(belname, id_I, id(buf));
+                portname = IdString(pairLookup(bel->ports.get(), bel->num_ports, ID_OE)->src_id);
+                snprintf(buf, 32, "R%dC%d_%s", row + 1, col + 1, portname.c_str(this));
+                addBelInput(belname, id_OEN, id(buf));
+                break;
 
             default:
                 break;
diff --git a/gowin/cells.cc b/gowin/cells.cc
index 57f3ab9c..dce3f456 100644
--- a/gowin/cells.cc
+++ b/gowin/cells.cc
@@ -64,14 +64,14 @@ std::unique_ptr<CellInfo> create_generic_cell(Context *ctx, IdString type, std::
         add_port(ctx, new_cell.get(), id_I1, PORT_IN);
         add_port(ctx, new_cell.get(), id_SEL, PORT_IN);
         add_port(ctx, new_cell.get(), id_OF, PORT_OUT);
-    } else if (type == id_IOB) {
+    } else if (type == id_IOB || type == id_IOBS) {
         new_cell->params[id_INPUT_USED] = 0;
         new_cell->params[id_OUTPUT_USED] = 0;
         new_cell->params[id_ENABLE_USED] = 0;
 
         add_port(ctx, new_cell.get(), id_PAD, PORT_INOUT);
         add_port(ctx, new_cell.get(), id_I, PORT_IN);
-        add_port(ctx, new_cell.get(), id_EN, PORT_IN);
+        add_port(ctx, new_cell.get(), id_OEN, PORT_IN);
         add_port(ctx, new_cell.get(), id_O, PORT_OUT);
     } else {
         log_error("unable to create generic cell of type %s\n", type.c_str(ctx));
@@ -140,9 +140,17 @@ void dff_to_lc(const Context *ctx, CellInfo *dff, CellInfo *lc, bool pass_thru_l
 void gwio_to_iob(Context *ctx, CellInfo *nxio, CellInfo *iob, pool<IdString> &todelete_cells)
 {
     if (nxio->type == id_IBUF) {
+        if (iob->type == id_IOBS) {
+            // VCC -> OEN
+            connect_port(ctx, ctx->nets[ctx->id("$PACKER_VCC_NET")].get(), iob, id_OEN);
+        }
         iob->params[id_INPUT_USED] = 1;
         replace_port(nxio, id_O, iob, id_O);
     } else if (nxio->type == id_OBUF) {
+        if (iob->type == id_IOBS) {
+            // VSS -> OEN
+            connect_port(ctx, ctx->nets[ctx->id("$PACKER_GND_NET")].get(), iob, id_OEN);
+        }
         iob->params[id_OUTPUT_USED] = 1;
         replace_port(nxio, id_I, iob, id_I);
     } else if (nxio->type == id_TBUF) {
diff --git a/gowin/constids.inc b/gowin/constids.inc
index 7de754fc..6a730d5d 100644
--- a/gowin/constids.inc
+++ b/gowin/constids.inc
@@ -358,6 +358,19 @@ X(IOBH)
 X(IOBI)
 X(IOBJ)
 
+// simplified iobs
+X(IOBS)
+X(IOBAS)
+X(IOBBS)
+X(IOBCS)
+X(IOBDS)
+X(IOBES)
+X(IOBFS)
+X(IOBGS)
+X(IOBHS)
+X(IOBIS)
+X(IOBJS)
+
 // Wide LUTs
 X(MUX2_LUT5)
 X(MUX2_LUT6)
diff --git a/gowin/pack.cc b/gowin/pack.cc
index cb63f1c9..553eeb4e 100644
--- a/gowin/pack.cc
+++ b/gowin/pack.cc
@@ -629,7 +629,7 @@ static void pack_constants(Context *ctx)
 
     std::vector<IdString> dead_nets;
 
-    bool gnd_used = false;
+    bool gnd_used = true; // XXX May be needed for simplified IO
 
     for (auto &net : ctx->nets) {
         NetInfo *ni = net.second.get();
@@ -718,8 +718,27 @@ static void pack_io(Context *ctx)
                 }
                 packed_cells.insert(iob->name);
             }
+            // what type to create
+            IdString new_cell_type = id_IOB;
+            std::string constr_bel_name = std::string("");
+            // check whether the given IO is limited to simplified IO cells
+            auto constr_bel = ci->attrs.find(id_BEL);
+            if (constr_bel != ci->attrs.end()) {
+                constr_bel_name = constr_bel->second.as_string();
+            }
+            constr_bel = iob->attrs.find(id_BEL);
+            if (constr_bel != iob->attrs.end()) {
+                constr_bel_name = constr_bel->second.as_string();
+            }
+            if (!constr_bel_name.empty()) {
+                BelId constr_bel = ctx->getBelByNameStr(constr_bel_name);
+                if (constr_bel != BelId()) {
+                    new_cell_type = ctx->bels[constr_bel].type;
+                }
+            }
+
             // Create a IOB buffer
-            std::unique_ptr<CellInfo> ice_cell = create_generic_cell(ctx, id_IOB, ci->name.str(ctx) + "$iob");
+            std::unique_ptr<CellInfo> ice_cell = create_generic_cell(ctx, new_cell_type, ci->name.str(ctx) + "$iob");
             gwio_to_iob(ctx, ci, ice_cell.get(), packed_cells);
             new_cells.push_back(std::move(ice_cell));
             auto gwiob = new_cells.back().get();