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machxo2: Add packing logic to forbid designs lacking FACADE_IO top-level ports.

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This commit is contained in:
William D. Jones 2021-11-03 13:53:57 -04:00
parent d2ac6dffbc
commit 365a871908
1 changed files with 46 additions and 0 deletions
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46
machxo2/pack.cc
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@ -229,6 +229,44 @@ static bool is_nextpnr_iob(Context *ctx, CellInfo *cell)
static bool is_facade_iob(const Context *ctx, const CellInfo *cell) { return cell->type == id_FACADE_IO; }
static bool nextpnr_iob_connects_only_facade_iob(Context *ctx, CellInfo *iob, NetInfo *&top) {
NPNR_ASSERT(is_nextpnr_iob(ctx, iob));
if(iob->type == ctx->id("$nextpnr_ibuf")) {
NetInfo *o = iob->ports.at(id_O).net;
top = o;
CellInfo *fio = net_only_drives(ctx, o, is_facade_iob, id_PAD, true);
return fio != nullptr;
} else if(iob->type == ctx->id("$nextpnr_obuf")) {
NetInfo *i = iob->ports.at(id_I).net;
top = i;
// If connected to a FACADE_IO PAD, the net attached to an I port of an
// $nextpnr_obuf will not have a driver, only users; an inout port
// like PAD cannot be a driver in nextpnr. So net_driven_by won't
// return anything. We exclude the IOB as one of the two users because
// we already know that the net drives the $nextpnr_obuf.
CellInfo *fio = net_only_drives(ctx, i, is_facade_iob, id_PAD, true, iob);
return fio != nullptr;
} else if(iob->type == ctx->id("$nextpnr_iobuf")) {
NetInfo *o = iob->ports.at(id_O).net;
top = o;
// When split_io is enabled in a frontend (it is for JSON), the I and O
// ports of a $nextpnr_iobuf are split; the I port connects to the
// driver of the original net before IOB insertion, and the O port
// connects everything else. Because FACADE_IO PADs cannot be a driver
// in nextpnr, the we can safely ignore the I port of an $nextpnr_iobuf
// for any JSON input we're interested in accepting.
CellInfo *fio_o = net_only_drives(ctx, o, is_facade_iob, id_PAD, true);
return fio_o != nullptr;
}
// Unreachable!
NPNR_ASSERT(false);
}
// Pack IO buffers- Right now, all this does is remove $nextpnr_[io]buf cells.
// User is expected to manually instantiate FACADE_IO with BEL/IO_TYPE
// attributes.
@ -241,6 +279,14 @@ static void pack_io(Context *ctx)
for (auto &cell : ctx->cells) {
CellInfo *ci = cell.second.get();
if (is_nextpnr_iob(ctx, ci)) {
NetInfo *top;
if(!nextpnr_iob_connects_only_facade_iob(ctx, ci, top))
log_error("Top level net '%s' is not connected to a FACADE_IO PAD port.\n", top->name.c_str(ctx));
if (ctx->verbose)
log_info("Removing top-level IOBUF '%s' of type '%s'\n", ci->name.c_str(ctx), ci->type.c_str(ctx));
for (auto &p : ci->ports)
disconnect_port(ctx, ci, p.first);
packed_cells.insert(ci->name);