ice40: Improve handling of unconstrained IO

Signed-off-by: David Shah <dave@ds0.me>

3 files changed, 23 insertions, 3 deletions

diff --git a/ice40/main.cc b/ice40/main.cc
index 543bd229..286f68db 100644
--- a/ice40/main.cc
+++ b/ice40/main.cc
@@ -70,6 +70,8 @@ po::options_description Ice40CommandHandler::getArchOptions()
     specific.add_options()("no-promote-globals", "disable all global promotion");
     specific.add_options()("opt-timing", "run post-placement timing optimisation pass (experimental)");
     specific.add_options()("tmfuzz", "run path delay estimate fuzzer");
+    specific.add_options()("pcf-allow-unconstrained", "don't require PCF to constrain all IO");
+
     return specific;
 }
 void Ice40CommandHandler::validate()
@@ -87,6 +89,8 @@ void Ice40CommandHandler::customAfterLoad(Context *ctx)
         std::ifstream pcf(filename);
         if (!apply_pcf(ctx, filename, pcf))
             log_error("Loading PCF failed.\n");
+    } else {
+        log_warning("No PCF file specified; IO pins will be placed automatically\n");
     }
 }
 void Ice40CommandHandler::customBitstream(Context *ctx)
@@ -164,6 +168,9 @@ std::unique_ptr<Context> Ice40CommandHandler::createContext()
         ctx->settings[ctx->id("no_promote_globals")] = "1";
     if (vm.count("opt-timing"))
         ctx->settings[ctx->id("opt_timing")] = "1";
+    if (vm.count("pcf-allow-unconstrained"))
+        ctx->settings[ctx->id("pcf_allow_unconstrained")] = "1";
+
     return ctx;
 }
 
diff --git a/ice40/pack.cc b/ice40/pack.cc
index 536b1b16..27387a75 100644
--- a/ice40/pack.cc
+++ b/ice40/pack.cc
@@ -478,9 +478,6 @@ static void pack_io(Context *ctx)
             }
             packed_cells.insert(ci->name);
             std::copy(ci->attrs.begin(), ci->attrs.end(), std::inserter(sb->attrs, sb->attrs.begin()));
-            if (!sb->attrs.count(ctx->id("BEL")))
-                log_warning("IO '%s' is not constrained to a pin and will be automatically placed\n",
-                            ci->name.c_str(ctx));
         } else if (is_sb_io(ctx, ci) || is_sb_gb_io(ctx, ci)) {
             NetInfo *net = ci->ports.at(ctx->id("PACKAGE_PIN")).net;
             if ((net != nullptr) && (net->users.size() > 1))
diff --git a/ice40/pcf.cc b/ice40/pcf.cc
index a351b95d..a8273dd6 100644
--- a/ice40/pcf.cc
+++ b/ice40/pcf.cc
@@ -21,6 +21,7 @@
 #include "pcf.h"
 #include <sstream>
 #include "log.h"
+#include "util.h"
 
 NEXTPNR_NAMESPACE_BEGIN
 
@@ -100,6 +101,21 @@ bool apply_pcf(Context *ctx, std::string filename, std::istream &in)
                 log_error("unsupported PCF command '%s' (on line %d)\n", cmd.c_str(), lineno);
             }
         }
+        for (auto cell : sorted(ctx->cells)) {
+            CellInfo *ci = cell.second;
+            if (ci->type == ctx->id("$nextpnr_ibuf") || ci->type == ctx->id("$nextpnr_obuf") ||
+                ci->type == ctx->id("$nextpnr_iobuf")) {
+                if (!ci->attrs.count(ctx->id("BEL"))) {
+                    if (bool_or_default(ctx->settings, ctx->id("pcf_allow_unconstrained")))
+                        log_warning("IO '%s' is unconstrained in PCF and will be automatically placed\n",
+                                    cell.first.c_str(ctx));
+                    else
+                        log_error("IO '%s' is unconstrained in PCF (override this error with "
+                                  "--pcf-allow-unconstrained)\n",
+                                  cell.first.c_str(ctx));
+                }
+            }
+        }
         ctx->settings.emplace(ctx->id("input/pcf"), filename);
         return true;
     } catch (log_execution_error_exception) {