From 576baa994f4b9e1746a231469bfd9e65d1d5a2b4 Mon Sep 17 00:00:00 2001
From: David Shah <dave@ds0.me>
Date: Fri, 9 Oct 2020 21:41:55 +0100
Subject: ecp5: Fix some tricky ECLKSYNCB/CLKDIVF packing cases

Signed-off-by: David Shah <dave@ds0.me>
---
 ecp5/pack.cc | 64 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 64 insertions(+)

(limited to 'ecp5')

diff --git a/ecp5/pack.cc b/ecp5/pack.cc
index fa92cc15..58737bfe 100644
--- a/ecp5/pack.cc
+++ b/ecp5/pack.cc
@@ -2653,6 +2653,7 @@ class Ecp5Packer
             }
         }
         flush_cells();
+        std::unordered_set<BelId> used_eclksyncb;
         for (auto cell : sorted(ctx->cells)) {
             CellInfo *ci = cell.second;
             if (ci->type == id_CLKDIVF) {
@@ -2687,6 +2688,7 @@ class Ecp5Packer
                         Loc loc = ctx->getBelLocation(bel);
                         ci->attrs[ctx->id("BEL")] =
                                 ctx->getBelName(ctx->getBelByLocation(Loc(loc.x, loc.y, 15))).str(ctx);
+                        used_eclksyncb.insert(bel);
                         goto eclksync_done;
                     }
                 }
@@ -2702,6 +2704,7 @@ class Ecp5Packer
                             Loc loc = ctx->getBelLocation(bel);
                             if (loc.x == eckbuf_loc.x && loc.y == eckbuf_loc.y && loc.z == eckbuf_loc.z - 2) {
                                 ci->attrs[ctx->id("BEL")] = ctx->getBelName(bel).str(ctx);
+                                used_eclksyncb.insert(bel);
                                 goto eclksync_done;
                             }
                         }
@@ -2768,6 +2771,67 @@ class Ecp5Packer
             }
         }
 
+        for (auto cell : sorted(ctx->cells)) {
+            CellInfo *ci = cell.second;
+            if (ci->type == id_ECLKSYNCB) {
+                // **All** ECLKSYNCBs must be constrained
+                // Most will be dealt with above, but there might be some rogue cases
+                if (ci->attrs.count(ctx->id("BEL")))
+                    continue;
+                for (BelId bel : ctx->getBels()) {
+                    if (ctx->getBelType(bel) != id_ECLKSYNCB)
+                        continue;
+                    // Might there be a better way to pick??
+                    if (used_eclksyncb.count(bel))
+                        continue;
+                    log_info("Constraining ECLKSYNCB '%s' to bel '%s'\n", ctx->nameOf(ci), ctx->nameOfBel(bel));
+                    ci->attrs[ctx->id("BEL")] = ctx->getBelName(bel).str(ctx);
+                    goto eclksync_ii_done;
+                }
+                if (0) {
+                eclksync_ii_done:
+                    continue;
+                }
+                log_error("Failed to constrain ECLKSYNCB '%s'\n", ctx->nameOf(ci));
+            }
+        }
+
+        for (auto cell : sorted(ctx->cells)) {
+            CellInfo *ci = cell.second;
+            if (ci->type == id_CLKDIVF) {
+                if (ci->attrs.count(ctx->id("BEL")))
+                    continue;
+                // Case of a CLKDIVF driven by an ECLKSYNC constrained above; without the input being used elsewhere as
+                // an edge clock
+                const NetInfo *clki = net_or_nullptr(ci, id_CLKI);
+                if (clki == nullptr || clki->driver.cell == nullptr)
+                    continue;
+                CellInfo *drv = clki->driver.cell;
+                if (drv->type != id_ECLKSYNCB || !drv->attrs.count(ctx->id("BEL")))
+                    continue;
+                BelId bel = ctx->getBelByName(ctx->id(drv->attrs.at(ctx->id("BEL")).as_string()));
+                // Find a CLKDIVF that is routeable from the ECLKSYNC
+                std::queue<WireId> visit;
+                visit.push(ctx->getBelPinWire(bel, id_ECLKO));
+                while (!visit.empty()) {
+                    WireId cursor = visit.front();
+                    visit.pop();
+                    for (BelPin bp : ctx->getWireBelPins(cursor)) {
+                        if (ctx->getBelType(bp.bel) != id_CLKDIVF || bp.pin != id_CLKI)
+                            continue;
+                        ci->attrs[ctx->id("BEL")] = ctx->getBelName(bp.bel).str(ctx);
+                        log_info("Constraining CLKDIVF '%s' to bel '%s' based on ECLKSYNCB.\n", ctx->nameOf(ci),
+                                 ctx->nameOfBel(bp.bel));
+                        goto clkdiv_ii_done;
+                    }
+                    for (PipId pip : ctx->getPipsDownhill(cursor))
+                        visit.push(ctx->getPipDstWire(pip));
+                }
+            clkdiv_ii_done:
+                continue;
+            }
+        }
+
         flush_cells();
     };
 
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