Merge branch 'master' of gitlab.com:SymbioticEDA/nextpnr

1 files changed, 96 insertions, 0 deletions

diff --git a/common/timing.cc b/common/timing.cc
new file mode 100644
index 00000000..47c82a03
--- /dev/null
+++ b/common/timing.cc
@@ -0,0 +1,96 @@
+/*
+ *  nextpnr -- Next Generation Place and Route
+ *
+ *  Copyright (C) 2018  David Shah <david@symbioticeda.com>
+ *
+ *  Permission to use, copy, modify, and/or distribute this software for any
+ *  purpose with or without fee is hereby granted, provided that the above
+ *  copyright notice and this permission notice appear in all copies.
+ *
+ *  THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ *  WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ *  MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ *  ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ *  WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ *  ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ *  OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ *
+ */
+
+#include "timing.h"
+#include <algorithm>
+#include <unordered_map>
+#include <utility>
+#include "log.h"
+
+NEXTPNR_NAMESPACE_BEGIN
+
+static delay_t follow_net(Context *ctx, NetInfo *net, int path_length,
+                          delay_t slack);
+
+// Follow a path, returning budget to annotate
+static delay_t follow_user_port(Context *ctx, PortRef &user, int path_length,
+                                delay_t slack)
+{
+    delay_t value;
+    if (ctx->getPortClock(user.cell, user.port) != IdString()) {
+        // At the end of a timing path (arguably, should check setup time
+        // here too)
+        value = slack / path_length;
+    } else {
+        // Default to the path ending here, if no further paths found
+        value = slack / path_length;
+        // Follow outputs of the user
+        for (auto port : user.cell->ports) {
+            if (port.second.type == PORT_OUT) {
+                delay_t comb_delay;
+                // Look up delay through this path
+                bool is_path = ctx->getCellDelay(user.cell, user.port,
+                                                 port.first, comb_delay);
+                if (is_path) {
+                    NetInfo *net = port.second.net;
+                    if (net) {
+                        delay_t path_budget = follow_net(ctx, net, path_length,
+                                                         slack - comb_delay);
+                        value = std::min(value, path_budget);
+                    }
+                }
+            }
+        }
+    }
+
+    if (value < user.budget) {
+        user.budget = value;
+    }
+}
+
+static delay_t follow_net(Context *ctx, NetInfo *net, int path_length,
+                          delay_t slack)
+{
+    delay_t net_budget = slack / path_length;
+    for (auto &usr : net->users) {
+        net_budget = std::min(
+                net_budget, follow_user_port(ctx, usr, path_length + 1, slack));
+    }
+    return net_budget;
+}
+
+void assign_budget(Context *ctx, float default_clock)
+{
+    for (auto cell : ctx->cells) {
+        for (auto port : cell.second->ports) {
+            if (port.second.type == PORT_OUT) {
+                IdString clock_domain =
+                        ctx->getPortClock(cell.second, port.first);
+                if (clock_domain != IdString()) {
+                    delay_t slack = delay_t(
+                            1.0e12 / default_clock); // TODO: clock constraints
+                    if (port.second.net)
+                        follow_net(ctx, port.second.net, 0, slack);
+                }
+            }
+        }
+    }
+}
+
+NEXTPNR_NAMESPACE_END