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-rw-r--r--common/timing.cc189
1 files changed, 166 insertions, 23 deletions
diff --git a/common/timing.cc b/common/timing.cc
index d91dea20..cefe36f0 100644
--- a/common/timing.cc
+++ b/common/timing.cc
@@ -22,19 +22,30 @@
#include <unordered_map>
#include <utility>
#include "log.h"
+#include "util.h"
NEXTPNR_NAMESPACE_BEGIN
-static delay_t follow_net(Context *ctx, NetInfo *net, int path_length, delay_t slack);
+typedef std::unordered_map<const PortInfo *, delay_t> UpdateMap;
+typedef std::list<const PortRef *> PortRefList;
+
+static delay_t follow_net(Context *ctx, NetInfo *net, int path_length, delay_t slack, UpdateMap *updates,
+ delay_t &min_slack, PortRefList *current_path, PortRefList *crit_path);
// Follow a path, returning budget to annotate
-static delay_t follow_user_port(Context *ctx, PortRef &user, int path_length, delay_t slack)
+static delay_t follow_user_port(Context *ctx, PortRef &user, int path_length, delay_t slack, UpdateMap *updates,
+ delay_t &min_slack, PortRefList *current_path, PortRefList *crit_path)
{
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;
+ if (slack < min_slack) {
+ min_slack = slack;
+ if (crit_path)
+ *crit_path = *current_path;
+ }
} else {
// Default to the path ending here, if no further paths found
value = slack / path_length;
@@ -47,7 +58,8 @@ static delay_t follow_user_port(Context *ctx, PortRef &user, int path_length, de
if (is_path) {
NetInfo *net = port.second.net;
if (net) {
- delay_t path_budget = follow_net(ctx, net, path_length, slack - comb_delay);
+ delay_t path_budget = follow_net(ctx, net, path_length, slack - comb_delay, updates, min_slack,
+ current_path, crit_path);
value = std::min(value, path_budget);
}
}
@@ -55,53 +67,96 @@ static delay_t follow_user_port(Context *ctx, PortRef &user, int path_length, de
}
}
- if (value < user.budget) {
- user.budget = value;
+ if (updates) {
+ auto ret = updates->emplace(&user.cell->ports.at(user.port), value);
+ if (!ret.second)
+ ret.first->second = std::min(value, ret.first->second);
}
return value;
}
-static delay_t follow_net(Context *ctx, NetInfo *net, int path_length, delay_t slack)
+static delay_t follow_net(Context *ctx, NetInfo *net, int path_length, delay_t slack, UpdateMap *updates,
+ delay_t &min_slack, PortRefList *current_path, PortRefList *crit_path)
{
delay_t net_budget = slack / (path_length + 1);
- for (auto &usr : net->users) {
- net_budget = std::min(net_budget, follow_user_port(ctx, usr, path_length + 1, slack));
+ for (unsigned i = 0; i < net->users.size(); ++i) {
+ auto &usr = net->users[i];
+ if (crit_path)
+ current_path->push_back(&usr);
+ net_budget = std::min(net_budget,
+ follow_user_port(ctx, usr, path_length + 1, slack - ctx->getNetinfoRouteDelay(net, i),
+ updates, min_slack, current_path, crit_path));
+ if (crit_path)
+ current_path->pop_back();
}
return net_budget;
}
-void assign_budget(Context *ctx)
+static delay_t compute_min_slack(Context *ctx, UpdateMap *updates, PortRefList *crit_path)
{
- log_break();
- log_info("Annotating ports with timing budgets\n");
- // Clear delays to a very high value first
delay_t default_slack = delay_t(1.0e12 / ctx->target_freq);
- for (auto &net : ctx->nets) {
- for (auto &usr : net.second->users) {
- usr.budget = default_slack;
- }
- }
- // Go through all clocked drivers and set up paths
+ delay_t min_slack = default_slack;
+
+ PortRefList current_path;
+
+ // Go through all clocked drivers and distribute the available path
+ // slack evenly into the budget of every sink on the path ---
+ // record this value into the UpdateMap
for (auto &cell : ctx->cells) {
for (auto port : cell.second->ports) {
if (port.second.type == PORT_OUT) {
IdString clock_domain = ctx->getPortClock(cell.second.get(), port.first);
if (clock_domain != IdString()) {
- delay_t slack = delay_t(1.0e12 / ctx->target_freq); // TODO: clock constraints
+ delay_t slack = default_slack; // TODO: clock constraints
delay_t clkToQ;
if (ctx->getCellDelay(cell.second.get(), clock_domain, port.first, clkToQ))
slack -= clkToQ;
if (port.second.net)
- follow_net(ctx, port.second.net, 0, slack);
+ follow_net(ctx, port.second.net, 0, slack, updates, min_slack, &current_path, crit_path);
}
}
}
}
- // Post-allocation check
+ return min_slack;
+}
+
+void assign_budget(Context *ctx)
+{
+ log_break();
+ log_info("Annotating ports with timing budgets\n");
+ // Clear delays to a very high value first
+ delay_t default_slack = delay_t(1.0e12 / ctx->target_freq);
for (auto &net : ctx->nets) {
- for (auto user : net.second->users) {
- if (user.budget < 0)
+ for (auto &usr : net.second->users) {
+ usr.budget = default_slack;
+ }
+ }
+
+ UpdateMap updates;
+ delay_t min_slack = compute_min_slack(ctx, &updates, nullptr);
+
+ // If user has not specified a frequency, adjust the target frequency
+ // to be equivalent to the estimate Fmax
+ if (!ctx->user_freq) {
+ ctx->target_freq = 1e12 / (default_slack - min_slack);
+ if (ctx->verbose)
+ log_info("minimum slack for this assign = %d, target Fmax for next update = %.2f MHz\n", min_slack,
+ ctx->target_freq / 1e6);
+ }
+
+ // Update the budgets
+ for (auto &net : ctx->nets) {
+ for (size_t i = 0; i < net.second->users.size(); ++i) {
+ auto &user = net.second->users[i];
+ auto pi = &user.cell->ports.at(user.port);
+ auto it = updates.find(pi);
+ if (it == updates.end())
+ continue;
+ user.budget = ctx->getNetinfoRouteDelay(net.second.get(), i) - it->second;
+
+ // Post-update check
+ if (ctx->user_freq && user.budget < 0)
log_warning("port %s.%s, connected to net '%s', has negative "
"timing budget of %fns\n",
user.cell->name.c_str(ctx), user.port.c_str(ctx), net.first.c_str(ctx),
@@ -117,4 +172,92 @@ void assign_budget(Context *ctx)
log_info("Checksum: 0x%08x\n", ctx->checksum());
}
+void update_budget(Context *ctx)
+{
+ UpdateMap updates;
+ delay_t default_slack = delay_t(1.0e12 / ctx->target_freq);
+ delay_t min_slack = compute_min_slack(ctx, &updates, nullptr);
+
+ // If user has not specified a frequency, adjust the frequency dynamically:
+ if (!ctx->user_freq) {
+ if (min_slack < 0)
+ ctx->target_freq = 1e12 / (default_slack - 0.99 * min_slack);
+ else
+ ctx->target_freq = 1e12 / (default_slack - 1.05 * min_slack);
+ if (ctx->verbose)
+ log_info("minimum slack for this update = %d, target Fmax for next update = %.2f MHz\n", min_slack,
+ ctx->target_freq / 1e6);
+ }
+
+ // Update the budgets
+ for (auto &net : ctx->nets) {
+ for (size_t i = 0; i < net.second->users.size(); ++i) {
+ auto &user = net.second->users[i];
+ auto pi = &user.cell->ports.at(user.port);
+ auto it = updates.find(pi);
+ if (it == updates.end())
+ continue;
+ user.budget = ctx->getNetinfoRouteDelay(net.second.get(), i) + it->second;
+
+ // Post-update check
+ if (ctx->verbose) {
+ if (ctx->user_freq && user.budget < 0)
+ log_warning("port %s.%s, connected to net '%s', has negative "
+ "timing budget of %fns\n",
+ user.cell->name.c_str(ctx), user.port.c_str(ctx), net.first.c_str(ctx),
+ ctx->getDelayNS(user.budget));
+ else
+ log_info("port %s.%s, connected to net '%s', has "
+ "timing budget of %fns\n",
+ user.cell->name.c_str(ctx), user.port.c_str(ctx), net.first.c_str(ctx),
+ ctx->getDelayNS(user.budget));
+ }
+ }
+ }
+}
+
+void compute_fmax(Context *ctx, bool print_fmax, bool print_path)
+{
+ delay_t default_slack = delay_t(1.0e12 / ctx->target_freq);
+ PortRefList crit_path;
+ delay_t min_slack = compute_min_slack(ctx, nullptr, &crit_path);
+ if (print_path) {
+ delay_t total = 0;
+ log_break();
+ log_info("Critical path report:\n");
+ log_info("curr total\n");
+ auto &front = crit_path.front();
+ auto &front_port = front->cell->ports.at(front->port);
+ auto &front_driver = front_port.net->driver;
+ auto last_port = ctx->getPortClock(front_driver.cell, front_driver.port);
+ for (auto sink : crit_path) {
+ auto sink_cell = sink->cell;
+ auto &port = sink_cell->ports.at(sink->port);
+ auto net = port.net;
+ unsigned i = 0;
+ for (auto &usr : net->users)
+ if (&usr == sink)
+ break;
+ auto &driver = net->driver;
+ auto driver_cell = driver.cell;
+ delay_t comb_delay;
+ ctx->getCellDelay(sink_cell, last_port, driver.port, comb_delay);
+ total += comb_delay;
+ log_info("%4d %4d Source %s.%s\n", comb_delay, total, driver_cell->name.c_str(ctx),
+ driver.port.c_str(ctx));
+ delay_t net_delay = ctx->getNetinfoRouteDelay(net, i);
+ total += net_delay;
+ auto driver_loc = ctx->getBelLocation(driver_cell->bel);
+ auto sink_loc = ctx->getBelLocation(sink_cell->bel);
+ log_info("%4d %4d Net %s budget %d (%d,%d) -> (%d,%d)\n", net_delay, total, net->name.c_str(ctx),
+ sink->budget, driver_loc.x, driver_loc.y, sink_loc.x, sink_loc.y);
+ log_info(" Sink %s.%s\n", sink_cell->name.c_str(ctx), sink->port.c_str(ctx));
+ last_port = sink->port;
+ }
+ log_break();
+ }
+ if (print_fmax)
+ log_info("estimated Fmax = %.2f MHz\n", 1e6 / (default_slack - min_slack));
+}
+
NEXTPNR_NAMESPACE_END
generated by cgit v1.2.3 (git 2.25.1) at 2024-08-21 18:48:27 +0000