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/*
* 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"
#include "util.h"
NEXTPNR_NAMESPACE_BEGIN
typedef std::list<const PortRef *> PortRefList;
static delay_t follow_net(Context *ctx, NetInfo *net, int path_length, delay_t slack, bool update, 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, bool update,
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;
// Follow outputs of the user
for (auto port : user.cell->ports) {
if (port.second.type == PORT_OUT) {
DelayInfo 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.maxDelay(), update,
min_slack, current_path, crit_path);
value = std::min(value, path_budget);
}
}
}
}
}
return value;
}
static delay_t follow_net(Context *ctx, NetInfo *net, int path_length, delay_t slack, bool update, delay_t &min_slack,
PortRefList *current_path, PortRefList *crit_path)
{
delay_t net_budget = slack / (path_length + 1);
for (auto &usr : net->users) {
if (crit_path)
current_path->push_back(&usr);
// If budget override is less than existing budget, then do not increment path length
int pl = path_length + 1;
auto budget = ctx->getBudgetOverride(net, usr, net_budget);
if (budget < net_budget) {
net_budget = budget;
pl = std::max(1, path_length);
}
auto delay = ctx->getNetinfoRouteDelay(net, usr);
net_budget = std::min(
net_budget, follow_user_port(ctx, usr, pl, slack - delay, update, min_slack, current_path, crit_path));
if (update)
usr.budget = std::min(usr.budget, delay + net_budget);
if (crit_path)
current_path->pop_back();
}
return net_budget;
}
static delay_t walk_paths(Context *ctx, bool update, PortRefList *crit_path)
{
delay_t default_slack = delay_t(1.0e12 / ctx->target_freq);
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
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 = default_slack; // TODO: clock constraints
DelayInfo clkToQ;
if (ctx->getCellDelay(cell.second.get(), clock_domain, port.first, clkToQ))
slack -= clkToQ.maxDelay();
if (port.second.net)
follow_net(ctx, port.second.net, 0, slack, update, min_slack, ¤t_path, crit_path);
}
}
}
}
return min_slack;
}
void assign_budget(Context *ctx, bool quiet)
{
if (!quiet) {
log_break();
log_info("Annotating ports with timing budgets for target frequency %.2f MHz\n", ctx->target_freq/1e6);
}
// 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;
}
}
delay_t min_slack = walk_paths(ctx, true, nullptr);
if (!quiet || ctx->verbose) {
for (auto &net : ctx->nets) {
for (auto &user : net.second->users) {
// Post-update check
if (!ctx->auto_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 if (ctx->verbose)
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));
}
}
}
// For slack redistribution, if user has not specified a frequency
// dynamically adjust the target frequency to be the currently
// achieved maximum
if (ctx->auto_freq && ctx->slack_redist_iter > 0) {
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);
}
if (!quiet)
log_info("Checksum: 0x%08x\n", ctx->checksum());
}
delay_t timing_analysis(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 = walk_paths(ctx, false, &crit_path);
if (print_path) {
if (crit_path.empty()) {
log_info("Design contains no timing paths\n");
} else {
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;
auto &driver = net->driver;
auto driver_cell = driver.cell;
DelayInfo comb_delay;
ctx->getCellDelay(sink_cell, last_port, driver.port, comb_delay);
total += comb_delay.maxDelay();
log_info("%4d %4d Source %s.%s\n", comb_delay.maxDelay(), total, driver_cell->name.c_str(ctx),
driver.port.c_str(ctx));
auto net_delay = ctx->getNetinfoRouteDelay(net, *sink);
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));
return min_slack;
}
NEXTPNR_NAMESPACE_END
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