220 lines
8.8 KiB
C++
220 lines
8.8 KiB
C++
/*
|
|
* 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\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;
|
|
}
|
|
}
|
|
|
|
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->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 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->user_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
|