diff options
Diffstat (limited to 'common/timing.cc')
-rw-r--r-- | common/timing.cc | 96 |
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 |