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author | Eddie Hung <e.hung@imperial.ac.uk> | 2018-07-21 01:55:20 -0700 |
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committer | Eddie Hung <e.hung@imperial.ac.uk> | 2018-07-21 01:55:20 -0700 |
commit | 27a79a3a4f464f2d038f66737d78aaa2fb6f2703 (patch) | |
tree | 6979e175ad0ca84492d4321c10bfd6548f9d50ff | |
parent | 6e7ba2a2be87bb1e0f323128283a87f59af596b7 (diff) | |
download | nextpnr-27a79a3a4f464f2d038f66737d78aaa2fb6f2703.tar.gz nextpnr-27a79a3a4f464f2d038f66737d78aaa2fb6f2703.tar.bz2 nextpnr-27a79a3a4f464f2d038f66737d78aaa2fb6f2703.zip |
Update comment
-rw-r--r-- | common/timing.cc | 118 |
1 files changed, 118 insertions, 0 deletions
diff --git a/common/timing.cc b/common/timing.cc index 3a48935f..479dba26 100644 --- a/common/timing.cc +++ b/common/timing.cc @@ -22,6 +22,7 @@ #include <unordered_map> #include <utility> #include "log.h" +#include "util.h" NEXTPNR_NAMESPACE_BEGIN @@ -114,4 +115,121 @@ void assign_budget(Context *ctx) log_info("Checksum: 0x%08x\n", ctx->checksum()); } +typedef std::unordered_map<const PortInfo*, delay_t> updates_t; +typedef std::unordered_map<const PortInfo*, delay_t> delays_t; + +static delay_t follow_net_update(Context *ctx, NetInfo *net, int path_length, delay_t slack, const delays_t& delays, updates_t& updates); + +// Follow a path, returning budget to annotate +static delay_t follow_user_port_update(Context *ctx, PortRef &user, int path_length, delay_t slack, const delays_t& delays, updates_t& updates) +{ + 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_update(ctx, net, path_length, slack - comb_delay, delays, updates); + value = std::min(value, path_budget); + } + } + } + } + } + + auto ret = updates.emplace(&user.cell->ports.at(user.port), value); + if (!ret.second && value < ret.first->second) { + ret.first->second = value; + } + return value; +} + +static delay_t follow_net_update(Context *ctx, NetInfo *net, int path_length, delay_t slack, const delays_t& delays,updates_t& updates) +{ + delay_t net_budget = slack / (path_length + 1); + for (auto& usr : net->users) { + net_budget = std::min(net_budget, follow_user_port_update(ctx, usr, path_length + 1, slack - get_or_default(delays, &usr.cell->ports.at(usr.port), 0.), delays, updates)); + } + return net_budget; +} + +void update_budget(Context *ctx) +{ + delays_t delays; + updates_t updates; + + // Compute the delay for every pin on every net + for (auto &n : ctx->nets) { + auto net = n.second.get(); + + int driver_x, driver_y; + bool driver_gb; + CellInfo *driver_cell = net->driver.cell; + if (!driver_cell) + continue; + if (driver_cell->bel == BelId()) + continue; + ctx->estimatePosition(driver_cell->bel, driver_x, driver_y, driver_gb); + WireId drv_wire = ctx->getWireBelPin(driver_cell->bel, ctx->portPinFromId(net->driver.port)); + if (driver_gb) + continue; + for (auto& load : net->users) { + if (load.cell == nullptr) + continue; + CellInfo *load_cell = load.cell; + if (load_cell->bel == BelId()) + continue; + WireId user_wire = ctx->getWireBelPin(load_cell->bel, ctx->portPinFromId(load.port)); + delay_t raw_wl = ctx->estimateDelay(drv_wire, user_wire); + delays.emplace(&load_cell->ports.at(load.port), raw_wl); + } + } + + // Go through all clocked drivers and distribute the available path slack evenly into every budget + 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()) { + if (port.second.net) + follow_net_update(ctx, port.second.net, 0, delay_t(1.0e12 / ctx->target_freq) - get_or_default(delays, &port.second, 0.), delays, updates); + } + } + } + } + + // Update the budgets + for (auto &net : ctx->nets) { + for (auto& user : net.second->users) { + auto pi = &user.cell->ports.at(user.port); + auto it = updates.find(pi); + if (it == updates.end()) continue; + user.budget = delays.at(pi) + it->second; + + // Post-update check +// if (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)); +// 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)); + } + } +} + NEXTPNR_NAMESPACE_END |