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ecp5: Derived constraint support for PLLs, clock dividers and oscillators

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Signed-off-by: David Shah <davey1576@gmail.com>
This commit is contained in:
David Shah 2019-02-22 11:34:31 +00:00
parent e50ab2106f
commit ae6c1170ef
2 changed files with 119 additions and 3 deletions
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3
ecp5/bitstream.cc
View File

@ -825,7 +825,8 @@ void write_bitstream(Context *ctx, std::string base_config_file, std::string tex
}
if (dir != "INPUT" &&
(ci->ports.find(ctx->id("T")) == ci->ports.end() || ci->ports.at(ctx->id("T")).net == nullptr) &&
(ci->ports.find(ctx->id("IOLTO")) == ci->ports.end() || ci->ports.at(ctx->id("IOLTO")).net == nullptr)) {
(ci->ports.find(ctx->id("IOLTO")) == ci->ports.end() ||
ci->ports.at(ctx->id("IOLTO")).net == nullptr)) {
// Tie tristate low if unconnected for outputs or bidir
std::string jpt = fmt_str("X" << bel.location.x << "/Y" << bel.location.y << "/JPADDT" << pio.back());
WireId jpt_wire = ctx->getWireByName(ctx->id(jpt));

115
ecp5/pack.cc
View File

@ -2147,6 +2147,120 @@ class Ecp5Packer
flush_cells();
};
void generate_constraints()
{
log_info("Generating derived timing constraints...\n");
auto MHz = [&](delay_t a) { return 1000.0 / ctx->getDelayNS(a); };
auto equals_epsilon = [](delay_t a, delay_t b) { return (std::abs(a - b) / std::max(double(b), 1.0)) < 1e-3; };
auto get_period = [&](CellInfo *ci, IdString port, delay_t &period) {
if (!ci->ports.count(port))
return false;
NetInfo *from = ci->ports.at(port).net;
if (from == nullptr || from->clkconstr == nullptr)
return false;
period = from->clkconstr->period.min_delay;
return true;
};
auto set_period = [&](CellInfo *ci, IdString port, delay_t period) {
if (!ci->ports.count(port))
return;
NetInfo *to = ci->ports.at(port).net;
if (to == nullptr)
return;
if (to->clkconstr != nullptr && !equals_epsilon(to->clkconstr->period.min_delay, period)) {
log_warning(" Overriding derived constraint of %.1f on net %s with user-specified constraint of "
"%.1f MHz.\n",
MHz(to->clkconstr->period.min_delay), to->name.c_str(ctx), MHz(period));
return;
}
to->clkconstr = std::unique_ptr<ClockConstraint>(new ClockConstraint());
to->clkconstr->low.min_delay = period / 2;
to->clkconstr->low.max_delay = period / 2;
to->clkconstr->high.min_delay = period / 2;
to->clkconstr->high.max_delay = period / 2;
to->clkconstr->period.min_delay = period;
to->clkconstr->period.max_delay = period;
log_info(" Derived frequency constraint of %.1f MHz for net %s\n", MHz(to->clkconstr->period.min_delay),
to->name.c_str(ctx));
};
auto copy_constraint = [&](CellInfo *ci, IdString fromPort, IdString toPort, double ratio = 1.0) {
if (!ci->ports.count(fromPort) || !ci->ports.count(toPort))
return;
NetInfo *from = ci->ports.at(fromPort).net, *to = ci->ports.at(toPort).net;
if (from == nullptr || from->clkconstr == nullptr || to == nullptr)
return;
if (to->clkconstr != nullptr &&
!equals_epsilon(to->clkconstr->period.min_delay, delay_t(from->clkconstr->period.min_delay / ratio))) {
log_warning(" Overriding derived constraint of %.1f MHz on net %s with user-specified constraint of "
"%.1f MHz.\n",
MHz(to->clkconstr->period.min_delay), to->name.c_str(ctx),
MHz(delay_t(from->clkconstr->period.min_delay / ratio)));
return;
}
to->clkconstr = std::unique_ptr<ClockConstraint>(new ClockConstraint());
to->clkconstr->low = ctx->getDelayFromNS(ctx->getDelayNS(from->clkconstr->low.min_delay) / ratio);
to->clkconstr->high = ctx->getDelayFromNS(ctx->getDelayNS(from->clkconstr->high.min_delay) / ratio);
to->clkconstr->period = ctx->getDelayFromNS(ctx->getDelayNS(from->clkconstr->period.min_delay) / ratio);
log_info(" Derived frequency constraint of %.1f MHz for net %s\n", MHz(to->clkconstr->period.min_delay),
to->name.c_str(ctx));
};
for (auto cell : sorted(ctx->cells)) {
CellInfo *ci = cell.second;
if (ci->type == id_CLKDIVF) {
std::string div = str_or_default(ci->params, ctx->id("DIV"), "2.0");
double ratio;
if (div == "2.0")
ratio = 1 / 2.0;
else if (div == "3.5")
ratio = 1 / 3.5;
else
log_error("Unsupported divider ratio '%s' on CLKDIVF '%s'\n", div.c_str(), ci->name.c_str(ctx));
copy_constraint(ci, id_CLKI, id_CDIVX, ratio);
} else if (ci->type == id_ECLKSYNCB || ci->type == id_TRELLIS_ECLKBUF) {
copy_constraint(ci, id_ECLKI, id_ECLKO, 1);
} else if (ci->type == id_EHXPLLL) {
delay_t period_in;
if (!get_period(ci, id_CLKI, period_in))
continue;
log_info(" Input frequency of PLL '%s' is constrained to %.1f MHz\n", ci->name.c_str(ctx),
MHz(period_in));
double period_in_div = period_in * int_or_default(ci->params, ctx->id("CLKI_DIV"), 1);
std::string path = str_or_default(ci->params, ctx->id("FEEDBK_PATH"), "CLKOP");
int feedback_div = int_or_default(ci->params, ctx->id("CLKFB_DIV"), 1);
if (path == "CLKOP" || path == "INT_OP")
feedback_div *= int_or_default(ci->params, ctx->id("CLKOP_DIV"), 1);
else if (path == "CLKOS" || path == "INT_OS")
feedback_div *= int_or_default(ci->params, ctx->id("CLKOS_DIV"), 1);
else if (path == "CLKOS2" || path == "INT_OS2")
feedback_div *= int_or_default(ci->params, ctx->id("CLKOS2_DIV"), 1);
else if (path == "CLKOS3" || path == "INT_OS3")
feedback_div *= int_or_default(ci->params, ctx->id("CLKOS3_DIV"), 1);
else {
log_info(" Unable to determine output frequencies for PLL '%s' with FEEDBK_PATH=%s\n",
ci->name.c_str(ctx), path.c_str());
continue;
}
double vco_period = period_in_div / feedback_div;
double vco_freq = MHz(vco_period);
if (vco_freq < 400 || vco_freq > 800)
log_info(" Derived VCO frequency %.1f MHz of PLL '%s' is out of legal range [400MHz, 800MHz]\n",
vco_freq, ci->name.c_str(ctx));
set_period(ci, id_CLKOP, vco_period * int_or_default(ci->params, ctx->id("CLKOP_DIV"), 1));
set_period(ci, id_CLKOS, vco_period * int_or_default(ci->params, ctx->id("CLKOS_DIV"), 1));
set_period(ci, id_CLKOS2, vco_period * int_or_default(ci->params, ctx->id("CLKOS2_DIV"), 1));
set_period(ci, id_CLKOS3, vco_period * int_or_default(ci->params, ctx->id("CLKOS3_DIV"), 1));
} else if (ci->type == id_OSCG) {
int div = int_or_default(ci->params, ctx->id("DIV"), 128);
set_period(ci, id_OSC, delay_t((1.0e6 / (2.0 * 155)) * div));
}
}
}
public:
void pack()
{
@ -2166,6 +2280,7 @@ class Ecp5Packer
pack_lut_pairs();
pack_remaining_luts();
pack_remaining_ffs();
generate_constraints();
promote_ecp5_globals(ctx);
ctx->check();
}