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ice40: Derive oscillator frequency constraints

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Signed-off-by: David Shah <dave@ds0.me>
This commit is contained in:
David Shah 2020-03-29 21:02:16 +01:00
parent 3d3b222e2a
commit 98e2f9ea81
1 changed files with 40 additions and 0 deletions
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40
ice40/pack.cc
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@ -1101,6 +1101,30 @@ static void pack_special(Context *ctx)
}
}
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 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) {
if (!equals_epsilon(to->clkconstr->period.delay, period))
log_warning(" Overriding derived constraint of %.1f MHz on net %s with user-specified constraint of "
"%.1f MHz.\n",
MHz(to->clkconstr->period.delay), to->name.c_str(ctx), MHz(period));
return;
}
to->clkconstr = std::unique_ptr<ClockConstraint>(new ClockConstraint());
to->clkconstr->low.delay = period / 2;
to->clkconstr->high.delay = period / 2;
to->clkconstr->period.delay = period;
log_info(" Derived frequency constraint of %.1f MHz for net %s\n", MHz(to->clkconstr->period.delay),
to->name.c_str(ctx));
};
for (auto cell : sorted(ctx->cells)) {
CellInfo *ci = cell.second;
if (is_sb_lfosc(ctx, ci)) {
@ -1112,10 +1136,12 @@ static void pack_special(Context *ctx)
replace_port(ci, ctx->id("CLKLFPU"), packed.get(), ctx->id("CLKLFPU"));
if (bool_or_default(ci->attrs, ctx->id("ROUTE_THROUGH_FABRIC"))) {
replace_port(ci, ctx->id("CLKLF"), packed.get(), ctx->id("CLKLF_FABRIC"));
set_period(packed.get(), ctx->id("CLKLF_FABRIC"), 100000000); // 10kHz
} else {
replace_port(ci, ctx->id("CLKLF"), packed.get(), ctx->id("CLKLF"));
std::unique_ptr<CellInfo> gb =
create_padin_gbuf(ctx, packed.get(), ctx->id("CLKLF"), "$gbuf_" + ci->name.str(ctx) + "_lfosc");
set_period(gb.get(), id_GLOBAL_BUFFER_OUTPUT, 100000000); // 10kHz
new_cells.push_back(std::move(gb));
}
new_cells.push_back(std::move(packed));
@ -1132,12 +1158,26 @@ static void pack_special(Context *ctx)
auto port = ctx->id("TRIM" + std::to_string(i));
replace_port(ci, port, packed.get(), port);
}
std::string div = packed->params[ctx->id("CLKHF_DIV")].as_string();
int frequency;
if (div == "0b00")
frequency = 48;
else if (div == "0b01")
frequency = 24;
else if (div == "0b10")
frequency = 12;
else if (div == "0b11")
frequency = 6;
else
log_error("Invalid HFOSC divider value '%s' - expecting 0b00, 0b01, 0b10 or 0b11\n", div.c_str());
if (bool_or_default(ci->attrs, ctx->id("ROUTE_THROUGH_FABRIC"))) {
replace_port(ci, ctx->id("CLKHF"), packed.get(), ctx->id("CLKHF_FABRIC"));
set_period(packed.get(), ctx->id("CLKHF_FABRIC"), 1000000 / frequency);
} else {
replace_port(ci, ctx->id("CLKHF"), packed.get(), ctx->id("CLKHF"));
std::unique_ptr<CellInfo> gb =
create_padin_gbuf(ctx, packed.get(), ctx->id("CLKHF"), "$gbuf_" + ci->name.str(ctx) + "_hfosc");
set_period(gb.get(), id_GLOBAL_BUFFER_OUTPUT, 1000000 / frequency);
new_cells.push_back(std::move(gb));
}
new_cells.push_back(std::move(packed));