caiyu/nextpnr
1
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

ecp5: Add support for promotion of LSRs to global network

Browse Source 
Signed-off-by: David Shah <dave@ds0.me>
This commit is contained in:
David Shah 2019-11-19 14:08:35 +00:00
parent c3d4117a21
commit 67e216f8fb
2 changed files with 74 additions and 5 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

76
ecp5/globals.cc
View File

@ -62,7 +62,12 @@ class Ecp5GlobalRouter
return true;
return false;
}
bool is_lsr_port(const PortRef &user)
{
if (user.cell->type == id_TRELLIS_SLICE && (user.port == id_LSR))
return true;
return false;
}
std::vector<NetInfo *> get_clocks()
{
std::unordered_map<IdString, int> clockCount;
@ -102,6 +107,32 @@ class Ecp5GlobalRouter
return clocks;
}
std::vector<NetInfo *> get_globalworthy_lsrs()
{
// Fanout threshold for LSRs is high (300), and we only promote up to two of them, in the nature of being
// conservative given the cost of a global
std::unordered_map<IdString, int> lsrCount;
for (auto &net : ctx->nets) {
NetInfo *ni = net.second.get();
lsrCount[ni->name] = 0;
for (const auto &user : ni->users)
if (is_lsr_port(user))
lsrCount[ni->name]++;
}
// DCCAs must always drive globals
std::vector<NetInfo *> lsrs;
while (lsrs.size() < 2) {
auto max = std::max_element(lsrCount.begin(), lsrCount.end(),
[](const decltype(lsrCount)::value_type &a,
const decltype(lsrCount)::value_type &b) { return a.second < b.second; });
if (max == lsrCount.end() || max->second < 300)
break;
lsrs.push_back(ctx->nets.at(max->first).get());
lsrCount.erase(max->first);
}
return lsrs;
}
PipId find_tap_pip(WireId tile_glb)
{
std::string wireName = ctx->getWireBasename(tile_glb).str(ctx);
@ -140,6 +171,9 @@ class Ecp5GlobalRouter
upstream.push(userWire);
bool already_routed = false;
WireId next;
IdString id_lsr1 = ctx->id("LSR1");
// Search back from the pin until we reach the global network
while (true) {
next = upstream.front();
@ -155,6 +189,11 @@ class Ecp5GlobalRouter
globalWire = next;
break;
}
// Forbid to use LSR1 for non-WRE LSRs; as this is reserved for WRE
if (ctx->getWireBasename(next) == id_lsr1 && user.port != id_WRE)
continue;
if (ctx->checkWireAvail(next)) {
for (auto pip : ctx->getPipsUphill(next)) {
WireId src = ctx->getPipSrcWire(pip);
@ -464,17 +503,34 @@ class Ecp5GlobalRouter
else
insert_dcc(clock);
}
if (clocks.size() < 12 && !bool_or_default(ctx->settings, ctx->id("arch.nolsrglobal"), false)) {
// Promote up to two set/resets to global
auto lsrs = get_globalworthy_lsrs();
for (auto lsr : lsrs) {
bool is_noglobal = bool_or_default(lsr->attrs, ctx->id("noglobal"), false);
if (is_noglobal)
continue;
log_info(" promoting LSR net %s to global network\n", lsr->name.c_str(ctx));
if (is_ooc) // Don't actually do anything in OOC mode, global routing will be done in the full design
lsr->is_global = true;
else
insert_dcc(lsr);
}
}
}
void route_globals()
{
log_info("Routing globals...\n");
std::set<int> all_globals, fab_globals;
std::set<int> all_globals, fab_globals, lsr_globals;
for (int i = 0; i < 16; i++) {
all_globals.insert(i);
if (i < 8)
if (i < 8) {
if (i >= 4)
lsr_globals.insert(i);
fab_globals.insert(i);
}
}
std::vector<std::pair<PortRef *, int>> toroute;
std::unordered_map<int, NetInfo *> clocks;
for (auto cell : sorted(ctx->cells)) {
@ -484,9 +540,18 @@ class Ecp5GlobalRouter
NPNR_ASSERT(clock != nullptr);
bool drives_fabric = std::any_of(clock->users.begin(), clock->users.end(),
[this](const PortRef &port) { return !is_clock_port(port); });
bool drives_lsr = std::any_of(clock->users.begin(), clock->users.end(),
[this](const PortRef &port) { return is_lsr_port(port); });
int glbid;
if (drives_fabric) {
if (drives_lsr) {
if (lsr_globals.empty()) {
// Route LSR through fabric (suboptimal)
NPNR_ASSERT(!fab_globals.empty());
glbid = *(fab_globals.begin());
} else {
glbid = *(lsr_globals.begin());
}
} else if (drives_fabric) {
if (fab_globals.empty())
continue;
glbid = *(fab_globals.begin());
@ -495,6 +560,7 @@ class Ecp5GlobalRouter
}
all_globals.erase(glbid);
fab_globals.erase(glbid);
lsr_globals.erase(glbid);
log_info(" routing clock net %s using global %d\n", clock->name.c_str(ctx), glbid);
bool routed = route_onto_global(clock, glbid);

3
ecp5/main.cc
View File

@ -74,6 +74,7 @@ po::options_description ECP5CommandHandler::getArchOptions()
specific.add_options()(
"out-of-context",
"disable IO buffer insertion and global promotion/routing, for building pre-routed blocks (experimental)");
specific.add_options()("no-lsr-globals", "don't promote local set/reset (LSR) signals to global networks");
return specific;
}
@ -239,6 +240,8 @@ std::unique_ptr<Context> ECP5CommandHandler::createContext(std::unordered_map<st
ctx->settings[ctx->id(val.first)] = val.second;
ctx->settings[ctx->id("arch.package")] = ctx->archArgs().package;
ctx->settings[ctx->id("arch.speed")] = speedString(ctx->archArgs().speed);
if (vm.count("no-lsr-globals"))
ctx->settings[ctx->id("arch.nolsrglobal")] = 1;
if (vm.count("out-of-context"))
ctx->settings[ctx->id("arch.ooc")] = 1;
return ctx;