rfnoc: Add MTU tracking

MTUs are now tracked through the framework for all childs of
noc_block_base. Every edge gets an 'mtu' property. MTU can be set and
get either through the prop API, or through new API calls (get_mtu(),
set_mtu()). It is also possible to create custom properties that depend
on the MTU by asking for a reference to the MTU property, and then
adding that to the input list of a property resolver.

The radio_control_impl includes a change in this commit where it sets
the spp based on the MTU.

Blocks can also set an MTU forwarding policy. The DDC block includes a
change in this commit that sets a forwarding policy of ONE_TO_ONE,
meaning that the MTU on an input edge is forwarded to the corresponding
output edge (but not the other edges, as with the tick rate).

1 files changed, 11 insertions, 1 deletions

diff --git a/host/lib/rfnoc/radio_control_impl.cpp b/host/lib/rfnoc/radio_control_impl.cpp
index 4ed0c4b60..f71c73289 100644
--- a/host/lib/rfnoc/radio_control_impl.cpp
+++ b/host/lib/rfnoc/radio_control_impl.cpp
@@ -170,10 +170,20 @@ radio_control_impl::radio_control_impl(make_args_ptr make_args)
         register_property(&_samp_rate_out.back());
         register_property(&_type_in.back());
         register_property(&_type_out.back());
-        add_property_resolver({&_spp_prop.back()},
+        add_property_resolver(
+            {&_spp_prop.back(), get_mtu_prop_ref({res_source_info::OUTPUT_EDGE, chan})},
             {&_spp_prop.back()},
             [this, chan, &spp = _spp_prop.back()]() {
                 RFNOC_LOG_TRACE("Calling resolver for spp@" << chan);
+                const int mtu =
+                    static_cast<int>(get_mtu({res_source_info::OUTPUT_EDGE, chan}));
+                const int max_spp_per_mtu = mtu / (_samp_width / 8) - (mtu % _spc);
+                if (spp.get() > max_spp_per_mtu) {
+                    RFNOC_LOG_WARNING("spp value " << spp.get() << " exceeds MTU of "
+                                                   << mtu << "! Coercing to "
+                                                   << max_spp_per_mtu);
+                    spp = max_spp_per_mtu;
+                }
                 if (spp.get() % _spc) {
                     spp = spp.get() - (spp.get() % _spc);
                     RFNOC_LOG_WARNING(