rfnoc: Add MTU property to TX streamer

3 files changed, 75 insertions, 7 deletions

diff --git a/host/lib/include/uhdlib/rfnoc/rfnoc_tx_streamer.hpp b/host/lib/include/uhdlib/rfnoc/rfnoc_tx_streamer.hpp
index 4acee45cc..3bfc9d05a 100644
--- a/host/lib/include/uhdlib/rfnoc/rfnoc_tx_streamer.hpp
+++ b/host/lib/include/uhdlib/rfnoc/rfnoc_tx_streamer.hpp
@@ -69,6 +69,15 @@ public:
     bool check_topology(const std::vector<size_t>& connected_inputs,
         const std::vector<size_t>& connected_outputs);
 
+    /*! Connects a channel to the streamer port
+     *
+     * Overrides method in tx_streamer_impl.
+     *
+     * \param channel The streamer channel to which to connect
+     * \param xport The transport for the specified channel
+     */
+    void connect_channel(const size_t channel, chdr_tx_data_xport::uptr xport);
+
 private:
     void _register_props(const size_t chan, const std::string& otw_format);
 
@@ -77,6 +86,7 @@ private:
     std::vector<property_t<double>> _samp_rate_out;
     std::vector<property_t<double>> _tick_rate_out;
     std::vector<property_t<std::string>> _type_out;
+    std::vector<property_t<size_t>> _mtu_out;
 
     // Streamer unique ID
     const std::string _unique_id;
diff --git a/host/lib/include/uhdlib/transport/tx_streamer_impl.hpp b/host/lib/include/uhdlib/transport/tx_streamer_impl.hpp
index 60881dad2..819ed5558 100644
--- a/host/lib/include/uhdlib/transport/tx_streamer_impl.hpp
+++ b/host/lib/include/uhdlib/transport/tx_streamer_impl.hpp
@@ -79,14 +79,14 @@ public:
         _spp = stream_args.args.cast<size_t>("spp", _spp);
     }
 
-    void connect_channel(const size_t channel, typename transport_t::uptr xport)
+    virtual void connect_channel(const size_t channel, typename transport_t::uptr xport)
     {
-        const size_t max_pyld_size = xport->get_max_payload_size();
+        const size_t mtu = xport->get_max_payload_size();
         _zero_copy_streamer.connect_channel(channel, std::move(xport));
 
-        // Set spp based on the transport frame size
-        const size_t xport_spp = max_pyld_size / _convert_info.bytes_per_otw_item;
-        _spp                   = std::min(_spp, xport_spp);
+        if (mtu < _mtu) {
+            set_mtu(mtu);
+        }
     }
 
     size_t get_num_channels() const
@@ -187,6 +187,22 @@ public:
     }
 
 protected:
+    //! Returns the size in bytes of a sample in a packet
+    size_t get_mtu() const
+    {
+        return _mtu;
+    }
+
+    //! Sets the MTU and calculates spp
+    void set_mtu(const size_t mtu)
+    {
+        _mtu = mtu;
+
+        // Check if spp needs to be lowered. SPP may already be lower than the
+        // value allowed by mtu if the user specified it using stream_args.
+        _spp = std::min(_spp, _mtu / _convert_info.bytes_per_otw_item);
+    }
+
     //! Configures scaling factor for conversion
     void set_scale_factor(const size_t chan, const double scale_factor)
     {
@@ -295,6 +311,9 @@ private:
     // Sample rate used to calculate metadata time_spec_t
     double _samp_rate = 1.0;
 
+    // Maximum payload size
+    size_t _mtu = std::numeric_limits<std::size_t>::max();
+
     // Maximum number of samples per packet
     size_t _spp = std::numeric_limits<std::size_t>::max();
 
diff --git a/host/lib/rfnoc/rfnoc_tx_streamer.cpp b/host/lib/rfnoc/rfnoc_tx_streamer.cpp
index 82feeaf1f..61d714a85 100644
--- a/host/lib/rfnoc/rfnoc_tx_streamer.cpp
+++ b/host/lib/rfnoc/rfnoc_tx_streamer.cpp
@@ -30,11 +30,35 @@ rfnoc_tx_streamer::rfnoc_tx_streamer(const size_t num_chans,
     _samp_rate_out.reserve(num_chans);
     _tick_rate_out.reserve(num_chans);
     _type_out.reserve(num_chans);
+    _mtu_out.reserve(num_chans);
 
     for (size_t i = 0; i < num_chans; i++) {
         _register_props(i, stream_args.otw_format);
     }
 
+    for (size_t i = 0; i < num_chans; i++) {
+        prop_ptrs_t mtu_resolver_out;
+        for (auto& mtu_prop : _mtu_out) {
+            mtu_resolver_out.insert(&mtu_prop);
+        }
+        //property_t<size_t>* mtu_out = &_mtu_out.back();
+
+        add_property_resolver({&_mtu_out[i]}, std::move(mtu_resolver_out),
+            [&mtu_out = _mtu_out[i], i, this]() {
+                RFNOC_LOG_TRACE("Calling resolver for `mtu_out'@" << i);
+                if (mtu_out.is_valid()) {
+                    const size_t mtu = mtu_out.get();
+                    // If the current MTU changes, set the same value for all chans
+                    if (mtu < tx_streamer_impl::get_mtu()) {
+                        for (auto& prop : this->_mtu_out) {
+                            prop.set(mtu);
+                        }
+                        tx_streamer_impl::set_mtu(mtu);
+                    }
+                }
+            });
+    }
+
     node_accessor_t node_accessor;
     node_accessor.init_props(this);
 }
@@ -72,8 +96,19 @@ bool rfnoc_tx_streamer::check_topology(
     return node_t::check_topology(connected_inputs, connected_outputs);
 }
 
-void rfnoc_tx_streamer::_register_props(const size_t chan,
-    const std::string& otw_format)
+void rfnoc_tx_streamer::connect_channel(
+    const size_t channel, chdr_tx_data_xport::uptr xport)
+{
+    UHD_ASSERT_THROW(channel < _mtu_out.size());
+
+    // Update MTU property based on xport limits
+    const size_t mtu = xport->get_max_payload_size();
+    set_property<size_t>(PROP_KEY_MTU, mtu, {res_source_info::OUTPUT_EDGE, channel});
+
+    tx_streamer_impl<chdr_tx_data_xport>::connect_channel(channel, std::move(xport));
+}
+
+void rfnoc_tx_streamer::_register_props(const size_t chan, const std::string& otw_format)
 {
     // Create actual properties and store them
     _scaling_out.push_back(property_t<double>(
@@ -84,18 +119,22 @@ void rfnoc_tx_streamer::_register_props(const size_t chan,
         PROP_KEY_TICK_RATE, {res_source_info::OUTPUT_EDGE, chan}));
     _type_out.emplace_back(property_t<std::string>(
         PROP_KEY_TYPE, otw_format, {res_source_info::OUTPUT_EDGE, chan}));
+    _mtu_out.push_back(property_t<size_t>(
+        PROP_KEY_MTU, {res_source_info::OUTPUT_EDGE, chan}));
 
     // Give us some shorthands for the rest of this function
     property_t<double>* scaling_out   = &_scaling_out.back();
     property_t<double>* samp_rate_out = &_samp_rate_out.back();
     property_t<double>* tick_rate_out = &_tick_rate_out.back();
     property_t<std::string>* type_out = &_type_out.back();
+    property_t<size_t>* mtu_out       = &_mtu_out.back();
 
     // Register them
     register_property(scaling_out);
     register_property(samp_rate_out);
     register_property(tick_rate_out);
     register_property(type_out);
+    register_property(mtu_out);
 
     // Add resolvers
     add_property_resolver({scaling_out}, {},