rfnoc: Add option to disable flow control on rx streaming

Disabling this feature will allow the USRP to send a continuous stream
of Rx data to a host machine without throttling due to lack of flow
control credits. This is unnecessary overhead on lossless transports
such as pcie or aurora.

Usage: add 'enable_fc=false' to stream_args.args

Signed-off-by: mattprost <matt.prost@ni.com>

1 files changed, 45 insertions, 25 deletions

diff --git a/host/lib/usrp/x300/x300_mb_iface.cpp b/host/lib/usrp/x300/x300_mb_iface.cpp
index c89374f82..a351864df 100644
--- a/host/lib/usrp/x300/x300_mb_iface.cpp
+++ b/host/lib/usrp/x300/x300_mb_iface.cpp
@@ -98,12 +98,17 @@ uhd::rfnoc::chdr_ctrl_xport::sptr x300_impl::x300_mb_iface::make_ctrl_transport(
     send_link_if::sptr send_link;
     recv_link_if::sptr recv_link;
     bool lossy_xport;
-    std::tie(send_link, std::ignore, recv_link, std::ignore, lossy_xport, std::ignore) =
-        _conn_mgr->get_links(link_type_t::CTRL,
-            local_device_id,
-            local_epid,
-            uhd::rfnoc::sep_id_t(),
-            uhd::device_addr_t());
+    std::tie(send_link,
+        std::ignore,
+        recv_link,
+        std::ignore,
+        lossy_xport,
+        std::ignore,
+        std::ignore) = _conn_mgr->get_links(link_type_t::CTRL,
+        local_device_id,
+        local_epid,
+        uhd::rfnoc::sep_id_t(),
+        uhd::device_addr_t());
 
     /* Associate local device ID with the adapter */
     _adapter_map[local_device_id] = send_link->get_send_adapter_id();
@@ -142,13 +147,18 @@ uhd::rfnoc::chdr_rx_data_xport::uptr x300_impl::x300_mb_iface::make_rx_data_tran
     send_link_if::sptr send_link;
     recv_link_if::sptr recv_link;
     size_t recv_buff_size;
-    bool lossy_xport, packet_fc;
-    std::tie(send_link, std::ignore, recv_link, recv_buff_size, lossy_xport, packet_fc) =
-        _conn_mgr->get_links(link_type_t::RX_DATA,
-            local_sep_addr.first,
-            local_epid,
-            remote_epid,
-            xport_args);
+    bool lossy_xport, packet_fc, enable_fc;
+    std::tie(send_link,
+        std::ignore,
+        recv_link,
+        recv_buff_size,
+        lossy_xport,
+        packet_fc,
+        enable_fc) = _conn_mgr->get_links(link_type_t::RX_DATA,
+        local_sep_addr.first,
+        local_epid,
+        remote_epid,
+        xport_args);
 
     /* Associate local device ID with the adapter */
     _adapter_map[local_sep_addr.first] = send_link->get_send_adapter_id();
@@ -159,14 +169,19 @@ uhd::rfnoc::chdr_rx_data_xport::uptr x300_impl::x300_mb_iface::make_rx_data_tran
 
     const double ratio = 1.0 / 32;
 
-    // Configure flow control frequency to use either bytes only or packets only
     uhd::rfnoc::stream_buff_params_t fc_freq;
-    if (packet_fc) {
-        fc_freq = {uhd::rfnoc::MAX_FC_FREQ_BYTES,
-            static_cast<uint32_t>(std::ceil(recv_link->get_num_recv_frames() * ratio))};
+    if (enable_fc) {
+        // Configure flow control frequency to use either bytes only or packets only
+        if (packet_fc) {
+            fc_freq = {uhd::rfnoc::MAX_FC_FREQ_BYTES,
+                static_cast<uint32_t>(
+                    std::ceil(recv_link->get_num_recv_frames() * ratio))};
+        } else {
+            fc_freq = {static_cast<uint64_t>(std::ceil(double(recv_buff_size) * ratio)),
+                uhd::rfnoc::MAX_FC_FREQ_PKTS};
+        }
     } else {
-        fc_freq = {static_cast<uint64_t>(std::ceil(double(recv_buff_size) * ratio)),
-            uhd::rfnoc::MAX_FC_FREQ_PKTS};
+        fc_freq = {0, 0};
     }
 
     uhd::rfnoc::stream_buff_params_t fc_headroom = {0, 0};
@@ -235,12 +250,17 @@ uhd::rfnoc::chdr_tx_data_xport::uptr x300_impl::x300_mb_iface::make_tx_data_tran
     send_link_if::sptr send_link;
     recv_link_if::sptr recv_link;
     bool lossy_xport;
-    std::tie(send_link, std::ignore, recv_link, std::ignore, lossy_xport, std::ignore) =
-        _conn_mgr->get_links(link_type_t::TX_DATA,
-            local_sep_addr.first,
-            local_epid,
-            remote_epid,
-            xport_args);
+    std::tie(send_link,
+        std::ignore,
+        recv_link,
+        std::ignore,
+        lossy_xport,
+        std::ignore,
+        std::ignore) = _conn_mgr->get_links(link_type_t::TX_DATA,
+        local_sep_addr.first,
+        local_epid,
+        remote_epid,
+        xport_args);
 
     /* Associate local device ID with the adapter */
     _adapter_map[local_sep_addr.first] = send_link->get_send_adapter_id();