From d689df23fb4bf38e1abc23b06767fc26aa27c163 Mon Sep 17 00:00:00 2001
From: mattprost <matt.prost@ni.com>
Date: Wed, 31 Mar 2021 11:33:33 -0500
Subject: 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>
---
 host/lib/usrp/x300/x300_eth_mgr.cpp | 17 ++++++++++++++---
 1 file changed, 14 insertions(+), 3 deletions(-)

(limited to 'host/lib/usrp/x300/x300_eth_mgr.cpp')

diff --git a/host/lib/usrp/x300/x300_eth_mgr.cpp b/host/lib/usrp/x300/x300_eth_mgr.cpp
index f428fc98e..dcc8195ae 100644
--- a/host/lib/usrp/x300/x300_eth_mgr.cpp
+++ b/host/lib/usrp/x300/x300_eth_mgr.cpp
@@ -20,6 +20,7 @@
 #include <uhd/transport/udp_zero_copy.hpp>
 #include <uhd/utils/algorithm.hpp>
 #include <uhd/utils/byteswap.hpp>
+#include <uhd/utils/cast.hpp>
 #include <uhdlib/rfnoc/device_id.hpp>
 #include <uhdlib/rfnoc/rfnoc_common.hpp>
 #include <uhdlib/transport/udp_boost_asio_link.hpp>
@@ -227,6 +228,10 @@ both_links_t eth_manager::get_links(link_type_t link_type,
     x300_eth_conn_t conn = eth_conns[local_device_id];
     zero_copy_xport_params default_buff_args;
 
+    const bool enable_fc = not link_args.has_key("enable_fc")
+                           || uhd::cast::from_str<bool>(link_args.get("enable_fc"));
+    const bool lossy_xport = enable_fc;
+
     const size_t send_mtu = get_mtu(uhd::TX_DIRECTION);
     const size_t recv_mtu = get_mtu(uhd::RX_DIRECTION);
 
@@ -278,8 +283,9 @@ both_links_t eth_manager::get_links(link_type_t link_type,
             link_params.send_buff_size,
             link,
             link_params.recv_buff_size,
+            lossy_xport,
             true,
-            true);
+            enable_fc);
 #else
         UHD_LOG_WARNING("X300", "Cannot create DPDK transport, falling back to UDP");
 #endif
@@ -289,8 +295,13 @@ both_links_t eth_manager::get_links(link_type_t link_type,
         link_params,
         link_params.recv_buff_size,
         link_params.send_buff_size);
-    return std::make_tuple(
-        link, link_params.send_buff_size, link, link_params.recv_buff_size, true, false);
+    return std::make_tuple(link,
+        link_params.send_buff_size,
+        link,
+        link_params.recv_buff_size,
+        lossy_xport,
+        false,
+        enable_fc);
 }
 
 /******************************************************************************
-- 
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