RFNoC: Prevent unnecessary FC ACK packets

Avoid sending flow control ACK packets for lossless transports.
Add 'send_no_fc_acks' device argument to explicitly prevent
flow control ACK packets from being sent.

Signed-off-by: michael-west <michael.west@ettus.com>

4 files changed, 13 insertions, 13 deletions

diff --git a/host/lib/include/uhdlib/rfnoc/xports.hpp b/host/lib/include/uhdlib/rfnoc/xports.hpp
index 06fd4713b..6b30fe5b1 100644
--- a/host/lib/include/uhdlib/rfnoc/xports.hpp
+++ b/host/lib/include/uhdlib/rfnoc/xports.hpp
@@ -18,7 +18,8 @@ namespace uhd {
      */
     struct both_xports_t
     {
-        both_xports_t(): recv_buff_size(0), send_buff_size(0) {}
+        both_xports_t(): recv_buff_size(0), send_buff_size(0), lossless(false)
+            {}
         uhd::transport::zero_copy_if::sptr recv;
         uhd::transport::zero_copy_if::sptr send;
         size_t recv_buff_size;
@@ -26,9 +27,9 @@ namespace uhd {
         uhd::sid_t send_sid;
         uhd::sid_t recv_sid;
         uhd::endianness_t endianness;
+        bool lossless;
     };
 
 };
 
 #endif /* INCLUDED_LIBUHD_XPORTS_HPP */
-
diff --git a/host/lib/usrp/device3/device3_io_impl.cpp b/host/lib/usrp/device3/device3_io_impl.cpp
index bf527e0ba..d0ec52971 100644
--- a/host/lib/usrp/device3/device3_io_impl.cpp
+++ b/host/lib/usrp/device3/device3_io_impl.cpp
@@ -731,9 +731,14 @@ tx_streamer::sptr device3_impl::get_tx_stream(const uhd::stream_args_t& args_)
         // CHDR does not support trailers
         my_streamer->set_enable_trailer(false);
 
-        my_streamer->set_xport_chan_post_send_cb(stream_i, [fc_cache, xport]() {
-            tx_flow_ctrl_ack(fc_cache, xport.send, xport.send_sid);
-        });
+        // Avoid sending FC ACKs if the transport is lossless or the user
+        // has explictly requested not to send them
+        if (not (xport.lossless or tx_hints.has_key("send_no_fc_acks")))
+        {
+            my_streamer->set_xport_chan_post_send_cb(stream_i, [fc_cache, xport]() {
+                tx_flow_ctrl_ack(fc_cache, xport.send, xport.send_sid);
+            });
+        }
     }
 
     // Notify all blocks in this chain that they are connected to an active streamer
diff --git a/host/lib/usrp/mpmd/mpmd_xport_ctrl_liberio.cpp b/host/lib/usrp/mpmd/mpmd_xport_ctrl_liberio.cpp
index 139683597..8f3014bc7 100644
--- a/host/lib/usrp/mpmd/mpmd_xport_ctrl_liberio.cpp
+++ b/host/lib/usrp/mpmd/mpmd_xport_ctrl_liberio.cpp
@@ -79,13 +79,11 @@ uhd::both_xports_t mpmd_xport_ctrl_liberio::make_transport(
     const std::string rx_dev = xport_info["rx_dev"];
 
     both_xports_t xports;
+    xports.lossless = true;
     xports.endianness = uhd::ENDIANNESS_LITTLE;
     xports.send_sid   = sid_t(xport_info["send_sid"]);
     xports.recv_sid   = xports.send_sid.reversed();
 
-    // if (xport_info["muxed"] == "True") {
-    //// FIXME tbw
-    //}
     if (xport_type == usrp::device3_impl::CTRL) {
         UHD_ASSERT_THROW(xport_info["muxed"] == "True");
         if (not _ctrl_dma_xport) {
@@ -130,11 +128,6 @@ bool mpmd_xport_ctrl_liberio::is_valid(
 
 size_t mpmd_xport_ctrl_liberio::get_mtu(const uhd::direction_t dir) const
 {
-    /* TODO: this is extremely hacky. We don't know yet what broke liberio.
-     * Putting a bandaid here to help TXing. Remove this as soon as possible!
-     */
-    if (dir == uhd::TX_DIRECTION)
-        return getpagesize();
     return LIBERIO_PAGES_PER_BUF * getpagesize();
 }
 
diff --git a/host/lib/usrp/x300/x300_impl.cpp b/host/lib/usrp/x300/x300_impl.cpp
index c42f8dece..d912d66c3 100644
--- a/host/lib/usrp/x300/x300_impl.cpp
+++ b/host/lib/usrp/x300/x300_impl.cpp
@@ -1277,6 +1277,7 @@ uhd::both_xports_t x300_impl::make_transport(const uhd::sid_t& address,
     both_xports_t xports;
     xports.endianness = mb.if_pkt_is_big_endian ? ENDIANNESS_BIG : ENDIANNESS_LITTLE;
     if (mb.xport_path == "nirio") {
+        xports.lossless = true;
         xports.send_sid =
             this->allocate_sid(mb, address, x300::SRC_ADDR0, x300::XB_DST_PCI);
         xports.recv_sid = xports.send_sid.reversed();