RFNoC: Disable FC ACK packets for lossless links

FC ACK packets are unnecessary on lossless links and degrade overall
performance.  This change disables those packets on all lossless links.

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

1 files changed, 4 insertions, 2 deletions

diff --git a/host/lib/rfnoc/source_block_ctrl_base.cpp b/host/lib/rfnoc/source_block_ctrl_base.cpp
index 6c41fae14..656ab26af 100644
--- a/host/lib/rfnoc/source_block_ctrl_base.cpp
+++ b/host/lib/rfnoc/source_block_ctrl_base.cpp
@@ -86,6 +86,7 @@ void source_block_ctrl_base::set_destination(
 }
 
 void source_block_ctrl_base::configure_flow_control_out(const bool enable_fc_output,
+    const bool lossless_link,
     const size_t buf_size_bytes,
     const size_t pkt_limit,
     const size_t block_port,
@@ -124,8 +125,9 @@ void source_block_ctrl_base::configure_flow_control_out(const bool enable_fc_out
     // count based flow control
     const bool enable_byte_fc    = (buf_size_bytes != 0);
     const bool enable_pkt_cnt_fc = (pkt_limit != 0);
-    const uint32_t config        = (enable_fc_output ? 1 : 0) | (enable_byte_fc << 1)
-                            | (enable_pkt_cnt_fc << 2);
+    const uint32_t config = (enable_fc_output ? 1 : 0) | ((enable_byte_fc ? 1 : 0) << 1)
+                            | ((enable_pkt_cnt_fc ? 1 : 0) << 2)
+                            | ((lossless_link ? 1 : 0) << 3);
 
     // Resize the FC window.
     // Precondition: No data can be buffered upstream.