uhd: Add device arg to enable dual ethernet for tx

UHD currently only uses a single ethernet link for tx data, even if the
device is initialized with dual 10GbE links. Using both links when a DMA
FIFO is present causes sequence errors due to DMA FIFO bandwidth
limitations. This maintains the current default behavior but allows
users to override it through a device arg "enable_tx_dual_eth".

2 files changed, 17 insertions, 2 deletions

diff --git a/host/lib/usrp/x300/x300_device_args.hpp b/host/lib/usrp/x300/x300_device_args.hpp
index 57e6e04cc..56b3c1078 100644
--- a/host/lib/usrp/x300/x300_device_args.hpp
+++ b/host/lib/usrp/x300/x300_device_args.hpp
@@ -32,7 +32,8 @@ public:
         _niusrprio_rpc_port("niusrprio_rpc_port", NIUSRPRIO_DEFAULT_RPC_PORT),
         _has_fw_file("fw", false),
         _fw_file("fw", ""),
-        _blank_eeprom("blank_eeprom", false)
+        _blank_eeprom("blank_eeprom", false),
+        _enable_tx_dual_eth("enable_tx_dual_eth", false)
     {
         // nop
     }
@@ -92,6 +93,10 @@ public:
     bool get_blank_eeprom() const {
         return _blank_eeprom.get();
     }
+    bool get_enable_tx_dual_eth() const {
+        return _enable_tx_dual_eth.get();
+    }
+
 
     inline virtual std::string to_string() const {
         return  _master_clock_rate.to_string() + ", " +
@@ -147,6 +152,9 @@ private:
             PARSE_DEFAULT(_fw_file);
         }
         PARSE_DEFAULT(_blank_eeprom)
+        if (dev_args.has_key("enable_tx_dual_eth")){
+            _enable_tx_dual_eth.set(true);
+        }
 
         //Sanity check params
         _enforce_discrete(_master_clock_rate, TICK_RATE_OPTIONS);
@@ -173,6 +181,7 @@ private:
     constrained_device_args_t::bool_arg            _has_fw_file;
     constrained_device_args_t::str_arg<true>       _fw_file;
     constrained_device_args_t::bool_arg            _blank_eeprom;
+    constrained_device_args_t::bool_arg            _enable_tx_dual_eth;
 };
 
 }}} //namespace
diff --git a/host/lib/usrp/x300/x300_impl.cpp b/host/lib/usrp/x300/x300_impl.cpp
index 0b173beb3..d3eeeef10 100644
--- a/host/lib/usrp/x300/x300_impl.cpp
+++ b/host/lib/usrp/x300/x300_impl.cpp
@@ -1286,7 +1286,13 @@ uhd::both_xports_t x300_impl::make_transport(
             next_src_addr==0 ? x300::SRC_ADDR0 : x300::SRC_ADDR1;
         const uint32_t xbar_src_dst =
             conn.type==X300_IFACE_ETH0 ? x300::XB_DST_E0 : x300::XB_DST_E1;
-        if (xport_type != TX_DATA) next_src_addr = (next_src_addr + 1) % mb.eth_conns.size();
+
+        // Do not increment src addr for tx_data by default, using dual ethernet
+        // with the DMA FIFO causes sequence errors to DMA FIFO bandwidth
+        // limitations.
+        if (xport_type != TX_DATA || mb.args.get_enable_tx_dual_eth()) {
+            next_src_addr = (next_src_addr + 1) % mb.eth_conns.size();
+        }
 
         xports.send_sid = this->allocate_sid(mb, address, xbar_src_addr, xbar_src_dst);
         xports.recv_sid = xports.send_sid.reversed();