device3: Constraint send/recv_frame_size based on down/upstream MTU

We need to properly contraint the send/recv_frame_size based on the
minimum MTU of all the down/upstream blocks. This fixes the issue with
E310 tx/rx streaming as it has smaller MTU sizes than the other usrps.

2 files changed, 9 insertions, 1 deletions

diff --git a/host/lib/usrp/x300/x300_impl.cpp b/host/lib/usrp/x300/x300_impl.cpp
index 796d422ad..b9b4a06f9 100644
--- a/host/lib/usrp/x300/x300_impl.cpp
+++ b/host/lib/usrp/x300/x300_impl.cpp
@@ -1526,7 +1526,7 @@ uhd::both_xports_t x300_impl::make_transport(const uhd::sid_t& address,
             // Increasing number of recv frames here because ctrl_iface uses it
             // to determine how many control packets can be in flight before it
             // must wait for an ACK
-            default_buff_args.num_recv_frames = 
+            default_buff_args.num_recv_frames =
                 uhd::rfnoc::CMD_FIFO_SIZE / uhd::rfnoc::MAX_CMD_PKT_SIZE;
         } else if (xport_type == TX_DATA) {
             size_t default_frame_size = conn.link_rate == x300::MAX_RATE_1GIGE
@@ -1993,6 +1993,11 @@ x300_impl::frame_size_t x300_impl::determine_max_frame_size(
     return frame_size;
 }
 
+size_t x300_impl::get_mtu(const size_t /*mb_index*/, const uhd::direction_t dir) {
+    return (dir == RX_DIRECTION) ? _max_frame_sizes.recv_frame_size :
+            _max_frame_sizes.send_frame_size;
+}
+
 /***********************************************************************
  * compat checks
  **********************************************************************/
diff --git a/host/lib/usrp/x300/x300_impl.hpp b/host/lib/usrp/x300/x300_impl.hpp
index c101b3032..8d50f9914 100644
--- a/host/lib/usrp/x300/x300_impl.hpp
+++ b/host/lib/usrp/x300/x300_impl.hpp
@@ -173,6 +173,9 @@ private:
         const xport_type_t xport_type,
         const uhd::device_addr_t& args);
 
+    //! get mtu
+    size_t get_mtu(const size_t, const uhd::direction_t);
+
     struct frame_size_t
     {
         size_t recv_frame_size;