title: SGMII without phy - external loopback on Xlinix Zynq UltraScale+ RFSoC board
body: <p>I have a costume board with Xilinx Zynq UltraScale+ RFSoC.
  I'm using 3 PS_GTR transceivers as sgmii.
  2 of them are connected to external Marvell phy and the third connects directly (fixed link - without phy).</p>
  <p>In the manufacturing stage i would like to make sure that the direct sgmii interface is assembled correctly - so I made an external loopback between tx and rx sgmii signals.
  Now, Is it possible to transmit something through this external loopback and compare with the received data?
  Is it possible to ping with yourself? (simple ping command not working: &quot;ping -I eth2 &quot;)</p>
  <p>perhaps there is a 'patch' under the 'macb' kernel driver that someone can guide me through?</p>
  <p>Thank you all,
  Tzipi Kluska</p>