I have an LS1021A board designed by our customer that is configured for RGMII eTSEC3 using the same PHY (AR8033) as LS1021A-TWR board and connected exactly the same as the LS1021A-TWR board. Good 1Gbps link on Ethernet port. U-boot reports "Speed: 1000, full duplex" but fails ping with "not alive".
On LS1021A-TWR observe 125MHz clock on EC3_GTX_CLK when transmitting (ping from u-boot with "alive").
On LS1021A board (not tower) there is no 125MHz clock on EC3_GTX_CLK when trying to transmit (ping from u-boot). There is activity on the EC3_GTX_CLK signal but it does not look like a clock (i.e., not 125MHz, 25MHz, or 2.5MHz clock).
I have not been able to find what is causing this yet.