Part Number: AM3359
Hello We have a custom Sitara board with a broadcom 548xx gigabit PHY. It's using the RGMII interface with the Sitara.
When we boot the board with the Ethernet cable plugged in to a PC, the connection is set up correctly at 1Gbps full duplex and we can ping both ends. The output of ethtool on the board lists the supported and advertised speeds correctly for the chip.
If we boot the board without establishing the physical Ethernet connection, the ethtool does not report 1000T mode as advertised or supported. If we connect a cable, we see that it tries to connect at 100T half duplex, and the link constantly goes up and down.
We checked the TxCLK and the RxCLK in both scenarios, and found that in the working case, RX clock starts at 125Mhz. The Tx clock of the PHY starts at 25Mh and then switches to 125 Mhz.
In the non working case, the RxCLK starts at 125 Mhz, but the TxCLK is at 25 Mhz. Once we connect the cable, the Tx clock stays at 25 Mhz and the Rx clock jumps between 125 and 25 Mhz.
We also notice that if we use a 100T USB/Eth adapter at the PC end, a stable connection is established in all scenarios.
Any ideas as to where should we be looking at?
Thanks.
