STM32MP1 - RGMII sending, but not receiving data

[SLitt.1]

Hello. I am currently working on a custom stm32mp157a Linux based board with a KSZ9896 as network switch. At this point everything works on the board expect the RGMII connection to the switch. The RGMII is currently running in 100MBit mode for easier debugging, all signals seem to be received correctly. The stm32mp1 s not receiving any data over RGMII. Even when enabling the loopback on the interface in RGMII no data is seen using tcpdump (-Qin -i eth0). This is interesting since running ethtool -S eth0 shows the rx and tx counters going up together as packages are sent and looped back. Both connections are 100Mbit with a 125 MHz clock coming from the switch and flow control has been disabled.

Could anyone point me in the right direction where to start looking?

[OlivierK]

Hi SLitt.1 (Community Member)

You can start looking on to related documentations:

• AN5031 (https://www.st.com/resource/en/application_note/dm00389996-getting-started-with-stm32mp151-stm32mp153-and-stm32mp157-line-hardware-development-stmicroelectronics.pdf)
• wiki page: https://wiki.st.com/stm32mpu/wiki/Ethernet_device_tree_configuration

The the configuration might be linked to the specificity of the switch KSZ9896:

• Is it declared in the menuconfig?
• have you looked at the product erratasheet for some limitations?

Regards,

Olivier

[OlivierK]

Hi SLitt.1 (Community Member)

Have you made any progress? Is it fixed?

Olivier