Understanding STM32MP257FAI3 ETHSW Ports

[cjb80]

Hello,

I am working on a schematic for the STM32MP257FAI3 and the documentation seems to be inconsistent and/or incomplete regarding which ports go where with the built-in Ethernet switch.  The data sheet says ETHSW has three ports in which the "The third port is connected internally to the ETH1 controller". This implies that ETH2 and ETH3 are the external RGMII interfaces.

The "Getting Started with ... Hardware Development" guide says "ETH1 is either ETH1 direct or ETHSW port2" (it is unstated, but combined with the data sheet this would be an internal connection), and ETH3 there is a note "ETH3 is ETHSW port1".  There is no such note for ETH2, so this omission implies that ETH2 is not connected to ETHSW (or perhaps it is connected through STNoC??).  The block diagram in the data sheet also matches this notion.

In any case, it would be very helpful if there was a table that show what is connected to what when ETHSW is enabled.  At this point I need to know what pins to connect to PHYs, it seems like it is either ETH1 and ETH3 (hardware design guide is correct) or ETH 2 and ETH3 (data sheet is correct).

Thanks

 

[Olivier GALLIEN]

Hi @cjb80 ,

 

I know that ETH port mapping could be confusing.

Please have a look to wiki doc ETH internal peripheral - stm32mp25-beta-v5 

 

Let us know if it help 

 

Olivier 

[cjb80]

Hello,

To be honest, that link doesn't answer the question. :) But I did find this link after digging around: https://wiki.st.com/stm32mp25-beta-v5/wiki/Ethernet_switch_overview

Based on the diagram, it looks like RGMII1 and RGMII3 are the two ports that connect to the switch and that internally GMAC1 is connected to the processor (the third port of the switch).  So I believe that the answer to my question is "RGMII1 and RGMII3 are the external connections to the switch".

Please let me know if you disagree. 

(Last night I thought that I should just hook up all of the ports so it pushes the problem to a later point in time)

Chris

 

[PatrickF]

Hi @cjb80 
I confirm your understanding. Please have a look to Reference Manual RM0457

What could be confusing is the assignment of ETHSW ports (port0, port1 and port2) wrt to names of the GMAC IP (ETH1) and names of the external pins (ETH1 and ETH3).

Regards.