AM6422: icssg_prueth port loop back

Hello Vaibhav,

In general, we do not have an example we can share on how to do a MAC loopback test in Linux. When we do this testing we connect the EVM to a link partner and use the HW MAC statistics available through ethtool with the -S option. Based on the associated https://e2e.ti.com/support/processors-group/processors/f/processors-forum/1343344/am6422-icssg_prueth-port-initializing-but-not-able-to-connect thread, you are already working on this method of testing.

I'm assuming the purpose of your question on loopback testing is to help troubleshoot the issue from the other thread? 

-Daolin

Dear Daolin Qiu,

Daolin Qiu said:

In general, we do not have an example we can share on how to do a MAC loopback test in Linux

On the page number 6928 of AM64x Processor Technical Reference Manual, We come across the statement: "Ethernet Mac transmit to Ethernet Mac receive Loopback mode (digital loopback) supported"

Can you please guide us and provide step to perform this loopback? this will help us to confirm the firmware implementation on MAC/Processor side regardless concerns on the EPHY, signal integrity/delay, ethernet cable and link partner.  

We would like to run this thread in parallel to original thread. because if come to know that EPHY setting is correct & signal integrity of RX data and clock signals is correct then we have to confirm the firmware implementation on MAC/Processor side regardless dependency of external interface like EPHY, signal integrity of RX & link partner. 

 let me know if any other information required from my side. 

-

Vaibhav 

Hello Vaibhav,

einfochips an Arrow Company said:

this will help us to confirm the firmware implementation on MAC/Processor side regardless concerns on the EPHY, signal integrity/delay, ethernet cable and link partner.

Based on your response, am I correct that you are more interested in MAC loopback test as opposed to PHY loopback tests?

We have RTOS examples for PHY loopback testing in the MCU+SDK documentation for PRU_ICSSG: https://software-dl.ti.com/mcu-plus-sdk/esd/AM64X/08_06_00_45/exports/docs/api_guide_am64x/EXAMPLES_ENET_ICSSG_LOOPBACK.html. Based on the documentation: "Note that ICSSG pheripheral does not support MAC loopback mode, unlike CPSW."

I am currently unable to find a Linux example of MAC loopback test in the SDK documentation for PRU_ICSSG: https://software-dl.ti.com/processor-sdk-linux/esd/docs/08_00_00_21/linux/Foundational_Components/PRU-ICSS/Linux_Drivers/PRU_ICSSG_Ethernet.html

Although the AM64x TRM states that loopback mode supported, that section was specifically stated for CPSW ethernet under 12.2.1.1.1 CPSW0 Features.

Even though MAC loopback may be supported, we currently don't have an example of how to do so in Linux. In Linux, there is not an easy way to do MAC loopback testing without potentially writing a lot of code (for instance, setting a clock source to replace the clock source from the PHY, etc). 

This is not ideal but might give some insights https://e2e.ti.com/support/processors-group/processors/f/processors-forum/1307124/am623-how-to-do-a-mac-loopback-test-with-cpsw-in-am62x-devices. Note that this discussion is for CPSW ethernet and never tested on AM64x or AM62x before.

-Daolin