AM623: CPSW linux phy loopback self-test implementation

Hi,

Please expect delayed responses due to the holidays.

Thanks for your patience.

Regards,

Vaibhav

Hi Li, 

Until the subject matter expert is back in office, I will offer some information that I know.

It looks like from the post you referenced, only changes were made to the ti-linux-kernel drivers for ethernet. Since changes to the linux drivers are independent of device/board, you should be able to change the same files as the patch in your referenced post. I would suggest trying out the changes in the referenced link and test it out. However, I'm unsure if this patch has been tested by TI previously so I cannot comment on the success of the result.

The concern I have is if changes to the Device Tree files need to be made to enable the driver changes for loopback, since Device Tree changes are board dependent. I'm checking with the team on this.

What Ethernet PHY are use using on your own evaluation board? Does this PHY have a loopback mode?

Best regards,

Daolin

Hi Daolin, 

The phy chip model used on my evaluation board is yt8531s, which has a loop back mode.

From the section 4.13. Loopback Mode of this chip, you can see the loop back modes it supports:

https://datasheet.lcsc.com/lcsc/2305061752_Motorcomm-YT8531SC_C5279059.pdf

Best regards,

Li

Hi Li,

Thanks for sharing information on the PHY you are using and confirming that it has loopback modes available.

I have not yet received information/confirmation from the team about any potential Device Tree changes that might be necessary; however, from my understanding the implementation to enable Linux phy loopback self test relies mainly on linux kernel and driver changes and shouldn't involve any changes in the Device Tree. The reason why I think it shouldn't involve any Device Tree changes is because if the am65-cpsw-nuss driver had supported loopback tests by default without any patches, I don't think there would be any specific changes in Device Tree since this a driver specific change.

Since the ti linux kernel and device drivers are shared across multiple TI processors, including AM62x devices, you should be able to apply the same changes as the FAQ you referenced. 

The subject matter expert might be able to provide additional information when he is back in office. Until then, give the patch from the FAQ a try and let us know if you have additional questions on this subject.

Best regards,

Daolin