AM4376: PRU Fixed Link Not Working

I wanted to add a little more information. We are starting to wonder if the DP83822H PHY/TLK105L PHYS are part of the issue. When we test at cold temperatures (-40C) the link never goes up on the IDK dev kit or the target hardware. We are using this PHY for the links we are experiencing issues with.

Hi Tony,

our subject matter expert is out of the office for the rest of the month but let me see if I can help move this along some.

One thing would be good to double check on your end. We have since released SDK v8.02 for AM437x (https://www.ti.com/tool/PROCESSOR-SDK-AM437X) so it would be great if you could check if you see the same issues with that latest SDK.

Regards, Andreas

Thanks Andreas,

We tested SDK v8.02 on the IDK and now the links are working as expected. We are currently locked into SDK v6 and are interested in implementing the changes made for the PRU driver and pushing them into SDK v6. Is there a patch available that we could implement into SDK v6?

Thanks,

Tony

Hi Tony,

glad to hear the issues seem to be resolved with the latest SDK. While ideally you would just move to the latest SDK I understand it's not that easy. If you want to just pick up the specific change that fixes your problem and backport it to SKD v6.03 it may be tricky to figure out as those are complex sub-systems. It could be any of these three things...

1. PHY driver
2. PRU Ethernet driver
3. PRU Ethernet firmware

So finding the exact change would usually involve reviewing Git commit histories and perhaps doing some bisect operations/test runs. I was just able to spend a little bit of time on this, but taking a shot in the blue with what you were saying there to be some temperature dependency which may involve PHY operation / settings, the following Git commit could be something you could try backporting to your system and see if that makes a difference:

net: phy: DP83822: Add setting the fixed internal delay
https://git.ti.com/cgit/ti-linux-kernel/ti-linux-kernel/commit/drivers/net/phy/dp83822.c?h=ti-linux-5.10.y&id=8095295292b564583bb5bee5ba69924c2fd40434

If this doesn't do the trick you could review the commits on the drivers/net/ethernet/ti/ subsystem folder (https://git.ti.com/cgit/ti-linux-kernel/ti-linux-kernel/log/drivers/net/ethernet/ti?h=ti-linux-5.10.y&ofs=250) to see if anything spikes out. And perhaps experiment with "cross-transplanting" the PRU Ethernet firmware from the new SDK back to the older one (I've never tried this, and it may not be a valid thing to do, but would certainly not hurt to give this a quick check).

Regards, Andreas