Debugging an i.MX6UL running Linux over JTAG with a J-Link

[jaydcarlson]

I have a custom i.MX6UL "breakout" dev board I'm bringing up that doesn't have any peripherals on it (other than RAM and uSDHC1). I've got some Linux instability issues that I'm working through, and I'm trying to attach my J-Link to the board to see where the kernel is when it hangs, as I'm getting no panic messages.

So, my question is: what's the right way to attach a J-Link to a running i.MX6UL to debug the Linux kernel?

I followed this post, which tells you to disable the 'clock off' wait state and use the -noir and -noreset options with the J-Link. Unfortunately, when I try starting my debug session with:

./JLinkGDBServer -if JTAG -endian little -device MCIMX6G3 -select USB -noir -noreset

the J-Link resets the MPU immediately. I thought maybe I could attach to it during U-Boot, and then start debugging once I was in Linux, but the connection gets closed between the U-Boot and Linux start-up phase.

I'm using JLink software V6.32c. My board doesn't use the sai2 interface, so there shouldn't be the widely-reported JTAG pin-muxing issue that others have struggled with.

[igorpadykov]

Hi Carlson

usually gdb is used for linux debug, one cam follow

AN4553 Using Open Source Debugging Tools for Linux on i.MX Processors
https://www.nxp.com/docs/en/application-note/AN4553.pdf 

http://www.cs.tut.fi/~sulo/harjoitustyo/ymparisto/JLinkGDBServer.pdf 

[SOLVED] I.MX6UL support in segger j-link probe - J-Link/Flasher related - SEGGER Forum 

look at AN5229 ARM DS-5 Development Studio Debug i.MX6UL - EVK

https://www.nxp.com/docs/en/application-note/AN5229.pdf 

Best regards
igor
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[jaydcarlson]

This is not a helpful response. I have a specific problem — My J-Link is resetting the i.MX6UL when I connect — that I'm trying to solve. Do you know why it's doing that, or how to fix it?

If not, please don't reply to my message with generic links to a 10-year-old user manual, unrelated app notes, and ancient forum posts that were solved by upgrading to a (now-ancient) J-Link version. 

[igorpadykov]

Hi Carlson

link below was about J-Link resetting the i.MX6UL - seems this is specific J-Link problem

[SOLVED] I.MX6UL support in segger j-link probe - J-Link/Flasher related - SEGGER - Forum 

had you tried to contact segger support.

Best regards
igor

[jaydcarlson]

Nope, as I said, that forum post question was solved by upgrading to version 6.18 (which was the latest version at the time). As I said in my original post, I'm running 6.32c, which has i.MX6UL support listed.

Thanks for trying to help, but I guess I'll have to talk to Segger.