JTAG debugger can't find Vybrid core

[sergei_p]

Hello,

We are observing a problem when JTAG debugger (we are using Segger JLink) fails to connect to the VF6 core after the routine

firmware upgrade:

[psl@skywanderer ~]$ sudo JLinkExe

SEGGER J-Link Commander V4.78k ('?' for help)

Compiled Dec  5 2013 20:30:34

DLL version V4.78k, compiled Dec  5 2013 20:30:31

Firmware: J-Link ARM V8 compiled Nov 25 2013 19:20:08

Hardware: V8.00

S/N: 58010557

Feature(s): GDB

VTarget = 3.306V

Info: TotalIRLen = 4, IRPrint = 0x01

****** Error: Could not power up debug port: Control/Status register reads D0000001

No devices found on JTAG chain. Trying to find device on SWD.

Info: Found SWD-DP with ID 0x3BA02477

****** Error: Could not power up debug port: Control/Status register reads D0000040

Info: Found SWD-DP with ID 0x3BA02477

****** Error: Could not power up debug port: Control/Status register reads D0000040

No device found on SWD.

Did not find any core.

Failed to identify target. Trying again with slow (4 kHz) speed.

Info: TotalIRLen = 4, IRPrint = 0x01

****** Error: Could not power up debug port: Control/Status register reads D0000001

No devices found on JTAG chain. Trying to find device on SWD.

Info: Found SWD-DP with ID 0x3BA02477

****** Error: Could not power up debug port: Control/Status register reads D0000040

Info: Found SWD-DP with ID 0x3BA02477

****** Error: Could not power up debug port: Control/Status register reads D0000040

No device found on SWD.

Did not find any core.

Our hardware is our own System-On-Module with MVF61NN151CMK50 SOC and the firmware is a port of U-Boot loaded to the QSPI flash.

Obviously, the failing module has been re-programmed with JLink many times successfully. Also we tried another JTAG debugger (an Open OCD model) with similar results.

Whatever errors could be in hardware design or software, given the above info - what could cause the above behavior and what could be done to analyze and recover?

We already have two such modules.

Any thoughts on this would be much appreciated.

Regards,

Sergei Poselenov

[naoumgitnik]

Dorogoy Sergei,

Our only supported JTAG tool is DS-5 (for about a year now)… and it is somewhat tricky to debug issues remotely, especially when being not a JLink expert… but I will try nonetheless

It looks like your boards have been working properly until you upgraded the Vybrid firmware (U-Boot) stored in the QSPI Flash, right?

So, since the JTAG worked before, IMO, there are no hardware errors in your design.

Since the problem appeared after you modified the Vybrid U-Boot code stored in the QuadSPI Flash, it is quite logic to assume the problem is related to the code. My understating of the information you provided is that this code is yours (although based on ours), so it might behave differently than ours.

Based on the above assumption and having consulted with my colleagues about your issue, I would recommend you to look at the https://community.freescale.com/docs/DOC-94802 web page describing our Tower board behavior, especially the below clause:

What other things can cause issues?

Make sure you're not booting off the SD Card or QuadSPI when trying to debug other code. Since that code might have already been running, it can interfere, for example in clock setup, with the code you're trying to load into DDR/SRAM and debug. Also if trying to boot off the QuadSPI and nothing is programmed into it, then odd things may happen. The best thing to try is to remove the jumpers on J22, pins 1-2 and 3-4, which puts the board into serial boot loader mode and prevents other code from running.

Actually, in order to verify if the observed issue is indeed related to the U-Boot code, may you make Vybrid boot from a source different that QSPI Flash (e.g. serial boot over USB) and replace the potentially problematic U-Boot code in it with the original one causing no problems?

Please, let me know if all the above helps.

Udachi v proekte, Naoum Gitnik.

jiri-b36968, RossMcLuckie

[sergei_p]

Hello Naoum,

Thank you for the advice. I finally recovered one of the modules (another one is still failing however it looks like having some reworks so I decided to consult with our hw guys).

Using this info u-boot on the Vybrid tower board in a few commands I was able to boot VF6 from microSD card and then programmed good U-Boot image to QSPI.

Actually we already had some hard times with the VF6 modules with bad QSPI image programmed and noted that the code from QSPI seem gets executed even before JTAG is able to hook up to the core. However we never before observed JTAG failure as above so we worried that it something bad happened with the core.

Again, thanks for the suggestion and udachi v sapporte!

Best regards,

Sergei Poselenov,