imx8mm Custom Board stuck at "Starting kernel", earlycon not working

[dpog]

I'm working with a custom PCB design using an i.MX8MMini. The ATF and u-boot are configured to use the UART3-interface. To debug my problem I tried to use the earlycon, but i get no additional output after setting earlycon to ec_imx6q,0x30880000,115200 in the UBoot and Kernel dts as well as in the bootargs. Any suggestions on how to debug this problem/get the earlycon up and running, so that I can address the non-starting kernel?

[dpog · Accepted solution]

The Problem was solved by using the right bootargs manually. Bootscript and/or the mmcargs probably overwrote them.

[Sanket_Parekh]

Hi @dpog 

I hope you are doing well.

There should be nothing special to earlycon.
Please make sure that you are set the same serial port options in bootargs and terminal running on the PC.

Thanks & Regards

Sanket Parekh

[dpog]

Hi @Sanket_Parekh, thanks for your answer. As mentioned in my other reply, earlycon doesnt seem to be the problem at all, the board is stuck still in uboot, when transitioning to EL2. Any suggestions this problem?

[dpog]

I traced my problem further down the line. It seems so be stuck right before entering the kernel. For further information: the design is inspired by the imx8mm evk, the blocking point seems to be in the arch->arm->lib->bootm.c when switching to el2. By adding debug messages I found out that the code runs until armv8_switch_to_el2((u64)images->ft_addr, 0, 0, 0, images->ep, ES_TO_AARCH64);, but it does not return from this function. The switch-function is defined in transition.S

I also tried commenting out this part, this leads to the board resetting.

Any help regarding this would be appreciated, thanks!

[karthick_kkmm__]

Hi @dpog 

We are working on Android porting from A11 to A13 on our custom board based on iMX8MQ. We have tested DDR, PMIC and all in U-boot. It looks good but, stuck at the same place(armv8_switch_to_el2).

We changed and verified the bootargs for A11 and A13, both are same. 

Can you please let me know how did you resolved it. I would be grateful for any assistance with this.

Thanks