IMX8MM based device stuck in recovery mode

[namanthaker]

Hello,

I am using a custom device based on IMX8MM-EVK with Android 9 (p9.0.0_2.3.0) OS.
I have multiple devices, but one of the device is stuck in recovery mode. I need help to boot the device back into normal mode.

Steps performed on this device before it rebooted into recovery mode:
1. Start my custom application which starts the IMX8MM processor watchdog and kicks it at regular interval from a thread.
2. Uninstall the app while it was running.
3. Watchdog bite occurred as it was not kicked within required interval by the application.
4. Board rebooted into recovery mode.

Further information about the application and watchdog use-case:
In our devices, we have a feature to reboot the device in case the Android application stops working for some reason like app hang or crash.
The application starts the watchdog and kicks it at regular interval. In case the app stops working, the watchdog will reboot the device.
We are able to access the watchdog from application and when the app stops the device reboots in normal mode.
But this time for some reason, the device rebooted into recovery mode.

Steps performed to recover the device:
1. Reboot the device multiple times using below methods:
a. Perform power cycle by removing and then reconnecting power supply.
b. Power-off the device using ONOFF switch and then power it back on using the same switch.

Both of the above methods worked on other devices which were put into recovery mode by running 'reboot recovery' command. But that does not happen on this one device.

2. Re-flash the BSP images using UUU tool after putting the device into Serial Download mode.
After flashing, the device booted in normal mode the first time. But then it stopped in the middle of booting and rebooted into recovery mode.

Refer attached normal_mode_bootup_logs.txt logs for the first time booting after flashing. The recovery_mode_bootup_logs.txt file contains logs observed while device boots into recovery mode.

Could someone please help to suggest some steps to recover the board from recovery mode?

Thanks in advance!

[igorpadykov]

Hi namanthaker

if issue is observed only on one of the device, this may be hardware issue,

for example poor soldering. One can try to resolder chip and check hardware

using  i.MX 8M Mini Hardware Developer’s Guide

Best regards
igor

[namanthaker · Accepted solution]

Hi Igor,

We were able to recover the device by flashing new images with Watchdog disabled in U-boot and erasing the User-data while flashing using '-e' option in uuu_imx_android_flash. The board is now booting properly in normal mode.

Thanks,
Naman

[namanthaker]

Hi Igor,

Thanks for the suggestion.

We will try to resolder the chip, but first we would like to find the root cause of the issue on the device.

Could you suggest if there is any specific pin on IMX8MM processor which need to be set either high or low to start the processor in recovery mode?

We have observed on other processors that when a device is booted while pressing the power button along with Volume Up or Down key, the device will boot into recovery mode. Does IMX8MM support any such feature?
If yes, we would like to debug that pin and its connection first before we resolder the chip.

Thanks,
Naman