I seem to have locked myself out of my verdin-imx8mp board. I was testing a u-boot patch where I set bootdelay to -2, which disables the u-boot prompt entirely. I booted from an SD card and from there, dd’ed my yocto image to the eMMC. The good news is my patch seems to have worked. u-boot no longer has a prompt, even if I hold down ESC.
Unfortunately the board is no longer booting from the SD card. It always boots to eMMC. I’ve rewritten my SD card image, and tested it on another board of the same type and it works fine. But on this one board, it refuses to boot from SD since I rewrote the eMMC. Something about that build changed how the boot process works, beyond just disabling the u-boot prompt.
How can I recover from this? I can’t get to u-boot. I also can’t just login to the eMMC build because it doesn’t seem to have good credentials. root: and root:root don’t seem to work at least.
I might make mistakes or occasionally get you wrong. Our support team will step in if needed.
I can help you recover your Verdin iMX8MP board. Since you’ve disabled the U-Boot prompt and can’t access it normally, you’ll need to use recovery mode to regain control.
Recovery Mode Solution
The Verdin iMX8MP supports recovery mode, which allows you to flash a new U-Boot image even when the current one is inaccessible (1). This bypasses the problematic U-Boot configuration entirely.
Hardware Recovery Method
To enter recovery mode on your Verdin iMX8MP:
Power off the board completely
Short the recovery pads - You can use scissors, tweezers, or a paper clip to short circuit the recovery pads (follow ESD precautions) (2)
Power on the board while maintaining the short circuit
Remove the short circuit only after the board starts powering up(2)
Using UUU Tool for Recovery
Once in recovery mode, you can use the UUU (Universal Update Utility) tool to flash a corrected U-Boot image (1). The recovery process allows you to:
Flash a new U-Boot binary with proper bootdelay settings
Restore normal boot behavior
Regain access to the U-Boot prompt
Alternative: Environment Variable Reset
If you can get into recovery mode and load a temporary U-Boot, you can reset the problematic environment variables. The issue might be related to saved U-Boot environment variables that are overriding your SD card boot priority (3).
Important Notes
Remove any SD card before entering recovery mode to ensure it works properly (2)
Power cycle (don’t just reset) after flashing new U-Boot firmware (2)
The recovery mode works independently of your current eMMC contents
Would you like me to provide more specific details about the recovery process? To give you the most accurate guidance, could you confirm which OS version you’re running on your development PC (Windows, Linux) and which carrier board you’re using with the Verdin iMX8MP?
Best regards, Toradex AI Assistant.
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All Toradex SoMs are fused to boot exclusively from on-module storage (eMMC or NAND). However, the OS can be loaded from an SD card once a functional bootloader is present on the eMMC/NAND and configured accordingly.
As mentioned by AI it is possible to flash U-Boot in recovery mode using the UUU tool. However, we recommend using the Toradex Easy Installer, as described in the documentation.
Booting from an SD card has been working in the past. The only thing that should have changed was setting u-boot bootdelay = -2. Does that break the “configured accordingly”? What configuration does the eMMC u-boot need in order to be able to boot from an SD card?
