Zero/install/Boot Troubleshooting

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    Radxa Zero >  Installation >  Boot troubleshooting

An detailed guide for troubleshooting Radxa Zero's boot issue

This is a more advanced guide aiming to help user fix their boot related issues. Due to how Zero's bootloader can be stored at various locations and how each distro usually has their own quirk about how bootloader is configured, user may find it confusing why the board is not booting as they are expected. This guide will help you understand how Zero decided which bootloader to boot, the current available bootloaders from Radxa, and how to wipe and reinstall any bootloader.

Experience with Linux, maskrom, and Android fastboot tool is highly recommended.

Amlogic's boot logic

When you boot a bare board without any bootloader, you will see the following string printed on your serial console:

   G12A:BL:0253b8:61aa2d;FEAT:E0F83180:2000;POC:F;RCY:0;EMMC:0;READ:0;CHK:1F;READ:0;CHK:1F;READ:0;CHK:1F;SD?:0;SD:0;READ:0;CHK:1F;USB:8;

This is how the SoC finds the boot target. It will search eMMC first with 3 read instructions, each for mmcblk0, mmcblk0boot0, and mmcblk0boot1. If it fails to boot from eMMC it will search microSD card next, and finally the USB devices.

This means, to boot off any given storage media, you need to make sure bootloaders stored before this chain get wiped. Otherwise a different boot configuration will be used, instead of the one that came with your installation media.

Some extra messages when boot from eMMC:

   # boot from mmcblk0
   G12A:BL:0253b8:61aa2d;FEAT:E0F83180:2000;POC:F;RCY:0;EMMC:0;READ:0;0.0
   # boot from mmcblk0boot0 after mmcblk0 is wiped
   G12A:BL:0253b8:61aa2d;FEAT:E0F83180:2000;POC:F;RCY:0;EMMC:0;READ:0;CHK:1F;READ:0;0.0
   # boot from mmcblk0boot1 after mmcblk0 and mmcblk0boot0 are wiped
   G12A:BL:0253b8:61aa2d;FEAT:E0F83180:2000;POC:F;RCY:0;EMMC:0;READ:0;CHK:1F;READ:0;CHK:1F;READ:0;0.0

You can read more about eMMC's hardware partitions from here.

Modify bootloader on eMMC

With fastboot

First, follow maskrom guide to setup and load android-bootloader.img.

Once a device with ID 18d1:0d02 is shown in lsusb and you can see a fastboot device is detected by sudo fastboot devices, you can run the following command to wipe/flash bootloader image to eMMC:

   # Unlock eMMC before we can do anything
   sudo fastboot flashing unlock
   sudo fastboot flashing unlock_critical
   # Erase bootloader
   sudo fastboot erase bootloader
   sudo fastboot erase bootloader-boot0
   sudo fastboot erase bootloader-boot1
   # Flash bootloader
   sudo fastboot flash bootloader bootloader.img
   sudo fastboot flash bootloader-boot0 bootloader.img
   sudo fastboot flash bootloader-boot1 bootloader.img

You do not need to erase before flashing, and you do not need to flash all 3 partitions.

From inside U-Boot

If your eMMC is so corrupted that any of those commands fails, you will need to erase those partitions from U-Boot console. Here is the instructions to do so as a last-ditch.

First set up serial console since U-Boot console can only be accessed via serial. Follow maskrom guide to setup and load android-bootloader.img. After the file is loaded keep hitting Enter key in serial console until the bootloader stopped with a console waiting for command.

   # mmcblk0
   mmc dev 1 0
   mmc erase 1 2000
   # mmcblk0boot0
   mmc dev 1 1
   mmc erase 0 2000
   # mmcblk0boot1
   mmc dev 1 2
   mmc erase 0 2000

Additionally if your main partition is too corrupted, that you cannot use fastboot to wipe those partitions, you can try the following command to wipe main partition's partition table and some extra data, making the partition non-bootable:

   # WARNING!
   # Potential data loss!
   mmc dev 1 0
   mmc erase 0 10000

Unplug and replug the power cable and now you should be able to flash bootloader according to the instruction listed in the previous section.

Modify bootloader on microSD or USB drive

microSD and USB drive both show in Linux system as block devices, so you can modify their bootloader in the same way. Additionally you can also use this method to flash bootloader to eMMC's main partition. However, fastboot has less potential to make a mistake, so it is still recommended.

First, make sure you have installed the OS of your choice to the storage media. OS installation usually comes with their own bootloader, so if you want to modify the bootloader you have to do so after the installation.

Run any of the following commands to modify bootloader on device /dev/sdX:

   # Backup bootloader
   sudo dd if=/dev/sdX of=bootloader.bak conv=fsync bs=512 skip=1 count=8192
   # Erase bootloader
   sudo dd if=/dev/zero of=/dev/sdX conv=fsync bs=512 seek=1 count=8192
   # Flash bootloader
   sudo dd if=bootloader.img of=/dev/sdX conv=fsync bs=512 seek=1 count=8192

Common boot related issues

Q: Board won't boot on my microSD/USB drive, and is booting stock Android instead.
A: Please wipe eMMC's all 3 bootloaders and try again.

Q: Manjaro won't boot.
A: As of 2021-12-24, Manjaro requires the usage of vendor U-Boot, and its image does not contain any bootloader. Please flash android-bootloader.img to your storage media.