Zero/install/Boot Troubleshooting

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    Radxa Zero >  Installation >  Boot troubleshooting

A 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
   # maskrom mode
   G12A:BL:0253b8:61aa2d;FEAT:E0F83180:2000;POC:D;RCY:0;USB:0;

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

Modify bootloader on eMMC

TL;DR

We have updated our eMMC erase guide, which does the below operations automatically, and should fix most boot related issues.

Beware this will result in data loss since the partition header will be wiped as well. If you need to preserve the data, either make a disk image before wiping, or follow the manual guide below.

With dd

If your bootloader is broken you can usually try manual in-place update first. This will preserve your data in eMMC.

First, follow maskrom guide to setup and load rz-udisk-loader.bin. Also download [u-boot.bin.sd.bin](https://dl.radxa.com/zero/images/loader/u-boot.bin.sd.bin) and put it in your current directory.

Once rz-udisk-loader.bin is loaded you should have a USB storage device detected by your Linux system. Here we call it /dev/sdX but replace it with your real block device.

Run the following command to update bootloader:

   DEVICE=/dev/sdX
   sudo dd if=u-boot.bin.sd.bin of=$DEVICE bs=1 count=444
   sudo dd if=u-boot.bin.sd.bin of=$DEVICE bs=512 skip=1 seek=1

With fastboot

First, follow maskrom guide to setup and load rz-fastboot-loader.bin.

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 image to eMMC:

   # Erase eMMC
   sudo fastboot erase mmc0
   sudo fastboot erase mmc0boot0
   sudo fastboot erase mmc0boot1
   # Flash eMMC
   sudo fastboot flash mmc0 linux_distro.img
   sudo fastboot flash mmc0boot0 bootloader.img
   sudo fastboot flash mmc0boot1 bootloader.img

You do not need to erase before flashing, and you do not need to flash all 3 partitions. Beware sudo fastboot flash mmc0 could potentially damage your existing data.

With Android fastboot

In some cases, you will have to use Android's bootloader. This is based on Amlogic's U-Boot source code, so it will behave differently from upstream U-Boot.

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 image to eMMC:

  # Unlock eMMC before we can do anything
  sudo fastboot unlock
  sudo fastboot unlock_critical
  # Backup bootloader
  sudo fastboot fetch bootloader bootloader.bak
  sudo fastboot fetch bootloader-boot0 bootloader-boot0.bak
  sudo fastboot fetch bootloader-boot1 bootloader-boot1.bak
  # 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. Beware sudo fastboot flash bootloader could potentially damage your existing data.

From inside U-Boot

If your eMMC is so corrupt that above 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 u-boot.bin. After the file is loaded keep hitting Ctrl+C in serial console until the bootloader stopped with a console waiting for command.

   # mmcblk0
   # WARNING!
   # Potential data loss!
   mmc dev 2 0
   mmc erase 0 20000
   # mmcblk0boot0
   mmc dev 2 1
   mmc erase 0 2000
   # mmcblk0boot1
   mmc dev 2 2
   mmc erase 0 2000

Restart and you should be able to flash the bootloader according to the instructions listed in the eMMC erase guide.

   #restart
   reset

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: Before 2022-02-04, 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. Release from 2022-02-04 will contain mainline U-Boot, so the image can be flashed like other distro.

Q: After using maskrom to start rz-udisk-loader.bin I cannot see the eMMC storage and see on the console (UART or HDMI): Couldn't find partition mmc 2
A: Use maskrom to load u-boot.bin and once the 'starting fastboot' message appears use 'fastboot reboot' and then use maskrom to push rz-udisk-loader.bin