How to update U-Boot


This page explains how to manually update the U-Boot binaries on an SD Card.

1 Copying a binary to an SD card with the Linux dd command[edit]

When you have access to the device (with the card reader of a PC, or the UMS command on a target), the 3 first partitions on the SDCard are:

  1. FSBL1
  2. FSBL2
  3. SSBL

See Boot_chains_overview, for the bootloader definitions.

You can use the Linux dd command to copy the FSBL and SSBL directly to the correct partition:

   dd if=<file> of=/dev/<dev> conv=fdatasync

<dev> is:

  • mmcblk<X>p<n> : PC-embedded card reader case
  • sd<X><N> : USB-connected SD card reader case

where <X> is the ID of the device, and <n> the ID of the partition.

Note: the dd option conv=fdatasync is used to force synchronous copying.

2 Trusted boot chain update example[edit]

The internal card reader is /dev/mmcblk0, partition <n> is /dev/mmcblk0p<n>:

   dd if=tf-a.stm32 of=/dev/mmcblk0p1 conv=fdatasync
   dd if=tf-a.stm32 of=/dev/mmcblk0p2 conv=fdatasync
   dd if=u-boot.stm32 of=/dev/mmcblk0p3 conv=fdatasync

3 Basic boot chain udpate example[edit]

The USB card reader is /dev/sdb, partition <n> is /dev/sdb<n>

   dd if=u-boot-spl.stm32 of=/dev/sdb1 conv=fdatasync
   dd if=u-boot-spl.stm32 of=/dev/sdb2 conv=fdatasync
   dd if=u-boot.img of=/dev/sdb3 conv=fdatasync