How to update U-Boot

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

1 To update an SD card with the Linux dd command[edit]

When a Linux console has access to the SD card device partitions:

  • on a Linux PC
    • with a card reader of this PC
    • through a USB connection to the target and the ums command executed on a U-Boot console
  • on target, with Linux console.

The 3 first GPT partitions on the SD card are:

  1. FSBL1
  2. FSBL2
  3. SSBL

See Boot_chain_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 or target Linux console
  • 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.

1.1 U-Boot environment[edit]

The U-Boot environment is saved at the end of the U-Boot partition, named "ssbl": ID = 3.

To clear this environment, erase the U-Boot partition before any update; for example, by writing 0 to this partition:

   dd if=/dev/zero of=/dev/mmcblk<X>p3 conv=fdatasync
   dd if=/dev/zero of=sd<X>3 conv=fdatasync

1.2 SD card update example[edit]

The internal card reader is /dev/mmcblk0 or for a target Linux console, GPT 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=/dev/zero of=/dev/mmcblk0p3 conv=fdatasync
  dd if=u-boot.stm32 of=/dev/mmcblk0p3 conv=fdatasync

Alternatively, with U-Boot console, dev = 0 (SD card device on ST Microelectronics board), GPT partition <n> is /dev/sda<n>:

  mmc dev 0 
  ums 0 mmc 0
  dd if=tf-a.stm32 of=/dev/sda1 conv=fdatasync
  dd if=tf-a.stm32 of=/dev/sda2 conv=fdatasync
  dd if=/dev/zero of=/dev/sda3 conv=fdatasync
  dd if=u-boot.stm32 of=/dev/sda3 conv=fdatasync

1.3 SD card update example with SPL as FSBL[edit]

The USB card reader is /dev/sdb, GPT 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=/dev/zero of=/dev/sdb3 conv=fdatasync
  dd if=u-boot.img of=/dev/sdb3 conv=fdatasync

2 Update of eMMC with the Linux dd command[edit]

The same command, dd, can be used to update e•MMC memory mapping:

  • SSBL U-Boot is the first GPT partition in the eMMC user area
  • FSBL = TF-A (or SPL) is saved at the beginning of the eMMC boot partition

The user needs to select the eMMC hardware partition to update: user data, boot1, or boot2.

2.1 On a Linux console[edit]

If dev = mmcblk1 for eMMC device (default on ST Microelectronics board)

The boot partitions are available in /dev/mmcblk1boot0 and /dev/mmcblk1boot1 [1].

The user perhaps needs to allow access, for example with:

   echo 0 > /sys/class/block/mmcblk1boot0/force_ro

The mmc tools allow the boot partition to be selected [2].

The STM32MP15x ROM code requires:

  • <send_ack> =1
  • the eMMC boot configuration is: 1 wire configuration and 25 MHz, it is done with the command:
   mmc bootbus set  single_backward x1 x1 dev/mmcblk1

To update TF-A in boot1 and select this boot partition:

  dd if=tf-a.stm32 of=/dev/mmcblk1boot0 conv=fdatasync
  mmc bootpart enable 1 1 /dev/mmcblk1

To update TF-A in boot2 and select this boot partition:

  dd if=tf-a.stm32 of=/dev/mmcblk1boot1 conv=fdatasync
  mmc bootpart enable 2 1 /dev/mmcblk1

To update U-Boot in the first GPT partition:

  dd if=/dev/zero of=/dev/mmcblk1p1 conv=fdatasync
  dd if=u-boot.stm32 of=/dev/mmcblk1p1 conv=fdatasync

See also [3].

2.2 On a U-Boot console[edit]

The eMMC update is done with the ums command and the targeted eMMC HW partition is selected in U-Boot by the third parameter partition_access of command mmc partconf:

  • 0: user data partition
  • 1: boot partition 1
  • 2: boot partition 2
   help mmc 
 mmc bootbus dev boot_bus_width reset_boot_bus_width boot_mode
- Set the BOOT_BUS_WIDTH field of the specified device
 mmc bootpart-resize <dev> <boot part size MB> <RPMB part size MB>
- Change sizes of boot and RPMB partitions of specified device
 mmc partconf dev [boot_ack boot_partition partition_access]
- Show or change the bits of the PARTITION_CONFIG field of the specified device

For example:

* dev = 1 (eMMC device on ST Microelectronics board)
* boot_ack=1 (Boot Acknowledge is needed by ROM code) 
* boot_partition = 1 (Boot partition 1 enabled for boot)
* partition_access =  0 (No access to boot partition - default) 
* or partition_access =  1 (R/W boot partition 1) 

And on a PC, the mass storage is mounted as /dev/sda

To update FSBL=TF-A, select the boot1 HW partition and come back to the user area at the end.

  mmc dev 1
  mmc partconf 1 1 1 1 
  ums 0 mmc 1
  dd if=tf-a.stm32 of=/dev/sda  conv=fdatasync
  mmc partconf 1 1 1 0

To update SSBL = U-Boot in the first GPT partition in the user partition

  mmc dev 1
  ums 0 mmc 1
  dd if=u-boot.stm32 of=/dev/sda1 conv=fdatasync

Before the first boot, select the eMMC correct boot configuration (1 wire, 25 MHz) with the command:

  mmc bootbus 1 0 0 0

3 References[edit]

Please refer to the following links for additional information: