How to manually update bootloaders

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

When you have access to the SD card device partitions:

• on Linux PC, with the card reader of a PC or with the ums command executed on a target 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_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 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

The environment of U-Boot 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, write 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

The internal card reader is /dev/mmcblk0, 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

1.3. SD card update example with SPL as FSBL

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 e•MMC with the Linux dd command

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

• For the user area, with GPT partitioning, SSBL U-Boot is the first user partition (the indexes of other partitions need to be adapted).
• For the SSBL = TF-A (or SPL) is saved at the beginning of the cached boot partitions: access to the 2 boot partition needs to requested:

2.1. on Linux console

If dev = mmcblk1 for e•MMC device (default on ST Microelectronics board)

The boot partition are available in /dev/mmcblk1boot0 and /dev/mmcblk1boot1 .

User perhaps need to allow access, for example with:

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

The mmc tools allows to select the boot partition ; <send_ack> =1 is required by STM32MP15x ROM code

This ROM code also requires that the eMMC boot configuration is: 1 wire configuration and 25Mz, 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

2.2. on U-Boot console

The e•MMC update is done with the ums command but the targeted e•MMC 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 (e•MMC 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) 

To update FSBL=TF-A, select booot1 and come back to the user area:

  mmc dev 1
  mmc partconf 1 1 1 1 
  ums 0 mmc 1
 
  dd if=tf-a.stm32 of=/dev/mmcblk0 conv=fdatasync
  
  mmc partconf 1 1 1 0

To update SSBL = U-Boot (access to user partition is already requested)

  mmc dev 1
 
  dd if=tf-a.stm32 of=/dev/mmcblk0p1 conv=fdatasync

'mmcblk0p1': the first GPT partition of mmcblk0 see by the HOST

The STM32MP15x ROM code also require the eMMC boot configuration set to 1 wire configuration and to 25Mz with the command on mmc device {HighlightParam|1}} (one need one time to configure eMMC):

  mmc bootbus {HighlightParam|1}} 0 0 0

3. References

Please refer to the following links for additional information:

SD memory card (https://www.sdcard.org)

Linux^® is a registered trademark of Linus Torvalds.

Das U-Boot -- the universal boot loader (see U-Boot)

Second stage boot loader

First stage boot loader

GUID partition table

Secondary program loader, Also known as U-Boot SPL

Multimedia card

Trusted firmware for Arm^® Cortex^®-A

Read only

Read only memory

Embedded multi-media card, Former spelling for e•MMC ('e' in italic)