How to update U-Boot

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

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

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:

FSBL1
FSBL2
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 source]

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 source]

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 source]

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[edit source]

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

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

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

2.1. On a Linux console[edit source]

If dev = mmcblk1 for e•MMC 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

2.2. On a U-Boot console[edit source]

The e•MMC update is done with the ums command and 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)

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 e•MMC correct boot configuration (1 wire, 25 MHz) with the command:

  mmc bootbus 1 0 0 0

3. References[edit source]

Please refer to the following links for additional information:

[1] ttps://www.kernel.org/doc/Documentation/mmc/mmc-dev-parts.txt

[2] ttps://manpages.debian.org/buster/mmc-utils/mmc.1.en.html

[3] ttps://www.emcraft.com/som/stm32mp1/booting-linux-from-emmc

[1]

[2]

[3]