DHCOM Update Mechanism

The DHCOM Update Mechanism for the i.MX6 Module can be used to flash a complete system image or to replace on some parts (e.g. linux kernel) of the system. It is not necessary to have a running os. The only requirement is a running bootloader.

Overview

The following updates and commands are supported by the mechanism:

command	description
bootloader	update the bootloader
script	bootloader executes the provided bootloader script e.g. to customize bootloader environment variables
splash	write a new *.bmp to display a bootloader splashscreen
settings	DHCOM bootloader settings
copy	copy a file e. g. uLinuxEnv.txt into the boot partition
linux	update the linux kernel binary e. g. zImage
devicetree	update the devicetree blob
rootfs	write a new rootfilesystem to the target
finetuning	run a provided script to do some finetuning on our installation (warning: experts only)
eeprom	update the display timings stored in the display adapter EEPROM
reset	reboot system after a successful update (warning: risk of a infinite update loop)

How does it work?

• The update mechanism has to be started with the bootloader command "update".
• The updates "bootloader", "script", and "eeprom" are processed by the bootloader. They can be started directly with "update <command> <imagefile>" for example "update bootloader u-boot_imx6dl-dhcom2_1G.imx"
• For the remaining updates you need a "update kernel". The "update kernel" is a file which contains the linux kernel binary (zImage), a busybox rootfilesystem with shell scripts (*.cpio), and a devicetree blob (*.dtb). This implies that the update kernel has to mach your board configuration like the bootloader, linux kernel, and devicetree concerning CPU Type, CPU Cores, RAM and NAND or eMMC memory.
• To control the processing of the updates you need to provide a "DHupdate.ini" file to the update kernel.
• For further Details see the following chapters.

Execution Modes

Automatic Mode

• To use the "automatic mode" the command "update auto" has to be called within the bootloader environment variable bootcmd. The functionality does search a DHupdate.ini file on the specified storage devices e. g. update devices. The update devices must be defined at the DHCOM settings block (Please have a look at DHCOM settings). The content of the DHupdate.ini file controls which updates have to be processed and which images have to be written to the storage device (eMMC or NAND) of the DHCOM computer on module system.

Commandline Mode

• Instruction: "update"

  The functionality tries to update the flash content via the DHupdate.ini file. In contrast to Automatically Update (which you can start with "update auto") the update mechanism is searching on every available storage device for the update files.

• Instruction: "update <command> [filename]"

  The functionality doesn't use the DHupdate.ini file. It allows only one update and the update mechanism is searching on every available storage device for the update files. With the <type> parameter you have to specify the update type.

The following <command> parameters are possible from command line:

command	description
bootloader	update the bootloader Note: The ENV in Flash memory is created on the first start of u-boot. If you run a bootloader update and the ENV at the new bootloader has changed, the ENV in Flash memory remains unchanged with the bootloader update. But you could delete the ENV block in flash memory before the update, then u-boot will create the new default ENV at the next start after the bootloader update.
script	bootloader executes the provided bootloader script e.g. to customize bootloader environment variables
eeprom	update the display timings stored in the display adapter EEPROM
reset	reboot system after a successful update. A reset can only be the last item in a DHupdate.ini file. Warning: risk of a infinite update loop.

The [filename] parameter could be used to specify a non default filename. The default filenames are:

command	default filename
bootloader	default file name is u-boot.imx
script	default file name is script.bin
eeprom	default file name is eeprom.bin
reset	no file to specify

DHupdate.ini file

The DHupdate.ini file is a text file, which describes the user specified update mechanism.

Syntax

The <type> parameter could be specified as follows:

<type>	description
bootloader	update the bootloader
script	bootloader executes the provided bootloader script e.g. to customize bootloader environment variables
splash	write a new *.bmp to display a bootloader splashscreen
settings	DHCOM bootloader settings Note: Please have a look at DHCOM settings.
refresh	Set the new display settings for the current update process
copy	copy a file e. g. uLinuxEnv.txt into the boot partition
linux	update the linux kernel binary e. g. zImage
devicetree	update the devicetree blob
rootfs	Create or replace the linux root-filesystem which is stored in the Flash. The rootfs update has to be the last item (or second to last item if you insert the reset command) in the DHupdate.ini file. For further Details: DHCOM Update: Linux Root Filesystem
finetuning	run a provided script to do some finetuning on our installation (warning: experts only)
eeprom	update the display timings stored in the display adapter EEPROM
reset	reboot system after a successful update Note: If you update the DHCOM settings, it is possible to use the new settings for the update progress notifications on the display, by inserting the "refresh" command to the [update] section. The bootloader loads the new settings and calls the update kernel with the new parameters.

Example

##DHCOMupdate##
[display]
800x480_progress.bmp
800x480_done.bmp
800x480_error.bmp
[led]
GPIO_E high
[update]
settings 13_DataImage_7inch_FG0700G3DSSW.bin
refresh
bootloader u-boot-nand.imx
splash DH_800x480.bmp
linux zImage
devicetree dtbs/imx6dl-dheva01.dtb
rootfs imx6_debian_rootfs.tar
[end]

For further DHupdate.ini File Examples please have a look at Download area iMX25 or Download area AM35x.

Notes:

• It is necessary to use UNIX End Of Line conversion!!!
• The order of the bitmap-filenames in the section display tells the system when to display which bitmap.

.*If you use "refresh" command, please ensure that settings bin update is listed in DHupdate.ini file before "refresh" command.

Bootloader Handled Updates

The following updates are done by the bootloader:

• bootloader (only in case of command line update)
• refresh
• eeprom
• script

"Update Kernel" Handled Updates

The following updates are done by the update kernel:

For this updates u-boot loads a minimal linux kernel which does the work. We call this tiny kernel in the further description "Update Kernel". The update kernel is loaded via the env variable "load_update_kernel". These variable needs to be set before. This could be done with the update script functionality.

Before the bootloader loads the update kernel the variables "dev" and "part" will be set with the current update medium. So this variable could be used in "load_update_kernel" as placeholder for loading the update kernel from the current update device.

• bootloader (only in case of DHupdate.ini File update)
• copy
• linux
• devicetree
• rootfs
• settings
• splash
• finetuning

Note: The [filename] parameter has to be defined if you use the update kernel.

Update progress LED description

The LED GPIO is activated as soon as update has started. This takes roughly 6 - 8 seconds. If the update was finished without an error, the LED GPIO is deactivated. If an error occurs during the update the LED GPIO begins blinking.

LED error code:

1 LED blinking interval = DHupdate.ini File error (Wrong file content or no valid file found)

2 LED blinking interval = Necessary File for Update not found

3 LED blinking interval = Flash write or erase error

4 LED blinking interval = Wrong OS Image type (e.g. no WinCE *.gz or *.bin file)

5 LED blinking interval = Specified file not valid (e.g. linux *.env file)

6 LED blinking interval = Image file size is to large

7 LED blinking interval = Can't load update kernel / Internal ERROR

Flowchart of the Update Process