DESK-MX6UL-L/Development/How to create a bootable microSD card

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How to create a bootable SD card

The procedure described here was tested with a physical machine. In case of a virtual machine such as the MVM, it might not work properly. Also, it is worth remembering that USB controller of the MVM is disabled by default. See also this section.

This article shows how to create a bootable microSD for the [[DESK-MX6UL-L/General/Release_Notes_(DESK-MX6UL-L)|DESK-MX6UL-L Release Notes] kit by using a simple bash script.
Note: Starting from this release the support for the SPL has been introduced in Uboot. Previous versions of this script will no longer produce a fully functional and bootable microSD card.

The procedure has been tested on a Linux PC running Ubuntu LTS (>=TBD) distribution with

• a 16 GB microSD card [1]
• the binary files delivered along with the DESKMX6UL-L 1.x.x.

The resulting card is partitioned as depicted here.

The script - named mksd.sh - looks like this:

TBD : cat of mksd.sh script

Here is an example that shows how to use this script. Let's assume that the binary files were downloaded in the desk subdirectory of the working directory. Before invoking the script, the following files has to be renamed in order to make them compatible with the default U-Boot environment variables:

• bootscript: boot.scr
• Linux kernel: uImage
• Device tree blob: carrier.dtb.

This is the list of the binary files that will be used by the script:

dvdk@vagrant:~/desk-{{{kit}}}$ ls -la
...
TBD directory listing
...

You can now run the script, by passing the following parameters:

• Device file of the microSD card (/dev/sdc in the example)
• U-Boot image
• SPL
• Path of the directory containing the bootscript file, the Linux kernel image, and the device tree blob files
• Archive of the target's root file system (compressed as .tar.bz2 file).

dvdk@vagrant:~/desk-{{{kit}}}$ ./mksd.sh /dev/sd<x> <u-boot.img> <SPL> <binaries_dir>/ <rfs_filename>
...
...
TBD 
...
...

[1] In case you have a different size, you'll need to change the sfdisk parameters accordingly.

bootscr

Once you got the new binaries compiled from your modified sources, they have to be installed on first SD partition preserving the original file names used into boot.scr u-boot bootscript.

Here below there is an example on how to create a boot.scr file from the bootscript.txt for booting from SD card:

TBD: bootscript.txt dump

echo 'bootscript generated with command "mkimage -A ARM -T script -C none -n AXEL-Lite-DESK-SBCX -d bootscript.txt boot.scr"'

setenv desk_release 'desk-mx6-l-1.0.0'

if test 0x${cb_configid#} = 0x00000012;
then
	if test ${cpu} = 6DL; then
		setenv fdtfile ${desk_release}_imx6dl-sbcx-cb0012.dtb
	else
		setenv fdtfile ${desk_release}_imx6q-sbcx-cb0012.dtb
	fi
elif test 0x${cb_configid#} = 0x00000013;
then
	if test ${cpu} = 6DL; then
		setenv fdtfile ${desk_release}_imx6dl-sbcx-cb0013.dtb
	else
		setenv fdtfile ${desk_release}_imx6q-sbcx-cb0013.dtb
	fi
elif test 0x${cb_configid#} = 0xffffffff;
then
	if test ${cpu} = 6DL; then
		setenv fdtfile ${desk_release}_imx6dl-desk-l-2.0.0.dtb
	else
		setenv fdtfile ${desk_release}_imx6q-desk-l-2.0.0.dtb
	fi
else
    echo Invalid CB! Autoreset ...
    sleep 30
	reset
fi

setenv bootfile ${desk_release}_uImage

setenv mmc_loadk 'fatload mmc ${mmcdev}:1 ${loadaddr} ${bootfile}'
setenv mmc_loadfdt 'fatload mmc ${mmcdev}:1 ${fdtaddr} ${fdtfile}'

echo Booting AxelLite-DESK-SBCX via mmcboot with ${fdtfile} as device tree

run mmcboot

echo mmcboot FAILURE

and compile it using:

mkimage -A ARM -T script -C none -n AXEL-Lite-DESK-SBCX -d bootscript.txt boot.scr

Then copy the boot.scr into the <binaries_dir> directories used by the script to create the SD card.

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