DESK-MX6-L/Development/How to create a bootable microSD card

History
ID#	Issue Date	Notes
14119	16/07/2021	First DESK release
16989	04/03/2022	DESK 3.0.0 release
	TBD/04/2023	DESK 4.0.0 release

How to create a bootable SD card

The procedure described here was tested with a virtual machine such as the MVM. The USB controller of the MVM should be enabled by default. If you are using Linux-based distribution and are having trouble detecting a USB device in virtual machine, please make sure your user belongs to the vboxusers group.

This article shows how to create a bootable microSD for the DESK-MX6-L Release Notes kit by using a simple bash script.
Note: Starting from DESK-MX6-L 1.0.0 release the support for the SPL has been introduced in U-Boot. Previous versions of this script will no longer produce a fully functional and bootable microSD card.

The procedure has been tested on a MVM released with DESK-MX6-L 4.0.0 release with

• a 32 GB microSD card [1]
• a USB SD card reader
• the binary files delivered along with the DESK-MX6-L 4.0.0.

The resulting card is partitioned as depicted here below:

• bootable partition (mmcblk0p1, vfat) containing:
  • binary images (U-Boot and kernel images)
• root file system partition (mmcblk0p2, ext3)
  • root file system binaries and init scripts

The script - named mksd.sh - can be realized with the following code:

#!/bin/bash

if [[ -z $1 || -z $2 || -z $3 || -z $4 || -z $5 ]]
then
        echo "$0 Usage:"
        echo "  $0 <device> <u-boot.img> <SPL> <binaries directory> <rootfs tar.bz2>"
        echo "  Example: $0 /dev/sdc u-boot.img SPL binaries/ rootfs.tar.bz2"
        exit
fi

if [ "$(whoami)" != "root" ]
then
        echo "you must be root to run this script!"
        exit
fi

if ! [[ -b $1 ]]
then
        echo "$1 is not a valid block device!"
        exit
fi

if ! [[ -e $2 ]]
then
        echo "Incorrect u-boot.img location!"
        exit
fi

if ! [[ -e $3 ]]
then
        echo "Incorrect SPL location!"
        exit
fi

if ! [[ -d $4 ]]
then
        echo "Incorrect Binaries location!"
        exit
fi

if ! [[ -f $5 ]]
then
        echo "Incorrect rootfs location!"
        exit
fi

DRIVE=$1
if [[ "$DRIVE" == *"mmcblk"* ]]
then
        echo "You're using a mmc device, I need to fix partition names"
        PART="p"
else
        PART=""
fi
UBOOT=$2
SPL=$3
BINARIES=$4
RFS=$5

echo "All data on "$DRIVE" now will be destroyed! Continue? [y/n]"
read ans
if ! [ $ans == 'y' ]
then
        exit
fi

echo "[Partitioning $1...]"

dd if=/dev/zero of=$DRIVE bs=1024 count=1024

SIZE=`fdisk -l $DRIVE | grep Disk | awk '{print $5}'`

echo DISK SIZE - $SIZE bytes

CYLINDERS=`echo $SIZE/255/63/512 | bc`

# check if we're running an old (e.g. 2.20.x) or new (e.g. 2.24.x) sfdisk
sfdisk --help | grep -- -H

if [ "$?" -eq "0" ]
then
        {
                echo 40,1380,0x0c,*
                echo 1420,,83,-
        } | sfdisk -D -H 255 -S 63 -C $CYLINDERS $DRIVE
else
{
    echo 16M,8176M,0x0c,*
    echo 8192M,,83,-
} | sfdisk $DRIVE
fi

partprobe


echo "[Making filesystems...]"
mkfs.vfat -F 32 -n BOOT "$DRIVE$PART"1 #> /dev/null
mkfs.ext3 -F -L ROOTFS "$DRIVE$PART"2 #> /dev/null

echo "[Copying files...]"

binaries_dir=${BINARIES%/}
mount "$DRIVE$PART"1 /mnt
cp -av --no-preserve=ownership $binaries_dir/* /mnt/
umount "$DRIVE$PART"1

echo "[Extracting rfs (this may take a while...)]"
mount "$DRIVE$PART"2 /mnt
tar jxf $RFS -C /mnt > /dev/null
chmod 755 /mnt
umount "$DRIVE$PART"2

echo "[Programming SPL]"
dd if=$SPL of=$DRIVE bs=512 seek=2 conv=fsync

echo "[Programming u-boot.img]"
dd if=$UBOOT of=$DRIVE bs=1k seek=69 conv=fsync

echo "[Done]"

Here is an example that shows how to use this script. We use here files delivered with DESK-MX6-L 3.0.0 release. 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
• splash image: splash_image.bmp
• Linux kernel: desk-mx6-l-4.0.0_uImage
• Device tree blob: desk-mx6-l-4.0.0_imx6dl-sbcx-cb0012.dtb.

We will copy them into ~/desk-mx-l/desk directory. Needed binary files can be found on MVM in the following location:

dvdk@vagrant:~$ ll /tftpboot/desk-mx-l/
total 11360
drwxr-xr-x 2 dvdk root    4096 Apr  3 17:57 ./
drwxr-xr-x 3 dvdk root    4096 Apr  4 07:16 ../
-rw-r--r-- 1 dvdk root   52247 Apr  3 17:38 desk-mx6-l-4.0.0_imx6dl-sbcx-cb0012.dtb
-rw-r--r-- 1 dvdk root   52560 Apr  3 17:38 desk-mx6-l-4.0.0_imx6dl-sbcx-cb0013.dtb
-rw-r--r-- 1 dvdk root   52161 Apr  3 17:38 desk-mx6-l-4.0.0_imx6dl-sbcx-cb0018.dtb
-rw-r--r-- 1 dvdk root   53231 Apr  3 17:38 desk-mx6-l-4.0.0_imx6dl-sbcx-cb0050.dtb
-rw-r--r-- 1 dvdk root   52536 Apr  3 17:38 desk-mx6-l-4.0.0_imx6dl-sbcx-cb0055.dtb
-rw-r--r-- 1 dvdk root   48736 Apr  3 17:38 desk-mx6-l-4.0.0_imx6dl-xelk-l.dtb
-rw-r--r-- 1 dvdk root   53524 Apr  3 17:38 desk-mx6-l-4.0.0_imx6q-sbcx-cb0012.dtb
-rw-r--r-- 1 dvdk root   53833 Apr  3 17:38 desk-mx6-l-4.0.0_imx6q-sbcx-cb0013.dtb
-rw-r--r-- 1 dvdk root   50177 Apr  3 17:38 desk-mx6-l-4.0.0_imx6q-xelk-l-2-0-0.dtb
-rw-r--r-- 1 dvdk root   50009 Apr  3 17:38 desk-mx6-l-4.0.0_imx6q-xelk-l.dtb
-rw-r--r-- 1 dvdk root   56320 Apr  3 17:38 desk-mx6-l-4.0.0_mx6qdldesk_SPL
-rw-r--r-- 1 dvdk root   56320 Apr  3 17:38 desk-mx6-l-4.0.0_mx6qdldesk_nand_SPL
-rw-r--r-- 1 dvdk root  576288 Apr  3 17:38 desk-mx6-l-4.0.0_mx6qdldesk_nand_u-boot.img
-rw-r--r-- 1 dvdk root   56320 Apr  3 17:38 desk-mx6-l-4.0.0_mx6qdldesk_spi_SPL
-rw-r--r-- 1 dvdk root  554004 Apr  3 17:38 desk-mx6-l-4.0.0_mx6qdldesk_spi_u-boot.img
-rw-r--r-- 1 dvdk root  576000 Apr  3 17:38 desk-mx6-l-4.0.0_mx6qdldesk_u-boot.img
-rw-r--r-- 1 dvdk root 8038640 Apr  3 17:38 desk-mx6-l-4.0.0_uImage
-rw-r--r-- 1 dvdk root 1152054 Apr  3 17:38 splash_image.bmp
dvdk@vagrant:~$ ll ~/desk-mx-l/desk-mx6-l-4.0.0-rc1_boot.scr 
-rw-rw-r-- 1 dvdk dvdk 1556 Apr  3 17:57 /home/dvdk/desk-mx-l/desk-mx6-l-4.0.0_boot.scr
dvdk@vagrant:~$ mkdir -p ~/desk-mx-l/desk/
dvdk@vagrant:~$ cp /tftpboot/desk-mx-l/desk-mx6-l-4.0.0_uImage ~/desk-mx-l/desk/desk-mx6-l-4.0.0_uImage
dvdk@vagrant:~$ cp /tftpboot/desk-mx-l/desk-mx6-l-4.0.0_imx6dl-sbcx-cb0012.dtb ~/desk-mx-l/desk/desk-mx6-l-4.0.0_imx6dl-sbcx-cb0012.dtb
dvdk@vagrant:~$ cp ~/desk-mx-l/desk-mx6-l-4.0.0_boot.scr ~/desk-mx-l/desk/boot.scr
dvdk@vagrant:~$ cp /tftpboot/desk-mx-l/splash_image.bmp ~/desk-mx-l/desk/

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

• Device file of the microSD card (/dev/sdb in the example)
• U-Boot image
• SPL
• Path of the directory containing the bootscript file, the splash image, 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-mx-l$ umount /dev/sdb*
dvdk@vagrant:~/desk-mx-l$ sudo ./desk-mx6-l-4.0.0_mksd.sh /dev/sdb /tftpboot/desk-mx-l/desk-mx6-l-4.0.0_mx6qdldesk_u-boot.img /tftpboot/desk-mx-l/desk-mx6-l-4.0.0_mx6qdldesk_SPL ~/desk-mx-l/desk ./rfs/desk-mx6-l-4.0.0_desk-image-qt6-desk-mx6.tar.bz2 
All data on /dev/sdb now will be destroyed! Continue? [y/n]
y
[Partitioning /dev/sdb...]
1024+0 records in
1024+0 records out
1048576 bytes (1.0 MB, 1.0 MiB) copied, 0.228364 s, 4.6 MB/s
DISK SIZE - 31914983424 bytes
Checking that no-one is using this disk right now ... OK

Disk /dev/sdb: 29.74 GiB, 31914983424 bytes, 62333952 sectors
Disk model: Transcend       
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes

>>> Created a new DOS disklabel with disk identifier 0xeba9791f.
/dev/sdb1: Created a new partition 1 of type 'W95 FAT32 (LBA)' and of size 8 GiB.
/dev/sdb2: Created a new partition 2 of type 'Linux' and of size 21.7 GiB.
/dev/sdb3: Done.

New situation:
Disklabel type: dos
Disk identifier: 0xeba9791f

Device     Boot    Start      End  Sectors  Size Id Type
/dev/sdb1  *       32768 16777215 16744448    8G  c W95 FAT32 (LBA)
/dev/sdb2       16777216 62333951 45556736 21.7G 83 Linux

The partition table has been altered.
Calling ioctl() to re-read partition table.
Syncing disks.
[Making filesystems...]
mkfs.fat 4.1 (2017-01-24)
mke2fs 1.45.5 (07-Jan-2020)
Creating filesystem with 5694592 4k blocks and 1425408 inodes
Filesystem UUID: 2b7edb0e-b75b-4685-87b9-1933bfd0c8f0
Superblock backups stored on blocks: 
        32768, 98304, 163840, 229376, 294912, 819200, 884736, 1605632, 2654208, 
        4096000

Allocating group tables: done                            
Writing inode tables: done                            
Creating journal (32768 blocks): done
Writing superblocks and filesystem accounting information: done   

[Copying files...]
'/home/dvdk/desk-mx-l/desk/boot.scr' -> '/mnt/boot.scr'
'/home/dvdk/desk-mx-l/desk/desk-mx6-l-4.0.0_imx6dl-sbcx-cb0012.dtb' -> '/mnt/desk-mx6-l-4.0.0_imx6dl-sbcx-cb0012.dtb'
'/home/dvdk/desk-mx-l/desk/desk-mx6-l-4.0.0_uImage' -> '/mnt/desk-mx6-l-4.0.0_uImage'
'/home/dvdk/desk-mx-l/desk/splash_image.bmp' -> '/mnt/splash_image.bmp'
[Extracting rfs (this may take a while...)]
[Programming SPL]
110+0 records in
110+0 records out
56320 bytes (56 kB, 55 KiB) copied, 0.0340295 s, 1.7 MB/s
[Programming u-boot.img]
562+1 records in
562+1 records out
576000 bytes (576 kB, 562 KiB) copied, 0.201931 s, 2.9 MB/s
[Done]

[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:

echo 'bootscript generated with command "mkimage -A ARM -T script -C none -n DESK-MX6-L -d bootscript.txt boot.scr"'

setenv desk_release 'desk-mx6-l-4.0.0'

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#} = 0x00000001;
then
        if test ${cpu} = 6DL; then
                setenv fdtfile ${desk_release}_imx6dl-xelk-l.dtb
        else
                setenv fdtfile ${desk_release}_imx6q-xelk-l.dtb
        fi
elif test 0x${cb_configid#} = 0x00000018;
then
        setenv fdtfile ${desk_release}_imx6dl-sbcx-cb0018.dtb
elif test 0x${cb_configid#} = 0x00000050;
then
        setenv fdtfile ${desk_release}_imx6dl-sbcx-cb0050.dtb
elif test 0x${cb_configid#} = 0x00000055;
then
        setenv fdtfile ${desk_release}_imx6dl-sbcx-cb0055.dtb
elif test 0x${cb_configid#} = 0xffffffff;
then
        setenv fdtfile ${desk_release}_imx6q-xelk-l-2-0-0.dtb
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 DESK-MX6-L via mmcboot with ${fdtfile} as device tree

run mmcboot

echo mmcboot FAILURE

and compile it using:

mkimage -A ARM -T script -C none -n DESK-MX6-L -d bootscript.txt boot.scr

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

Attention !

• /home/dvdk/desk-mx-l/desk-mx6-l-4.0.0_boot.scr has been generated using the images available at the moment of VM creation: please, use the previous indication as an example on how to create a proper bootscript for your own purposes
• /home/dvdk/desk-mx-l/desk-mx6-l-4.0.0_mksd.sh bash script has been validated using a single SD card version: the size of the partitions and the related sfdisk parameters have to be properly modified according to your own SD card used and to your partitions specification. You can use it an an example to be modified according your use case

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