VAR-SOM-MX6 NAND Flash Burning Jethro

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VAR-SOM-MX6 - NAND Flash Burning


The Variscite VAR-SOM-MX6 / VAR-SOM-SOLO SOMs use the on-SOM NAND flash to boot.
The file system can reside either on the NAND flash or the eMMC.
When the file system resides on NAND, UBIFS file system is used.
When file system resides on eMMC, ext4 file system is used.
Regardless of the file system type and location, U-Boot will always boot from NAND. The only exception is the VAR-DART-MX6, where boot is from eMMC completely.

This Wiki is only valid for VAR-SOM-MX6, VAR-SOM-SOLO/DUAL. For DART-MX6 please use: DART eMMC flashing

NAND flash structure

These are the defined MTD partitions on the NAND flash:
0x000000000000-0x000000200000 : "spl"
0x000000200000-0x000000400000 : "bootloader"
0x000000400000-0x000000c00000 : "kernel"
0x000000c00000-End                       : "rootfs"

Yocto Built binaries for NAND flash / eMMC

The resulted images are located at tmp/deploy/images/var-som-mx6.
Looking at tmp/deploy/images/var-som-mx6 you will find the following five required files for a complete NAND flash based system:
SPL, U-Boot, uImage, dtb file, file system image file.

Image Name
How to use
fsl-image-gui-var-som-mx6.tar.bz2 Tarball of the rootfs used for eMMC (for extracting into the ext4 partition on eMMC)
(Needed only in case of using the eMMC for file system)
fsl-image-gui-var-som-mx6.ubi A complete UBI file system binary ("rootfs")
(Needed only in case of using the NAND flash for file system)
uImage Linux kernel image ("kernel")
SPL-nand The SPL is pre-U-Boot SW component, required for DDR intialization ("spl")
u-boot.img-nand U-Boot built for NAND ("bootloader")
Device Tree Name
(Choose only one, according to your SOM and carrier board)
SOM type
Carrier Board type
LCD Type
Evaluation Kit name
uImage-imx6q-var-som-cap.dtb VAR-SOM-MX6_V2 (Quad / Dual) VAR-MX6CustomBoard Capacitive touch VAR-DVK-MX6_V2-PRO
uImage-imx6q-var-som-res.dtb VAR-SOM-MX6_V2 (Quad / Dual) VAR-MX6CustomBoard Resistive touch VAR-DVK-MX6_V2-PRO
uImage-imx6q-var-som-vsc.dtb VAR-SOM-MX6_V2 (Quad / Dual) VAR-SOLOCustomBoard Capacitive LVDS touch N/A
uImage-imx6dl-var-som-cap.dtb VAR-SOM-MX6_V2 (DualLite/ Solo) VAR-MX6CustomBoard Capacitive touch N/A
uImage-imx6dl-var-som-res.dtb VAR-SOM-MX6_V2 (DualLite/ Solo) VAR-MX6CustomBoard Resistive touch N/A
uImage-imx6dl-var-som-vsc.dtb VAR-SOM-MX6_V2 (DualLite/ Solo) VAR-SOLOCustomBoard Capacitive LVDS touch N/A
uImage-imx6dl-var-som-solo-vsc.dtb VAR-SOM-SOLO / VAR-SOM-DUAL VAR-SOLOCustomBoard Capacitive LVDS touch VAR-DVK-SOLO/DUAL
uImage-imx6dl-var-som-solo-cap.dtb VAR-SOM-SOLO / VAR-SOM-DUAL VAR-MX6CustomBoard Capacitive touch N/A
uImage-imx6dl-var-som-solo-res.dtb VAR-SOM-SOLO / VAR-SOM-DUAL VAR-MX6CustomBoard Resistive touch N/A

Installing the Yocto binaries

If you followed the Create an extended SD card steps, the Yocto binaries and the flashing scripts will be included in your SD card.
The flashing scripts are easy-to-use example scripts for flashing images into NAND flash / eMMC.
There is also a section below describing how to flash the images manually.

Images locations

Following is the directory structure on your SD card, which elaborates the files' location that the below installation scripts are expecting:

└── Yocto
    ├── SPL
    ├── rootfs.tar.bz2
    ├── rootfs.ubi.img
    ├── u-boot.img
    ├── uImage
    ├── uImage-imx6dl-var-som-cap.dtb
    ├── uImage-imx6dl-var-som-res.dtb
    ├── uImage-imx6dl-var-som-solo-cap.dtb
    ├── uImage-imx6dl-var-som-solo-res.dtb
    ├── uImage-imx6dl-var-som-solo-vsc.dtb
    ├── uImage-imx6dl-var-som-vsc.dtb
    ├── uImage-imx6q-var-som-cap.dtb
    ├── uImage-imx6q-var-som-res.dtb
    └── uImage-imx6q-var-som-vsc.dtb

Prepare the images for NAND flash / eMMC flashing

Plug the bootable SD card into your host machine and mount the rootfs partition - here we assume it is mounted on /media/rootfs.
Copy all the mentioned yocto-built binaries to the SD card:

$ export YOCTO_IMGS_PATH=~/var-som-mx6-yocto-jethro/build_x11/tmp/deploy/images/var-som-mx6
$ export P2_MOUNT_DIR=/media/rootfs/

$ sudo cp ${YOCTO_IMGS_PATH}/uImage			${P2_MOUNT_DIR}/opt/images/Yocto/

$ sudo cp ${YOCTO_IMGS_PATH}/SPL-nand			${P2_MOUNT_DIR}/opt/images/Yocto/SPL
$ sudo cp ${YOCTO_IMGS_PATH}/u-boot-nand-2015.04-r0.img	${P2_MOUNT_DIR}/opt/images/Yocto/u-boot.img

File System:
$ sudo cp ${YOCTO_IMGS_PATH}/fsl-image-gui-var-som-mx6.tar.bz2	${P2_MOUNT_DIR}/opt/images/Yocto/rootfs.tar.bz2
$ sudo cp ${YOCTO_IMGS_PATH}/fsl-image-gui-var-som-mx6.ubi	${P2_MOUNT_DIR}/opt/images/Yocto/rootfs.ubi.img

Device Tree:
$ sudo cp ${YOCTO_IMGS_PATH}/uImage-imx6dl-var-som-cap.dtb	${P2_MOUNT_DIR}/opt/images/Yocto/
$ sudo cp ${YOCTO_IMGS_PATH}/uImage-imx6dl-var-som-res.dtb	${P2_MOUNT_DIR}/opt/images/Yocto/
$ sudo cp ${YOCTO_IMGS_PATH}/uImage-imx6dl-var-som-solo-cap.dtb	${P2_MOUNT_DIR}/opt/images/Yocto/
$ sudo cp ${YOCTO_IMGS_PATH}/uImage-imx6dl-var-som-solo-res.dtb	${P2_MOUNT_DIR}/opt/images/Yocto/
$ sudo cp ${YOCTO_IMGS_PATH}/uImage-imx6dl-var-som-solo-vsc.dtb	${P2_MOUNT_DIR}/opt/images/Yocto/
$ sudo cp ${YOCTO_IMGS_PATH}/uImage-imx6dl-var-som-vsc.dtb	${P2_MOUNT_DIR}/opt/images/Yocto/
$ sudo cp ${YOCTO_IMGS_PATH}/uImage-imx6q-var-dart.dtb		${P2_MOUNT_DIR}/opt/images/Yocto/
$ sudo cp ${YOCTO_IMGS_PATH}/uImage-imx6q-var-som-cap.dtb	${P2_MOUNT_DIR}/opt/images/Yocto/
$ sudo cp ${YOCTO_IMGS_PATH}/uImage-imx6q-var-som-res.dtb	${P2_MOUNT_DIR}/opt/images/Yocto/
$ sudo cp ${YOCTO_IMGS_PATH}/uImage-imx6q-var-som-vsc.dtb	${P2_MOUNT_DIR}/opt/images/Yocto/

Flashing scripts

The flashing scripts are located on the SD card at /usr/bin/:	- Flash Yocto into NAND flash or eMMC (Run and follow usage instructions)
(	- This script is being called by when choosing to install the rootfs to eMMC - it should not be called directly!)

Manual step-by-step flashing to NAND flash / eMMC

Use the prepared SD card to boot the board and run the following:

$ cd /opt/images/Yocto

Flash SPL & U-Boot:

$ flash_erase /dev/mtd0 0 0
$ kobs-ng init -x SPL --search_exponent=1 -v
$ flash_erase /dev/mtd1 0 0
$ nandwrite -p /dev/mtd1 u-boot.img

Flash the Linux Kernel image & Device Tree:
You need to use the right .dtb file for you hardware setup. See the table above for a complete description.

$ flash_erase /dev/mtd2 0 0
$ nandwrite -p /dev/mtd2 uImage
$ nandwrite -p /dev/mtd1 -s 0x1e0000 uImage-imx6q-var-som.dtb (Example, select the right one!)

Flash the (UBI) File System to NAND flash:

$ ubiformat /dev/mtd3 -f rootfs.ubi.img

Flash the (ext4) File System to eMMC:
Flashing the eMMC requires several steps including partitioning, file system formatting and image extraction.
We recommend to use our provided scripts to perform this task.

$ export node=/dev/mmcblk0

Make sure the eMMC is not mounted:
$ umount ${node}p*

Delete current data on eMMC:
$ dd if=/dev/zero of=${node}p1 bs=1024 count=1024
$ dd if=/dev/zero of=${node}p2 bs=1024 count=1024
$ dd if=/dev/zero of=${node}p3 bs=1024 count=1024
$ dd if=/dev/zero of=${node}p4 bs=1024 count=1024
$ dd if=/dev/zero of=${node}p5 bs=1024 count=1024
$ dd if=/dev/zero of=${node}p6 bs=1024 count=1024
$ dd if=/dev/zero of=${node}p7 bs=1024 count=1024
$ sync
$ (echo d; echo 1; echo d; echo 2; echo d; echo 3; echo d; echo w) | fdisk $node
$ sync
$ dd if=/dev/zero of=$node bs=1M count=4
$ sync

Create a partition table:
$ (echo n; echo p; echo 1; echo; echo; echo p; echo w) | fdisk -u $node
$ sync

Format the rootfs partition with ext4 file system:
$ mkfs.ext4 ${node}p1 -L rootfs

Flash the rootfs:
$ mkdir /run/media/mmcblk0p1
$ mount ${node}p1 /run/media/mmcblk0p1
$ tar xvpf rootfs.tar.bz2 -C /run/media/mmcblk1p1/
$ sync
$ umount /run/media/mmcblk0p1

And finally, set the U-Boot env. variable "rootfs_device" to "emmc" by one of the following two methods:
$ fw_setenv rootfs_device emmc
(A "Warning: Bad CRC, using default environment" message is expected, since this is the first write of the U-Boot environment to the NAND flash)

Reboot and stop at the U-Boot command line, and enter the following:
=> setenv rootfs_device emmc
=> saveenv


This page is not valid for DART-MX6. For DART-MX6, please follow the link to the relevant page.
We described the results of a Yocto build, how to copy it to a bootable SD card and how to flash it to NAND and eMMC.
With our extended SD card and our recovery SD card we provide an installation script located at /usr/bin/ It is much safer to use it instead of flashing the system manually.