VAR-SOM-MX6 NAND Flash Burning Jethro

VAR-SOM-MX6 - NAND Flash Burning

Introduction

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.

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

NAND Structure

When system boots, kernel logs will present 4 relevant partitions defined.
0x000000000000-0x000000200000 : "spl"
0x000000200000-0x000000400000 : "bootloader"
0x000000400000-0x000000c00000 : "kernel"
0x000000c00000-0x000040000000 : "rootfs"

Yocto Built binaries for NAND flash

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-nand-2015.04-r0.img	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 VAR-STK-MX6_V2
uImage-imx6q-var-som-res.dtb	VAR-SOM-MX6_V2 (Quad / Dual)	VAR-MX6CustomBoard	Resistive touch	VAR-DVK-MX6_V2-PRO VAR-STK-MX6_V2
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 VAR-STK-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

NAND Flashing scripts

If you followed the Create an extended SD card steps, the NAND flashing scripts will be included in your SD card.
The NAND flashing scripts are easy-to-use example scripts for burning images into NAND flash / eMMC.

NAND flash images locations

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

/opt/images/
└── 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 images for NAND flash / eMMC flashing

Plug the bootable SD card into your host machine. Then your host machine should mount the rootfs partition on /media/rootfs.
Copy all the mentioned yocto-built binaries to the SD card:

• Note: If you followed the Create an extended SD card steps, the NAND flashing scripts and all relevant binaries are already included in your SD card, and the below commands are redundant!
  

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

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

SPL/U-Boot:
$ 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/

NAND flash flashing scripts

The flashing scripts are located on the SD card at /usr/bin/:

install_yocto.sh	- Flash Yocto into NAND flash or eMMC (Run and follow usage instructions)
(install_yocto_emmc.sh	- This script is being called by install_yocto.sh when choosing to install the rootfs to eMMC - it should not be called directly!)

Manual step-by-step flashing to NAND

Assuming you followed the Prepare images for NAND flash / eMMC flashing section above:

Flash SPL & U-Boot

$ cd /opt/images/Yocto
$ 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 Linux Kernel image & Device Tree

You need to pick and choose the right .dtb file. See the table above for a complete description.

$ cd /opt/images/Yocto
$ 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 UBIFS

$ cd /opt/images/Yocto
$ ubiformat /dev/mtd3 -f rootfs.ubi.img

Flash File System to eMMC

Flashing eMMC requires several steps including partition, format and untar of the file system. We recommend to use our provided scripts to perform this task.

$ export node=/dev/mmcblk0
$ cd /opt/images/Yocto

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)

or:

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

Summary

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/install_yocto.sh. It is much safer to use it instead of flashing the system manually.