Yocto EMMC Burning TI
This page is using the default release am62-yocto-dunfell-5.10.168_08.06.00.42-v1.0.
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Introduction
The VAR-SOM-AM62 can boot from an SD card or from internal storage.
The Variscite VAR-SOM-AM62 comes with eMMC, which holds U-Boot, the kernel image and the ext4 root file system.
eMMC structure
The eMMC has the following structure:
| Offset Address | Offset (MiB) | Size |
Partition |
Description |
|---|---|---|---|---|
| 0x0 | 0 | 1 MiB | Reserved | Reserved |
| 0x100000 | 1 MiB |
128 MiB | Boot | Boot partition containing U-Boot images |
| 0x8600000 | 134 MiB | 1 MiB | U-Boot Env | Reserved for U-Boot environment. |
| 0x8700000 | 135 MiB | Rest of eMMC | rootfs |
An ext4 partition containing the root file system (including Linux image and the device tree blobs under /boot |
For example, an 16 GiB eMMC has the following layout:
root@am62x-var-som:~# fdisk -l /dev/mmcblk0 Disk /dev/mmcblk0: 14.69 GiB, 15758000128 bytes, 30777344 sectors Units: sectors of 1 * 512 = 512 bytes Sector size (logical/physical): 512 bytes / 512 bytes I/O size (minimum/optimal): 512 bytes / 512 bytes Disklabel type: dos Disk identifier: 0xe3dbe120 Device Boot Start End Sectors Size Id Type /dev/mmcblk0p1 * 2048 264191 262144 128M c W95 FAT32 (LBA) /dev/mmcblk0p2 276480 30777343 30500864 14.6G 83 Linux
Installing the Yocto binaries
If you followed the Create a Recovery 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
The following is the directory structure of the SD card, which includes the installation scripts and files for installation:
/usr/bin/install_yocto.sh /usr/bin/echos.sh /opt/images/Yocto/ /opt/images/Yocto/boot /opt/images/Yocto/boot/u-boot.img /opt/images/Yocto/boot/tiboot3.bin /opt/images/Yocto/boot/tispl.bin /opt/images/Yocto/boot/uEnv.txt /opt/images/Yocto/rootfs.tar.zst
Prepare the images for flashing to eMMC
If you followed the Create a Recovery SD card steps, the Yocto binaries and the flashing scripts are already included in the sD card.
If you wish to add them manually, you can follow these steps to manually copy the mentioned yocto-built binaries to the SD card. The following steps assume the SD card is mounted on /media/rootfs:
Setup environment variables:
$ export YOCTO_IMGS_PATH=arago-tmp-external-arm-glibc/deploy/images/am62x-var-som $ export P2_MOUNT_DIR=/media/rootfs/
Make directory for Yocto images:
$ sudo mkdir -p ${P2_MOUNT_DIR}/opt/images/Yocto/boot
Copy the images:
U-Boot:
$ sudo cp ${YOCTO_IMGS_PATH}/tiboot3-am62x-gp-evm.bin ${P2_MOUNT_DIR}/opt/images/Yocto/boot/tiboot3.bin
$ sudo cp ${YOCTO_IMGS_PATH}/tispl.bin ${P2_MOUNT_DIR}/opt/images/Yocto/boot/
$ sudo cp ${YOCTO_IMGS_PATH}/u-boot.img ${P2_MOUNT_DIR}/opt/images/Yocto/boot/
$ sudo cp ${YOCTO_IMGS_PATH}/uEnv.txt ${P2_MOUNT_DIR}/opt/images/Yocto/boot/
Filesystem:
$ sudo cp ${YOCTO_IMGS_PATH}/var-default-image-am62x-var-som.tar.zst ${P2_MOUNT_DIR}/opt/images/Yocto/rootfs.tar.zst
Flashing eMMC using scripts
The flashing scripts are located on the SD card at /usr/bin/:
install_yocto.sh - Flash Yocto into eMMC (Run and follow usage instructions)
The source code for the script is maintained https://github.com/varigit/meta-variscite-sdk-ti/blob/dunfell_var01/scripts/variscite/am6_install_yocto.sh
Flashing eMMC manually
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. To flash it manually, you may review Variscite's example script: https://github.com/varigit/meta-variscite-sdk-ti/blob/dunfell_var01/scripts/variscite/am6_install_yocto.sh