2026-06-08 SD Card Flashing Bring-up Note

Goal

Build a full i.MX6ULL AES SD card image, write it through a host SD card reader, then boot the board from SD.

This flow is intentionally different from the eMMC UUU + UMS flow:

• SD card: write the raw image directly with a card reader.
• eMMC: boot U-Boot through UUU, expose eMMC with UMS, then write the raw image.

Project Assumptions

Current project convention:

SD:   U-Boot mmc 0, Linux root /dev/mmcblk0p2
eMMC: U-Boot mmc 1, Linux root /dev/mmcblk1p2

Generated SD image:

out/release-latest/images/imx6ull-aes-sd.img

Generated eMMC image:

out/release-latest/images/imx6ull-aes-emmc.img

Build SD Image

From the project root:

./scripts/release-all.sh --continue --stage 5 --boot-media sd

Equivalent direct image-builder command:

./scripts/image_builder/build_imx6ull_image.sh --release-dir=out/release-latest --boot-media=sd

Expected outputs:

out/release-latest/images/imx6ull-aes-sd.img
out/release-latest/images/imx6ull-aes-sd.img.manifest
out/release-latest/images/imx6ull-aes-sd.img.sha256

The manifest should include:

boot_media=sd
uboot_mmc_dev=0
linux_root_dev=/dev/mmcblk0p2

Find Host SD Card Device

Before inserting the SD card:

lsblk

Insert the SD card, then run again:

lsblk

Record the new whole-disk device, for example:

/dev/sdX

Do not use a partition path such as /dev/sdX1 when writing the full image.

Write SD Image

Replace /dev/sdX with the actual whole-disk SD card device:

sudo dd if=out/release-latest/images/imx6ull-aes-sd.img of=/dev/sdX bs=4M status=progress conv=fsync
sync

Alternative GUI tools:

• Rufus: choose DD/raw image mode.
• BalenaEtcher: choose the .img file and the SD card device.

Boot From SD

Insert the SD card into the board and set the board boot mode to SD.

In U-Boot, useful manual checks:

mmc list
mmc dev 0
mmc part
ext4ls mmc 0:1 /
ext4ls mmc 0:2 /

If the default environment contains sdbootaes, boot with:

run sdbootaes

Manual boot fallback:

setenv bootargs console=ttymxc0,115200 root=/dev/mmcblk0p2 rootwait rw
ext4load mmc 0:1 ${loadaddr} /zImage
ext4load mmc 0:1 ${fdt_addr} /imx6ull-aes.dtb
bootz ${loadaddr} - ${fdt_addr}

Linux Verification

After Linux boots:

cat /proc/cmdline
mount | grep ' / '
lsblk

Expected root device:

/dev/mmcblk0p2

Pitfall Log

This v1.0.0 baseline did not keep a detailed pitfall record for SD boot. The SD card image boot flow was experimentally verified by repository author CharlieChen114514 on the ALIENTEK Alpha i.MX6ULL board.

Future issues should be appended here using:

Symptom:
Root cause:
Fix: