Booting my custom U-Boot (built with Yocto) from SD card without overwriting the preinstalled one on Verdin iMX8MP

Technical Support
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SD Card U-Boot Placement Requirements

Based on the Toradex documentation, simply placing the U-Boot binary in partition 1 (the boot partition) will not work for the i.MX8MP boot ROM(1).

Correct U-Boot Placement for SD Card Boot

The U-Boot binary needs to be written to specific raw sectors on the SD card, not to a filesystem partition(1). According to the documentation, when deploying U-Boot to an image, you need to integrate the U-Boot artifacts into a Toradex Easy Installer package by replacing the bootloader binaries with the ones you have built(1).

Image.json Configuration

The deployment process requires adjusting the image.json file to ensure the bootloader binaries are loaded correctly(1). Here’s an example configuration from the documentation:

"name": "mmcblk0boot0",
"erase": true,
"content": {
    "filesystem_type": "raw",
    "rawfiles": [
        {
            "filename": "u-boot.imx",
            "dd_options": "seek=2"
        }
    ]
}

(1)

Recommended Approach

For your Verdin iMX8MP with Mender integration:

  1. Use Toradex Easy Installer: The recommended approach is to create a proper Toradex Easy Installer package that includes your custom U-Boot binary(1).

  2. Raw Sector Writing: The flash.bin-verdin-imx8mp-sd needs to be written to the raw SD card sectors at the correct offset, not placed in a filesystem partition(1).

  3. Preserve Your Current Setup: Since you’re using a .gptimg image with Mender, you’ll need to modify the image creation process to include your custom U-Boot at the proper raw offset while maintaining the existing partition structure.

Technical Details

The i.MX8MP boot ROM looks for the bootloader at specific raw offsets on the storage device, not within filesystem partitions(1). This is why your current partition-based approach won’t work - the boot ROM never examines the contents of filesystem partitions during the initial boot process.

The community discussion confirms this behavior, where a user discovered that for NAND flash modules, the Image Vector Table (IVT) is located at specific offsets rather than in filesystem locations(2).

Best regards, Toradex AI Assistant.

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