Hi everyone,
we're using U-Boot as our primary bootloader on the Raspberry Pi Compute Module 4 - meaning the CM4 firmware does not directly boot the kernel, but hands over control to U-Boot instead. As part of our OTA update strategy, we also want to update Device Trees and Overlays, so we’re trying to replicate the overlay logic entirely in U-Boot, rather than relying on the proprietary firmware. After digging into how the CM4 firmware handles overlays, I realized it's doing more than just applying .dtbo files - it interprets dtparam=..., activates fragments, resolves __symbols__, handles __overrides__, etc. Since we’re not aiming to become a full BSP maintainer and want to avoid reimplementing the firmware's overlay/param logic from scratch in U-Boot, I’m wondering:
Is there any existing work or tooling to reproduce the firmware’s overlay and dtparam behavior entirely in U-Boot, or perhaps a way to preprocess overlays (e.g. patch and merge .dts statically)?
Any pointers or shared experiences are appreciated.
Best regards,
Julian
we're using U-Boot as our primary bootloader on the Raspberry Pi Compute Module 4 - meaning the CM4 firmware does not directly boot the kernel, but hands over control to U-Boot instead. As part of our OTA update strategy, we also want to update Device Trees and Overlays, so we’re trying to replicate the overlay logic entirely in U-Boot, rather than relying on the proprietary firmware. After digging into how the CM4 firmware handles overlays, I realized it's doing more than just applying .dtbo files - it interprets dtparam=..., activates fragments, resolves __symbols__, handles __overrides__, etc. Since we’re not aiming to become a full BSP maintainer and want to avoid reimplementing the firmware's overlay/param logic from scratch in U-Boot, I’m wondering:
Is there any existing work or tooling to reproduce the firmware’s overlay and dtparam behavior entirely in U-Boot, or perhaps a way to preprocess overlays (e.g. patch and merge .dts statically)?
Any pointers or shared experiences are appreciated.
Best regards,
Julian
Statistics: Posted by Delete8994 — Thu May 08, 2025 4:16 pm