Vybrid Cortex-M4 boot utility
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README.md

m4boot

Vybrid Cortex-M4 boot utility to boot Linux

Usage: m4boot IMAGE [INITRD] [DTB] [BOOTARGS]

IMAGE - XIP Linux Kernel image INITRD - initramfs (optionally compressed) DTB - Binary device tree file BOOTARGS - Linux kernel boot args

The utility loads the file in fixed locations of the physical memory of the SoC and starts the secondary Cortex-M4 CPU. The default addresses are: IMAGE: 0x8f000000 INITRD: 0x89000000 DTB: 0x8fff0000

Hence the upper 128MiB of memory on the external DDR RAM should be free for the Cortex-M4 (use mem=128M to restrict memory usage of the kernel running on the Cortex-A5 CPU).

The utility makes sure the bootargs and the initrd start/end address end up in the device tree file as the Linux kernel expects it (/chosen nodes).