Raspberry Pi Stack Exchange is a question and answer site for users and developers of hardware and software for Raspberry Pi. It only takes a minute to sign up.
Sign up to join this community
I've compiled a kernel for Raspberry Pi 4 (CM4 on IO board) and made a sd card and installed overlays, modules, copied the kernel to fat32 etc.
When i boot, it gives only some messages to the point where it reads the "config.txt" but says "Firmware not found"
Where can i get the firmware and install it manually?
When i boot, it gives only some messages to the point where it reads the "config.txt" but says "Firmware not found"
config.txt is read by the early bootloader, not the kernel, so this might apply to the contents of /boot. You do not say what else you've put in there, but a kernel and a config.txt file are not enough. What's supposed to be there can be found at https://github.com/raspberrypi/firmware/tree/master/boot.
If you are sure that's not the issue because you created and populated the boot partition properly, firmware used by the linux kernel goes in /lib/firmware. This is distinct from and unrelated to the firmware in /boot used before or when the kernel is loaded; it is loaded subsequently as needed (generally by device drivers). Some of it is (or can be) built and installed with the kernel but some of it comes in separate packages (on RpiOS/Debian look at apt-file search /lib/firmware). In any case, it isn't used by the CPU so not bound to specific platform architectures; it's the same everywhere and usually distributed as binary blobs.
Note that /lib/firmware is used by any kernel for reasons just mentioned, but you also need a version specific module directory in /lib/modules.
/lib/firmware. This is distinct from and unrelated to the firmware in /boot, which is where your .dtb file is from (or should go). No .dtb files in /lib/firmware, that is not what it is for. Both these are referred to as "firmware" and the problem you describe could refer to either one of them (you did not give enough information to tell), so you have to figure that out but do not confuse one with the other.
/boot. Whatever is missing though is unlikely to be a .dtb file unless you reference one explicitly in config.txt.