On Sun, 20 Dec 2020 at 09:02, Jonas Vautherin <jonas.vautherin@...> wrote:
>
> Hello!
>
> I am new to Yocto, and hope that this is the right way to ask for help :-).
>
> I would like to have a way to flash my RPi over USB using `fastboot`, and it seems to me that one way to do that is to enable a "fastboot mode" in U-boot. Therefore, I am trying to use U-boot in my Yocto image.
>
> There seems to be a recipe for it, hence I just added the package to my `-image.bb` file:
>
> ```
> IMAGE_INSTALL += "u-boot"
> ```
>
> However, I am not really used to bootloaders, and I am not sure it is booting with it. How can I check if my system is booting with U-boot? It does not seem like it's appearing in `dmesg` (which I presume is only starting with the kernel). Do I need to observe that with a serial connection to my RPi, or is there a log saved somewhere on the system?
>
> Note that my image uses `meta-raspberrypi` for MACHINE "raspberrypi4-64" (Raspberry Pi 4 Model B).

The IMAGE_INSTALL variable is used for packages to install into the
rootfs. Typically bootloaders need some special handling and simply
adding them to IMAGE_INSTALL either doesn't work or isn't sufficient
to enable booting via the chosen bootloader.

For Raspberry Pi we made this simple by adding the RPI_USE_U_BOOT
variable which you can set in your distro config or in local.conf. See
https://meta-raspberrypi.readthedocs.io/en/latest/extra-build-config.html#boot-to-u-boot
for more details.

The layer documentation for meta-raspberrypi is actually pretty good,
you can find it at
https://meta-raspberrypi.readthedocs.io/en/latest/index.html.

Thanks,

--
Paul Barker
Konsulko Group