[Buildroot] [PATCH v3 3/3] configs/raspberrypicm4io_64_uboot_defconfig: new defconfig

[Fiona Klute]

Am 10.02.25 um 08:44 schrieb Arnout Vandecappelle:
>
>
> On 07/02/2025 23:36, bryce.schober at gmail.com wrote:
>>
>> Hi Arnout,
>>
>> On Fri, Feb 7, 2025 at 1:37 PM Arnout Vandecappelle via buildroot
>> <buildroot at buildroot.org <mailto:buildroot at buildroot.org>> wrote:
>>
>>        Looks good at first sight. I'm thinking though: wouldn't it be
>> easier if we
>>     convert all RPi configs (gradually) to U-Boot, and mention in the
>> readme (and
>>     config.txt comments) how to boot without U-Boot?
>>
>>
>> FYI, U-Boot doesn't support the RPi PCI/NVMe interface because of a
>> current lack of support in the upstream kernel. So we are actually
>> moving away from U-Boot in a previous project toward using the rpi
>> firmware support for integrating with A/ B update systems. I'm not
>> saying that it has to be easy for people like us, I'm just chiming in
>> with the fact that U-Boot isn't always the best answer for all use cases.
>
>   What I had in mind is: _removing_ U-Boot is actually quite easy, you
> just need to change two lines in the config.txt (AFAIU). Thus, it makes
> sense to me that our defconfigs should all have U-Boot, and the
> readme.txt can explain how to build without U-Boot.
That makes sense to me, maintaining defconfigs for a full matrix of
board type/mainline or downstream kernel/u-boot or not doesn't seem
practical. Maybe it'd make sense to have a standard, and one example for
each of the possible deviations?

And maybe mention possible pitfalls in the readme as far as known, e.g.
I recently bumped into different kernel config options to make the
microSD slot on Pi Zero 2W work (result: kernel can't find rootfs if you
switch between downstream and mainline and reuse the config).

Best regards,
Fiona