[U-Boot] RFC: Alternative boot_jump_linux() function

[Ramon Fried]

On Thu, May 17, 2018 at 2:48 PM, Peter Robinson <pbrobinson at gmail.com> wrote:
> Hi,
>
>> I'm currently working on snapdragon bootloader support and in the
>> particular case where U-boot is running in Aarch32 and the kernel is
>> Aarch64 the specific implementation is to jump to Linux through SCM
>> call.
>
> I seem to remember the Allwinner A64 Pine64 starts in 32 bit mode and
> switches too so you might get some ideas from there or the maintainer
> might have some suggestions.
Hi Peter.
Thanks for the tip.

I looked at the code, it appears that the Pine64 starts in 32bit SPL and jumps
to U-boot in 64bit mode.
This is done in a way which is not compatible with Snapdragons.
Although it's possible to implement Snapdragon with SPL, but I think it's an
overhead and I generally prefer just to run U-boot completely in 32bit mode.

Thanks,
Ramon.

>
>> I try to find the best possible way to provide an alternative boot function.
>> Adding #ifdef ARCH_SNAPDRAGON will just be too specific in
>> arm/lib/bootm.c in my opinion and I'm thinking of introducing kind of
>> a callback function in gd. that if exists will jump there instead of
>> executing boot_jump_linux().
>>
>> What do you think ?
>>
>> Waiting for your thoughts on the subject.
>>
>> Warm regards,
>> Ramon.
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