[U-Boot] U-boot SPL direct Linux boot

[Simon Schwarz]

Thanks for your feedback Igor!

2011/7/1 Igor Grinberg <grinberg at compulab.co.il>:
> On 07/01/11 12:17, Simon Schwarz wrote:
>> Ok, topic ATAGS:
>> I see three ways doing ATAGS init for SPL:
>> 1. use bootm.c which means init bd correctly and add a bunch of #ifdef
>> CONFIG_PRELOADER to it - maybe also to some others i don't have on the
>> radar yet.
>
> While this is not clean, it might work good.
>
>> 2. Have ATAGS config in board config file and init it at compile time
>
> This is a problematic approach, because memory size, board revision,
> serial number and may be some others are only known in runtime.
>
>> 3. Doing it like Heiko and copy the ATAGS config done by u-boot
>
> This one is probably the most clean way.
>

The problem with approach 3 is that you need to copy the ATAGS image.
Is there a way to do this without a debugger? If yes it really could
be an alternative. If ATAGS and Kernel can be reflashed you can update
the kernel without a bootloader update (That's the main reason why i
switched to 1).

> Regarding the device tree on ARM, it is still not fully functional.
> Nevertheless, currently there is an attempt ([1] and [2]) to make kernel
> work with both, device tree and ATAGS and if I understood correctly,
> the ATAGS will have precedence over the DT, so closed source
> boot loaders will still work.
>
> [1] - http://www.spinics.net/lists/arm-kernel/msg128172.html
> [2] - http://www.spinics.net/lists/arm-kernel/msg129270.html

So, IMHO an ATAGS implementation for now is the better choice - a DT
patch then is, depending on the approach, not a big problem.

Regards
Simon