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

[Simon Schwarz]

Dear Wolfgang Denk,

a comment from your side would be nice - in what approach do you see
the best chance for getting it into mainline?

Regards
Simon

2011/7/1 Simon Schwarz <simonschwarzcor at googlemail.com>:
> 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
>