[U-Boot] [PATCH v7 1/2] armv8: Support loading 32-bit OS in AArch32 execution state

[Alexander Graf]

On 04/11/2016 16:43, york sun wrote:
> On 11/04/2016 09:32 AM, Ryan Harkin wrote:
>>>>
>>>> Yes, with the attached patch on top of your original 2 patches,
>>>> everything works again.  I tested on FVP Foundation and AEMv8 models
>>>> and Juno R0, R1 and R2.
>>>>
>>>> I don't think it would be good to stack these three patches the way
>>>> they are presented in the upstream tree because it would not be
>>>> bisect-able.  Some re-work or re-ordering would be needed.
>>>>
>>>> Note: I haven't attempted to understand what any of this code is
>>>> doing, I'm just testing it with my standard boot flow to make sure
>>>> nothing is broken for me.
>>>
>>> Ryan,
>>>
>>> I support Alison's patch order for her 32-bit patch sets. This feature
>>> doesn't exist before her first set. It is functional if you run U-Boot
>>> at EL3 after the first patch.
>>
>> Which I don't do.  I follow the boot flow recommended by ARM and it
>> doesn't work for that setup, which I don't think is the right thing to
>> do.
>>
>>
>>> It gets EL2 working after the 2nd set. If
>>> there is room to clarify in the commit message, please kindly suggest.
>>>
>>
>> Well, I'm not the maintainer of the tree, but I wouldn't want to have
>> a tree that wasn't bootable at any point in the patch sequence.
>> That's generally unacceptable on most projects I work on.  Keeping the
>> tree bisect-able to prove which commit caused a problem is considered
>> to be a valuable tool.
>>
>
> Ryan,
>
> Thanks for sharing your concern. I support git-bisect. It is valuable,
> no doubt. Let me try to understand the issue here. Without Alison's
> patches, everything boots OK. With her first set, does something break?

Yes, with the patches booting 64bit Linux with U-Boot running in EL2 
breaks according to Ryan.

> My understanding is 32-bit OS can boot. If existing 64-bit OS fails,
> then she needs to fix it.

That's his point :). And I concur.

(btw, you guys really should start thinking about following the ARM 
recommended boot model. It's pretty cumbersome to do everything 
different just for NXP)

Alex