support of arm64 architecture

[Sascha Hauer]

Hi Raphaël,

On Fri, Apr 08, 2016 at 02:01:21PM +0200, Raphaël Poggi wrote:
> Hi all,
> 
> I am working on porting barebox on arm64 architecture.
> 
> So I have some questions about it:
> 
> - Is there any interest for barebox to support this architecture ?

Definitely, yes.

> 
> - My port is running at EL1 for the moment, does the bootloader have
> to run at EL3 ? If yes, do you have hint to achieve this ?
>       I think UEFI is running at EL3, but I am confused about that,
> what is the difference between UEFI and barebox ? Are they both
> booloader ? (I guess it is a "noob" question :/)

UEFI is an interface to the firmware whereas barebox is a firmware. We
could implement a UEFI interface for barebox (the U-Boot guys already
did this). Also barebox can run on top of firmware with a (U)Efi
interface.

> 
> - I have some issues with malloc, when I use tlsf all malloc failed,
> but not with dlmalloc implementation, do you have an idea about this ?

Do you have TLSF_64BIT defined? You may have defined it automatically
when you have CONFIG_64BIT defined, but if not tlsf malloc will not
work.

> 
> 
> At the moment the current limitations of my port are :
>      - MMU not implemented
>      - barebox running at EL1
>      - barebox env not working
>      - only test on qemu
> 
> If you want to test it:
> https://github.com/raphui/barebox/tree/dev/armv8a_cleanup

>From a first look it the arm64 code looks very familiar. Do you think we
could merge it into the arm architecture rather than creating a new
architecture?

I don't know in which exception level barebox should finally run in, but
I don't think that's a showstopper.

Sascha

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