[U-Boot] U-Boot bring-up x86 Baytrail/ multiboot2 specification

[Bin Meng]

Hi Mathias,

On Tue, Nov 20, 2018 at 9:26 PM <Mathias.Boos at sew-eurodrive.de> wrote:
>
> Hi all,
>
> thanks for your quick answer.
> I wanted to test the u-boot option with coreboot payload on x86 first.
> So I built coreboot and did a target download with 2 dead devices at the end.

Does coreboot already support your board? If not, you probably have
risks bricking it.

> I am just about to restore these devices (customized ones) with some difficulties in doing this ;-)...
>
> When I have restored the devices I will continue my u-boot attempts.
>
> I will still have another x86 board soon with Apollo Lake E3950. The board vendor told me
> that there is really no way to use u-boot as BIOS replacement. Has anyone experience with u-boot and Apollo Lake?
>

What the vendor told you is not true. U-Boot of course can be used as
the BIOS replacement, as long as it has all the necessary bits to
initialize the chipset. For Apollo Lake, Intel FSP can be used to do
the chipset initialization. I have an Apollo Lake CRB at my hand for
quite a long time, but have not been allocated any time working on
U-Boot porting. If you can have a try, welcome!

> @ Bin and Simon: do you have any idea if u-boot has multiboot2 support?
> https://www.gnu.org/software/grub/manual/multiboot2/multiboot.html
>

In arch/x86/cpu/start.S, there is a comment regarding to this:

/* Add a multiboot header so U-Boot can be loaded by GRUB2 */

Per what the comment says, I suspect U-Boot can be loaded by grub via
the multiboot protocol. However I personally have not tried this yet.

PS: please avoid top-posting next time.

[snip]

Regards,
Bin