[oe] Request for Help : Porting linux to custom x86 (AMD SC520) board

[Graeme Russ]

On Wed, Jan 27, 2010 at 10:19 AM, Paul Menzel
<paulepanter at users.sourceforge.net> wrote:
> Dear Graeme,
>
>
> Am Mittwoch, den 27.01.2010, 09:52 +1100 schrieb Graeme Russ:
>
> […]
>
>> To date, I have been doing a lot of work getting a functionaly stable
>> boot loader up and running. I ended up choosing U-Boot because it
>> appeared to be the most open of all mature boot loaders.
>
> coreboot also seems to support some boards with the AMD SC520 [1].

Thanks, I will have a look but I think Coreboot is geared more towards
a BIOS replacement for mainstream PC motherboards? I am working an a
real embedded (custom) board.

>
>> U-Boot had a
>> very old and incomplete x86 / sc520 port which I have put a lot of
>> work into maturing and stabalising. Nearly all of this work to date
>> has been fed back into the U-Boot source (you can track my progress on
>> their mailing list). I am now at the point where I feel confident that
>> U-Boot can launch a Linux kernel.
>>
>> The problem is - I don't know how to proceed. It looks like PPC and
>> ARM have very strong embedded followings and there is a lot of
>> information out there for people that want to get an embedded kernel
>> running on these platforms. x86 seems to be a very poor cousin.
>>
>> So far, I have cloned the 2.6.33 linux kernel Git repository and
>> configured and compiled the kernel.
>
> Where does Linux stop if you try to boot it?

I haven't actually attempted to boot the kernel yet - mostly because
I don't really know how. I have confirmed in U-Boot the ability to
execute a stand-alone application loaded at a given address in
memory (U-Boot has a 'Hello World' example that I have managed to
get running). The problem is, U-Boot runs in x86 protected mode, so
I would assume U-Boot needs to drop out of protected mode before
starting up the kernel in order to allow the kernel to setup the
descriptor tables as required.

>
>> I think my first question is about how to get hardware information
>> (RAM layout etc) to the Kernel. It looks like the initial U-Boot
>> implementation setup a very basic BIOS which emulated part of the
>> traditional PC BIOS. Surely there is a better way to do this. Is the
>> Simple Firmware Interface an option?
>>
>> Any help would be greatly appreciated.
>
> Sorry I cannot help further. Should not the guys on the U-Boot list know
> more about how to get U-Boot and Linux running on a x86 system?

I have asked this same question on the U-Boot mailing list. Unfortunately,
U-Boot has more traditionally been geared towards PPC and ARM. The only
person I know of that ever got U-Boot to boot an x86 kernel has not been
active on the U-Boot mailing list for a number of years.

>
>
> Thanks,
>
> Paul
>
>
> [1] http://www.coreboot.org/Supported_Motherboards
>

Thanks,

Graeme