Preliminary doubts

[John Praveen]

Hi,
                 I have the custom board (geode
sc1200) with some external peripherals.  I will have
to have my BIOS program, linux kernel and specific
application program in my Flash memory. I have hard
disk only for storing files.

My Flash memory is of 32 Mbits and
SDRAM 32MBytes.

I want to use LinuxBios. I build it
for nano mainboard. But still I have many doubts. In
normal BIOS, we will say the bios program to load the
bootloader from hard disk into location 0000:7C00.

What part of the program in Linuxbios
will bring my linux kernel image from Flash into
SDRAM?

Is any options or something to be
included in the configuration file to say to boot from
Flash memory?

In my embedded device the Flash
memory is mapped to physical address 00000h to
3FFFFFh. So at what location should i place the
linuxbios romimage and linux kernel image in my Flash
memory?

Where shall my application program be
placed in Flash? I hope I should have a filesystem. Is
the MTD meant for the filesystem?

Please help me.

Thanks in advance.

Regards,
John.

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[SONE Takeshi]

Although luck of documentation is the problem the project faces,
the source and the list archive are always open to people.
If you investigate them yourself first, then ask,
you will get more helpful response.

On Sat, Aug 09, 2003 at 11:33:48PM -0700, John Praveen wrote:
>              What part of the program in Linuxbios
>
> will bring my linux kernel image from Flash into
> SDRAM?

freebios/src/lib/elfboot.c

There is also a old linux-only loader, linuxbiosmain.
"grep -r" is your friend.
>              Is any options or something to be
>
> included in the configuration file to say to boot from
> Flash memory?

USE_GENERIC_ROM
>              In my embedded device the Flash
>
> memory is mapped to physical address 00000h to
> 3FFFFFh. So at what location should i place the
> linuxbios romimage and linux kernel image in my Flash
> memory?

I have my doubt here.
AFAIK, every x86 system has its ROM at the top of
address space (eg. if ROM is 256K, it's at 0xfffc0000 = 4G-256K),
since x86 starts execution at last 16 byte of address space (0xfffffff0).

Does your board have another ROM at here?
Or the flash is shadowed/aliased to here?

Also, if the bottom 4MB is ROM and it can't be remapped,
you will have to modify the kernel as well as LinuxBIOS.
Convenional x86 systems has 640KB of RAM
at bottom (from address 0), then 384KB of hole for legacy BIOS and I/O,
then rest of RAM from address 1M.
x86 port of Linux and LinuxBIOS is written for such system.
>             Where shall my application program be
>
> placed in Flash? I hope I should have a filesystem. Is
> the MTD meant for the filesystem?

I'm not sure but if your flash will be used for BIOS, you most certainly 
have to use it as a raw storage.
You can put the LinuxBIOS, Linux kernel, and initrd there.
Your application code will be in the initrd.

[Gregg C Levine]

Hello from Gregg C Levine
Are we discussing the strangeness behind the Geode here? If I remember
correctly, everything about that device is documented. Even the boards
that NSC developed for us to try out, before committing to a bigger
board were documented. About the only thing that wasn't, were the
binary only drivers, and loaders, that they supplied. They did give
use instructions, but that was all. As our correspondent in Japan
says, investigate the source, the lists, everything. When in doubt
ask. So far you're heading in the right direction with this. 
-------------------
Gregg C Levine [e-mail]
------------------------------------------------------------
"The Force will be with you...Always." Obi-Wan Kenobi
"Use the Force, Luke."  Obi-Wan Kenobi
(This company dedicates this E-Mail to General Obi-Wan Kenobi )
(This company dedicates this E-Mail to Master Yoda )
> -----Original Message-----
> From: [e-mail] [mailto:linuxbios-
> [e-mail]] On Behalf Of SONE Takeshi
> Sent: Sunday, August 10, 2003 3:32 PM
> To: John Praveen
> Cc: [e-mail]
> Subject: Re: Preliminary doubts
>
> Although luck of documentation is the problem the project faces,
> the source and the list archive are always open to people.
> If you investigate them yourself first, then ask,
> you will get more helpful response.
>
> On Sat, Aug 09, 2003 at 11:33:48PM -0700, John Praveen wrote:
> >              What part of the program in Linuxbios
> >
> > will bring my linux kernel image from Flash into
> > SDRAM?
>
> freebios/src/lib/elfboot.c
>
> There is also a old linux-only loader, linuxbiosmain.
> "grep -r" is your friend.
> >              Is any options or something to be
> >
> > included in the configuration file to say to boot from
> > Flash memory?
>
> USE_GENERIC_ROM
> >              In my embedded device the Flash
> >
> > memory is mapped to physical address 00000h to
> > 3FFFFFh. So at what location should i place the
> > linuxbios romimage and linux kernel image in my Flash
> > memory?
>
> I have my doubt here.
> AFAIK, every x86 system has its ROM at the top of
> address space (eg. if ROM is 256K, it's at 0xfffc0000 = 4G-256K),
> since x86 starts execution at last 16 byte of address space

(0xfffffff0).
> Does your board have another ROM at here?
> Or the flash is shadowed/aliased to here?
>
> Also, if the bottom 4MB is ROM and it can't be remapped,
> you will have to modify the kernel as well as LinuxBIOS.
> Convenional x86 systems has 640KB of RAM
> at bottom (from address 0), then 384KB of hole for legacy BIOS and

I/O,
> then rest of RAM from address 1M.
> x86 port of Linux and LinuxBIOS is written for such system.
> >             Where shall my application program be
> >
> > placed in Flash? I hope I should have a filesystem. Is
> > the MTD meant for the filesystem?
>
> I'm not sure but if your flash will be used for BIOS, you most

certainly
> have to use it as a raw storage.
> You can put the LinuxBIOS, Linux kernel, and initrd there.
> Your application code will be in the initrd.