linux ppc boot parameters R3, R5

linux ppc boot parameters R3, R5

[ramanathan G A]

Hi All,

I am trying to boot an MPC8260 board with Linux 2.4.4. I cross
compiled the kernel for PPC using GCC 3.2 and prepared a
'zImage.initrd'. Since the board has a working bootloader for
pSOS, I decide to use the same with minimum modifications to suite
for loading the linux image.

Going through the literature, I could understand that the linux
image is expecting TWO arguments; in registers R3 and R5.
R3 - Pointer to board information structure
R5 - Open Firmware Data. (??)

Now, I have to modify my boot loader in order to boot linux
image.
The boot loader is supposed to do the basic initialization of the
processor, load the image on to the RAM from flash and give
control to the image entry point.

Could some one help me giving pointers to what is meant by this R5
parameter (Open Firmware Data)? What is the significance? Can I
avoid this parameter and proceed?
(I am stuck at this point.)

Any suggestions to improve the situation is welcome.

Thank you.

Rgds,
Ramanathan G A


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RE: linux ppc boot parameters R3, R5

[Claus Gindhart]

Hi Ramanathan,
The Open Firmware Data is provided, if You use the Open Firmware Bootloader.
For every proprietary BootLoader, you can proceed without this.
Please pay some attention for the have_of flag, which is used in some places
of the ppc tree of the kernel. You have to ensure, that have_of is always
set to FALSE for your board.

-----Original Message-----
From: ramanathan G A [mailto:ramanathan_ga@rediffmail.com]
Sent: Mittwoch, 14. Mai 2003 16:36
To: linuxppc-embedded@lists.linuxppc.org
Subject: linux ppc boot parameters R3, R5



Hi All,

I am trying to boot an MPC8260 board with Linux 2.4.4. I cross
compiled the kernel for PPC using GCC 3.2 and prepared a
'zImage.initrd'. Since the board has a working bootloader for
pSOS, I decide to use the same with minimum modifications to suite
for loading the linux image.

Going through the literature, I could understand that the linux
image is expecting TWO arguments; in registers R3 and R5.
R3 - Pointer to board information structure
R5 - Open Firmware Data. (??)

Now, I have to modify my boot loader in order to boot linux
image.
The boot loader is supposed to do the basic initialization of the
processor, load the image on to the RAM from flash and give
control to the image entry point.

Could some one help me giving pointers to what is meant by this R5
parameter (Open Firmware Data)? What is the significance? Can I
avoid this parameter and proceed?
(I am stuck at this point.)

Any suggestions to improve the situation is welcome.

Thank you.

Rgds,
Ramanathan G A


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Re: linux ppc boot parameters R3, R5

[Gary Thomas]

On Wed, 2003-05-14 at 08:36, ramanathan G A wrote:
> Hi All,
>
> I am trying to boot an MPC8260 board with Linux 2.4.4. I cross
> compiled the kernel for PPC using GCC 3.2 and prepared a
> 'zImage.initrd'. Since the board has a working bootloader for
> pSOS, I decide to use the same with minimum modifications to suite
> for loading the linux image.
>
> Going through the literature, I could understand that the linux
> image is expecting TWO arguments; in registers R3 and R5.
> R3 - Pointer to board information structure
> R5 - Open Firmware Data. (??)
>
> Now, I have to modify my boot loader in order to boot linux
> image.
> The boot loader is supposed to do the basic initialization of the
> processor, load the image on to the RAM from flash and give
> control to the image entry point.
>
> Could some one help me giving pointers to what is meant by this R5
> parameter (Open Firmware Data)? What is the significance? Can I
> avoid this parameter and proceed?
> (I am stuck at this point.)
>
> Any suggestions to improve the situation is welcome.
>

That pointer is only important for systems which utilize Open Firmware
booting (like the Apple boxes).  It's not used [AFAIK] on embedded
devices like an 8260.

Also, the bootstrap on many platforms does not provide the board data.
In this case, you can just "hardwire" the parameters.  Look at the
code in "arch/ppc/boot/simple/embed_config.c" to see how it's done.

--
Gary Thomas <gary@mlbassoc.com>
MLB Associates


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