Port Linux w/ mbxboot to PPCBoot system

Port Linux w/ mbxboot to PPCBoot system

[Jessica Chen]

Hi,



     I am new to embedded system, I am studying ppcboot-1.1.5 and linux
kernel-2.4.4 that comes with an mpc852 base board, we want to modify it in
the future.  In the build process, they use the zImage.initrd
(arch/ppc/mbxboot/zvmlinux.initrd) instead of the raw Linux kernel image
(arch/ppc/coffboot/vmlinux.gz) + separate initrd which is the way README
file suggested.



My question is:

since ppcboot is already running, what happens when I boot the kernel that
has old boot loader code in arch/ppc/mbxboot?  Will some parameters be
overwritten?  If not, why?



     I am very tempted to follow the README to re-build the kernel with only
vmlinux.gz and port it, but I don't want to create any un-recoverable
results.  So I am here to seek advice, maybe this is something obvious to
many people.



Thanks in advance,





Jessica Chen

Re: Port Linux w/ mbxboot to PPCBoot system

[Wolfgang Denk]

Dear Jessica,

in message <002701c6601f$15b27f30$9afea8c0@tcdomain.com> you wrote:
> 
>      I am new to embedded system, I am studying ppcboot-1.1.5 and linux
> kernel-2.4.4 that comes with an mpc852 base board, we want to modify it in

Both PPCBoot and Linux 2.4.4 are *hoplessly* obsolete. It may  be  ok
to study this to understand the workings, but please don't even dream
of using it for any current work.

> the future.  In the build process, they use the zImage.initrd
> (arch/ppc/mbxboot/zvmlinux.initrd) instead of the raw Linux kernel image

Somebody didn't know what he was doing, it seems.

> since ppcboot is already running, what happens when I boot the kernel that
> has old boot loader code in arch/ppc/mbxboot?  Will some parameters be
> overwritten?  If not, why?

The Linux bootstrap loader code (arch/ppc/mbxboot)  will  ignore  the
parameteres  passed  by  U-Boot,  will set up is own (hardwired), and
duplicate some of the things that PPCboot did or would do.

>      I am very tempted to follow the README to re-build the kernel with only
> vmlinux.gz and port it, but I don't want to create any un-recoverable
> results.  So I am here to seek advice, maybe this is something obvious to
> many people.

Don't change anything. Look at it, then drop it. Start using  current
code, i. e. a recent version of U-Boot and a recent Linux kernel.

Best regards,

Wolfgang Denk

-- 
Software Engineering:  Embedded and Realtime Systems,  Embedded Linux
Phone: (+49)-8142-66989-10 Fax: (+49)-8142-66989-80 Email: wd@denx.de
Good morning. This is the telephone company. Due  to  repairs,  we're
giving  you  advance notice that your service will be cut off indefi-
nitely at ten o'clock. That's two minutes from now.

Re: Port Linux w/ mbxboot to PPCBoot system

[Jessica Chen]

Thank you for your reply Wolfgang!

In u-boot-1.1.4 README "Where we come from" section, it says u-boot "provide
extended interface to Linux boot loader".  Does it mean that there is still
some sort of boot loader in arch/ppc/coffboot/vmlinux.gz ?  If yes, when
does it start?  Does it boot the kernel?

To build u-boot, I will need to get the manual for MPC852 and check the
configurations in include/configs/TQM860L.h file.

I am trying to find the machine specific header file in linux-2.4.25
(include/asm-ppc/tqm8xx.h file in linux-2.4.4) which should have the same
definition of structure bd_info as in include/asm-ppc/u-boot.h.  And you
recommend using linux-2.4 instead of linux-2.6 on your website.

So am I heading the right directions here?  Because the u-boot README
doesn't have the new directories and filenames, I am a little confused.



Thanks again,

Jessica



> >      I am new to embedded system, I am studying ppcboot-1.1.5 and linux
> > kernel-2.4.4 that comes with an mpc852 base board, we want to modify it
in
>
> Both PPCBoot and Linux 2.4.4 are *hoplessly* obsolete. It may  be  ok
> to study this to understand the workings, but please don't even dream
> of using it for any current work.
>
> > the future.  In the build process, they use the zImage.initrd
> > (arch/ppc/mbxboot/zvmlinux.initrd) instead of the raw Linux kernel image
>
> Somebody didn't know what he was doing, it seems.
>
> > since ppcboot is already running, what happens when I boot the kernel
that
> > has old boot loader code in arch/ppc/mbxboot?  Will some parameters be
> > overwritten?  If not, why?
>
> The Linux bootstrap loader code (arch/ppc/mbxboot)  will  ignore  the
> parameteres  passed  by  U-Boot,  will set up is own (hardwired), and
> duplicate some of the things that PPCboot did or would do.
>
> >      I am very tempted to follow the README to re-build the kernel with
only
> > vmlinux.gz and port it, but I don't want to create any un-recoverable
> > results.  So I am here to seek advice, maybe this is something obvious
to
> > many people.
>
> Don't change anything. Look at it, then drop it. Start using  current
> code, i. e. a recent version of U-Boot and a recent Linux kernel.