[U-Boot-Users] Sequence of Xilinx ML403/PPC

Wolfgang Denk wd at denx.de
Fri Jan 27 11:13:00 CET 2006

In message <43D9E2AB.5020108 at sbcglobal.net> you wrote:
> 3. U-boot Scripting occurs which copies Linux OS from flash into where?
>  Next highest or lowest portion of RAM?  Is it dependent on whether

On PowerPC the kernel starts always at physical address 0x0000 in RAM ==> lowest address.

> dual-stage vmlinux.initrd or single-stage vmlinux is used or not?

With U-Boot you use neither vmlinux.initrd nor  vmlinux  but  uImage,
eventually  with  a  separate ramdisk image, or eventually a combined
"multi-file image".

> At power-up, with U-Boot 1.1.4 being unusually low-RAM-based before
> starting up (instead of executing straight out of ROM), I noticed that
> despite being relocated to MONITOR (higher RAM) region, the PIT
> exception vector appears to be active in 0000_10c0-ish.

U-Boot installs it's own exception vectors.

> Despite this RAM-to-RAM relocation, this "mtest" clobbering of the
> 0000_10C0 region caused Machine Exception error whenever I attempt to

Yes, of course. What else do you expect when you overwrite active code?

> perform memory test over this supposedly former exception vector region.

Former and current in your case.

>  I thought that the objective during U-boot relocation was to ensure a
> completely discontinued RAM region (formerly occupied by U-boot
> ROM-based session).

I cannot parse this. Pleasee see the README  for  the  U-Boot  memory
layout. It's all written there. Just RTFM.

> 1.  Where do I go from there with regard to the 0000_1000
> (PIT_EXCEPTION).  Isn't the PIT specific to Motorola 8xx-series (this
> here is a PPC 405).  What exception did the lib_ppc/start.S/trap_init()
> exactly skipped? Skipped an exception mentioned vaguely in this source
> code vaguely.  Do I need to tweak the trap_init() some more to relocate
> these untransfered exception vectors into the high MONITOR region?

I really don't understand the question, nor your concerns.  The  code
is working find on many, many boards. No tweaking isnecessary.

> 2. And lastly, do I go high or low for Linux OS?

I tend to keep my feet on the ground; no idea what you do.

What exactly is the question? "go high"??? Can't parse that.

Best regards,

Wolfgang Denk

Software Engineering:  Embedded and Realtime Systems,  Embedded Linux
Phone: (+49)-8142-66989-10 Fax: (+49)-8142-66989-80 Email: wd at denx.de
Human beings were created by water to transport it uphill.

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