Re: mem= flag behaviour

Dear David,

in message [ref] you wrote:

I'm trying to keep a small trace buffer over re-boots
of linux from ppcboot, so give a mem=31M flag to linux
kernel.  Yet by the time linux is up, it has overwritten
that memory anyway..   PPCBOOT is properly leaving it
be (with PRAM feature) and correct arg. goes to kernel..

Let me guess... you boot with a ramdisk image?

After 'reboot' from linux, the memory contents of
the last meg are still valid (in ppcboot) but by the time linux
is back up, the region has been trashed.  Why?

If you use a ramdisk image, you should read the documentation for the
"initrd_high" environment variable in
http://www.denx.de/doc/TQM8xxL/ppcboot.html#PPCBOOT-VARIABLES
(or in the PPCBoot README).

Help, please.  How to prevent linux from talking to
that memory region during bootup?

Linux does not use the memory beyond what you tell it with "mem=".

Hope this helps...

[BTW: your CD is in the mail.]

Wolfgang Denk

--
Software Engineering:  Embedded and Realtime Systems,  Embedded Linux
Phone: (+49)-8142-4596-87  Fax: (+49)-8142-4596-88  Email: wd@denx.de
Machines take me by surprise with great frequency.      - Alan Turing

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