Subject: Re: Need help Understanding initial memory conditions.

From: "David H. Lynch Jr." <[email-masked]>
Date: Tue, 18 Oct 2005 15:15:14 -0400

Kalle Pokki wrote:

> David H. Lynch Jr wrote:
>
>>    What exactly is the minimal startup system state the Linux 2.6.13 
>> Kernel expects ?
>
>
> It's pretty hard to describe the system state fully, as there are so 
> many registers it may depend on. However, I can point out a few things 
> from your setup:
>
> 1. Put RAM to 0x0000000 and flash to some location it mirrors to your 
> boot vector. Linux always expects your physical memory to be at zero. 
> It is then mapped to virtual address 0xC0000000.

    In both this list and elsewhere I have seen several references to 
the difficulty setting up Linux with a physical RAM base other than 0x0. 
I was hoping that I could bypass that by re-arranging physical memory 
using the BAT's or MMU.
I am gathering that while this is possible, that it not sufficient. That 
if memory is re-arranged after power-on it has to be done by something 
Linux is not aware of.

>
> 2. You don't need to have MMU enabled.

    There is a god. I am a compitent developer with lots of low level 
experience, but I have thus far completely missed out on both PPC 
assembler and memory management.

>
> 3. Make sure your boot arguments are passed properly to the kernel. 
> This includes the settings in registers r3 ... r7 and the bd_info 
> structure . There are many variants of that structure, make sure you 
> use the same ones in the boot loader and in Linux.

    That I should have no problem with.

Thank You very much