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Re: BootLoader on MIPS

To: "Y.H. Ku" <iskoo@ms45.hinet.net>
Subject: Re: BootLoader on MIPS
From: Jun Sun <jsun@mvista.com>
Date: Tue, 26 Mar 2002 10:08:36 -0800
Cc: Marc Karasek <marc_karasek@ivivity.com>, linux-mips@oss.sgi.com
References: <NGBBILOAMLLIJMLIOCADOENICCAA.iskoo@ms45.hinet.net>
Sender: owner-linux-mips@oss.sgi.com
User-agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:0.9.4) Gecko/20011126 Netscape6/6.2.1
Y.H. Ku wrote:

> Ya,
> I have traced the PMON code (www.carmel.com/pmon/) with NEC DDB5476 board 
> (linux package from Montavista),
> (LSI Logic' Software Support Package for MIPS processors version 5.3.33)
> 
> However, though it seem clear that function "_go" of pmon/head.S transfer 
> control to client program
> by "j k0" (a exception)
> BUT I do not understand what information tha PMON transfer to LINUX-MIPS 
> KERNEL
> I found the KERNEL's entry is "kernel_entry" of ~arch/mips/kernel/head.S.
> But, I can not find any information just like "board information" be 
> transferred well.
> where is it!?


"board information" is not transferred to kernel.  However, parameters you
pass (as in "go <param>") are passed in as standard C main argument style.
These are processed in arch/mips/ddb5xxx/common/prom.c file, i.e., held in a0,
a1 registers.

> using sp register with "j k0" command?


No. sp is not meaningful when kernel starts.


> where is the memory setting be transferred?


system ram size?  It is hardcode in ddb5476 code.  See
include/asm/ddb5xxx/ddb5476.h file.


> What MIPS LINUX needed!?


I thought you have montavista linux (probably hardhat 2.0?).


> (PPCBOOT to PPC-LINUX is clear with a board_info struct, initrd_start and 
> initrd_end ... and work well...
> 


PPC booting is more regular than MIPS in general.  So they have a more uniform
 bootup process and structure.  MIPS have a lot of vendors who are usually
very creative.

Jun



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