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Re: Help! got stuck on the DS2100/3100

To: linux-mips@fnet.fr
Subject: Re: Help! got stuck on the DS2100/3100
From: Stu Allen <stu@cinops.xerox.com>
Date: Sun, 7 Sep 1997 21:59:09 -0400 (EDT)
Cc: linux-mips@fnet.fr
In-reply-to: <Pine.LNX.3.91.970905085425.12777A-100000@lehr.chem.tu-berlin.de> from Frieder Streffer at "Sep 5, 97 09:29:07 am"
Hi Frieder!

> probably the only problem you have is that Paul did forget to copy the 
> execption handle to the correct location. There were some Mail's around 
> just after ther e release of Paul's "linux-2.1.14.2.dec" concerning that 
> topic. I do not have the source here but it was something like
> 
>   memcopy(KSEG0+0x80, execpt_vec0, 0x80);
> 
> just in the beginning of get_pmax_memorysize of arch/mips/dec/decstation.c.
> May be you can find the original mail of Paul, or I will post the correct 
> statment tomorrow.

OK.  (Got your other message with the real statement.)  Well, I'm
reinstalling the OS on my NFS server tonight, so unfortunately I can do any
recompiling right now :-(  But I _did_ make much progress last night!

I ended up just hard-coding the memory size for my box (a whopping 8 meg!)
and then I pressed on.  Couple other things I found:

1)  In linux/arch/mips/dec/decstation.c, there is a call to prom_getenv to
get the console type.  As is implied by the comment directly above, the 
environment variable is different on the 5100 (and 2100/3100 too, I assume) -
it is "console" not "osconsole".  This returns "0" on my box, so I modified
the if/then/else below to set serial console for this value.

2)  Hmm.  I guess this should have been 1, since it appears first - but I
think I found it second!  Anyways, there is a call to register_console which
passed "rex_printf".  This lead to an immediate core dump the first time
printk was called (at the end of boot.S).  Once I changed this to prom_printf
I was rewarded with a bunch more of the boot sequence!  Now I get to the
loop delay calibration, where the machine hangs.

Can anyone give me a quick explanation of how this routine works, and why
it _isn't_ working?  I notice that just above there is a note requesting
that someone "write the time init code for the DECstation" -- is this why
it isn't working (because the clock interrupt isn't being serviced?)

This is fun!
-- 
Stu Allen             Phone: (716) 231-0073
EDS / GNS             Internet: stu@cinops.xerox.com

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