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Deskstation progress and questions...

To: Linux/MIPS Mailing List <>
Subject: Deskstation progress and questions...
From: Warner Losh <>
Date: Wed, 07 Feb 1996 22:36:59 -0700
I've managed to get to my first "out_p" statement!  I'm hanging there
because mipsconfig.h defines PORT_BASE to be 0xe2000000.  On the
Dekstation, this needs to be 0xb0000000, so I've hacked mipsconfig.h
and am rebuilding.  Ideally, we'd have some way to do this that didn't
require a recompile of the whole kernel, but it would also have to be
fast, and I'm not sure that fast and configurable are both attainable
here.  For the moment, I'm just punting and putting the ifdef in...

However, I couldn't help notice some comments in mipsconfig.h that I
need to ask some questions about...  Since this might later prove
useful to other porters, I thought I'd ask them here...

TLBMAP is defined to be 0xe4000000.  Where does one find what this
address is for one's machine? I don't think I have physical memory at
0xexxxxxxx.  Is this a magic address, or can it be anywhere?  Looking
at the MIPS User's Manual seems to indicate to me that this is
something other than TLB, which lives in the CP0 register space, so
this must be something else...  What, I'm not sure.  Have I overlooked
something silly in the MUM?

TLB_ROOT is defined to be 0xe4390000.  (or more accurrately, (TLBMAP +
(TLBMAP >> (12 - 2)))).  Once I find TLBMAP, then I'll have this, I'm
sure...  Just thought I'd confirm this.

Grepping the sources, TLBMAP shows up in
include/asm-mips/mipsconfig.h, arch/mips/kernel{head,r4xx0}.S  From
looking at the code there, and the MUM, it would appear that kseg3 is
being setup to handle the TLB misses.  Hmmm, looking at r4xx0.S it
appears that it is reloading the TLB from the PTE array that lives at
TLBMAP.  I don't see where this gets created, however.  What am I

Thanks for any help you might be able to render...


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