Subject: Re: "pmap_unwire: wiring ... didn't change!"
To: Alex Pelts <email@example.com>
From: Simon Burge <firstname.lastname@example.org>
Date: 03/07/2005 11:58:57
"Alex Pelts" wrote:
> Some of the processors will allow you to make it write-trough instead of
> write-back. I am not sure if the cube is of that variety but I think it
> is not. Although I dont know if that would help.
> The closest thing to disabling cache would be to allocate buffers for
> suspected operation from Kseg1 segment which is uncached. Unfortunately
> I dont think it is possible as this memory also unmapped which would
> kill its use in user space. Although it might be possible to setup some
> specific test with hacked kernel just to find this bug.
> Is that a bad idea ?
Thinking about this a little, I guess we could just map all TLB pages
uncached if we want to mostly disable caches. Could someone try
changing the this line in sys/arch/mips/include/mips3_pte.h (around
#define MIPS3_DEFAULT_PG_CACHED MIPS3_CCA_TO_PG(3)
#define MIPS3_DEFAULT_PG_CACHED MIPS3_CCA_TO_PG(2)
For the RM5200, using 1 or 2 will also select write-through modes
so that may well be worth trying too.
Simon Burge <email@example.com>
NetBSD Support and Service: http://www.wasabisystems.com/