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Re: Going over 512M of memory

To: Alex Gonzalez <linux-mips@packetvision.com>
Subject: Re: Going over 512M of memory
From: Rojhalat Ibrahim <imr@rtschenk.de>
Date: Mon, 25 Jul 2005 09:43:56 +0200
Cc: linux-mips@linux-mips.org
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Hi,

I am not sure what patch you are actually talking about.
In the mentioned thread there were several. Did you only apply
the last one or all of them, i.e. did you also apply
the patches that keep flushing the caches?
Because those are really only a workaround and not a
solution to the root cause of the problem.

Rojhalat Ibrahim


Alex Gonzalez wrote:
It's a RM9020.

Quoting Ibrahim's,

"With a slightly extended patch it actually works. But afterwards
I get a lot of Illegal instructions and Segmentation faults, where
there shouldn't be any. Below is the patch I used."

And after you post an improved patch, he says,

"I presume CKSEG is CKSEG0 in the above patch. With that it works
about the same as before. So do you have any clue what the problem
behind all that really is? Furthermore I still have all those
"Illegal instruction" and "Segmentation fault" messages that
shouldn't be there."

The illegal instructions and segmentation faults turned to be the 
cpu_has_64bit_gp_regs setting. So I presume it worked for him.

In our case, it seems to work completely OK. I am running a complete memory 
test over the whole 1G to be completely sure (with memtester), and I'll report 
the result back.

Thanks,
Alex


On Fri, 2005-07-22 at 14:14, Ralf Baechle wrote:

On Fri, Jul 22, 2005 at 10:04:47AM +0100, Alex Gonzalez wrote:


Our target experienced a kernel panic at startup when trying to access
memory above 512MB.

Reading the list archives I found this thread with a proposed patch:

http://www.linux-mips.org/archives/linux-mips/2005-02/msg00115.html

After applying the patch our target boots OK and appears to be able to
access the whole memory range without problems.

Any idea why this patch didn't make it to the repository? Is it safe?

It is - but according to Ibrahim's posting that you're pointing to it
didn't solve his problem.

What CPU are you using, btw?

 Ralf


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