From: Matt Porter <mporter@kernel•crashing.org>
To: David Hawkins <dwh@ovro•caltech.edu>
Cc: linuxppc-embedded@ozlabs•org
Subject: Re: Maximum ioremap size for ppc arch?
Date: Mon, 3 Dec 2007 13:07:23 -0600 [thread overview]
Message-ID: <20071203190723.GB30746@gate.crashing.org> (raw)
In-Reply-To: <475441DD.9030601@ovro.caltech.edu>
On Mon, Dec 03, 2007 at 09:50:21AM -0800, David Hawkins wrote:
> Could you comment on a similar problem I had/have.
>
> I have a CPU with 1GB memory, and I use about 20 cPCI boards that
> I give 8MB windows in PCI space. When I was trying to load my
> custom driver with these boards, it would give me ioremap failures.
> On a CPU that had 512MB of memory it worked fine. My 'temporary hack'
> (which is still in place) for the 1GB CPUs was to add mem=512M (or
> whatever it is) to the kernel command line. That was a good
> enough fix at the time :)
>
> I have figured I was running out of page table entries or something
> like that and was going to investigate one of these days ...
>
> However, perhaps it was that I was running out of address space.
> But 0xC0000000 is at 3GB, I can't see that I would be triggering
> an address space issue:
>
> 1GB = 0x40000000
> 20 x 8MB = 160MB
>
> But, I figured I'd ask anyway :)
Yes, same thing. There's N ways to fix it. But I see you're talking
x86.
> PS. The CPUs in this case are x86 based, while the PCI boards use
> PLX-9054 bridges. I'm building new peripheral boards with MPC8349EAs
> so this problem is going to rear its ugly head again soon, when
> I work on the drivers for the new peripheral boards.
You should be able to do something similar on x86 but the details
are TBD. I would probably try to limit low memory to 512MB in the
x86 case.
-Matt
next prev parent reply other threads:[~2007-12-03 19:07 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-12-03 9:22 Maximum ioremap size for ppc arch? michael.firth
2007-12-03 10:20 ` Arnd Bergmann
2007-12-03 15:30 ` Matt Porter
2007-12-03 17:50 ` David Hawkins
2007-12-03 19:07 ` Matt Porter [this message]
2007-12-03 19:51 ` David Hawkins
2007-12-05 9:50 ` michael.firth
2007-12-05 17:46 ` Scott Wood
2007-12-05 17:50 ` Scott Wood
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