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Re: [ts-7000] Re: Only 32M detected by RedBoot

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Subject: Re: [ts-7000] Re: Only 32M detected by RedBoot
From: Doug Chapman <>
Date: Wed, 3 Jan 2007 12:07:07 -0800 (PST)
--- charliem_1216 <> wrote:
> 
> Hi Doug --
> 
> Yes, I tried.  Lennert Buytenhek knew the problem right away, and
> gave
> me some insight on the linux-cirrus ML [1].
> 
> To summarize, in Linux 2.6, the ep93xx memory subsystem expects all
> of
> the RAM to be mapped within a 1G physical address range.  I haven't
> looked into the 7260, but the 7250 doesn't doesn't do this when there
> are two memory chips.  It is fixable, but not by mortals like me, and
> there is no "quick hack" to make it work in the meantime.  (More
> details are in the linux-cirrus ML archive.)
> 

Now I wish I hadn't dug into this until 1AM last night ;)  Actually it
was interesting and educational so probably was worth the time.  After
fixing (ok hacking really) the __phys_to_virt and __virt_to_phys macros
to get a little farther I came to the same conclusion that you got from
Lennert.

I played around a bit today with the kernel code with using the
CONFIG_DISCONTIGMEM stuff which I hope will fix the issue (this allows
for big holes in the physical address space).  This is implemented on
other ARM platforms so I don't think it will be too difficult to make
work for the TS-72XX boards.  I was able to get a kernel built with
this but I won't be able to try booting it until tonight when I get
home.

Probably isn't this simple however but anything that helps me learn the
deep kernel internals is worthwhile.

If I do get this workign I will post patches to the files section of
the yahoo group.

- Doug




 
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