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Re: Setting the physical RAM map

To: Adam Nielsen <a.nielsen@shikadi.net>
Subject: Re: Setting the physical RAM map
From: Ralf Baechle <ralf@linux-mips.org>
Date: Mon, 30 Nov 2009 21:41:19 +0000
Cc: linux-mips@linux-mips.org
In-reply-to: <4B1135FF.9050908@shikadi.net>
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References: <4B1135FF.9050908@shikadi.net>
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On Sun, Nov 29, 2009 at 12:38:55AM +1000, Adam Nielsen wrote:

> I'm attempting to port the Linux kernel to an NCD HMX, an R4600-based 
> X-Terminal.
> 
> I've currently got it to the point where it will download the kernel
> and execute it, and start printing some messages out on the screen.
> 
> It gets as far as printing the physical RAM map and then crashes,
> but I'm not sure why:
> 
>   Determined physical RAM map:
>    memory: 00800000 @ 40250000 (usable)
>    memory: 00040000 @ 9fc00000 (ROM data)
>   Wasting 8407552 bytes for tracking 262736 unused pages
> 
>   TLB refill exception PC = 40024094 address = 7FFFF000
> 
> The last message is from the boot monitor (the kernel is loaded at
> address 0x40020000.)  I'm just guessing with the memory map, but
> I've tried lots of different values with the same result, and I'm
> fairly sure there is RAM mapped to the address I have used above
> (it's after the end of the kernel.)  At any rate the error message
> is from a completely different address, and it still happens if I
> flag that area as reserved memory in the RAM map.

Are you sure it's a R4600, not R4640 or R4650?

It's like a decade that I last read up on these but afair they have a
fixed mapping starting at 0x40000000.  It would make perfect sense to
use such a CPU in an X terminal.

  Ralf

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