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Setting the physical RAM map

To: linux-mips@linux-mips.org
Subject: Setting the physical RAM map
From: Adam Nielsen <a.nielsen@shikadi.net>
Date: Sun, 29 Nov 2009 00:38:55 +1000
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Hi all,

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.

Some of the MIPS devices don't seem to have code to create a memory map, so I'm wondering whether this is necessary or if there's a generic MIPS way to retrieve the current mapping.

Also, if anyone has any ideas what the kernel is trying to do accessing that invalid address I could use some hints!

Many thanks,
Adam.

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