Re: lemote-3a-itx-a1101 kernel and pmon

James Cowgill <[email protected]> Tue, 19 Jan 2016 13:21:22 +0000
Newsgroups	gmane.linux.debian.ports.mips
Message-ID	<[email protected]>
Hi,

On Sun, 2016-01-17 at 06:39 +0100, David Kuehling wrote:
> long time ago I was told that I need a newer PMON to boot recent linux
> kernels [5], but then read on debian-mips about problems after PMON
> upgrades [1].
> 
> I'm tired of running an ancient 3.5 linux kernel on my Loongson-3A
> system.  Are there any updates about the PMON vs. kernel situation?
> Anybody knows where I can find the latest *official* PMON 4.0.1 binary?
> Googeling around, I found [2-4], which aren't even byte-for-byte equal.

Firstly this is all from memory since I haven't dealt with these
machines for some time now and things may have changed (or I might have
forgotten something).

So the old PMON in those machines (only itx-a1101) has a bug where it
loads the kernel at an address to close to the address the bootloader
is stored at. If the kernel being loaded has a large bss section (or is
large in memory for any reason), PMON will overwrite itself and crash.

The bug appeared after this kernel commit:
https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=c46173183657bbdbe0d54a981c28807581648422which increased the size of the bss section to something like 20M on
all Loongson 3 kernels.

Back then I tried using PMON 4.something but it wouldn't boot any
kernel I threw at it.

In the end I patched the kernel to reduce the value of MAX_PHYSMEM_BITS
from 48 to 35 and it worked again - I think this should be ok on all
Loongson 3A machines.

Hopefully if you try that, any recent kernel will work with the old
PMON.

> According to /proc/cpuinfo my system is a :
> 
> system type             : lemote-3a-itx-a1101
> processor               : 0
> cpu model               : ICT Loongson-3A V0.5  FPU V0.1
> 
> My invoice says something like "Lemote Xinghuo 6100 Desktop" (I think in
> chinese it's "星火 6100").  This was bought in November 2013.
> 
> I see that debian archives now carry linux-image-3.16.0-4-loongson-3 .
> What are my chances to use this kernel on my system?

I think the kernel in jessie has the 3B patched backported to it so I
would guess it won't work - but you could try it anyway :)

James
signature.asc (application/pgp-signature, 819 B)