Re: [BUG] R5000 failure in kmap_coherent on Lasat board, bug that has been there for a while?

[David Daney <ddaney@avtrex.com>]

Thomas Horsten wrote:
> Hi all,
> 
> (resending w/ more info because the first one didn't make it to the
> list - I'm subscribed now so hopefully it'll go through this time):
> 
> This crash happens (late) during boot with 2.6.25.6. I think this is a
> general R5k issue with the cache handling code. It only seems to
> happen when the swap is in use like someone else observed, but usually
> only after some big processes like mysql have been started.
> 
> As far as I can see it's the same issue that has been reported several
> other places, but with no resolution in any of them:
> 
> http://www.linux-mips.org/archives/linux-mips/2007-12/msg00128.html
> http://www.linux-mips.org/archives/linux-mips/2008-01/msg00132.html
> and also seen by someone else here:
> http://lists.debian.org/debian-mips/2007/11/msg00034.html
> 
> I'm thinking some subtle difference between R4k and R5k caches which
> isn't taken into account, or an aliasing bug that only triggers on
> R5k?

I have a mips 4KEc based system where I think it is happening too (sigma8634 based w/ 2.6.15 kernel).


> 
> I also found what seems to be a related patch from OpenWRT but I have
> no idea what it's supposed to solve as I could only find the raw
> patch:
> 
> https://dev.openwrt.org/browser/trunk/target/linux/brcm47xx/patches-2.6.25/160-kmap_coherent.patch?rev=11155
> 
> In any case I tried to apply it to my Lasat kernel, but using the
> _atomic functions instead of _coherent just causes a much earlier
> crash.
> 

I will try said patch on my O2/R5000 and the sigma8634.

Thanks,
David Daney