linux-kernel - Re: 2.6.24-rc8 hangs at mfgpt-timer

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Message-ID: <478FB255.5040001@i4.informatik.rwth-aachen.de>
Date:	Thu, 17 Jan 2008 20:53:57 +0100
From:	Arnd Hannemann <hannemann@...informatik.rwth-aachen.de>
To:	Andres Salomon <dilinger@...ued.net>
CC:	linux-kernel@...r.kernel.org, Jordan Crouse <jordan.crouse@....com>
Subject: Re: 2.6.24-rc8 hangs at mfgpt-timer

Andres Salomon schrieb:
> On Thu, 17 Jan 2008 10:54:30 +0100
> Arnd Hannemann <hannemann@...informatik.rwth-aachen.de> wrote:
> 
>> Andres Salomon schrieb:
>>> On Wed, 16 Jan 2008 16:19:12 -0500
>>> Andres Salomon <dilinger@...ued.net> wrote:
>>>
>>>> On Wed, 16 Jan 2008 18:44:07 +0100
>>>> Arnd Hannemann <hannemann@...informatik.rwth-aachen.de> wrote:
>>>>
>>>>> Hi,
>>>>>
>>>>> I'm trying to boot 2.6.24-rc8 on a GEODE LX board (ALIX.3),
>>>>> and it hangs during boot:
>>>>>
>>>>> [   12.689971] NET: Registered protocol family 16
>>>>> [   12.703329] geode-mfgpt:  Registered timer 0
>>>>> [   12.716149] mfgpt-timer:  registering the MFGT timer as a clock event...
>>>>>
>>>> What BIOS are you using?  It's possible that our detection code is
>>>> failing to detect in-use timers.
>> I'm using v0.99 (latest available).
> 
> 
> v0.99 of what?  Jordan seems to think it's an Award BIOS, but I'd like
> to make sure.

Its an ALIX board from PCEngines, they have their own BIOS
implementation (tinyBios).
http://www.pcengines.ch/alix.htm

> 
>> Also note when I do enable the mysterios "MFGPT workaround" option in
>> the bios the machine hangs directly after:
>> [   36.780990] NET: Registered protocol family 16
> 
> 
> "MFGPT workaround"?  That sounds a bit frightening.
> 
> Presumably, the BIOS is using the MFGPTs, but we're not detecting them as
> being in use.
Yes I think so too, for the fun of it I compiled a 2.6.16.29 kernel with
the attached patch from fi4l.

relevant output is this:
[   31.015425] geode-mfgpt:  7 timers available.
...
[   31.245875] geode-mfgpt:  Registered timer 0

So the above kernel detects only 7 timers not 8, and it works. But note
that timer 0 is not used as a clock event source but as a watchdog,
which btw actually works fine :-)
The funny thing is the #define workaround part of this dubious patch and
its interaction with the bios:

#ifdef WORKAROUND:
 I have to turn the "MFPGT workaround" option in the bios ON, to boot
the kernel probably.

#ifndef WORKAROUND:
 I have to turn the "MFPGT workaround" option in the bios OFF, to boot
the kernel probably.

All other combinations will hang the system.

Doest it make sense to try to boot older release candidates of 2.6.24 ?

> 
> I'm assuming that booting with 'nomfgpt' works for you?
In fact it does.
It just says:
geode-mfgpt:  Skipping MFGPT setup
and boots.

> 
>>>
>>> Also, could you provide a log with the following (untested) patch?  I'm
>>> curious how many MFGPTs we're actually detecting as being available, and
>>> the existing code is backwards.
>> The relevant part would be:
>> [   23.092507] NET: Registered protocol family 16
>> [   23.105875] geode-mfgpt:  8 MFGPT timers available
>> [   23.120247] geode-mfgpt:  Registered timer 0
>> [   23.133076] mfgpt-timer:  registering the MFGT timer as a clock event.


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