linux-kernel - [GEODE] Geode GX/LX watchdog timer (was 2.6.24-rc8 hangs at mfgpt-timer)

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Message-ID: <20080119010624.GA25328@cosmic.amd.com>
Date:	Fri, 18 Jan 2008 18:06:24 -0700
From:	"Jordan Crouse" <jordan.crouse@....com>
To:	"Arnd Hannemann" <hannemann@...informatik.rwth-aachen.de>
cc:	"Andres Salomon" <dilinger@...ued.net>, marc.jones@....com,
	"Linux Kernel Mailing List" <linux-kernel@...r.kernel.org>,
	wim@...ana.be
Subject: [GEODE] Geode GX/LX watchdog timer (was 2.6.24-rc8 hangs at
 mfgpt-timer)

On 17/01/08 23:52 +0100, Arnd Hannemann wrote:
> >> Watchdog for the new API would be great :-)
> > 
> > Coming soon.

As promised, a watchdog driver for the Geode GX/LX processors is attached.
I basically just ported the previous patch forward to 2.6.24.

I also have good news or bad news depending on your perspective.  I wanted
to test this against 2.6.24, and OLPC is stuck at an older kernel version,
so I had to test this with coreboot (LinuxBIOS) on another Geode 
platform.  Like all BIOSen execpt for the OLPC firmware, coreboot uses
VSA (SMM handler) which consumes all the timers.

So I used the magical MSR and surprise! - the timer tick hung.  
I compiled out the timer tick, and tested the watchdog timer instead,
and it worked fine on timer 0.  So I don't think the MFGPTs themselves
have anything to do with this problem, but I do think it might be 
related to VSA and possibly interrupts too.  I'm going to invoke the
strong BIOS fu of our LinuxBIOS / BIOS expert Marc Jones, and see what
he comes up with.

I don't know how much of a hassle it would be for Andres to get a 2.6.24
kernel running on the OLPC to make sure that this isn't a regression
in the timer tick code (I suspect it isn't a regression, but you never
know).  I also think that it would probably be in our best interest to
default CONFIG_GEODE_MFGPT_TIMER to 'n' until we get this figured
out.  Since most BIOSen don't have timers available, that shouldn't affect
too many people.

So, anyway, enjoy the watchdog timer - I hope it meets everybody's
expectations for the 2.6.25 kernel.

Jordan
-- 
Jordan Crouse
Systems Software Development Engineer 
Advanced Micro Devices, Inc.

View attachment "geode-watchdog.patch" of type "text/plain" (9938 bytes)