linux-kernel - Re: Geode GX/LX watchdog timer (was 2.6.24-rc8 hangs at mfgpt-timer)

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Message-ID: <20080120163447.GA1711@cosmic.amd.com>
Date:	Sun, 20 Jan 2008 09:34:47 -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: Re: Geode GX/LX watchdog timer (was 2.6.24-rc8 hangs at
 mfgpt-timer)

On 20/01/08 14:22 +0100, Arnd Hannemann wrote:
> Hi,
> 
> Jordan Crouse wrote:
> > 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.
> 
> Great work!
> 
> > 
> > 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.
> 
> Thanks a lot for this, it works great! (with CONFIG_GEODE_MFGPT_TIMER
> not set).
> However some minor issues:
> Could the name of the /dev entry perhaps be changed from
> "geode-watchdog" to "watchdog" instead?
> I think all other watchdogs use "watchdog", and using two different
> watchdogs in the same machine won't work anyway, because of the same
> minor number, right?

Very much yes -  complete oversight on my part.

> As a second point my gcc (4.1.2) issues a warning:
> 
> drivers/watchdog/geodewdt.c: In function ‘geodewdt_remove’:
> drivers/watchdog/geodewdt.c:256: warning: control reaches end of
> non-void function
> 
> which I think is a valid one.

Yes again.  I'll refactor.  Thanks for your comments.

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


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