linux-kernel - Re: Lenovo 3000 N100 i8042 problems

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Date:	Wed, 3 Sep 2008 10:26:30 -0400
From:	Dmitry Torokhov <dmitry.torokhov@...il.com>
To:	Daniel Barkalow <barkalow@...ervon.org>
Cc:	Jiri Kosina <jkosina@...e.cz>, linux-kernel@...r.kernel.org,
	Christopher Desjardins <cddesjardins@...il.com>
Subject: Re: Lenovo 3000 N100 i8042 problems

On Tue, Sep 02, 2008 at 12:16:15PM -0400, Daniel Barkalow wrote:
> On Tue, 2 Sep 2008, Dmitry Torokhov wrote:
> 
> > On Tue, Sep 02, 2008 at 11:23:25AM +0200, Jiri Kosina wrote:
> > > 
> > > so the product name both of System and Base Board are different, and 
> > > apparently the systems differ. Dmitry, what fields would you propose to be 
> > > put in the DMI matching here? I will do the patch then.
> > > 
> > 
> > I guess we could use System's product name to differentiate between
> > Cristopher's and Daniel's boards. Although I must admit it is the very
> > first time when I see a box that behaves better with active mux. DOes
> > Vista use active mux nowadays? Because if it is not then I bet there
> > is (or shortly will be) a BIOS update fixing legacy mode on Daniel's
> > box.
> 
> Mine's actually old (came with XP). It's still got the original BIOS 
> (because I haven't found a way to upgrade the BIOS without reformatting my 
> hard drive to include Windows), and I remember there being an upgrade 
> available, but I don't think it had anything to do with keyboard/trackpad 
> stuff.
> 
> In what way does active mux usually behave badly? It's possible that 

It usually manifests with a touchpad/mouse missing because they don't
responf to kernel's queries. Quite a few Fujitsus exibit this
behavior.

> legacy mode only has a bug that doesn't matter to Windows, and active mux 
> may have some of the usual problems but nothing I particularly noticed.
> 
> I noticed that, when my i8042 would stop working, it would generally have 
> just delivered one mouse interrupt to CPU1 after never previously doing 
> so. Perhaps there's some sort of deadlock in the Linux i8042 driver when 
> both cores are unexpectedly getting interrupts from the two devices at 
> once? I could understand there being a Linux bug only triggered by quirky 
> hardware that only applies to legacy mode, which was just uncovered by 
> this patch.
>

I am not sure, internally we the kernel still deals with 2 interrupt
sources (KBD and AUX) regardless whether it is in legacy or active
multiplexing mode...

Does it take long to trigger the bug? You coudl try doing "echo 1 >
/sys/modules/i8042/parameters/debug" and thend me dmesg or
/var/log/messages after the bug was triggered - I might see something
there. But please be aware that if you send me such a log I can decode
everything that you have been typing...

-- 
Dmitry
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