linux-kernel - Re: Lenovo 3000 N100 i8042 problems

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Message-ID: <alpine.LNX.1.00.0809031250561.19665@iabervon.org>
Date:	Wed, 3 Sep 2008 13:16:59 -0400 (EDT)
From:	Daniel Barkalow <barkalow@...ervon.org>
To:	Dmitry Torokhov <dmitry.torokhov@...il.com>
cc:	Jiri Kosina <jkosina@...e.cz>, linux-kernel@...r.kernel.org,
	Christopher Desjardins <cddesjardins@...il.com>
Subject: Re: Lenovo 3000 N100 i8042 problems

On Wed, 3 Sep 2008, Dmitry Torokhov wrote:

> 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.

Right from the beginning? I'm not seeing that on any kernel with this 
hardware. I don't suppose the kernel could detect that it's using active 
mux and one of the devices isn't responding, and use legacy mode in that 
case, and only use quirks for systems where the active mux does something 
particularly weird?

> > 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...

It's usually within an hour of the right usage pattern. I'll try to 
trigger it with debugging on while not typing anything secret Thursday 
evening.

The other thing that might be useful, if there's some way to find out, is 
whether the kernel lost an interrupt somehow, since this feels like the 
hardware is waiting patiently for a lost interrupt to get serviced. Also, 
is there some way to get the kernel to re-initialize the i8042? It might 
be useful to see if the firmware has really stopped working or if the 
kernel is just failing to do anything further with it. I can unbind the 
driver, but I don't seem to be able to bind it again.

	-Daniel
*This .sig left intentionally blank*
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