linux-kernel - Re: [BUG] Stuck key syndrome (was: Re: [PATCH net-next v2] net: dsa: microchip: Add SGMII port support to KSZ9477 switch)

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Message-ID: <aBsu-WBlPQy5g-Jn@shell.armlinux.org.uk>
Date: Wed, 7 May 2025 10:59:21 +0100
From: "Russell King (Oracle)" <linux@...linux.org.uk>
To: Maxime Chevallier <maxime.chevallier@...tlin.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Andrew Lunn <andrew@...n.ch>, Woojung Huh <woojung.huh@...rochip.com>,
	Vladimir Oltean <olteanv@...il.com>,
	Heiner Kallweit <hkallweit1@...il.com>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	Dmitry Torokhov <dmitry.torokhov@...il.com>,
	linux-input@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [BUG] Stuck key syndrome (was: Re: [PATCH net-next v2] net: dsa:
 microchip: Add SGMII port support to KSZ9477 switch)

On Wed, May 07, 2025 at 10:23:17AM +0100, Russell King (Oracle) wrote:
> [Sorry for going off topic here - changed the Cc list, added Linus,
> changed the subject.]
> 
> On Wed, May 07, 2025 at 10:54:57AM +0200, Maxime Chevallier wrote:
> > On Wed, 7 May 2025 09:31:48 +0100
> > "Russell King (Oracle)" <linux@...linux.org.uk> wrote:
> > > [rest of the email got deleted because Linux / X11 / KDE got confused
> > > about the state the backspace key and decided it was going to be
> > > continuously pressed and doing nothing except shutting the laptop
> > > down would stop it.]
> > 
> > Funny how I have the same exact issue on my laptop as well... 
> 
> I've had the "stuck key" behaviour with the HP Pavilion 15-au185sa
> laptop I had previously (normally with ctrl-F keys). However, hitting
> ctrl/shift/alt would stop it.
> 
> This is the first time I've seen the behaviour with the Carbon X1
> laptop, but this was way more severe. No key would stop it. Trying to
> move the focus using the trackpad/nipple had any effect. Meanwhile
> the email was being deleted one character at a time. So I shut the
> laptop lid causing it to suspend, and wondered what to do... on
> re-opening the laptop, it didn't restart and is back to normal.
> 
> This suggests that the entire input subsystem in the software stack
> collapsed just after the backspace key was pressed, and Xorg never
> saw the key-release event. So Xorg duitifully did its key-repeat
> processing, causing the email to be deleted one character at a time.
> 
> The problem is, not only did this destroy the email reply, but it
> also destroyed my train of thought for the reply as well through
> the panic of trying to stop the entire email being deleted.
> 
> I don't think this is a hardware issue - I think there's a problem
> in the input handling somewhere in the stack of kernel, Xorg,
> whatever multiple input libraries make up modern systems, and KDE.
> 
> I did check the logs. Nothing in the kernel messages that suggests
> a problem. Nothing in Xorg's logs (which are difficult to tie up
> because it doesn't use real timestamps that one can relate to real
> time.) There's no longer any ~/.xsession-errors logfile for logging
> the stuff below Xorg.
> 
> I'm running Debian Stable here - kernel 6.1.0-34-amd64, X.Org X Server
> 1.21.1.7, KDE Plasma (5.27.5, frameworks 5.103.0, QT 5.15.8).

I'll also add that The Carbon X1, being a laptop, its built-in keyboard
uses the i8042:

[    1.698156] i8042: PNP: PS/2 Controller [PNP0303:KBD,PNP0f13:MOU] at 0x60,0x64 irq 1,12
[    1.698543] i8042: Warning: Keylock active
[    1.700170] serio: i8042 KBD port at 0x60,0x64 irq 1
[    1.700174] serio: i8042 AUX port at 0x60,0x64 irq 12
[    1.700271] mousedev: PS/2 mouse device common for all mice
[    1.702951] input: AT Translated Set 2 keyboard as /devices/platform/i8042/serio0/input/input0

I don't have the HP laptop with me to check what that was using.

The mysterious thing is "Keylock active" - clearly it isn't because I
can write this email typing on that very keyboard. However, I wonder
if it needs i8042_unlock=1 to set I8042_CTR_IGNKEYLOCK.

Unfortunately, it's probably going to take a year on the Carbon X1
to work out if this makes any difference.

> Anyone else seeing this kind of behaviour - if so, what are you
> using?
> 
> -- 
> RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
> FTTP is here! 80Mbps down 10Mbps up. Decent connectivity at last!

-- 
RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
FTTP is here! 80Mbps down 10Mbps up. Decent connectivity at last!