linux-kernel - Re: i8042 error at booting an Intel Cherry Trail-based device

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Date:   Thu, 01 Dec 2016 08:19:46 +0100
From:   Takashi Iwai <tiwai@...e.de>
To:     Dmitry Torokhov <dmitry.torokhov@...il.com>
Cc:     Jiri Slaby <jslaby@...e.cz>, linux-input@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: i8042 error at booting an Intel Cherry Trail-based device

On Thu, 01 Dec 2016 03:29:23 +0100,
Dmitry Torokhov wrote:
> 
> Hi Takashi,
> 
> On Mon, Nov 28, 2016 at 02:56:36PM +0100, Takashi Iwai wrote:
> > Hi Dmitry,
> > 
> > I've been testing a small machine with Intel Cherry Trail chipset, and
> > noticed that the kernel spews errors always like:
> > 
> >  i8042: PNP: No PS/2 controller found. Probing ports directly.
> >  i8042: Can't read CTR while initializing i8042
> >  i8042: probe of i8042 failed with error -5
> > 
> > Especially the second one ("Can't read CTR...") is annoying since it's
> > in KERN_ERR level and thus appears even booted with quiet boot
> > option.  Actually this is the only error message appearing at boot, so
> > I'd love to get rid of it.
> > 
> > What is the preferred way to reduce this?  For example, is a patch
> > like below OK to simply change the log level and the error code?
> 
> No, because if controller is actually present this is a hard failure and
> we should be reporting it, not suppressing it.
> 
> The issue is that we did not believe PNP data and in this case we should
> have. Unfortunately in old days there was a lot of crap in PNP/ACPI
> tables, but it could be better now. We can try, in addition to PNP
> matching, checking 8042 flag in "Fixed ACPI Description Table Boot
> Architecture Flags" in FADT and if it also shows there is no 8042 then
> bail.

That sounds promising.  Indeed FACL.dsl shows like:

[000h 0000   4]                    Signature : "FACP"    [Fixed ACPI Description Table (FADT)]
[004h 0004   4]                 Table Length : 0000010C
....
               Legacy Devices Supported (V2) : 0
            8042 Present on ports 60/64 (V2) : 0

If a test patch gets ready, let me know, I'll give it a try.


Thanks!

Takashi