Hi Takashi,
On Fri, Dec 02, 2016 at 11:55:07AM +0100, Takashi Iwai wrote:
> On Thu, 01 Dec 2016 08:19:46 +0100,
> Takashi Iwai wrote:
> >
> > 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.
>
> FYI, a hack like below seems working.
>
>
> Takashi
>
> ---
> diff --git a/drivers/input/serio/i8042-x86ia64io.h b/drivers/input/serio/i8042-x86ia64io.h
> index 073246c7d163..ed6ab702e4b7 100644
> --- a/drivers/input/serio/i8042-x86ia64io.h
> +++ b/drivers/input/serio/i8042-x86ia64io.h
> @@ -9,6 +9,7 @@
>
> #ifdef CONFIG_X86
> #include <asm/x86_init.h>
> +#include <linux/acpi.h>
> #endif
>
> /*
> @@ -1055,6 +1056,13 @@ static int __init i8042_pnp_init(void)
> #if defined(__ia64__)
> return -ENODEV;
> #else
> +#ifdef CONFIG_ACPI
> + if (acpi_gbl_FADT.header.revision >= 3 &&
> + !(acpi_gbl_FADT.boot_flags & ACPI_FADT_8042)) {
> + pr_info("PNP: No PS/2 controller found and disabled in ACPI\n");
> + return -ENODEV;
> + }
> +#endif
> pr_info("PNP: No PS/2 controller found. Probing ports directly.\n");
> return 0;
> #endif
I'm not an expert in any subsystem but, maybe this "hack" could be added
to default_i8042_detect in arch/x86/kernel/x86_init.c? Currently it is
enabled by default, but different Intel platform like ce4100 and
intel-mid disables it explicit.
I mentioned "hack" because following osdev.org[1] using ACPI is the
correct way to detect if i8042 exists. Pardon me if this not applies in
this situation, or if I missed something.
[1]
http://wiki.osdev.org/%228042%22_PS/2_Controller#Step_2:_Determine_if_the_PS.2F2_Controller_Exists
Thanks,
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