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

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Date:   Fri, 02 Dec 2016 11:55:07 +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 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