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

On December 5, 2016 4:56:05 PM PST, Marcos Paulo de Souza [off-list ref] wrote:

Hi Takashi,

On Fri, Dec 02, 2016 at 11:55:07AM +0100, Takashi Iwai wrote:

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On Thu, 01 Dec 2016 08:19:46 +0100,
Takashi Iwai wrote:

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On Thu, 01 Dec 2016 03:29:23 +0100,
Dmitry Torokhov wrote:

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Hi Takashi,

On Mon, Nov 28, 2016 at 02:56:36PM +0100, Takashi Iwai wrote:

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Hi Dmitry,

I've been testing a small machine with Intel Cherry Trail

chipset, and

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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

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in KERN_ERR level and thus appears even booted with quiet boot
option.  Actually this is the only error message appearing at

boot, so

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I'd love to get rid of it.

What is the preferred way to reduce this?  For example, is a

patch

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like below OK to simply change the log level and the error

code?

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No, because if controller is actually present this is a hard

failure and

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we should be reporting it, not suppressing it.

The issue is that we did not believe PNP data and in this case we

should

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have. Unfortunately in old days there was a lot of crap in

PNP/ACPI

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tables, but it could be better now. We can try, in addition to

PNP

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matching, checking 8042 flag in "Fixed ACPI Description Table

Boot

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Architecture Flags" in FADT and if it also shows there is no 8042

then

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bail.

That sounds promising.  Indeed FACL.dsl shows like:

[000h 0000   4]                    Signature : "FACP"    [Fixed

ACPI Description Table (FADT)]

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[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

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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");

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 		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.

That is the proper way of detecting i8042 if you trust firmware; historically we do not, and so we want to make sure that PNP data agrees with fadt data.


Thanks.

-- 
Dmitry