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

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

quoted

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

quoted

Hi Takashi,

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

quoted

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