linux-kernel - Re: [PATCH v3] Enable A20 using KBC for some MSI laptops to fix S3 resume

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Date:	Tue, 11 Dec 2012 21:29:12 +0100
From:	Ondrej Zary <linux@...nbow-software.org>
To:	"H. Peter Anvin" <hpa@...or.com>
Cc:	Alan Cox <alan@...rguk.ukuu.org.uk>,
	"Rafael J. Wysocki" <rjw@...k.pl>, linux-acpi@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3] Enable A20 using KBC for some MSI laptops to fix S3 resume

On Tuesday 11 December 2012 20:07:50 H. Peter Anvin wrote:
> On 12/11/2012 10:59 AM, Ondrej Zary wrote:
> > As I said before, the BIOS probably breaks on resume before any Linux
> > code is executed. So any fix must be done before suspending.
>
> Well, that code should be independent of A20, being in low memory, but
> if the BIOS itself crashes, then that's... yeah.
>
> > I hate quirks too. A general solution would be to always enable A20 using
> > KBC (if KBC is present) but that's probably not acceptable.
>
> I don't see why not.  If so we could just do it as part of the
> initialization of the i8042 driver.

Something like this? (It works.)

diff --git a/drivers/input/serio/i8042-x86ia64io.h b/drivers/input/serio/i8042-x86ia64io.h
index d6cc77a..0807ac7 100644
--- a/drivers/input/serio/i8042-x86ia64io.h
+++ b/drivers/input/serio/i8042-x86ia64io.h
@@ -921,6 +921,7 @@ static int __init i8042_platform_init(void)
 	int retval;
 
 #ifdef CONFIG_X86
+	u8 a20_on = 0xdf;
 	/* Just return if pre-detection shows no i8042 controller exist */
 	if (!x86_platform.i8042_detect())
 		return -ENODEV;
@@ -960,6 +961,13 @@ static int __init i8042_platform_init(void)
 
 	if (dmi_check_system(i8042_dmi_dritek_table))
 		i8042_dritek = true;
+
+	/*
+	 * A20 was already enabled during early kernel init. But some buggy
+	 * BIOSes (in MSI Laptops) require A20 to be enabled using 8042 to
+	 * resume from S3. So we do it here and hope that nothing breaks.
+	 */
+	i8042_command(&a20_on, 0x10d1);
 #endif /* CONFIG_X86 */
 
 	return retval;
-- 
Ondrej Zary
--
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