From: Ondrej Zary <linux@rainbow-software.org>
To: "H. Peter Anvin" <hpa@zytor.com>
Subject: Re: [PATCH v2] Enable A20 using KBC for some MSI laptops to fix S3 resume
Date: Thu, 25 Oct 2012 10:17:37 +0200
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Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>, "Rafael J. Wysocki" <rjw@sisk.pl>,
        linux-acpi@vger.kernel.org, linux-kernel@vger.kernel.org
References: <201210242316.22028.linux@rainbow-software.org> <50885BBB.9010904@zytor.com>
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On Wednesday 24 October 2012, H. Peter Anvin wrote:
> On 10/24/2012 02:16 PM, Ondrej Zary wrote:
> > Some MSI laptop BIOSes are broken - INT 15h code uses port 92h to enable
> > A20 line but resume code assumes that KBC was used.
> > The laptop will not resume from S3 otherwise but powers off after a while
> > and then powers on again stuck with a blank screen.
> >
> > Fix it by enabling A20 using KBC. Affected laptop list and DMI data are
> > from bug reports at Ubuntu Launchpad.
> >
> > Also add kernel parameter to easily activate this quirk on any system.
> >
> > Only compile tested. The original patch was tested with EX600 and PR200.
> >
> > Fixes https://bugzilla.kernel.org/show_bug.cgi?id=12878
>
> Are we guaranteed that this executes *before* the keyboard driver
> initializes?  If not, this needs to use the i8042 interface in the input
> subsystem or at least acquire i8042_lock.
>
> 	-hpa

The code is called in:
start_kernel()->setup_arch()->acpi_boot_table_init()

I think that it's before any drivers are initialized.

-- 
Ondrej Zary
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