linux-kernel - Re: [PATCH] acpi: Fall back to manually changing SCI

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Message-ID: <20100420150010.GA17935@canonical.com>
Date:	Tue, 20 Apr 2010 09:00:10 -0600
From:	Alex Chiang <achiang@...onical.com>
To:	Matthew Garrett <mjg@...hat.com>
Cc:	linux-kernel@...r.kernel.org, linux-acpi@...r.kernel.org,
	lenb@...nel.org
Subject: Re: [PATCH] acpi: Fall back to manually changing SCI_EN

* Matthew Garrett <mjg@...hat.com>:
> The ACPI spec tells us that the ACPI SCI_EN bit is under hardware control
> and shouldn't be touched by the OS. It seems that the Leading Other OS
> ignores this and some machines expect this behaviour. We have a blacklist
> for these, but given that we're able to detect the failure case and the
> alternative to breaking the spec is letting the machine crash and burn,
> let's try falling back when we know the alternative is a mostly-dead
> machine.

Yes, we got a hint from a Lenovo BIOS developer:

	A SCI_EN bit had not been set at S3 resume post. It
	should be set as ACPI defines. It seems that Windows OS
	sets SCI_EN bit by itself after S3 resume....

So I believe that Matthew's approach is reasonably safe and
correct.

Acked-by: Alex Chiang <achiang@...onical.com>

/ac
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