Re: [PATCH] acpi: Fall back to manually changing SCI_EN

Alex Chiang
2010-04-20T15:00:19Z

* Matthew Garrett <mjg@redhat.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@canonical.com>

/ac