Re: [git pull request] ACPI patches for 2.6.34-rc6

[Linus Torvalds <torvalds@linux-foundation.org>]

On Tue, 11 May 2010, Matthew Garrett wrote:
> 
> I've now checked the behaviour of Windows. It turns out that it never 
> makes the ACPI enable SMM call on resume. This is consistent with 
> http://bugzilla.kernel.org/show_bug.cgi?id=13745 which shows a bug 
> being introduced by us making the enable call in the first place. 
> Merging my patch and removing the blacklist would re-break these 
> machines. Instead, we should just unconditionally set SCI_EN since this 
> is the tested configuration. I'll send a followup patch.

Hmm. But that's the thing that Rafael claims doesn't work on his machine. 

Maybe windows does something else? Or do you _see_ windows doing that 
write?

Note that our acpi_enable() won't do anything either if the machine comes 
up in ACPI mode, so maybe you checked the behavior on that kind of 
machine, and Windows does the same? IOW, if acpi_hw_get_mode() already 
returns ACPI_SYS_MODE_ACPI, the whole thing is a no-op.

Finally, it's possible that we really should just write the dang SCI_EN 
bit directly, but that what we do wrong is that doing so with

	acpi_write_bit_register()

will write it _even_if_ the bit was already set. That could explain 
Rafael's problems too - writing the register directly may be the 
RightThing(tm), but writing it if the bit was already set may well cause 
some confusion.

				Linus