disabled CST_CNT write

[Andriy Gapon]

on 08/07/2012 13:19 Taku YAMAMOTO said the following:
> On Sun, 08 Jul 2012 12:11:32 +0300
> Andriy Gapon <avg at FreeBSD.org> wrote:
> 
>>
>> acpi_cpu.c has a block of code to write CST_CNT to SMI_CMD, but the block is
>> under #ifdef notyet.  It seems that the code was added that many years ago and
>> never enabled.
>> Now, judging from the reports I've seen on this mailing list, it appears that
>> _CST changes do happen and the driver seem to handle them sufficiently well.
>> I think that a lot of modern platforms do not even provide CST_CNT and assume
>> that an OS is able to handle C-state change notifications.
>> So, I guess that it should be safe to enable the code in question now.
>>
>> Could anyone with a FreeBSD laptop and non-zero CST_CNT in FADT please test this?
> 
> My Thinkpad X60 (Core 2 Duo) is such one of them.
> Enabling that code makes this laptop correctly raise _CST change
> notification on AC status change without a single problem.
> Without enabling that, this laptop never generates such notifications.
> 
> In fact, I have been enabling that code locally for more than a couple of
> years without a problem :)
> 
> In addition, that does not interfere with jkim's acpi_cx_native2.diff;
> I've been enjoying MWAIT C3 with varying sleep depth based upon AC availability.
> 

Thank you very much for the information!
I will commit this change.

-- 
Andriy Gapon