On Sun, 08 Jul 2012 12:11:32 +0300
Andriy Gapon a...@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.
--
-|-__ YAMAMOTO, Taku
| __ t...@tackymt.homeip.net
- A chicken is an egg's way of producing more eggs. -
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