Date: Sun, 8 Jul 2012 19:19:37 +0900 From: Taku YAMAMOTO <taku@tackymt.homeip.net> To: Andriy Gapon <avg@FreeBSD.org> Cc: "freebsd-acpi@freebsd.org" <freebsd-acpi@FreeBSD.org> Subject: Re: disabled CST_CNT write Message-ID: <20120708191937.46148f65.taku@tackymt.homeip.net> In-Reply-To: <4FF94EC4.1060109@FreeBSD.org> References: <4FF94EC4.1060109@FreeBSD.org>
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On Sun, 08 Jul 2012 12:11:32 +0300
Andriy Gapon <avg@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
| __ < <taku@tackymt.homeip.net>
- A chicken is an egg's way of producing more eggs. -
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