Date: Tue, 10 Jul 2012 11:46:00 +0300 From: Andriy Gapon <avg@FreeBSD.org> To: Nate Lawson <nate@root.org> Cc: "freebsd-acpi@freebsd.org" <freebsd-acpi@FreeBSD.org> Subject: Re: disabled CST_CNT write Message-ID: <4FFBEBC8.2090309@FreeBSD.org> In-Reply-To: <023CA42F-C5FD-4F67-AD70-84DE68B3FBA8@root.org> References: <4FF94EC4.1060109@FreeBSD.org> <023CA42F-C5FD-4F67-AD70-84DE68B3FBA8@root.org>
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on 08/07/2012 19:49 Nate Lawson said the following: > On Jul 8, 2012, at 2:11 AM, Andriy Gapon 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? > > It was only under an #ifdef because at the time our CST implementation couldn't handle CST changes cleanly. I had added some support for it, but since it couldn't be tested, I wasn't sure how actual hardware would behave. > > I think it's fine to enable now. I think 2007-era Thinkpads were some of the first to add this feature. Nate, thank you for the information/explanation. -- Andriy Gapon
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