Date: Sun, 8 Jul 2012 09:49:57 -0700 From: Nate Lawson <nate@root.org> To: Andriy Gapon <avg@freebsd.org> Cc: "freebsd-acpi@freebsd.org" <freebsd-acpi@FreeBSD.org> Subject: Re: disabled CST_CNT write Message-ID: <023CA42F-C5FD-4F67-AD70-84DE68B3FBA8@root.org> In-Reply-To: <4FF94EC4.1060109@FreeBSD.org> References: <4FF94EC4.1060109@FreeBSD.org>
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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. >=20 > 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
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