Date: Wed, 3 Feb 2010 15:21:00 +0000 From: Rui Paulo <rpaulo@FreeBSD.org> To: Andriy Gapon <avg@icyb.net.ua> Cc: freebsd-acpi@FreeBSD.org, John Baldwin <jhb@FreeBSD.org> Subject: Re: acpi_cpu: _PDC vs _OSC Message-ID: <43E821DA-BBD8-4ADD-ACA6-BDDD1ECB8B8F@FreeBSD.org> In-Reply-To: <4B698DD8.4010404@icyb.net.ua> References: <4B698DD8.4010404@icyb.net.ua>
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On 3 Feb 2010, at 14:53, Andriy Gapon wrote: > > What do you think about changing logic of evaluating _PDC and _OSC for Processor > object in acpi_cpu_attach? > It seems that later versions of ACPI standard deprecate _PDC in favor of _OSC. > Although, in practice they seem to be present or not present together, sometimes > _PDC being only a wrappper around _OSC. There are still, of course, systems with > only _PDC present. I assume that there are systems with only _OSC too. > > I would like to change the order, so that _OSC evaluation is attempted first and > only if it fails then proceed with _PDC. > > Also, I would like to print status returned by _OSC (in case of successful > evaluation) if it is not zero. (Note: this is not the same as status of evaluating > _OSC). > > And I am going to fix the following comment: > * On some systems we need to evaluate _OSC so that the ASL > * loads the _PSS and/or _PDC methods at runtime. > > Although on many systems either _PDC or _OSC or both dynamically load SSDTs that > contain additional Processor objects like _PSS and _PCT, I haven't seen any system > where _OSC would load _PDC. And, honestly, that wouldn't make any sense. > Perhaps, comment's author meant _PCT in place of _PDC, or something like that. I added the comment and I have such system. It's a MacBook first generation. By evaluating _OSC we were able to make _PDC visible, thus enabling cpufreq(4). -- Rui Paulo
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