Date: Thu, 23 Jun 2005 14:25:17 -0700 From: Nate Lawson <nate@root.org> To: "Alexandre \"Sunny\" Kovalenko" <Alex.Kovalenko@verizon.net> Cc: freebsd-acpi@freebsd.org, Matthew Flanagan <flanagan.matt@gmail.com> Subject: Re: Changing temperature threshold Message-ID: <42BB28BD.5080202@root.org> In-Reply-To: <1130426516.777.7.camel@RabbitsDen> References: <7cd06a2d05062205331d03372c@mail.gmail.com> <7cd06a2d050623073452e3c3f9@mail.gmail.com> <1130426516.777.7.camel@RabbitsDen>
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Alexandre "Sunny" Kovalenko wrote:
>>When I try to raise hw.acpi.thermal.tz0._CRT to 85C (which is the
>>threshold in the BIOS setup) it doesn't work:
>>
>>bell# sysctl hw.acpi.thermal.tz0._CRT=3580 # 3580 tenths of Kelvin=85C
>>sysctl: oid 'hw.acpi.thermal.tz0._CRT' is read only
>>
>>Now, my question is: how do I change this value? I've read several
>>manpages (acpi(4), acpi_thermal(4), acpiconf(8), loader(8), and many
>>others) and checked the handbook, to no avail. Can anyone point me
>>to the right direction?
>
> One of the ways to deal with that would be to dump your ASL (see
> Handbook for guidance), find lines which look like:
> Method (_CRT, 0, NotSerialized)
> {
> Return (KELV (0x5d))
> }
> modify them to your liking, compile ASL and override it during boot
> (instructions on how to compile and override are in Handbook as well).
> Please, note that actual value returned is in the 1/10th of the degree
> of Kelvin. Function KELV above has following ASL code associated with
> it:
> Method (KELV, 1, NotSerialized)
> {
> Store (Arg0, Local1)
> Multiply (0x0A, Local1, Local1)
> Add (Local1, 0x0AAC, Local1)
> Return (Local1)
> }
> Thermal management chapter of the ACPI specification should provide you
> with ample explanation of what this is all about.
This explanation is correct. The reason why the sysctl is read-only is
because the values are supplied by the BIOS and are what the OEM thinks
are critical temperatures. However, we need a way to allow override in
the case of obviously wrong values like this. I'll probably change it
to allow overriding from the loader but be read-only in sysctl to avoid
accidental changes from users experimenting.
--
Nate
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