From: Dominik Brodowski <linux@dominikbrodowski.net>
To: Pavel Machek <pavel@ucw.cz>
Cc: vatsa@in.ibm.com, Theodore Ts'o <tytso@mit.edu>,
Zwane Mwaikambo <zwane@arm.linux.org.uk>,
Tony Lindgren <tony@atomide.com>,
Daniel Petrini <d.pensator@gmail.com>,
linux kernel mailing list <linux-kernel@vger.kernel.org>,
ck list <ck@vds.kolivas.org>, Adam Belay <abelay@novell.com>,
ACPI mailing list <acpi-devel@lists.sourceforge.net>,
ipw2100-admin@linux.intel.com
Subject: C4 non-strangeness [was: C4 strangeness [was Re: [PATCH] i386 No Idle HZ aka dynticks 051221]
Date: Tue, 27 Dec 2005 16:33:30 +0100 [thread overview]
Message-ID: <20051227153330.GA32545@isilmar.linta.de> (raw)
In-Reply-To: <20051227142238.GA1696@elf.ucw.cz>
Hi,
On Tue, Dec 27, 2005 at 03:22:38PM +0100, Pavel Machek wrote:
> So... I guess I found out what is going on.
>
> When power is unplugged, X32 adds C4 state. When power is plugged, X32
> removes C4 state (behaviour Ted seen). When I load ipw2200, this
> behaviour stops, and I see everything up-to C4. Strange. I remember
> ipw had some problems with C3 and C4, perhaps this is related?
Nothing strange at all. The C-States are exported by the BIOS to the OS
using the _CST method/object/whatever. This can change on runtime. When the
BIOS recognizes it is on battery power, the _CST contains the C4 state, if
it is on AC power, the _CST doesn't contain it. The ACPI code follows what
it is told by the BIOS, for it has no chance to know about this additional
C-State if on AC power, and it wouldn't be wise to second-guess the BIOS.
Ipw does limit the max_cstate setting dynamically if it recognizes problems;
however I haven't seen _any_ such things lately on my own system. Might be
related to dyntick being _enabled_, though ;-)
Dominik
next prev parent reply other threads:[~2005-12-27 15:33 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <200512210310.51084.kernel@kolivas.org>
[not found] ` <20051225171617.GA6929@thunk.org>
[not found] ` <20051226025525.GA6697@thunk.org>
[not found] ` <20051226203806.GC1974@elf.ucw.cz>
[not found] ` <20051226225246.GA9915@thunk.org>
[not found] ` <20051226232712.GH1974@elf.ucw.cz>
[not found] ` <20051227140325.GA1620@elf.ucw.cz>
2005-12-27 14:22 ` C4 strangeness [was Re: [PATCH] i386 No Idle HZ aka dynticks 051221] Pavel Machek
2005-12-27 15:33 ` Dominik Brodowski [this message]
2005-12-27 16:13 ` C4 non-strangeness [was: " Pavel Machek
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