Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751110AbVL0Pdc (ORCPT ); Tue, 27 Dec 2005 10:33:32 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751111AbVL0Pdc (ORCPT ); Tue, 27 Dec 2005 10:33:32 -0500 Received: from isilmar.linta.de ([213.239.214.66]:35735 "EHLO linta.de") by vger.kernel.org with ESMTP id S1751110AbVL0Pdc (ORCPT ); Tue, 27 Dec 2005 10:33:32 -0500 Date: Tue, 27 Dec 2005 16:33:30 +0100 From: Dominik Brodowski To: Pavel Machek Cc: "Theodore Ts'o" , Con Kolivas , linux kernel mailing list , Daniel Petrini , Tony Lindgren , vatsa@in.ibm.com, ck list , Adam Belay , Zwane Mwaikambo , ACPI mailing list , ipw2100-admin@linux.intel.com Subject: C4 non-strangeness [was: C4 strangeness [was Re: [PATCH] i386 No Idle HZ aka dynticks 051221] Message-ID: <20051227153330.GA32545@isilmar.linta.de> Mail-Followup-To: Dominik Brodowski , Pavel Machek , Theodore Ts'o , Con Kolivas , linux kernel mailing list , Daniel Petrini , Tony Lindgren , vatsa@in.ibm.com, ck list , Adam Belay , Zwane Mwaikambo , ACPI mailing list , ipw2100-admin@linux.intel.com References: <200512210310.51084.kernel@kolivas.org> <20051225171617.GA6929@thunk.org> <20051226025525.GA6697@thunk.org> <20051226203806.GC1974@elf.ucw.cz> <20051226225246.GA9915@thunk.org> <20051226232712.GH1974@elf.ucw.cz> <20051227140325.GA1620@elf.ucw.cz> <20051227142238.GA1696@elf.ucw.cz> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20051227142238.GA1696@elf.ucw.cz> User-Agent: Mutt/1.5.9i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1293 Lines: 27 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 - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/