Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1763311AbYBSXxn (ORCPT ); Tue, 19 Feb 2008 18:53:43 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1755967AbYBSXxg (ORCPT ); Tue, 19 Feb 2008 18:53:36 -0500 Received: from idcmail-mo1so.shaw.ca ([24.71.223.10]:16725 "EHLO pd2mo2so.prod.shaw.ca" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755956AbYBSXxf (ORCPT ); Tue, 19 Feb 2008 18:53:35 -0500 Date: Tue, 19 Feb 2008 17:52:54 -0600 From: Robert Hancock Subject: Re: Intel Core2Duo mobile - how does the VID get set? In-reply-to: To: Brian Morrison Cc: linux-kernel@vger.kernel.org Message-id: <47BB6BD6.1090105@shaw.ca> MIME-version: 1.0 Content-type: text/plain; charset=ISO-8859-1; format=flowed Content-transfer-encoding: 7bit References: User-Agent: Thunderbird 2.0.0.9 (Windows/20071031) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1476 Lines: 37 Brian Morrison wrote: > Pallipadi, Venkatesh wrote: > >>> After a fair bit of Googling and reading around, I'm none the wiser >>> about exactly how Linux 2.6.x sets the processor VID (or for that >>> matter how it decides the FID settings) when using the ondemand >>> governor and cpufreq stuff. >>> >>> Can anyone tell me a) whether this is obtained from the BIOS, >>> something in the MSR of the processor or elsewhere and >> >> Yes. The freq and voltage supported comes from the platform BIOS. BIOS >> exports this in an ACPI table which is handled by acpi-cpufreq driver in >> Linux kernel. >> > > OK, thanks for that. > >> >>> b) whether there is an interface in /proc or /sys where one can find >>> out what is set and modify it? >> >> There is no way of modifying and using new VIDs etc in Linux kernel >> (other than exporting your own DSDT and hacking the related code). > > Is there a way of viewing the ACPI table contents relating to the VIDs > and FIDs? Viewing the decompiled ACPI DSDT may provide some hints, however the kernel itself knows nothing about VID/FID settings for acpi-cpufreq, basically the kernel writes to magic ACPI registers and the BIOS or hardware take over to do what's required.. -- 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/