From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758820AbYIASnT (ORCPT ); Mon, 1 Sep 2008 14:43:19 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751018AbYIASnK (ORCPT ); Mon, 1 Sep 2008 14:43:10 -0400 Received: from smtp1.linux-foundation.org ([140.211.169.13]:58627 "EHLO smtp1.linux-foundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750738AbYIASnJ (ORCPT ); Mon, 1 Sep 2008 14:43:09 -0400 Date: Mon, 1 Sep 2008 11:42:38 -0700 (PDT) From: Linus Torvalds To: Larry Finger cc: Thomas Gleixner , LKML , "Rafael J. Wysocki" , Alok Kataria , Michael Buesch Subject: Re: Regression in 2.6.27 caused by commit bfc0f59 In-Reply-To: <48BC2A03.9000104@lwfinger.net> Message-ID: References: <48BB2116.1060904@lwfinger.net> <48BC2A03.9000104@lwfinger.net> User-Agent: Alpine 1.10 (LFD 962 2008-03-14) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, 1 Sep 2008, Larry Finger wrote: > > TSC calibrated against PIT > Detected 428.823 MHz processor. Ok, Thomas, that means that the PIT is reliable (not surprising), and the PM_TIMER isn't (again, I'm not horribly surprised). And HPET isn't available, of course. The old x86-32 code never even bothered with the PM_TIMER for calibration. I don't understand why the x86-64 code bothers with it either. Why not just drop that whole broken thing, and just depend on the PIT if there is no HPET? I would also like to point out that the 32-bit code actually had a much nicer PIT setup, using the much better documented mach_prepare_counter() and mach_countup() helper functions. I'm unhappy to note that the new "common" code uses what appears to be the inferior code. Also, note that this is _not_ a new issue. See "verify_pmtmr_rate()" in drivers/clocksource/acpi_pm.c, along with all the code to check that the reads are stable in "init_acpi_pm_clocksource()". IOW, the PM_TIMER has been found to be broken before. Depending on it for calibration is broken. Linus