From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751067AbaDOHpl (ORCPT ); Tue, 15 Apr 2014 03:45:41 -0400 Received: from mga02.intel.com ([134.134.136.20]:24769 "EHLO mga02.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750873AbaDOHpk (ORCPT ); Tue, 15 Apr 2014 03:45:40 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.97,862,1389772800"; d="scan'208";a="520969288" Date: Tue, 15 Apr 2014 15:44:43 +0800 From: Feng Tang To: Ingo Molnar Cc: Clemens Ladisch , tglx@linutronix.de, mingo@elte.hu, hpa@zytor.com, linux-kernel@vger.kernel.org, John Stultz , Andy Lutomirski Subject: Re: [PATCH v2] x86: hpet: Don't default CONFIG_HPET_TIMER to be y for X86_64 Message-ID: <20140415074443.GA10911@feng-snb> References: <1395975316-4795-1-git-send-email-feng.tang@intel.com> <20140328071716.GC30107@gmail.com> <20140328073718.GA12762@feng-snb> <53352DE5.2090600@ladisch.de> <20140328081117.GA32308@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20140328081117.GA32308@gmail.com> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Ingo, On Fri, Mar 28, 2014 at 09:11:17AM +0100, Ingo Molnar wrote: > > * Clemens Ladisch wrote: > > > Feng Tang wrote: > > > On Fri, Mar 28, 2014 at 08:17:16AM +0100, Ingo Molnar wrote: > > >> * Feng Tang wrote: > > >> - or the kernel should have a quirk to reliably disable it. Why > > >> should we crash or misbehave if a driver is built into the > > >> kernel? > > > > > > I thought about this before, HPET doesn't have PCI ID like stuff, > > > > HPET does have the PCI vendor ID in the first register. > > > > > only thing I can think of to identify them may be the CPU family/ID. > > > > The HPET is implemented by some actual chip, and that chip also has lots > > of PCI devices. (In the case of a SoC, the CPU ID would work, too). > > Correct. See arch/x86/kernel/hpet.c, which has a large number of HPET > quirks keyed off chipset PCI IDs: > > DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_INTEL, PCI_DEVICE_ID_INTEL_ESB2_0, > ich_force_enable_hpet); > DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_INTEL, PCI_DEVICE_ID_INTEL_ICH6_0, > ich_force_enable_hpet); > DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_INTEL, PCI_DEVICE_ID_INTEL_ICH6_1, > ich_force_enable_hpet); > [...] I just gave it another thought, that the HPET on our platform currently do have some problem to be used as clocksource/clockevent, but it may get fixed in future version (by Silicon or BIOS). If I add quirk to block it now, I may revert this code in future when it get fixed, same problem applis for the future generation of platform. So can we do a small change like below, so that we are able to disable the HPET_TIMER in our own x86_64 .config, while all exising distributions are not affected as it is still default "y" . --- diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig index f67e839..a1027a5 100644 --- a/arch/x86/Kconfig +++ b/arch/x86/Kconfig @@ -711,7 +711,7 @@ source "arch/x86/Kconfig.cpu" config HPET_TIMER def_bool X86_64 - prompt "HPET Timer Support" if X86_32 + prompt "HPET Timer Support" ---help--- Use the IA-PC HPET (High Precision Event Timer) to manage time in preference to the PIT and RTC, if a HPET is Thanks, Feng