From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757501AbaC1CtG (ORCPT ); Thu, 27 Mar 2014 22:49:06 -0400 Received: from mga02.intel.com ([134.134.136.20]:54032 "EHLO mga02.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757010AbaC1CtD (ORCPT ); Thu, 27 Mar 2014 22:49:03 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.97,747,1389772800"; d="scan'208";a="481858325" Date: Fri, 28 Mar 2014 10:48:13 +0800 From: Feng Tang To: Andy Lutomirski Cc: Clemens Ladisch , tglx@linutronix.de, mingo@elte.hu, hpa@zytor.com, linux-kernel@vger.kernel.org Subject: Re: [PATCH] x86: hpet: Don't default CONFIG_HPET_TIMER to be y for X86_64 Message-ID: <20140328024813.GB31111@feng-snb> References: <1395906309-7519-1-git-send-email-feng.tang@intel.com> <53340561.4050708@ladisch.de> <53348199.7070207@mit.edu> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <53348199.7070207@mit.edu> 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 On Thu, Mar 27, 2014 at 12:52:57PM -0700, Andy Lutomirski wrote: > On 03/27/2014 04:02 AM, Clemens Ladisch wrote: > > Feng Tang wrote: > >> On many new phone/tablet platforms like Baytrail/Merrifield etc, > >> the HPET are either defeatured or has some problem to be used > >> as a reliable timer. As these platforms also have X86_64, we > >> should not make HPET_TIMER default y for all X86_64. > > Wouldn't it be better to fix the hpet driver so that the hpet doesn't > used on these platforms? > > > > > The help text still says: > > | You can safely choose Y here. [...] > > | Choose N to continue using the legacy 8254 timer. > > > > Are these statements still true for those platforms? > > They aren't true for modern desktop and server platforms -- the TSC is > used regardless of hpet availability. The way of using TSC varies depends on the generations of platforms. Thomas Gleixner once gave a very good description, which link I personally bookmarked, and would share here: https://lkml.org/lkml/2013/5/8/202 Thanks, Feng