From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S262971AbTHZXvK (ORCPT ); Tue, 26 Aug 2003 19:51:10 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S262962AbTHZXvK (ORCPT ); Tue, 26 Aug 2003 19:51:10 -0400 Received: from fmr09.intel.com ([192.52.57.35]:19416 "EHLO hermes.hd.intel.com") by vger.kernel.org with ESMTP id S262971AbTHZXvH convert rfc822-to-8bit (ORCPT ); Tue, 26 Aug 2003 19:51:07 -0400 content-class: urn:content-classes:message MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 8BIT X-MimeOLE: Produced By Microsoft Exchange V6.0.6375.0 Subject: RE: [PATCH][2.6][2/5]Support for HPET based timer Date: Tue, 26 Aug 2003 16:50:59 -0700 Message-ID: X-MS-Has-Attach: X-MS-TNEF-Correlator: Thread-Topic: [PATCH][2.6][2/5]Support for HPET based timer Thread-Index: AcNsKjH9V5kc6qmsRMGYcCxS4EG9uQAAKQ6Q From: "Pallipadi, Venkatesh" To: "john stultz" , "Andrew Morton" Cc: , "Andi Kleen" , "Dave H" , , "Nakajima, Jun" , "Siddha, Suresh B" , "lkml" X-OriginalArrivalTime: 26 Aug 2003 23:50:59.0608 (UTC) FILETIME=[E6627980:01C36C2C] Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org > -----Original Message----- > From: john stultz [mailto:johnstul@us.ibm.com] > > Well, the difficult part is deciding in time_init() if we are going to > use HPET without touching the hardware (to say, check if its actually > there). > Yes. But, currently we are using ACPI early table parse to look at HPET. So we should be OK here. Even if accessing HPET hardware fails later, in the late_time_init(), we can fallback to PIT, as long as calibrate_delay() is done after late_time_init(). > We could pick a simple time source (ie: PIT) that would get us through > early boot, then choose the real time source in late_time_init(). That > would also make implementing the ACPI PM time-source much simpler as we > could wait until after ACPI is up, letting us avoid having to parse the > tables by hand. > > However I'm not sure it would be trivial and bug free. ;) > Depending on multiple time sources may not be good idea, IMO. May be, one day we will have a fully-legacy-free system with no PIT. :) Thanks, -Venkatesh