From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S268236AbUIPUgi (ORCPT ); Thu, 16 Sep 2004 16:36:38 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S268257AbUIPUgh (ORCPT ); Thu, 16 Sep 2004 16:36:37 -0400 Received: from twilight.ucw.cz ([81.30.235.3]:35732 "EHLO ucw.cz") by vger.kernel.org with ESMTP id S268236AbUIPUfL (ORCPT ); Thu, 16 Sep 2004 16:35:11 -0400 Date: Thu, 16 Sep 2004 22:34:51 +0200 From: Vojtech Pavlik To: Jesse Barnes Cc: Bjorn Helgaas , Christoph Lameter , linux-kernel@vger.kernel.org, Bob Picco , venkatesh.pallipadi@intel.com Subject: Re: device driver for the SGI system clock, mmtimer Message-ID: <20040916203451.GA5260@ucw.cz> References: <200409161003.39258.bjorn.helgaas@hp.com> <200409160909.12840.jbarnes@engr.sgi.com> <20040916181426.GA5052@ucw.cz> <200409161135.52987.jbarnes@engr.sgi.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <200409161135.52987.jbarnes@engr.sgi.com> User-Agent: Mutt/1.4.1i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Sep 16, 2004 at 11:35:52AM -0700, Jesse Barnes wrote: > On Thursday, September 16, 2004 11:14 am, Vojtech Pavlik wrote: > > On Thu, Sep 16, 2004 at 09:09:12AM -0700, Jesse Barnes wrote: > > > On Thursday, September 16, 2004 9:03 am, Bjorn Helgaas wrote: > > > > Christoph Lameter wrote: > > > > > The timer hardware was designed around the multimedia timer > > > > > specification by Intel but to my knowledge only SGI has implemented > > > > > that standard. The driver was written by Jesse Barnes. > > > > > > > > As far as I can see, drivers/char/hpet.c talks to the same hardware. > > > > HP sx1000 machines (and probably others) also implement the HPET. > > > > > > No, it's different hardware. > > > > mmtimer and hpet are the same hardware actually, just a different > > specification revision, hpet being the newer one. > > Well, the SHub RTC hardware (which mmtimer accesses) isn't really HPET or > mmtimer hardware, but I tried to make the mmtimer *API* useful for HPET style > hardware. The idea was to have several drivers supporting the mmtimer API > with different hardware underneath. Sorry, I got confused by the driver name. > > HPET registers are MMIO so it's in theory possible, while not really > > useful if you're using it as your system timer as well. > > I don't think anyone does this. x86-64 does if SMP is enabled and HPET is present. -- Vojtech Pavlik SuSE Labs, SuSE CR