From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752714Ab0CRWEg (ORCPT ); Thu, 18 Mar 2010 18:04:36 -0400 Received: from jurassic.park.msu.ru ([195.208.223.243]:58821 "EHLO jurassic.park.msu.ru" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751790Ab0CRWEe (ORCPT ); Thu, 18 Mar 2010 18:04:34 -0400 X-Greylist: delayed 1474 seconds by postgrey-1.27 at vger.kernel.org; Thu, 18 Mar 2010 18:04:33 EDT Date: Fri, 19 Mar 2010 00:40:30 +0300 From: Ivan Kokshaysky To: john stultz Cc: Richard Henderson , lkml , Thomas Gleixner , Matt Turner Subject: Re: [RFC][PATCH] Convert alpha to use clocksource Message-ID: <20100318214030.GA8934@jurassic.park.msu.ru> References: <1268877702-2236-1-git-send-email-johnstul@us.ibm.com> <4BA23974.5030503@twiddle.net> <1268934923.1855.8.camel@work-vm> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1268934923.1855.8.camel@work-vm> User-Agent: Mutt/1.5.17 (2007-11-01) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Mar 18, 2010 at 10:55:23AM -0700, john stultz wrote: > On Thu, 2010-03-18 at 07:32 -0700, Richard Henderson wrote: > > On 03/17/2010 07:01 PM, John Stultz wrote: > > > Alpha has a tsc like rpcc counter that it uses to manage time. > > > This can be converted to an actual clocksource instead of utilizing > > > the arch_gettimeoffset method that is really only there for legacy > > > systems with no continuous counter. > > > > With 8 seconds or less between roll-overs, do you actually consider > > this a continuous counter? I don't. I suggest this be left alone. > > The timekeeping code handles this (although the shift value I picked may > need some adjustment - what is the expected counter freq range on > alpha?). The ACPI PM counter which is very common on x86 is only 24 bits > and rolls over in ~5 seconds. It works fine. Yeah, that looks cool. I'm typing this on the 800MHz UP1500 running 2.6.34-rc1 plus your patch, and the timekeeping works fine so far. Though, even after a glance over the clocksource code, I've not gotten yet to how one could estimate the "shift" value... Any hints? And if I recall correctly, production alphas have been clocked in the range of 60-1250 MHz. Ivan.