From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from gate.crashing.org (gate.crashing.org [63.228.1.57]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (Client did not present a certificate) by ozlabs.org (Postfix) with ESMTP id 14FE1DE0D4 for ; Fri, 12 Oct 2007 06:58:58 +1000 (EST) Subject: Re: [PATCH] Make clockevents work on PPC601 processors From: Benjamin Herrenschmidt To: Kumar Gala In-Reply-To: <96C1AFB8-784F-445E-A3F2-5D68494541CD@kernel.crashing.org> References: <18190.3365.54961.935346@cargo.ozlabs.ibm.com> <96C1AFB8-784F-445E-A3F2-5D68494541CD@kernel.crashing.org> Content-Type: text/plain Date: Fri, 12 Oct 2007 06:58:52 +1000 Message-Id: <1192136332.8476.58.camel@pasglop> Mime-Version: 1.0 Cc: linuxppc-dev@ozlabs.org, Paul Mackerras Reply-To: benh@kernel.crashing.org List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On Thu, 2007-10-11 at 09:12 -0500, Kumar Gala wrote: > On Oct 11, 2007, at 6:46 AM, Paul Mackerras wrote: > > > In testing the new clocksource and clockevent code on a PPC601 > > processor, I discovered that the clockevent multiplier value for the > > decrementer clockevent was overflowing. Because the RTCL register in > > the 601 effectively counts at 1GHz (it doesn't actually, but it > > increases by 128 every 128ns), and the shift value was 32, that meant > > the multiplier value had to be 2^32, which won't fit in an unsigned > > long on 32-bit. The same problem would arise on any platform where > > the timebase frequency was 1GHz or more (not that we actually have any > > such machines today). > > do you still have a 601 running somewhere? On my desk :-) (and he also has a 601 card for the 7500 iirc) /me remembers to revive his dual 604 8500 one of these days. Ben.