From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from gateway-1237.mvista.com (gateway-1237.mvista.com [63.81.120.158]) by ozlabs.org (Postfix) with ESMTP id 11CB7DDE1B for ; Thu, 20 Sep 2007 11:57:50 +1000 (EST) Subject: Re: [PATCH 2/5] Implement generic time of day clocksource for powerpc machines. From: Daniel Walker To: Paul Mackerras In-Reply-To: <18161.53509.342082.588911@cargo.ozlabs.ibm.com> References: <20070919064947.4B5A1399910@thor> <1190216594.11899.3.camel@imap.mvista.com> <18161.50240.599267.768383@cargo.ozlabs.ibm.com> <1190252151.11899.66.camel@imap.mvista.com> <18161.53509.342082.588911@cargo.ozlabs.ibm.com> Content-Type: text/plain Date: Wed, 19 Sep 2007 18:54:41 -0700 Message-Id: <1190253281.11899.74.camel@imap.mvista.com> Mime-Version: 1.0 Cc: linuxppc-dev@ozlabs.org, Thomas Gleixner , johnstul@us.ibm.com, Realtime Kernel List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On Thu, 2007-09-20 at 11:46 +1000, Paul Mackerras wrote: > Daniel Walker writes: > > > On Thu, 2007-09-20 at 10:52 +1000, Paul Mackerras wrote: > > > Daniel Walker writes: > > > > > > > If you switch to the rtc do the shift and mult need to change? > > > > > > You can't switch; any given CPU chip will have either the RTC or the > > > timebase but not both. > > > > The code is switching between to clock read functions .. If they are > > What part of "you can't switch" wasn't clear? __USE_RTC() is a > constant on any given machine. Maybe say "It a constant" up front .. The value that is output from the clocksource read is converted to nanoseconds .. This clocksource is only designed to work with the timebase, so it doesn't make sense to output an rtc value. Daniel