From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Mosberger Date: Tue, 08 Apr 2003 21:41:52 +0000 Subject: Re: [Linux-ia64] [patch] 2.4 timer_interrupt/gettimeoffset machvec Message-Id: List-Id: References: In-Reply-To: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: linux-ia64@vger.kernel.org >>>>> On Tue, 8 Apr 2003 16:35:56 -0400, Jes Sorensen said: Jes> Hi, On systems with a drifting ITC, such as the SGI SN2, the Jes> current implementation of timer_interrupt() and gettimeoffset() Jes> wont work as they rely heavily on ar.itc. Jes> On SN2 this has been solved by using the synchronized RTC in Jes> the system, which results a different implementation of the two Jes> above mentioned functions. Jes> To get around this I suggest we change gettimeoffset() and Jes> timer_intererupt() to be machvec's. I suspect we're better off in the long term making gettimeoffset() a function pointer. I can certainly imagine platforms where multiple interpolation sources are available and depending on parameters (e.g., long-term stability or overhead), one might want to choose one or another. The motivation for changing timer_interrupt() seems suspect to me. The timer interupt is generated PER CPU, so there is no drift issue at all (in fact, we intentionally _skew_ things at boot time to reduce the likelihood of getting all timer interrupts at the same time). --david