From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Brownell Subject: Re: High resolution timers on AT91SAM926x Date: Mon, 3 Mar 2008 17:29:18 -0800 Message-ID: <200803031729.19264.david-b@pacbell.net> References: <200803011457.40857.david-b@pacbell.net> <200803031039.57909.david-b@pacbell.net> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Cc: lkml , linux-rt-users@vger.kernel.org, tglx@linutronix.de To: "Bosko Radivojevic" Return-path: Received: from smtp117.sbc.mail.sp1.yahoo.com ([69.147.64.90]:47970 "HELO smtp117.sbc.mail.sp1.yahoo.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S1754780AbYCDB3V (ORCPT ); Mon, 3 Mar 2008 20:29:21 -0500 In-Reply-To: Content-Disposition: inline Sender: linux-rt-users-owner@vger.kernel.org List-ID: On Monday 03 March 2008, Bosko Radivojevic wrote: > I had CONFIG_ATMEL_TCLIB enabled, but not TCB_CLKSRC and > TCB_CLKSRC_BLOCK=0. With all those options, I finally have HRT > functionality. But, strange thing is that jitter of my little example > (get time, sleep 1ms, get time, show the difference) is around 250us. > Maybe this is normal for this architecture? I have no idea why that would be. Maybe you can find out. :) > System is (as noted on rt.wik site) very slow with NO_HZ option enabled. It doesn't exactly say *why* or compare to other arm926ejs chips ... Could the 64-bit math (ktime stuff) be a factor there? Your board probably only runs at 95 (or-so) bogomips after all. And is that just a NO_HZ issue, or generically an issue when oneshot timer modes are in heavy use? - Dave