From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932100AbVLQV3a (ORCPT ); Sat, 17 Dec 2005 16:29:30 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S932125AbVLQV3a (ORCPT ); Sat, 17 Dec 2005 16:29:30 -0500 Received: from lame.durables.org ([64.81.244.120]:58539 "EHLO calliope.durables.org") by vger.kernel.org with ESMTP id S932100AbVLQV3a (ORCPT ); Sat, 17 Dec 2005 16:29:30 -0500 Subject: Re: [PATCH 07/13] [RFC] ipath core misc files From: Robert Walsh To: Andrew Morton Cc: Roland Dreier , linux-kernel@vger.kernel.org, openib-general@openib.org In-Reply-To: <20051217123850.aa6cfd53.akpm@osdl.org> References: <200512161548.KglSM2YESlGlEQfQ@cisco.com> <200512161548.3fqe3fMerrheBMdX@cisco.com> <20051217123850.aa6cfd53.akpm@osdl.org> Content-Type: text/plain Date: Sat, 17 Dec 2005 13:29:23 -0800 Message-Id: <1134854963.20575.17.camel@phosphene.durables.org> Mime-Version: 1.0 X-Mailer: Evolution 2.2.3 (2.2.3-2.fc4) Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org > > +void ipath_init_picotime(void) > > +{ > > + int i; > > + u_int64_t ts, te, delta = -1ULL; > > + > > + for (i = 0; i < 5; i++) { > > + ts = get_cycles(); > > + udelay(250); > > + te = get_cycles(); > > + if ((te - ts) < delta) > > + delta = te - ts; > > + yield(); > > + } > > + _ipath_pico_per_cycle = 250000000 / delta; > > +} > > hm, I hope this is debug code which is going away. If not, we should take > a look at what it's trying to do here. This isn't debug code. It's used to calculate the roughly number picoseconds per cycle. This is used in the driver to make sure HyperTransport reads haven't timed out (see ipath_snap_cntr in ipath_driver.c) when reading chip counters. If you can think of a better way of figuring out whether a read took greater than a certain length of time, I'd be interested in knowing it. Regards, Robert. -- Robert Walsh Email: rjwalsh@pathscale.com PathScale, Inc. Phone: +1 650 934 8117 2071 Stierlin Court, Suite 200 Fax: +1 650 428 1969 Mountain View, CA 94043.