Return-path: Received: from gw.indranet.co.nz ([203.167.203.10]:3590 "EHLO enso.acheron.indranet.co.nz" rhost-flags-OK-FAIL-OK-FAIL) by vger.kernel.org with ESMTP id S1754057AbYATCWj (ORCPT ); Sat, 19 Jan 2008 21:22:39 -0500 Date: Sun, 20 Jan 2008 15:12:11 +1300 (NZDT) From: Derek Smithies To: "Luis R. Rodriguez" cc: Bruno Randolf , jirislaby@gmail.com, Michael Wu , ath5k-devel@lists.ath5k.org, linux-wireless@vger.kernel.org, linville@tuxdriver.com, Johannes Berg Subject: Re: [ath5k-devel] [PATCH 2/4] ath5k: always extend rx timestamp with tsf In-Reply-To: <43e72e890801191420p5c25e32aid790748a982bd54d@mail.gmail.com> Message-ID: (sfid-20080120_022250_359821_9F324922) References: <20080118125018.6342.94435.stgit@one> <20080118125059.6342.18514.stgit@one> <43e72e890801191420p5c25e32aid790748a982bd54d@mail.gmail.com> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-wireless-owner@vger.kernel.org List-ID: Hi, On Sat, 19 Jan 2008, Luis R. Rodriguez wrote: > On Jan 18, 2008 7:50 AM, Bruno Randolf wrote: > > + * always extend the mac timestamp, since this information is > > + * also needed for proper IBSS merging. > > + * > > + * XXX: it might be too late to do it here, since rs_tstamp is > > + * 15bit only. that means TSF extension has to be done within > > + * 32.768usec = 32ms. it might be necessary to move this to the > > + * interrupt handler, like it is done in madwifi. > > + */ > > I'm trying to understand this a bit more and am confused. The TSF > timer is based on 1MHz clock so it has a resolution of 1 microsecond > (us). For 15 bits that would mean 32768 us so don't you mean it should > be done within 32.768 ms instead of usec (or us)? > Hi, it is a typo. You are correct. It should be done within 32.768 ms. On a high end laptop, it is almost guaranteed that the bottom half will process the packet within 32 ms. However, on an embedded box (low spec cpu) that has a temporarily high load, 32 ms is a short time, and the timestamp may have wrapped around. this is unfortunate. Derek. -- Derek Smithies Ph.D. IndraNet Technologies Ltd. Email: derek@indranet.co.nz ph +64 3 365 6485 Web: http://www.indranet-technologies.com/