From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from crystal.sipsolutions.net ([195.210.38.204]:51238 "EHLO sipsolutions.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1762827AbXLMRde (ORCPT ); Thu, 13 Dec 2007 12:33:34 -0500 Subject: iwl4965 vs b43 time drift? From: Johannes Berg To: Tomas Winkler Cc: linux-wireless Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="=-BFVdVZgn/w49r6tlw7G9" Date: Thu, 13 Dec 2007 18:33:17 +0100 Message-Id: <1197567197.8313.27.camel@johannes.berg> (sfid-20071213_173345_742079_655EF7D5) Mime-Version: 1.0 Sender: linux-wireless-owner@vger.kernel.org List-ID: --=-BFVdVZgn/w49r6tlw7G9 Content-Type: text/plain Content-Transfer-Encoding: quoted-printable Hi, I'm debugging a timing problem with b43, can you tell me exactly when the timestamp iwl4965 shows in radiotap is taken? Is it the first bit of the preamble? When associated to my b43 AP, I'd expect the difference between the beacon/proberesp timestamp and the MAC timestamp of the iwl4965 monitor mode to be 192us for the MAC header and another 192us for the PLCP preamble/PLCP header, a total of 384 us. However, when I have just associated, the difference starts out at 383us and decreases, down to ~370us and then varies between 370-380us, afaict never reaching 384us. The strange thing is that it doesn't seem to recover. No matter which of the timers is actually wrong (I guess I could find out by comparing with the system timestamp and hoping that the delay through mac80211 into wireshark is constant) shouldn't it recover the time? Another problem is that when I enable powersave on the iwl4965, I see no beacons at all. And oddly, the difference between the timestamp in the probe responses and the iwl4965 MAC timestamp starts varying wildly, up to almost 5000us. I guess that b43 has a timing problem otherwise we'd be seeing totally bad behaviour of iwl4965 on stock APs. I'm just trying to understand the problem better right now. Do you know when iwl4965 will resync the timer? Thanks, johannes --=-BFVdVZgn/w49r6tlw7G9 Content-Type: application/pgp-signature; name=signature.asc Content-Description: This is a digitally signed message part -----BEGIN PGP SIGNATURE----- Comment: Johannes Berg (powerbook) iQIVAwUAR2Fs3KVg1VMiehFYAQIyDRAApnCJjf6h5kL3evKj57XmC2ncuNqnLmyd 87wmIJ6S5bYZHdYGVOEgqz0clV8NVl4zdF+u7w74b5x643qB15/SqBOVu3DGD2fz 8opWgjN6CAmSUsf6stx0IAkn9UJCBKPrNoYhJw3bzDtfX5H0CoAeD14I9sScqxH8 aFyQxGEaHJXj2oTvucDJifYRFueaW6hu15oMjIYib88970E9oBDWSylNY2062lCz x9YKHtk6P0P/suos84onsx/4CLV4xqKfaECl49n++2LE1ZPrsnskkK2bbVNSoSVV YZUR6WSeZl28qloqHCg/Z3xVcY94W3YU+rLF+7zdr7sr4F4p+gG5+l44snG1d1nI xU5smPGGmcrn5lrXtj0R9Nf3y1SFCfjwV+txBXa06j1tJNG6UVDMSexxcl3HiKKg 8CxRmcREZ05BqYeCKFOwn2gHQtw6OvTDlJtZvBOpLq92snAadJd5Xq0oxqT+Ug7U gSz1U+lt3OIF4Kug9+tkuLpaJ38hmy516nJ2OVWRixELe28ywz08tXe0nWAVpIev +DGvkbVGMfdtXjU6zVQB+Ov8A7ErU/Csurz55Bbff/uYbjuHtGnGgEX8ebwui0dX +D0xmdWkyHN09LSwTrF1osWsH47sJfPYpfLt/X2/lOJn6wkDhO0yGF0QAsxcou24 m6fdq4cviPs= =na1T -----END PGP SIGNATURE----- --=-BFVdVZgn/w49r6tlw7G9--