Return-path: Received: from xc.sipsolutions.net ([83.246.72.84]:56388 "EHLO sipsolutions.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752314AbZCKRaV (ORCPT ); Wed, 11 Mar 2009 13:30:21 -0400 Subject: Re: [ath9k-devel] [PATCH v5 1/4] ath9k: implement IO serialization From: Johannes Berg To: "Luis R. Rodriguez" Cc: "ath9k-devel@lists.ath9k.org" , "linux-wireless@vger.kernel.org" , "John W. Linville" , Luis Rodriguez In-Reply-To: <43e72e890903111020m10537058wbca980eb07ceb132@mail.gmail.com> (sfid-20090311_182051_361038_EF61AB10) References: <1236739953-17701-1-git-send-email-lrodriguez@atheros.com> <1236739953-17701-2-git-send-email-lrodriguez@atheros.com> <1236762611.9658.87.camel@johannes.local> <20090311160740.GB5669@tesla> <1236791626.20266.37.camel@johannes.local> <43e72e890903111020m10537058wbca980eb07ceb132@mail.gmail.com> (sfid-20090311_182051_361038_EF61AB10) Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="=-YIasxbfJwnmTtWuzjM7N" Date: Wed, 11 Mar 2009 18:30:16 +0100 Message-Id: <1236792616.20266.39.camel@johannes.local> (sfid-20090311_183025_273280_2C8BB8AB) Mime-Version: 1.0 Sender: linux-wireless-owner@vger.kernel.org List-ID: --=-YIasxbfJwnmTtWuzjM7N Content-Type: text/plain Content-Transfer-Encoding: quoted-printable On Wed, 2009-03-11 at 10:20 -0700, Luis R. Rodriguez wrote: > > Hmm. I really don't understand this at all. Most operations won't be > > single writes and reads, and if you need multiple like a write+read for > > indirect register accesses then I'm sure you need to serialise them > > against each other in some other way too, no? >=20 > The issue is not serializing against separate routines calling some > reads or writes, this serialization prevents the PCI hardware FIFO > queue from getting more than two requests as otherwise the hardware > poops out. But as you can see this is only an issue with PCI devices, > not PCI express devices. Well yes, but if you ever do multi-read/write operations then you need to synchronise at a higher level anyway -- hence I don't quite understand why this is necessary at all. johannes --=-YIasxbfJwnmTtWuzjM7N Content-Type: application/pgp-signature; name=signature.asc Content-Description: This is a digitally signed message part -----BEGIN PGP SIGNATURE----- Comment: Johannes Berg (powerbook) iQIcBAABAgAGBQJJt/UmAAoJEKVg1VMiehFY0x0QAKz0cGsW0nsDCV2u47bxoipJ uf7ijDGIHQLxQPKYdefdBMwB0YnQhrrTVfedHndM5eiPUWI4Rj+lrFIbgLjfFV8y FwqXZ23GTV/u5dCmIUr+FCuXjUDw3Bg+L5VPQILI2hNSIYnMZXii+JdbNJtaTpon adbBVTRRb2EwT9I91r9VQ479GQg7PwN/SjpeL1jTxoNuc5rgXLuHYVhFXP2PJ1NW vKH8Gsf39Ohp4NuJx1fZwub8CPlln6iR1+PP3eyE9qn0ibj9jIHmy8qViZiVkFRm zAZkyDe+Or8qKKnD7dBSbRS0He7xBEmNfslAd7VXpD/DTr37JZEAb+2m1udS861D 0Y8hdQkpClgiRpeFuJj8SS2iDzXhWfI6+G+VPeJLYxblNBc1PPxXOgEEZxme7JhU oUS+A2rCcG7p13IWoSW2hPW0mb0YfgxQCy2AX2gXJcipHVFpeZelrNzfLqVeCTmQ TyF0eVeuJiL+3jWgJkQpJMQc4Bq9SkpVxj7BehAi0BXx8Zw4Vq6xEIuqQDR8LrZt z5VZUIoNVOKm+sKm9gNDN42HqUGkEGNC39jOV1Ggjp1LB3+T0UdWzoFtRX6B0KEZ FZq3Ekx4V6M4PFC9ZtD2h/K4MeKnR6mAZ/BvLNO8rzNvPVWdBVa5r/KR/eg1XDfe ru1c2MG57BLZKLJr8+Gy =P/DZ -----END PGP SIGNATURE----- --=-YIasxbfJwnmTtWuzjM7N--