From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932140AbbC0P1B (ORCPT ); Fri, 27 Mar 2015 11:27:01 -0400 Received: from sauhun.de ([89.238.76.85]:59032 "EHLO pokefinder.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752239AbbC0P07 (ORCPT ); Fri, 27 Mar 2015 11:26:59 -0400 Date: Fri, 27 Mar 2015 16:27:28 +0100 From: Wolfram Sang To: Guenter Roeck Cc: linux-i2c@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] eeprom: at24: Add support for large EEPROMs connected to SMBus adapters Message-ID: <20150327152727.GA27238@katana> References: <20150318132707.GD3580@katana> <550A4162.8000009@roeck-us.net> <20150319081612.GA900@katana> <20150319174314.GA17329@roeck-us.net> <20150319213937.GA899@katana> <5512C213.7030705@roeck-us.net> <20150327080947.GA900@katana> <5515523F.9010609@roeck-us.net> <20150327130108.GA19151@katana> <551557B4.5000504@roeck-us.net> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="SLDf9lqlvOQaIe6s" Content-Disposition: inline In-Reply-To: <551557B4.5000504@roeck-us.net> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org --SLDf9lqlvOQaIe6s Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Fri, Mar 27, 2015 at 06:14:28AM -0700, Guenter Roeck wrote: > On 03/27/2015 06:01 AM, Wolfram Sang wrote: > >On Fri, Mar 27, 2015 at 05:51:11AM -0700, Guenter Roeck wrote: > >>On 03/27/2015 01:09 AM, Wolfram Sang wrote: > >>> > >>>>just to give you an update: I do have some code, but it is a bit mess= y, > >>>>and it doesn't work well for ds2482 (the chip behind it still hangs up > >>>>if I access it in parallel through i2c-dev). On top of that, it causes > >>>>pretty significant slow-downs when accessing other devices on the same > >>>>bus at the same time. Not surprising, I guess, since it expands the s= cope > >>>>of the bus lock significantly. > >>> > >>>Just to get a better idea: Did you try taking the adapter_lock before > >>>the two SMBus command which needed to be concatenated (and use > >>>smbus_xfer directly)? > >>> > >>I did. I didn't use smbus_xfer directly, though, but introduced lockless > >>versions of the various smbus commands, and kept using those. > > > >And then the chip still hangs? Or was that the performance penalty here? > > > Parallel access to a second eeprom chip on the same bus was much slower > than before. Interesting. I wonder what is the reason, I would have expected just a small delay. Would you mind sending the patches for the non-locked smbus routines? Would be nice to have that around in case I or someone else find some time to try as well. > Also, the new code did not solve the problem for ds2482 (completely unrel= ated > to the at24 driver of course). Even with proper locking, the chip ended up > hanging after some parallel accesses through i2c-dev. Granted, ds2482 is > a difficult beast, but it is still annoying how access through i2c-dev > can mess it up. I assume you basically replaced the access_lock with the adapter_lock with this one? >=20 > The latter is what bothered me more: What is the point of all this if we > still can not ensure correct operation ? Yeah, this is not good at all. How do you use i2c-dev BTW? i2c_rdwr_msgs? What about iterating over all msgs in that and check for busy addresses? --SLDf9lqlvOQaIe6s Content-Type: application/pgp-signature; name="signature.asc" Content-Description: Digital signature -----BEGIN PGP SIGNATURE----- Version: GnuPG v1 iQIcBAEBAgAGBQJVFXbfAAoJEBQN5MwUoCm2yHsP/RbnlGOfSoWzdk6tUN8uUN2H 1abKglp0+2hcXamcVyNfcFgslAHY97dn+ZmrppRyWBiCoXoWn6lLjXMLGjbADZqH GLN1uLTguUZ2h1tR85c4buECIWcdGozC/TDF9t5jPdMEVCPyzjzTXAqUL1OqAeq5 APwpipxKT8NSuSpvMwBCNUYtjGw8UnjfQdJGOhxcKnSBi9yDz4EKgqCtsFokIaW7 K4iL+PfDDiNT7GyZER2gaeX2O+yI0v3QMG6kiFfC3WS7KC+IxUnj87RLEQTtO0eL odTSyX9iFVKwHRUKL/Pa3PEYrUEqSIUYKjEX3Ip6pI1ZEwptzZaetwzhanKmjzH6 nEtGrswNO/1Fume65Qz/o4hE2H3DmBY60/eWoIw7TDraikqSnYbkEkGMRHbQFAUL UC5DUOS38cy9iyAPIaX4CMgX6GJBcsd+Y+f+cQF8z+nA3dGE/dFe5M5HN33pL2uR lJ6Md3XQxJcHPp+RZdaFXF64Q1Ad5v3B335k9xPkN0uvYT4dkrtx8p7n6grgaCdx 7BoaeTStPCgzorSttDJqGI1PrWLcdhsUcVLVpHSjZp7eKNGSZamAqBHxmfrobX5P LSe3fs4ZROaqgQL2TNR4k1bXgu9y65tJFXi6L8yOwzrCfqZEoHsUk0x6UqE2nOrD UJUw6gTwiaTxeZpzwuEx =4GV0 -----END PGP SIGNATURE----- --SLDf9lqlvOQaIe6s--