From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753503AbbC0PmM (ORCPT ); Fri, 27 Mar 2015 11:42:12 -0400 Received: from bh-25.webhostbox.net ([208.91.199.152]:39159 "EHLO bh-25.webhostbox.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752441AbbC0PmI (ORCPT ); Fri, 27 Mar 2015 11:42:08 -0400 Message-ID: <55157A4A.1090305@roeck-us.net> Date: Fri, 27 Mar 2015 08:42:02 -0700 From: Guenter Roeck User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.5.0 MIME-Version: 1.0 To: Wolfram Sang 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 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> <20150327152727.GA27238@katana> In-Reply-To: <20150327152727.GA27238@katana> Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit X-Authenticated_sender: linux@roeck-us.net X-OutGoing-Spam-Status: No, score=-1.0 X-CTCH-PVer: 0000001 X-CTCH-Spam: Unknown X-CTCH-VOD: Unknown X-CTCH-Flags: 0 X-CTCH-RefID: str=0001.0A020203.55157A4F.041A,ss=1,re=0.001,recu=0.000,reip=0.000,cl=1,cld=1,fgs=0 X-CTCH-Score: 0.001 X-CTCH-ScoreCust: 0.000 X-CTCH-Rules: C_4847, X-CTCH-SenderID: linux@roeck-us.net X-CTCH-SenderID-Flags: 0 X-CTCH-SenderID-TotalMessages: 1 X-CTCH-SenderID-TotalSpam: 0 X-CTCH-SenderID-TotalSuspected: 0 X-CTCH-SenderID-TotalConfirmed: 0 X-CTCH-SenderID-TotalBulk: 0 X-CTCH-SenderID-TotalVirus: 0 X-CTCH-SenderID-TotalRecipients: 0 X-AntiAbuse: This header was added to track abuse, please include it with any abuse report X-AntiAbuse: Primary Hostname - bh-25.webhostbox.net X-AntiAbuse: Original Domain - vger.kernel.org X-AntiAbuse: Originator/Caller UID/GID - [47 12] / [47 12] X-AntiAbuse: Sender Address Domain - roeck-us.net X-Get-Message-Sender-Via: bh-25.webhostbox.net: mailgid no entry from get_relayhosts_entry X-Source: X-Source-Args: X-Source-Dir: Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 03/27/2015 08:27 AM, Wolfram Sang wrote: > 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 messy, >>>>>> 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 scope >>>>>> 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. > I pushed it into my linux repository at github (https://github.com/groeck/linux, branch at24). >> Also, the new code did not solve the problem for ds2482 (completely unrelated >> 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? > yes. >> >> 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? > In this case, I just used i2cdump from one session while accessing the chip from another session using the driver. Guenter