Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751558Ab1FYMyJ (ORCPT ); Sat, 25 Jun 2011 08:54:09 -0400 Received: from smarthost3.mail.uk.easynet.net ([212.135.6.13]:42076 "EHLO smarthost3.mail.uk.easynet.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751348Ab1FYMyG convert rfc822-to-8bit (ORCPT ); Sat, 25 Jun 2011 08:54:06 -0400 thread-index: AcwzNwe2Yl2JEBs1TOS3ta5nBypKMA== Subject: Re: w1/ds1wm regression after 2.6.39: "bus error, retrying" MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" From: =?iso-8859-1?Q?Jean-Fran=E7ois_Dagenais?= In-Reply-To: <29629.64539.qm@web29014.mail.ird.yahoo.com> Date: Sat, 25 Jun 2011 08:54:01 -0400 Cc: , Content-Transfer-Encoding: 8BIT Message-ID: <53BB78ED-FEDC-471F-A371-2B902A359B65@sonatest.com> References: <29629.64539.qm@web29014.mail.ird.yahoo.com> To: "Paul Parsons" X-Mailer: Apple Mail (2.1084) Content-Class: urn:content-classes:message Importance: normal X-OriginalArrivalTime: 25 Jun 2011 12:54:32.0705 (UTC) FILETIME=[07630710:01CC3337] X-MimeOLE: Produced By Microsoft MimeOLE V6.00.3790.4841 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4477 Lines: 88 On 2011-06-24, at 17:32, Paul Parsons wrote: > Here's the debug output from ds1wm_search(): > > ds1wm ds1wm: search begin > ds1wm ds1wm: pass: 1 r : 0x0000000000000000 writing SEARCH_ROM > ds1wm ds1wm: pass: 1 entering ASM > ds1wm ds1wm: pass: 1 begining nibble loop > ds1wm ds1wm: pass: 1 r': 0xd300001085da8430 d:0x0000000000000000 > ds1wm ds1wm: pass: 1 nibble loop complete, exiting ASM > ds1wm ds1wm: pass: 1 resetting bus > ds1wm ds1wm: pass: 1 found 0xd300001085da8430 > ds1wm ds1wm: pass: 1 complete, preparing next pass > ds1wm ds1wm: pass: 1 new d:0x0000000000000000 MS discrep bit:-1 > ds1wm ds1wm: pass: 1 total: 1 search done ms d bit pos: -1 > > The hx4700 does indeed have a ds2760 connected to the ds1wm. I believe the ds1wm is integrated into the HTC ASIC3, but my knowledge of the hardware is almost zero. > > Regards, > Paul Hi again Paul, This seems to be the output after you have restored the msleep. Could you provide it without so we can get a better idea as to what happened. If indeed this is a major regression for many devices, we'll have to submit a patch to the main branch. /jfd > > --- On Fri, 24/6/11, Jean-Fran?ois Dagenais wrote: >> The sleep I removed there only delays the time between the >> reset pulse and the function exiting, it doesn't populate >> the "slave_present" variable with a different value. The >> reset pulse and the wait that the ds1wm implements (by >> raising an interrupt at the end of it all) is spec'ed on the >> 1-wire specification, and the DS1WM_TIMEOUT is a really long >> time. So there should be plenty of time for the slaves to >> acknowledge the reset and participate in further >> communications. >> >> So here's my hunch. We observed this here on our circuit >> too. It is possible that the pull-up resistor on your >> circuit is too resistive which would make the slave device >> fail to properly come back to life after the reset pulse >> (bus shorted to the ground) when the drain opens, and hence >> not able to cope well with the search that follows. The 1ms >> wait basically gives the slave(s) time to charge up again >> (with the drain open, the voltage is high). >> >> The weird thing is that the ds1wm_reset function returns 0, >> since the while loop executes more than once, so it did find >> a slave (slave_present obtained from the PDR status bit), so >> the slave is kinda there... But the search fails somehow >> after that. Maybe there is something in your slave's spec >> sheet that could help, although the ds1wm reset timings. So >> I still think the debug trace and knowing if you have only >> one slave on the bus would help me figure this out. New >> question: what slave(s)? is it the DS2760? >> >> PS: there are also controls in the DS1WM_CNTRL register >> that has to do with strong-pull-ups which are just not used >> by the driver yet. refer to: http://datasheets.maxim-ic.com/en/ds/DS1WM.pdf > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/ Jean-Francois Dagenais Software Architect - B.Sc.A Experience the new veo phased array flaw detector at www.sonatestveo.com. 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