Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754097Ab1FXVcH (ORCPT ); Fri, 24 Jun 2011 17:32:07 -0400 Received: from nm10.bullet.mail.ird.yahoo.com ([77.238.189.39]:26655 "HELO nm10.bullet.mail.ird.yahoo.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S1751436Ab1FXVcE convert rfc822-to-8bit (ORCPT ); Fri, 24 Jun 2011 17:32:04 -0400 X-Yahoo-Newman-Property: ymail-3 X-Yahoo-Newman-Id: 133600.76971.bm@omp1005.mail.ird.yahoo.com DomainKey-Signature: a=rsa-sha1; q=dns; c=nofws; s=s1024; d=yahoo.com; h=Message-ID:X-YMail-OSG:Received:X-Mailer:Date:From:Subject:To:Cc:In-Reply-To:MIME-Version:Content-Type:Content-Transfer-Encoding; b=XTX1IbXotZ32DvF3kBF6GVBcflSLP6xcYENKf9gYiqyijOeqJcElY+Q1680X6MPOhBkVY4SEZ5aakYhEPVRV25LdUiadzJd8BrYuemASoNK6hooRwf9KarxCXOfZOT6BbYbvGPxl342NU82IjT6oSJspSnbiWyf5rgNz1HJIE5k=; Message-ID: <29629.64539.qm@web29014.mail.ird.yahoo.com> X-YMail-OSG: l3T3HkUVM1m3GZeMNNVdPpzqdsMd_iXsPuSMsZiS0aKO1.. rCG9d70xGMGwevO0ys2TMbpHpvH7xjE7QpSyRKw4KRGoteS3KJwd0FYULXSZ RYXnc.ccmyspFGpq89ACHiQODusZLbmwts7pZ6B2cVBPgQKp5AU7LCgD33IS L8byzQrUp6Q3DCNSlF2M4YkeRJaUfjQFztJS.JO_3NTSYcuznqd2foCdwTmV qW8_XJhetyShdJ0dq2Hkj_UV1IQ.2Z3_Lb1Chg.1WRjC4UgbSntd9Wft1zEn JUROu2sSYjXIiRVAzk0LTEeMKPkRg37C7HK82MFFtKVv22gKbRz6TYpqWIsJ aKySvyb.6GBR7LNPdNGgHfPpIXeNen98Pzj0gQ84I2sFKBMWff4g.aNkgVhA BX8WXK3XNITSE2AhrejjcvN2O9cOHJzS_FYCWNoDlmanC3P.agDdrIGmL4aL X X-Mailer: YahooMailClassic/14.0.3 YahooMailWebService/0.8.111.304355 Date: Fri, 24 Jun 2011 22:32:01 +0100 (BST) From: Paul Parsons Subject: Re: w1/ds1wm regression after 2.6.39: "bus error, retrying" To: =?iso-8859-1?Q?Jean-Fran=E7ois_Dagenais?= Cc: linux-kernel@vger.kernel.org, johnpol@2ka.mipt.ru In-Reply-To: MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2785 Lines: 57 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 --- 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/