From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from gate.crashing.org (gate.crashing.org [63.228.1.57]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (Client did not present a certificate) by ozlabs.org (Postfix) with ESMTPS id CD048B7B9D for ; Tue, 13 Oct 2009 20:32:49 +1100 (EST) Subject: Re: i2c-powermac fails From: Benjamin Herrenschmidt To: Jean Delvare In-Reply-To: <20091013112304.74083fd1@hyperion.delvare> References: <20091013112304.74083fd1@hyperion.delvare> Content-Type: text/plain; charset="UTF-8" Date: Tue, 13 Oct 2009 20:32:28 +1100 Message-Id: <1255426348.2192.187.camel@pasglop> Mime-Version: 1.0 Cc: linuxppc-dev@ozlabs.org, Paul Mackerras , Tim Shepard List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On Tue, 2009-10-13 at 11:23 +0200, Jean Delvare wrote: > Hi Ben, Paul, > > I had a report by Tim Shepard (Cc'd) that the therm_adt746x driver > sometimes fails to initialize on his PowerBook G4 running kernel > 2.6.31. The following error message can be seen in the logs when the > failure happens: > > therm_adt746x 7-002e: Thermostat failed to read config! > > After enabling low-level i2c debugging, it turns out that the problem > is caused by low-level errors at the I2C bus level: Nothing comes to mind immediately, but I'll have another look tomorrow. Maybe we are configuring the i2c bus too fast ? Another possibility would be that the device needs some retries ... Ben.