From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from bamako.nerim.net (bamako.nerim.net [62.4.17.28]) by ozlabs.org (Postfix) with ESMTP id 89220B7B80 for ; Fri, 16 Oct 2009 01:05:16 +1100 (EST) Date: Thu, 15 Oct 2009 16:05:13 +0200 From: Jean Delvare To: Benjamin Herrenschmidt Subject: Re: i2c-powermac fails Message-ID: <20091015160513.5c356b7e@hyperion.delvare> In-Reply-To: <1255605559.2347.102.camel@pasglop> References: <20091013112304.74083fd1@hyperion.delvare> <1255426348.2192.187.camel@pasglop> <20091013114948.03608b7f@hyperion.delvare> <20091014230252.0d0cba8d@hyperion.delvare> <1255555575.2347.56.camel@pasglop> <20091015124923.23863a94@hyperion.delvare> <1255605559.2347.102.camel@pasglop> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Cc: Paul Mackerras , Tim Shepard , linuxppc-dev@ozlabs.org List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On Thu, 15 Oct 2009 22:19:19 +1100, Benjamin Herrenschmidt wrote: > On Thu, 2009-10-15 at 12:49 +0200, Jean Delvare wrote: > > Oh. Well, if that was the case, we would see errors all the time, not > > just during initialization, right? Or does the I2C clock frequency > > change over time somehow? > > No but maybe we are a bit on the "limit" of the device and some > registers take long to respond than others ? Unlikely. The ADT7460 can run at I2C clock rates up to 400 kHz while the Keywest I2C runs at 25, 50 or 100 kHz if I read the code properly. I don't know what exact speed is used on Tim's system, apparently it is read from the hardware in the device tree directly? We could have low_i2c.c log the I2C clock frequency and/or try to force the lowest speed (25 kHz) and see if it helps, but I very much doubt it. And I'd rather wait for Tim to report the result with my last patch first. -- Jean Delvare