From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from vega.surpasshosting.com (vega.surpasshosting.com [72.29.83.9]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (Client did not present a certificate) by ozlabs.org (Postfix) with ESMTPS id 410A5B7BDF for ; Wed, 23 Dec 2009 02:38:37 +1100 (EST) Received: from bzq-82-81-146-158.red.bezeqint.net ([82.81.146.158]:50909 helo=[10.0.0.3]) by vega.surpasshosting.com with esmtpa (Exim 4.69) (envelope-from ) id 1NN6oj-0003T6-Ah for linuxppc-dev@ozlabs.org; Tue, 22 Dec 2009 10:38:33 -0500 Message-ID: <4B30E7F5.8080201@embedded-sol.com> Date: Tue, 22 Dec 2009 17:38:29 +0200 From: Felix Radensky MIME-Version: 1.0 To: linuxppc-dev@ozlabs.org Subject: I2C bus clock on MPC85XX systems Content-Type: text/plain; charset=ISO-8859-1; format=flowed List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Hi, Almost all MPC85XX based systems have the compatible=:"fsl-i2c" in respective i2c device tree nodes. This causes FSL i2c driver to use the following "backward compatible" values: FSR=0x31 DFSR=0x10. This is regardless of CCB clock frequency and i2c clock prescaler. On my custom MPC8536 based board with 432MHz CCB clock this results in 65KHz i2c clock frequency (checked with scope). U-Boot correctly configures the clock to 400KHz. I've fixed the problem by modifying device tree to use different compatible value, similar to what socrates board does. Is this the right approach ? Thanks. Felix.