Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753840AbbFISiB (ORCPT ); Tue, 9 Jun 2015 14:38:01 -0400 Received: from mail-ob0-f195.google.com ([209.85.214.195]:33142 "EHLO mail-ob0-f195.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752041AbbFIShw (ORCPT ); Tue, 9 Jun 2015 14:37:52 -0400 MIME-Version: 1.0 In-Reply-To: <20150609085146.GD1478@lahna.fi.intel.com> References: <1433785828-4100-1-git-send-email-lucas.de.marchi@gmail.com> <20150609085146.GD1478@lahna.fi.intel.com> From: Lucas De Marchi Date: Tue, 9 Jun 2015 15:29:01 -0300 Message-ID: Subject: Re: [PATCH] i2c: designware: use enable on resume instead initialization To: Mika Westerberg Cc: linux-i2c@vger.kernel.org, lkml , Wolfram Sang , Jarkko Nikula , Fabio Mello , Lucas De Marchi , Christian Ruppert Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1778 Lines: 43 Hi Mika, On Tue, Jun 9, 2015 at 5:51 AM, Mika Westerberg wrote: > On Mon, Jun 08, 2015 at 02:50:28PM -0300, lucas.de.marchi@gmail.com wrote: >> From: Fabio Mello >> >> According to documentation and tests, initialization is not >> necessary on module resume, since the controller keeps its state >> between disable/enable. Change the target address is also allowed. >> >> So, this patch replaces the initialization on module resume with a >> simple enable, and removes the (non required anymore) enables and >> disables. >> >> Signed-off-by: Fabio Mello >> Signed-off-by: Lucas De Marchi >> --- >> >> These pictures explain a little more the consequence of letting the >> enable+disable in the code: >> >> http://pub.politreco.com/paste/TEK0011-before.jpg >> http://pub.politreco.com/paste/TEK0007-after.jpg >> >> The yellow line is a GPIO toggle in userspace to mark when we start and finish >> the i2c transactions. The blue line is the SCL in that i2c bus. Take a look on >> the huge pauses we have between any 2 transactions. These pauses are removed >> with this patch and we are able to read our sensor's values in 950usec rather >> than 5.24msec we had before. We are testing this using a Minnowboard Max that >> has a designware i2c controller. > > Did you test this on any other platform than Intel Baytrail? No. The only soc we have here with this controller is the Baytrail. -- Lucas De Marchi -- 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/