Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933363AbbFJHJl (ORCPT ); Wed, 10 Jun 2015 03:09:41 -0400 Received: from mga09.intel.com ([134.134.136.24]:14260 "EHLO mga09.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753866AbbFJHJe (ORCPT ); Wed, 10 Jun 2015 03:09:34 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.13,586,1427785200"; d="scan'208";a="744109194" Date: Wed, 10 Jun 2015 10:07:22 +0300 From: Mika Westerberg To: Lucas De Marchi Cc: linux-i2c@vger.kernel.org, lkml , Wolfram Sang , Jarkko Nikula , Fabio Mello , Lucas De Marchi , Christian Ruppert Subject: Re: [PATCH] i2c: designware: use enable on resume instead initialization Message-ID: <20150610070722.GM1478@lahna.fi.intel.com> References: <1433785828-4100-1-git-send-email-lucas.de.marchi@gmail.com> <20150609085146.GD1478@lahna.fi.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Organization: Intel Finland Oy - BIC 0357606-4 - Westendinkatu 7, 02160 Espoo User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2021 Lines: 44 On Tue, Jun 09, 2015 at 03:29:01PM -0300, Lucas De Marchi wrote: > 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. My concern is that this patch might break some non-Intel platform. It would be nice if someone (Christian?) could try this out. -- 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/