From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752198AbaFBRef (ORCPT ); Mon, 2 Jun 2014 13:34:35 -0400 Received: from mga14.intel.com ([192.55.52.115]:7089 "EHLO mga14.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751063AbaFBRed (ORCPT ); Mon, 2 Jun 2014 13:34:33 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.98,958,1392192000"; d="scan'208";a="541345755" Date: Mon, 2 Jun 2014 20:34:08 +0300 From: Mika Westerberg To: Wolfram Sang Cc: Yao Jin , Aubrey Li , linux-i2c@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 1/4] i2c: designware: No need to disable already disabled controller Message-ID: <20140602173408.GB1730@lahna.fi.intel.com> References: <1400164644-3222-1-git-send-email-mika.westerberg@linux.intel.com> <1400164644-3222-2-git-send-email-mika.westerberg@linux.intel.com> <20140602161234.GG2654@katana> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20140602161234.GG2654@katana> 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 On Mon, Jun 02, 2014 at 06:12:34PM +0200, Wolfram Sang wrote: > On Thu, May 15, 2014 at 05:37:21PM +0300, Mika Westerberg wrote: > > If the controller is already in desired state (enabled/disabled) there is > > no point in setting its state again. > > > > Signed-off-by: Mika Westerberg > > --- > > Does it have a side-effect when setting then enable bit again? Otherwise > it will exit the loop immediately on the first try. Not too bad IMO > given the additional code saved. AFAICT there shouldn't be any side effect. So the $subject patch just saves one register write in the best case. You are right, maybe it's not worth adding 3 extra lines of code just for that :) > > > drivers/i2c/busses/i2c-designware-core.c | 4 ++++ > > 1 file changed, 4 insertions(+) > > > > diff --git a/drivers/i2c/busses/i2c-designware-core.c b/drivers/i2c/busses/i2c-designware-core.c > > index b58ecf19e767..b0792675b970 100644 > > --- a/drivers/i2c/busses/i2c-designware-core.c > > +++ b/drivers/i2c/busses/i2c-designware-core.c > > @@ -258,6 +258,10 @@ static void __i2c_dw_enable(struct dw_i2c_dev *dev, bool enable) > > { > > int timeout = 100; > > > > + /* In case the controller is already in desired state */ > > + if ((dw_readl(dev, DW_IC_ENABLE_STATUS) & 1) == enable) > > + return; > > + > > do { > > dw_writel(dev, enable, DW_IC_ENABLE); > > if ((dw_readl(dev, DW_IC_ENABLE_STATUS) & 1) == enable) > > -- > > 2.0.0.rc2 > >