From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752335AbcAIEgS (ORCPT ); Fri, 8 Jan 2016 23:36:18 -0500 Received: from mail-ob0-f170.google.com ([209.85.214.170]:34752 "EHLO mail-ob0-f170.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751046AbcAIEgO (ORCPT ); Fri, 8 Jan 2016 23:36:14 -0500 Date: Fri, 8 Jan 2016 22:36:11 -0600 From: Andy Gross To: Sricharan R Cc: iivanov@mm-sol.com, devicetree@vger.kernel.org, linux-arm-msm@vger.kernel.org, galak@codeaurora.org, linux-kernel@vger.kernel.org, linux-i2c@vger.kernel.org, agross@codeaurora.org, dmaengine@vger.kernel.org, linux-arm-kernel@lists.infradead.org Subject: Re: [V5, 3/6] i2c: qup: Transfer each i2c_msg in i2c_msgs without a stop bit Message-ID: <20160109043611.GB4616@hector.attlocal.net> References: <1447760727-4897-4-git-send-email-sricharan@codeaurora.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1447760727-4897-4-git-send-email-sricharan@codeaurora.org> User-Agent: Mutt/1.5.23.1 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Nov 17, 2015 at 05:15:24PM +0530, Sricharan R wrote: > The definition of i2c_msg says that > > "If this is the last message in a group, it is followed by a STOP. > Otherwise it is followed by the next @i2c_msg transaction segment, > beginning with a (repeated) START" > > So the expectation is that there is no 'STOP' bit inbetween individual > i2c_msg segments with repeated 'START'. The QUP i2c hardware has no way > to inform that there should not be a 'STOP' at the end of transaction. > The only way to implement this is to coalesce all the i2c_msg in i2c_msgs > in to one transaction and transfer them. Adding the support for the same. > > This is required for some clients like touchscreen which keeps > incrementing counts across individual transfers and 'STOP' bit inbetween > resets the counter, which is not required. > > This patch adds the support in non-dma mode. > > Signed-off-by: Sricharan R Reviewed-by: Andy Gross