Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758900Ab2BJJfN (ORCPT ); Fri, 10 Feb 2012 04:35:13 -0500 Received: from mail-vx0-f174.google.com ([209.85.220.174]:39004 "EHLO mail-vx0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757894Ab2BJJfI convert rfc822-to-8bit (ORCPT ); Fri, 10 Feb 2012 04:35:08 -0500 MIME-Version: 1.0 In-Reply-To: <1324898081-10308-1-git-send-email-alokc@nvidia.com> References: <1324898081-10308-1-git-send-email-alokc@nvidia.com> Date: Fri, 10 Feb 2012 15:05:07 +0530 Message-ID: Subject: Re: [PATCH v2] i2c: tegra: Add delay before reset the controller From: Shubhrajyoti Datta To: Alok Chauhan Cc: khali@linux-fr.org, ben-linux@fluff.org, swarren@nvidia.com, olof@lixom.net, bones@secretlab.ca, paul.gortmaker@windriver.com, dgreid@google.com, ldewangan@nvidia.com, linux-tegra@vger.kernel.org, linux-i2c@vger.kernel.org, linux-kernel@vger.kernel.org Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2143 Lines: 53 Hello Alok, On Mon, Dec 26, 2011 at 4:44 PM, Alok Chauhan wrote: > From: Alok Chauhan > > In NACK error condition, I2C controller violates > clock-to-data setup time before stop. In Software, > because of this reset of controller is happening > before I2C controller could complete STOP condition. > > Added delay of 2 clock period before reset the > controller in case of NACK error. > > Signed-off-by: Alok Chauhan > --- > Instead of setting constant value for delay as was in previous patch, now in > the current modification delay will be calculated based on clock frequency of the bus. > ?drivers/i2c/busses/i2c-tegra.c | ? ?8 ++++++++ > ?1 files changed, 8 insertions(+), 0 deletions(-) > > diff --git a/drivers/i2c/busses/i2c-tegra.c b/drivers/i2c/busses/i2c-tegra.c > index 6381604..62e197c 100644 > --- a/drivers/i2c/busses/i2c-tegra.c > +++ b/drivers/i2c/busses/i2c-tegra.c > @@ -517,6 +517,14 @@ static int tegra_i2c_xfer_msg(struct tegra_i2c_dev *i2c_dev, > ? ? ? ?if (likely(i2c_dev->msg_err == I2C_ERR_NONE)) > ? ? ? ? ? ? ? ?return 0; > > + ? ? ? /* > + ? ? ? ?* In NACK error condition resetting of I2C controller happens > + ? ? ? ?* before STOP condition is properly completed by I2C controller, > + ? ? ? ?* so wait for 2 clock cycle to complete STOP condition. > + ? ? ? ?*/ Why do you need to reset the controller in case of a NACK. > + ? ? ? if (i2c_dev->msg_err == I2C_ERR_NO_ACK) > + ? ? ? ? ? ? ? udelay(DIV_ROUND_UP(2 * 1000000, i2c_dev->bus_clk_rate)); > + > ? ? ? ?tegra_i2c_init(i2c_dev); > ? ? ? ?if (i2c_dev->msg_err == I2C_ERR_NO_ACK) { > ? ? ? ? ? ? ? ?if (msg->flags & I2C_M_IGNORE_NAK) > -- > 1.7.4.1 > > -- > To unsubscribe from this list: send the line "unsubscribe linux-i2c" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at ?http://vger.kernel.org/majordomo-info.html -- 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/