From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1030433Ab2AFQhZ (ORCPT ); Fri, 6 Jan 2012 11:37:25 -0500 Received: from trinity.fluff.org ([89.16.178.74]:33074 "EHLO trinity.fluff.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1030373Ab2AFQhW (ORCPT ); Fri, 6 Jan 2012 11:37:22 -0500 X-Greylist: delayed 1151 seconds by postgrey-1.27 at vger.kernel.org; Fri, 06 Jan 2012 11:37:22 EST Date: Fri, 6 Jan 2012 16:18:03 +0000 From: Ben Dooks 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 Subject: Re: [PATCH v2] i2c: tegra: Add delay before reset the controller Message-ID: <20120106161803.GQ19115@trinity.fluff.org> References: <1324898081-10308-1-git-send-email-alokc@nvidia.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1324898081-10308-1-git-send-email-alokc@nvidia.com> X-Disclaimer: These are my views alone. X-URL: http://www.fluff.org/ User-Agent: Mutt/1.5.18 (2008-05-17) X-SA-Exim-Connect-IP: X-SA-Exim-Mail-From: ben@trinity.fluff.org X-SA-Exim-Scanned: No (on trinity.fluff.org); SAEximRunCond expanded to false Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Dec 26, 2011 at 04:44:41PM +0530, 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. > + */ > + if (i2c_dev->msg_err == I2C_ERR_NO_ACK) > + udelay(DIV_ROUND_UP(2 * 1000000, i2c_dev->bus_clk_rate)); > + Is a delay here good, would it be better to sleep so that some other process can gain cpu time? 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 -- Ben Dooks, ben@fluff.org, http://www.fluff.org/ben/ Large Hadron Colada: A large Pina Colada that makes the universe disappear.