From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ben Dooks Subject: Re: [PATCH v2] i2c: tegra: Add delay before reset the controller Date: Fri, 6 Jan 2012 16:18:03 +0000 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 Return-path: Content-Disposition: inline In-Reply-To: <1324898081-10308-1-git-send-email-alokc-DDmLM1+adcrQT0dZR+AlfA@public.gmane.org> Sender: linux-i2c-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Alok Chauhan Cc: khali-PUYAD+kWke1g9hUCZPvPmw@public.gmane.org, ben-linux-elnMNo+KYs3YtjvyW6yDsg@public.gmane.org, swarren-DDmLM1+adcrQT0dZR+AlfA@public.gmane.org, olof-nZhT3qVonbNeoWH0uzbU5w@public.gmane.org, bones-s3s/WqlpOiPyB63q8FvJNQ@public.gmane.org, paul.gortmaker-CWA4WttNNZF54TAoqtyWWQ@public.gmane.org, dgreid-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org, ldewangan-DDmLM1+adcrQT0dZR+AlfA@public.gmane.org, linux-tegra-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-i2c-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-Id: linux-i2c@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-u79uwXL29TY76Z2rM5mHXA@public.gmane.org > More majordomo info at http://vger.kernel.org/majordomo-info.html -- Ben Dooks, ben-elnMNo+KYs3YtjvyW6yDsg@public.gmane.org, http://www.fluff.org/ben/ Large Hadron Colada: A large Pina Colada that makes the universe disappear.