From mboxrd@z Thu Jan 1 00:00:00 1970 From: Shubhrajyoti Datta Subject: Re: [PATCH v2] i2c: tegra: Add delay before reset the controller Date: Fri, 10 Feb 2012 15:05:07 +0530 Message-ID: References: <1324898081-10308-1-git-send-email-alokc@nvidia.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: In-Reply-To: <1324898081-10308-1-git-send-email-alokc@nvidia.com> Sender: linux-kernel-owner@vger.kernel.org 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 List-Id: linux-i2c@vger.kernel.org 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 freq= uency of the bus. > =A0drivers/i2c/busses/i2c-tegra.c | =A0 =A08 ++++++++ > =A01 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_d= ev *i2c_dev, > =A0 =A0 =A0 =A0if (likely(i2c_dev->msg_err =3D=3D I2C_ERR_NONE)) > =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0return 0; > > + =A0 =A0 =A0 /* > + =A0 =A0 =A0 =A0* In NACK error condition resetting of I2C controlle= r happens > + =A0 =A0 =A0 =A0* before STOP condition is properly completed by I2C= controller, > + =A0 =A0 =A0 =A0* so wait for 2 clock cycle to complete STOP conditi= on. > + =A0 =A0 =A0 =A0*/ Why do you need to reset the controller in case of a NACK. > + =A0 =A0 =A0 if (i2c_dev->msg_err =3D=3D I2C_ERR_NO_ACK) > + =A0 =A0 =A0 =A0 =A0 =A0 =A0 udelay(DIV_ROUND_UP(2 * 1000000, i2c_de= v->bus_clk_rate)); > + > =A0 =A0 =A0 =A0tegra_i2c_init(i2c_dev); > =A0 =A0 =A0 =A0if (i2c_dev->msg_err =3D=3D I2C_ERR_NO_ACK) { > =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0if (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 =A0http://vger.kernel.org/majordomo-info.html