From mboxrd@z Thu Jan 1 00:00:00 1970 From: Alok Chauhan Subject: [PATCH v2] i2c: tegra: Add delay before reset the controller Date: Mon, 26 Dec 2011 16:44:41 +0530 Message-ID: <1324898081-10308-1-git-send-email-alokc@nvidia.com> Return-path: Sender: linux-i2c-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: 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 Cc: linux-tegra-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-i2c-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Alok Chauhan List-Id: linux-i2c@vger.kernel.org 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)); + 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