linux-kernel - [PATCH] i2c: tegra: Add delay before reset the controller

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Message-Id: <1324550480-26308-1-git-send-email-alokc@nvidia.com>
Date:	Thu, 22 Dec 2011 16:11:20 +0530
From:	Alok Chauhan <alokc@...dia.com>
To:	khali@...ux-fr.org, ben-linux@...ff.org, swarren@...dia.com,
	olof@...om.net, bones@...retlab.ca, paul.gortmaker@...driver.com
Cc:	linux-i2c@...r.kernel.org, linux-kernel@...r.kernel.org,
	Alok Chauhan <alokc@...dia.com>
Subject: [PATCH] i2c: tegra: Add delay before reset the controller

From: Alok Chauhan <alokc@...dia.com>

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 worst case delay of 1 ms (assuming lowest
clock frequency will be 1 KHZ) before reset the
controller in case of NACK error.

Signed-off-by: Alok Chauhan <alokc@...dia.com>
---
 drivers/i2c/busses/i2c-tegra.c |    9 +++++++++
 1 files changed, 9 insertions(+), 0 deletions(-)

diff --git a/drivers/i2c/busses/i2c-tegra.c b/drivers/i2c/busses/i2c-tegra.c
index 6381604..b731499 100644
--- a/drivers/i2c/busses/i2c-tegra.c
+++ b/drivers/i2c/busses/i2c-tegra.c
@@ -517,6 +517,15 @@ 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 worst case delay of 1 ms (assuming lowest clock
+	 * frequency will be 1 KHz) to complete STOP condition.
+	 */
+	if (i2c_dev->msg_err == I2C_ERR_NO_ACK)
+		mdelay(1);
+
 	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

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