[PATCH v2] i2c: tegra: Add delay before reset the controller

From: Alok Chauhan
Date: Mon Dec 26 2011 - 06:15:18 EST

From: Alok Chauhan <alokc@xxxxxxxxxx>

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 <alokc@xxxxxxxxxx>
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));
if (i2c_dev->msg_err == I2C_ERR_NO_ACK) {
if (msg->flags & I2C_M_IGNORE_NAK)

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