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

From: Alok Chauhan
Date: Fri Mar 30 2012 - 08:06:53 EST


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>
---
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 e978635..344282e 100644
--- a/drivers/i2c/busses/i2c-tegra.c
+++ b/drivers/i2c/busses/i2c-tegra.c
@@ -516,6 +516,14 @@ 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

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/