[PATCH] i2c: tegra: dynamically control fast clk

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Tegra I2C driver enables the fast clock during initialization
and does not disable till driver removed.
Enable this clock before transfer and disable after transfer done.

Signed-off-by: Laxman Dewangan <ldewangan@xxxxxxxxxx>
This patch is on top of the clock chnages which is in Tegra sub system and
based on 
 i2c: tegra: I2_M_NOSTART functionality not supported in Tegra20
So recommend to go on tegra sub-system.

 drivers/i2c/busses/i2c-tegra.c |   35 ++++++++++++++++++++++++++++-------
 1 files changed, 28 insertions(+), 7 deletions(-)

diff --git a/drivers/i2c/busses/i2c-tegra.c b/drivers/i2c/busses/i2c-tegra.c
index 554f713..24f7cee 100644
--- a/drivers/i2c/busses/i2c-tegra.c
+++ b/drivers/i2c/busses/i2c-tegra.c
@@ -362,12 +362,36 @@ static void tegra_dvc_init(struct tegra_i2c_dev *i2c_dev)
 	dvc_writel(i2c_dev, val, DVC_CTRL_REG1);
+static inline int tegra_i2c_clock_enable(struct tegra_i2c_dev *i2c_dev)
+	int ret;
+	ret = clk_prepare_enable(i2c_dev->fast_clk);
+	if (ret < 0) {
+		dev_err(i2c_dev->dev,
+			"Enabling fast clk failed, err %d\n", ret);
+		return ret;
+	}
+	ret = clk_prepare_enable(i2c_dev->div_clk);
+	if (ret < 0) {
+		dev_err(i2c_dev->dev,
+			"Enabling div clk failed, err %d\n", ret);
+		clk_disable_unprepare(i2c_dev->fast_clk);
+	}
+	return ret;
+static inline void tegra_i2c_clock_disable(struct tegra_i2c_dev *i2c_dev)
+	clk_disable_unprepare(i2c_dev->div_clk);
+	clk_disable_unprepare(i2c_dev->fast_clk);
 static int tegra_i2c_init(struct tegra_i2c_dev *i2c_dev)
 	u32 val;
 	int err = 0;
-	clk_prepare_enable(i2c_dev->div_clk);
+	tegra_i2c_clock_enable(i2c_dev);
@@ -398,7 +422,7 @@ static int tegra_i2c_init(struct tegra_i2c_dev *i2c_dev)
 	if (tegra_i2c_flush_fifos(i2c_dev))
 		err = -ETIMEDOUT;
-	clk_disable_unprepare(i2c_dev->div_clk);
+	tegra_i2c_clock_disable(i2c_dev);
 	if (i2c_dev->irq_disabled) {
 		i2c_dev->irq_disabled = 0;
@@ -584,7 +608,7 @@ static int tegra_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg msgs[],
-	clk_prepare_enable(i2c_dev->clk);
+	tegra_i2c_clock_enable(i2c_dev);
 	for (i = 0; i < num; i++) {
 		enum msg_end_type end_type = MSG_END_STOP;
 		if (i < (num - 1)) {
@@ -597,7 +621,7 @@ static int tegra_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg msgs[],
 		if (ret)
-	clk_disable_unprepare(i2c_dev->div_clk);
+	tegra_i2c_clock_disable(i2c_dev);
 	return ret ?: i;
@@ -734,8 +758,6 @@ static int __devinit tegra_i2c_probe(struct platform_device *pdev)
 		return ret;
-	clk_prepare_enable(i2c_dev->fast_clk);
 	i2c_set_adapdata(&i2c_dev->adapter, i2c_dev);
 	i2c_dev->adapter.owner = THIS_MODULE;
 	i2c_dev->adapter.class = I2C_CLASS_HWMON;
@@ -749,7 +771,6 @@ static int __devinit tegra_i2c_probe(struct platform_device *pdev)
 	ret = i2c_add_numbered_adapter(&i2c_dev->adapter);
 	if (ret) {
 		dev_err(&pdev->dev, "Failed to add I2C adapter\n");
-		clk_disable_unprepare(i2c_dev->fast_clk);
 		return ret;

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