[PATCH] i2c: tegra: check the clk_prepare_enable() return value

[PATCH] i2c: tegra: check the clk_prepare_enable() return value

[Laxman Dewangan]

NVIDIA's Tegra SoC allows read/write of controller register only
if controller clock is enabled. System hangs if read/write happens
to registers without enabling clock.

clk_prepare_enable() can be fail due to unknown reason and hence
adding check for return value of this function. If this function
success then only access register otherwise return to caller with
error.

Signed-off-by: Laxman Dewangan <ldewangan-DDmLM1+adcrQT0dZR+AlfA@public.gmane.org>
---
 drivers/i2c/busses/i2c-tegra.c |   13 +++++++++++--
 1 files changed, 11 insertions(+), 2 deletions(-)

diff --git a/drivers/i2c/busses/i2c-tegra.c b/drivers/i2c/busses/i2c-tegra.c
index 36704e3..b714776 100644
--- a/drivers/i2c/busses/i2c-tegra.c
+++ b/drivers/i2c/busses/i2c-tegra.c
@@ -411,7 +411,11 @@ static int tegra_i2c_init(struct tegra_i2c_dev *i2c_dev)
 	int clk_multiplier = I2C_CLK_MULTIPLIER_STD_FAST_MODE;
 	u32 clk_divisor;
 
-	tegra_i2c_clock_enable(i2c_dev);
+	err = tegra_i2c_clock_enable(i2c_dev);
+	if (err < 0) {
+		dev_err(i2c_dev->dev, "Clock enable failed %d\n", err);
+		return err;
+	}
 
 	tegra_periph_reset_assert(i2c_dev->div_clk);
 	udelay(2);
@@ -628,7 +632,12 @@ static int tegra_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg msgs[],
 	if (i2c_dev->is_suspended)
 		return -EBUSY;
 
-	tegra_i2c_clock_enable(i2c_dev);
+	ret = tegra_i2c_clock_enable(i2c_dev);
+	if (ret < 0) {
+		dev_err(i2c_dev->dev, "Clock enable failed %d\n", ret);
+		return ret;
+	}
+
 	for (i = 0; i < num; i++) {
 		enum msg_end_type end_type = MSG_END_STOP;
 		if (i < (num - 1)) {
-- 
1.7.1.1

Re: [PATCH] i2c: tegra: check the clk_prepare_enable() return value

[Stephen Warren]

On 03/15/2013 09:34 AM, Laxman Dewangan wrote:
> NVIDIA's Tegra SoC allows read/write of controller register only
> if controller clock is enabled. System hangs if read/write happens
> to registers without enabling clock.
> 
> clk_prepare_enable() can be fail due to unknown reason and hence
> adding check for return value of this function. If this function
> success then only access register otherwise return to caller with
> error.

Wolfram,

Reviewed-by: Stephen Warren <swarren-DDmLM1+adcrQT0dZR+AlfA@public.gmane.org>

This is probably suitable for Cc: stable.

Re: [PATCH] i2c: tegra: check the clk_prepare_enable() return value

[Wolfram Sang]

On Fri, Mar 15, 2013 at 09:04:08PM +0530, Laxman Dewangan wrote:
> NVIDIA's Tegra SoC allows read/write of controller register only
> if controller clock is enabled. System hangs if read/write happens
> to registers without enabling clock.
> 
> clk_prepare_enable() can be fail due to unknown reason and hence
> adding check for return value of this function. If this function
> success then only access register otherwise return to caller with
> error.
> 
> Signed-off-by: Laxman Dewangan <ldewangan@nvidia.com>

Applied to for-current, thanks!