[ 3.5.y.z extended stable ] Patch "i2c: tegra: check the clk_prepare_enable() return value" has been added to staging queue

[Luis Henriques]

This is a note to let you know that I have just added a patch titled

    i2c: tegra: check the clk_prepare_enable() return value

to the linux-3.5.y-queue branch of the 3.5.y.z extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.5.y-queue

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.5.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Luis

------

>From 0391b6e610fdd9520823b0368aa9946e0a3e5f15 Mon Sep 17 00:00:00 2001
From: Laxman Dewangan <ldewangan at nvidia.com>
Date: Fri, 15 Mar 2013 05:34:08 +0000
Subject: [PATCH] i2c: tegra: check the clk_prepare_enable() return value

commit 132c803f7b70b17322579f6f4f3f65cf68e55135 upstream.

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 at nvidia.com>
Reviewed-by: Stephen Warren <swarren at nvidia.com>
Signed-off-by: Wolfram Sang <wsa at the-dreams.de>
[ luis: backport to 3.5: keep calling clk_enable ]
Luis Henriques <luis.henriques at canonical.com>
---
 drivers/i2c/busses/i2c-tegra.c | 13 +++++++++++--
 1 file changed, 11 insertions(+), 2 deletions(-)

diff --git a/drivers/i2c/busses/i2c-tegra.c b/drivers/i2c/busses/i2c-tegra.c
index 8b2e555..12776b3 100644
--- a/drivers/i2c/busses/i2c-tegra.c
+++ b/drivers/i2c/busses/i2c-tegra.c
@@ -341,7 +341,11 @@ static int tegra_i2c_init(struct tegra_i2c_dev *i2c_dev)
 	u32 val;
 	int err = 0;

-	clk_enable(i2c_dev->clk);
+	err = clk_enable(i2c_dev->clk);
+	if (err < 0) {
+		dev_err(i2c_dev->dev, "Clock enable failed %d\n", err);
+		return err;
+	}

 	tegra_periph_reset_assert(i2c_dev->clk);
 	udelay(2);
@@ -546,7 +550,12 @@ static int tegra_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg msgs[],
 	if (i2c_dev->is_suspended)
 		return -EBUSY;

-	clk_enable(i2c_dev->clk);
+	ret = clk_enable(i2c_dev->clk);
+	if (ret < 0) {
+		dev_err(i2c_dev->dev, "Clock enable failed %d\n", ret);
+		return ret;
+	}
+
 	for (i = 0; i < num; i++) {
 		int stop = (i == (num - 1)) ? 1  : 0;
 		ret = tegra_i2c_xfer_msg(i2c_dev, &msgs[i], stop);
--
1.8.1.2