[RFC] i2c: bcm2835: Store pointer to bus clock

Commit Message

Stefan Wahren Oct. 26, 2019, 12:34 p.m. UTC

The commit bebff81fb8b9 ("i2c: bcm2835: Model Divider in CCF") introduced
a NULL pointer dereference on driver unload. It seems that we can't fetch
the bus clock via devm_clk_get in bcm2835_i2c_remove. As an alternative
approach store a pointer to the bus clock in the private driver structure.

Fixes: bebff81fb8b9 ("i2c: bcm2835: Model Divider in CCF")
Signed-off-by: Stefan Wahren <[e-mail]>
---
 drivers/i2c/busses/i2c-bcm2835.c | 17 ++++++++---------
 1 file changed, 8 insertions(+), 9 deletions(-)

--
2.7.4

Comments

Wolfram Sang Oct. 26, 2019, 3:33 p.m. UTC | #1

> a NULL pointer dereference on driver unload. It seems that we can't fetch
> the bus clock via devm_clk_get in bcm2835_i2c_remove. As an alternative

Uh, yes, devm_* doesn't make sense in a remove function. We could
probably use plain clk_get/put here, but a pointer seems fine, too.

Patch

diff --git a/drivers/i2c/busses/i2c-bcm2835.c b/drivers/i2c/busses/i2c-bcm2835.c
index e01b2b5..5ab901a 100644
--- a/drivers/i2c/busses/i2c-bcm2835.c
+++ b/drivers/i2c/busses/i2c-bcm2835.c
@@ -58,6 +58,7 @@  struct bcm2835_i2c_dev {
 	struct i2c_adapter adapter;
 	struct completion completion;
 	struct i2c_msg *curr_msg;
+	struct clk *bus_clk;
 	int num_msgs;
 	u32 msg_err;
 	u8 *msg_buf;
@@ -404,7 +405,6 @@  static int bcm2835_i2c_probe(struct platform_device *pdev)
 	struct resource *mem, *irq;
 	int ret;
 	struct i2c_adapter *adap;
-	struct clk *bus_clk;
 	struct clk *mclk;
 	u32 bus_clk_rate;

@@ -427,11 +427,11 @@  static int bcm2835_i2c_probe(struct platform_device *pdev)
 		return PTR_ERR(mclk);
 	}

-	bus_clk = bcm2835_i2c_register_div(&pdev->dev, mclk, i2c_dev);
+	i2c_dev->bus_clk = bcm2835_i2c_register_div(&pdev->dev, mclk, i2c_dev);

-	if (IS_ERR(bus_clk)) {
+	if (IS_ERR(i2c_dev->bus_clk)) {
 		dev_err(&pdev->dev, "Could not register clock\n");
-		return PTR_ERR(bus_clk);
+		return PTR_ERR(i2c_dev->bus_clk);
 	}

 	ret = of_property_read_u32(pdev->dev.of_node, "clock-frequency",
@@ -442,13 +442,13 @@  static int bcm2835_i2c_probe(struct platform_device *pdev)
 		bus_clk_rate = 100000;
 	}

-	ret = clk_set_rate_exclusive(bus_clk, bus_clk_rate);
+	ret = clk_set_rate_exclusive(i2c_dev->bus_clk, bus_clk_rate);
 	if (ret < 0) {
 		dev_err(&pdev->dev, "Could not set clock frequency\n");
 		return ret;
 	}

-	ret = clk_prepare_enable(bus_clk);
+	ret = clk_prepare_enable(i2c_dev->bus_clk);
 	if (ret) {
 		dev_err(&pdev->dev, "Couldn't prepare clock");
 		return ret;
@@ -491,10 +491,9 @@  static int bcm2835_i2c_probe(struct platform_device *pdev)
 static int bcm2835_i2c_remove(struct platform_device *pdev)
 {
 	struct bcm2835_i2c_dev *i2c_dev = platform_get_drvdata(pdev);
-	struct clk *bus_clk = devm_clk_get(i2c_dev->dev, "div");

-	clk_rate_exclusive_put(bus_clk);
-	clk_disable_unprepare(bus_clk);
+	clk_rate_exclusive_put(i2c_dev->bus_clk);
+	clk_disable_unprepare(i2c_dev->bus_clk);

 	free_irq(i2c_dev->irq, i2c_dev);
 	i2c_del_adapter(&i2c_dev->adapter);