Re: [PATCH v2] i2c: ocores: use devm_ managed clks

[Peter Rosin]

2023-04-17 at 16:05, Wang Zhang wrote:
> Smatch Warns:
> drivers/i2c/busses/i2c-ocores.c:701 ocores_i2c_probe() warn:
> missing unwind goto?
> 
> If any wrong occurs in ocores_i2c_of_probe, the i2c->clk needs to be
> released. But the function returns directly in line 701 without freeing
> the clock. Even though we can fix it by freeing the clock manually if
> platform_get_irq_optional fails, it may not be following the best practice.
> The original code for this driver contains if (IS_ERR()) checks 
> throughout, explicitly allowing the driver to continue loading even if 
> devm_clk_get() fails.
> 
> While it is not entirely clear why the original author implemented this
> behavior, there may have been certain circumstances or issues that were not
> apparent to us. It's possible that they were trying to work around a bug by
> employing an unconventional solution.Using `devm_clk_get_enabled()` rather
> than devm_clk_get() can automatically track the usage of clocks and free
> them when they are no longer needed or an error occurs.
> 
> fixing it by changing `ocores_i2c_of_probe` to use `devm_clk_get_enabled()`
> rather than `devm_clk_get()`, changing `goto err_clk' to direct return and
> removing `err_clk`.
> 
> Signed-off-by: Wang Zhang <silver_code@xxxxxxxxxxx>
> ---
> v1->v2: change `ocores_i2c_of_probe` to use `devm_clk_get_enabled()`
>  
>  drivers/i2c/busses/i2c-ocores.c | 62 +++++++++++++--------------------
>  1 file changed, 24 insertions(+), 38 deletions(-)
> 
> diff --git a/drivers/i2c/busses/i2c-ocores.c b/drivers/i2c/busses/i2c-ocores.c
> index a0af027db04c..1dcb1af1ad13 100644
> --- a/drivers/i2c/busses/i2c-ocores.c
> +++ b/drivers/i2c/busses/i2c-ocores.c
> @@ -549,28 +549,24 @@ static int ocores_i2c_of_probe(struct platform_device *pdev,
>  							&clock_frequency);
>  	i2c->bus_clock_khz = 100;
>  
> -	i2c->clk = devm_clk_get(&pdev->dev, NULL);
> +	i2c->clk = devm_clk_get_enabled(&pdev->dev, NULL);
>  
> -	if (!IS_ERR(i2c->clk)) {
> -		int ret = clk_prepare_enable(i2c->clk);
> -
> -		if (ret) {
> -			dev_err(&pdev->dev,
> -				"clk_prepare_enable failed: %d\n", ret);
> -			return ret;
> -		}
> -		i2c->ip_clock_khz = clk_get_rate(i2c->clk) / 1000;
> -		if (clock_frequency_present)
> -			i2c->bus_clock_khz = clock_frequency / 1000;
> +	if (IS_ERR(i2c->clk)) {
> +		dev_err(&pdev->dev,
> +			"devm_clk_get_enabled failed\n");
> +		return PTR_ERR(i2c->clk);
>  	}
>  
> +	i2c->ip_clock_khz = clk_get_rate(i2c->clk) / 1000;
> +	if (clock_frequency_present)
> +		i2c->bus_clock_khz = clock_frequency / 1000;
> +
>  	if (i2c->ip_clock_khz == 0) {

This branch seems hard to hit with this patch.

Cheers,
Peter

>  		if (of_property_read_u32(np, "opencores,ip-clock-frequency",
>  						&val)) {
>  			if (!clock_frequency_present) {
>  				dev_err(&pdev->dev,
>  					"Missing required parameter 'opencores,ip-clock-frequency'\n");
> -				clk_disable_unprepare(i2c->clk);
>  				return -ENODEV;
>  			}
>  			i2c->ip_clock_khz = clock_frequency / 1000;
> @@ -675,8 +671,7 @@ static int ocores_i2c_probe(struct platform_device *pdev)
>  		default:
>  			dev_err(&pdev->dev, "Unsupported I/O width (%d)\n",
>  				i2c->reg_io_width);
> -			ret = -EINVAL;
> -			goto err_clk;
> +			return -EINVAL;
>  		}
>  	}
>  
> @@ -707,13 +702,13 @@ static int ocores_i2c_probe(struct platform_device *pdev)
>  						   pdev->name, i2c);
>  		if (ret) {
>  			dev_err(&pdev->dev, "Cannot claim IRQ\n");
> -			goto err_clk;
> +			return ret;
>  		}
>  	}
>  
>  	ret = ocores_init(&pdev->dev, i2c);
>  	if (ret)
> -		goto err_clk;
> +		return ret;
>  
>  	/* hook up driver to tree */
>  	platform_set_drvdata(pdev, i2c);
> @@ -725,7 +720,7 @@ static int ocores_i2c_probe(struct platform_device *pdev)
>  	/* add i2c adapter to i2c tree */
>  	ret = i2c_add_adapter(&i2c->adap);
>  	if (ret)
> -		goto err_clk;
> +		return ret;
>  
>  	/* add in known devices to the bus */
>  	if (pdata) {
> @@ -734,10 +729,6 @@ static int ocores_i2c_probe(struct platform_device *pdev)
>  	}
>  
>  	return 0;
> -
> -err_clk:
> -	clk_disable_unprepare(i2c->clk);
> -	return ret;
>  }
>  
>  static int ocores_i2c_remove(struct platform_device *pdev)
> @@ -752,9 +743,6 @@ static int ocores_i2c_remove(struct platform_device *pdev)
>  	/* remove adapter & data */
>  	i2c_del_adapter(&i2c->adap);
>  
> -	if (!IS_ERR(i2c->clk))
> -		clk_disable_unprepare(i2c->clk);
> -
>  	return 0;
>  }
>  
> @@ -768,8 +756,7 @@ static int ocores_i2c_suspend(struct device *dev)
>  	ctrl &= ~(OCI2C_CTRL_EN | OCI2C_CTRL_IEN);
>  	oc_setreg(i2c, OCI2C_CONTROL, ctrl);
>  
> -	if (!IS_ERR(i2c->clk))
> -		clk_disable_unprepare(i2c->clk);
> +	clk_disable_unprepare(i2c->clk);
>  	return 0;
>  }
>  
> @@ -777,19 +764,18 @@ static int ocores_i2c_resume(struct device *dev)
>  {
>  	struct ocores_i2c *i2c = dev_get_drvdata(dev);
>  
> -	if (!IS_ERR(i2c->clk)) {
> -		unsigned long rate;
> -		int ret = clk_prepare_enable(i2c->clk);
> +	unsigned long rate;
> +	int ret = clk_prepare_enable(i2c->clk);
>  
> -		if (ret) {
> -			dev_err(dev,
> -				"clk_prepare_enable failed: %d\n", ret);
> -			return ret;
> -		}
> -		rate = clk_get_rate(i2c->clk) / 1000;
> -		if (rate)
> -			i2c->ip_clock_khz = rate;
> +	if (ret) {
> +		dev_err(dev,
> +			"clk_prepare_enable failed: %d\n", ret);
> +		return ret;
>  	}
> +	rate = clk_get_rate(i2c->clk) / 1000;
> +	if (rate)
> +		i2c->ip_clock_khz = rate;
> +
>  	return ocores_init(dev, i2c);
>  }
>