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From:   Wang Zhang <silver_code@hust.edu.cn>
To:     Peter Korsgaard <peter@korsgaard.com>, Andrew Lunn <andrew@lunn.ch>
Cc:     hust-os-kernel-patches@googlegroups.com,
        Wang Zhang <silver_code@hust.edu.cn>,
        linux-i2c@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: [PATCH v2] i2c: ocores: use devm_ managed clks
Date:   Mon, 17 Apr 2023 21:27:14 +0800
Message-Id: <20230417132714.81627-1-silver_code@hust.edu.cn>
In-Reply-To: <843fab4d-0fdd-4610-91ed-1d8e9accbd25@lunn.ch>
References: <843fab4d-0fdd-4610-91ed-1d8e9accbd25@lunn.ch>
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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@hust.edu.cn>
---
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) {
 		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);
 }
 
-- 
2.34.1