linux-kernel - [PATCH 1/3] i2c: uniphier: avoid WARN_ON() of clk

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Message-Id: <1472730390-8907-2-git-send-email-yamada.masahiro@socionext.com>
Date:   Thu,  1 Sep 2016 20:46:28 +0900
From:   Masahiro Yamada <yamada.masahiro@...ionext.com>
To:     linux-i2c@...r.kernel.org
Cc:     Masahiro Yamada <yamada.masahiro@...ionext.com>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        Wolfram Sang <wsa@...-dreams.de>
Subject: [PATCH 1/3] i2c: uniphier: avoid WARN_ON() of clk_disable() in failure path

If clk_prepare_enable() fails, clk_disable_unprepare() is called in
the failure path, where the enable_count is still zero, so it hits
WARN_ON(core->enable_count == 0) in the clk_core_disable().

To fix this, make the clock setting more linear in the probe function
so that it can exploit "goto err" in case of error.

Signed-off-by: Masahiro Yamada <yamada.masahiro@...ionext.com>
---

 drivers/i2c/busses/i2c-uniphier.c | 73 +++++++++++++++++----------------------
 1 file changed, 31 insertions(+), 42 deletions(-)

diff --git a/drivers/i2c/busses/i2c-uniphier.c b/drivers/i2c/busses/i2c-uniphier.c
index d6e612a..56e92af 100644
--- a/drivers/i2c/busses/i2c-uniphier.c
+++ b/drivers/i2c/busses/i2c-uniphier.c
@@ -316,50 +316,15 @@ static struct i2c_bus_recovery_info uniphier_i2c_bus_recovery_info = {
 	.unprepare_recovery = uniphier_i2c_unprepare_recovery,
 };
 
-static int uniphier_i2c_clk_init(struct device *dev,
-				 struct uniphier_i2c_priv *priv)
+static void uniphier_i2c_hw_init(struct uniphier_i2c_priv *priv,
+				 u32 bus_speed, unsigned long clk_rate)
 {
-	struct device_node *np = dev->of_node;
-	unsigned long clk_rate;
-	u32 bus_speed;
-	int ret;
-
-	if (of_property_read_u32(np, "clock-frequency", &bus_speed))
-		bus_speed = UNIPHIER_I2C_DEFAULT_SPEED;
-
-	if (!bus_speed) {
-		dev_err(dev, "clock-frequency should not be zero\n");
-		return -EINVAL;
-	}
-
-	if (bus_speed > UNIPHIER_I2C_MAX_SPEED)
-		bus_speed = UNIPHIER_I2C_MAX_SPEED;
-
-	/* Get input clk rate through clk driver */
-	priv->clk = devm_clk_get(dev, NULL);
-	if (IS_ERR(priv->clk)) {
-		dev_err(dev, "failed to get clock\n");
-		return PTR_ERR(priv->clk);
-	}
-
-	ret = clk_prepare_enable(priv->clk);
-	if (ret)
-		return ret;
-
-	clk_rate = clk_get_rate(priv->clk);
-	if (!clk_rate) {
-		dev_err(dev, "input clock rate should not be zero\n");
-		return -EINVAL;
-	}
-
 	uniphier_i2c_reset(priv, true);
 
 	writel((clk_rate / bus_speed / 2 << 16) | (clk_rate / bus_speed),
 	       priv->membase + UNIPHIER_I2C_CLK);
 
 	uniphier_i2c_reset(priv, false);
-
-	return 0;
 }
 
 static int uniphier_i2c_probe(struct platform_device *pdev)
@@ -367,8 +332,9 @@ static int uniphier_i2c_probe(struct platform_device *pdev)
 	struct device *dev = &pdev->dev;
 	struct uniphier_i2c_priv *priv;
 	struct resource *regs;
-	int irq;
-	int ret;
+	u32 bus_speed;
+	unsigned long clk_rate;
+	int irq, ret;
 
 	priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
 	if (!priv)
@@ -385,6 +351,31 @@ static int uniphier_i2c_probe(struct platform_device *pdev)
 		return irq;
 	}
 
+	if (of_property_read_u32(dev->of_node, "clock-frequency", &bus_speed))
+		bus_speed = UNIPHIER_I2C_DEFAULT_SPEED;
+
+	if (!bus_speed || bus_speed > UNIPHIER_I2C_MAX_SPEED) {
+		dev_err(dev, "invalid clock-frequency %d\n", bus_speed);
+		return -EINVAL;
+	}
+
+	priv->clk = devm_clk_get(dev, NULL);
+	if (IS_ERR(priv->clk)) {
+		dev_err(dev, "failed to get clock\n");
+		return PTR_ERR(priv->clk);
+	}
+
+	ret = clk_prepare_enable(priv->clk);
+	if (ret)
+		return ret;
+
+	clk_rate = clk_get_rate(priv->clk);
+	if (!clk_rate) {
+		dev_err(dev, "input clock rate should not be zero\n");
+		ret = -EINVAL;
+		goto err;
+	}
+
 	init_completion(&priv->comp);
 	priv->adap.owner = THIS_MODULE;
 	priv->adap.algo = &uniphier_i2c_algo;
@@ -395,9 +386,7 @@ static int uniphier_i2c_probe(struct platform_device *pdev)
 	i2c_set_adapdata(&priv->adap, priv);
 	platform_set_drvdata(pdev, priv);
 
-	ret = uniphier_i2c_clk_init(dev, priv);
-	if (ret)
-		goto err;
+	uniphier_i2c_hw_init(priv, bus_speed, clk_rate);
 
 	ret = devm_request_irq(dev, irq, uniphier_i2c_interrupt, 0, pdev->name,
 			       priv);
-- 
1.9.1