misc: atmel-ssc: lock with mutex instead of spinlock

commit b037d60 upstream.

Uninterruptible context is not needed in the driver and causes lockdep
warning because of mutex taken in of_alias_get_id(). Convert the lock to
mutex to avoid the issue.

Cc: stable@vger.kernel.org
Fixes: 099343c ("ARM: at91: atmel-ssc: add device tree support")
Signed-off-by: Michał Mirosław <mirq-linux@rere.qmqm.pl>
Link: https://lore.kernel.org/r/50f0d7fa107f318296afb49477c3571e4d6978c5.1592998403.git.mirq-linux@rere.qmqm.pl
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/misc/atmel-ssc.c

@@ -13,23 +13,23 @@
 #include <linux/clk.h>
 #include <linux/err.h>
 #include <linux/io.h>
-#include <linux/spinlock.h>
+#include <linux/mutex.h>
 #include <linux/atmel-ssc.h>
 #include <linux/slab.h>
 #include <linux/module.h>
 
 #include <linux/of.h>
 
 /* Serialize access to ssc_list and user count */
-static DEFINE_SPINLOCK(user_lock);
+static DEFINE_MUTEX(user_lock);
 static LIST_HEAD(ssc_list);
 
 struct ssc_device *ssc_request(unsigned int ssc_num)
 {
 	int ssc_valid = 0;
 	struct ssc_device *ssc;
 
-	spin_lock(&user_lock);
+	mutex_lock(&user_lock);
 	list_for_each_entry(ssc, &ssc_list, list) {
 		if (ssc->pdev->dev.of_node) {
 			if (of_alias_get_id(ssc->pdev->dev.of_node, "ssc")
@@ -44,18 +44,18 @@ struct ssc_device *ssc_request(unsigned int ssc_num)
 	}
 
 	if (!ssc_valid) {
-		spin_unlock(&user_lock);
+		mutex_unlock(&user_lock);
 		pr_err("ssc: ssc%d platform device is missing\n", ssc_num);
 		return ERR_PTR(-ENODEV);
 	}
 
 	if (ssc->user) {
-		spin_unlock(&user_lock);
+		mutex_unlock(&user_lock);
 		dev_dbg(&ssc->pdev->dev, "module busy\n");
 		return ERR_PTR(-EBUSY);
 	}
 	ssc->user++;
-	spin_unlock(&user_lock);
+	mutex_unlock(&user_lock);
 
 	clk_prepare(ssc->clk);
 
@@ -67,14 +67,14 @@ void ssc_free(struct ssc_device *ssc)
 {
 	bool disable_clk = true;
 
-	spin_lock(&user_lock);
+	mutex_lock(&user_lock);
 	if (ssc->user)
 		ssc->user--;
 	else {
 		disable_clk = false;
 		dev_dbg(&ssc->pdev->dev, "device already free\n");
 	}
-	spin_unlock(&user_lock);
+	mutex_unlock(&user_lock);
 
 	if (disable_clk)
 		clk_unprepare(ssc->clk);
@@ -194,9 +194,9 @@ static int ssc_probe(struct platform_device *pdev)
 		return -ENXIO;
 	}
 
-	spin_lock(&user_lock);
+	mutex_lock(&user_lock);
 	list_add_tail(&ssc->list, &ssc_list);
-	spin_unlock(&user_lock);
+	mutex_unlock(&user_lock);
 
 	platform_set_drvdata(pdev, ssc);
 
@@ -210,9 +210,9 @@ static int ssc_remove(struct platform_device *pdev)
 {
 	struct ssc_device *ssc = platform_get_drvdata(pdev);
 
-	spin_lock(&user_lock);
+	mutex_lock(&user_lock);
 	list_del(&ssc->list);
-	spin_unlock(&user_lock);
+	mutex_unlock(&user_lock);
 
 	return 0;
 }