diff --git a/lib/test_firmware.c b/lib/test_firmware.c
index b5e779bcfb34..be3baea88b61 100644
--- a/lib/test_firmware.c
+++ b/lib/test_firmware.c
@@ -284,16 +284,26 @@ static ssize_t config_test_show_str(char *dst,
 	return len;
 }
 
+static inline int __test_dev_config_update_bool(const char *buf, size_t size,
+						bool *cfg)
+{
+	int ret;
+
+	if (strtobool(buf, cfg) < 0)
+		ret = -EINVAL;
+	else
+		ret = size;
+
+	return ret;
+}
+
 static int test_dev_config_update_bool(const char *buf, size_t size,
 				       bool *cfg)
 {
 	int ret;
 
 	mutex_lock(&test_fw_mutex);
-	if (strtobool(buf, cfg) < 0)
-		ret = -EINVAL;
-	else
-		ret = size;
+	ret = __test_dev_config_update_bool(buf, size, cfg);
 	mutex_unlock(&test_fw_mutex);
 
 	return ret;
@@ -323,7 +333,7 @@ static ssize_t test_dev_config_show_int(char *buf, int cfg)
 	return snprintf(buf, PAGE_SIZE, "%d\n", val);
 }
 
-static int test_dev_config_update_u8(const char *buf, size_t size, u8 *cfg)
+static inline int __test_dev_config_update_u8(const char *buf, size_t size, u8 *cfg)
 {
 	int ret;
 	long new;
@@ -335,14 +345,23 @@ static int test_dev_config_update_u8(const char *buf, size_t size, u8 *cfg)
 	if (new > U8_MAX)
 		return -EINVAL;
 
-	mutex_lock(&test_fw_mutex);
 	*(u8 *)cfg = new;
-	mutex_unlock(&test_fw_mutex);
 
 	/* Always return full write size even if we didn't consume all */
 	return size;
 }
 
+static int test_dev_config_update_u8(const char *buf, size_t size, u8 *cfg)
+{
+	int ret;
+
+	mutex_lock(&test_fw_mutex);
+	ret = __test_dev_config_update_u8(buf, size, cfg);
+	mutex_unlock(&test_fw_mutex);
+
+	return ret;
+}
+
 static ssize_t test_dev_config_show_u8(char *buf, u8 cfg)
 {
 	u8 val;
@@ -375,10 +394,10 @@ static ssize_t config_num_requests_store(struct device *dev,
 		mutex_unlock(&test_fw_mutex);
 		goto out;
 	}
-	mutex_unlock(&test_fw_mutex);
 
-	rc = test_dev_config_update_u8(buf, count,
-				       &test_fw_config->num_requests);
+	rc = __test_dev_config_update_u8(buf, count,
+					 &test_fw_config->num_requests);
+	mutex_unlock(&test_fw_mutex);
 
 out:
 	return rc;