mailbox: mailbox-test: fix debugfs in multi-instances

Create one debug entry directory per instance to support the multi
instantiation.

Signed-off-by: Ludovic Barre <ludovic.barre@st.com>
Signed-off-by: Fabien Dessenne <fabien.dessenne@st.com>
Signed-off-by: Jassi Brar <jaswinder.singh@linaro.org>

Author: FDESTM

drivers/mailbox/mailbox-test.c

@@ -31,7 +31,6 @@
 				 (MBOX_MAX_MSG_LEN / MBOX_BYTES_PER_LINE))
 
 static bool mbox_data_ready;
-static struct dentry *root_debugfs_dir;
 
 struct mbox_test_device {
 	struct device		*dev;
@@ -45,6 +44,7 @@ struct mbox_test_device {
 	spinlock_t		lock;
 	wait_queue_head_t	waitq;
 	struct fasync_struct	*async_queue;
+	struct dentry		*root_debugfs_dir;
 };
 
 static ssize_t mbox_test_signal_write(struct file *filp,
@@ -262,16 +262,16 @@ static int mbox_test_add_debugfs(struct platform_device *pdev,
 	if (!debugfs_initialized())
 		return 0;
 
-	root_debugfs_dir = debugfs_create_dir("mailbox", NULL);
-	if (!root_debugfs_dir) {
+	tdev->root_debugfs_dir = debugfs_create_dir(dev_name(&pdev->dev), NULL);
+	if (!tdev->root_debugfs_dir) {
 		dev_err(&pdev->dev, "Failed to create Mailbox debugfs\n");
 		return -EINVAL;
 	}
 
-	debugfs_create_file("message", 0600, root_debugfs_dir,
+	debugfs_create_file("message", 0600, tdev->root_debugfs_dir,
 			    tdev, &mbox_test_message_ops);
 
-	debugfs_create_file("signal", 0200, root_debugfs_dir,
+	debugfs_create_file("signal", 0200, tdev->root_debugfs_dir,
 			    tdev, &mbox_test_signal_ops);
 
 	return 0;
@@ -416,7 +416,7 @@ static int mbox_test_remove(struct platform_device *pdev)
 {
 	struct mbox_test_device *tdev = platform_get_drvdata(pdev);
 
-	debugfs_remove_recursive(root_debugfs_dir);
+	debugfs_remove_recursive(tdev->root_debugfs_dir);
 
 	if (tdev->tx_channel)
 		mbox_free_channel(tdev->tx_channel);