diff --git a/drivers/usb/musb/musb_debugfs.c b/drivers/usb/musb/musb_debugfs.c
index 78a283e9ce40b112a44fc3ab22e5b43bc75e5685..04382ec31d3f07adf5a19d21d3cca49c5a1b85ca 100644
--- a/drivers/usb/musb/musb_debugfs.c
+++ b/drivers/usb/musb/musb_debugfs.c
@@ -191,9 +191,16 @@ static ssize_t musb_test_mode_write(struct file *file,
 {
 	struct seq_file		*s = file->private_data;
 	struct musb		*musb = s->private;
-	u8			test = 0;
+	u8			test;
 	char			buf[18];
 
+	test = musb_readb(musb->mregs, MUSB_TESTMODE);
+	if (test) {
+		dev_err(musb->controller, "Error: test mode is already set. "
+			"Please do USB Bus Reset to start a new test.\n");
+		return count;
+	}
+
 	memset(buf, 0x00, sizeof(buf));
 
 	if (copy_from_user(buf, ubuf, min_t(size_t, sizeof(buf) - 1, count)))