Input: synaptics - retry failed resets when reconnecting

On some machines, like Dell Studio XPS 16 (1640), touchpad fails to
respond to the standard query after first reset but may start
responding later, so let's repeat reset sequence several (3) times.
Signed-off-by: Alexandre Peixoto Ferreira <alexandref75@gmail.com>
Signed-off-by: Dmitry Torokhov <dtor@mail.ru>

drivers/input/mouse/synaptics.c

@@ -755,12 +755,21 @@ static int synaptics_reconnect(struct psmouse *psmouse)
 {
 	struct synaptics_data *priv = psmouse->private;
 	struct synaptics_data old_priv = *priv;
+	int retry = 0;
+	int error;
 
+	do {
 		psmouse_reset(psmouse);
+		error = synaptics_detect(psmouse, 0);
+	} while (error && ++retry < 3);
 
-	if (synaptics_detect(psmouse, 0))
+	if (error)
 		return -1;
 
+	if (retry > 1)
+		printk(KERN_DEBUG "Synaptics reconnected after %d tries\n",
+			retry);
+
 	if (synaptics_query_hardware(psmouse)) {
 		printk(KERN_ERR "Unable to query Synaptics hardware.\n");
 		return -1;