Input: synaptics - fix touchpad not working after S2R on Vostro V13

Synaptics touchpads on several Dell laptops, particularly Vostro V13
systems, may not respond properly to PS/2 commands and queries immediately
after resuming from suspend to RAM. This leads to unresponsive touchpad
after suspend/resume cycle.

Adding a 1-second delay after resetting the device allows touchpad to
finish initializing (calibrating?) and start reacting properly.
Reported-by: Daniel Manrique <daniel.manrique@canonical.com>
Tested-by: Daniel Manrique <daniel.manrique@canonical.com>
Cc: stable@kernel.org
Signed-off-by: Dmitry Torokhov <dtor@mail.ru>

drivers/input/mouse/synaptics.c

@@ -24,6 +24,7 @@
  */
 
 #include <linux/module.h>
+#include <linux/delay.h>
 #include <linux/dmi.h>
 #include <linux/input/mt.h>
 #include <linux/serio.h>
@@ -1220,6 +1221,16 @@ static int synaptics_reconnect(struct psmouse *psmouse)
 
 	do {
 		psmouse_reset(psmouse);
+		if (retry) {
+			/*
+			 * On some boxes, right after resuming, the touchpad
+			 * needs some time to finish initializing (I assume
+			 * it needs time to calibrate) and start responding
+			 * to Synaptics-specific queries, so let's wait a
+			 * bit.
+			 */
+			ssleep(1);
+		}
 		error = synaptics_detect(psmouse, 0);
 	} while (error && ++retry < 3);