[ARM] 3523/1: Serial core pm_state

Patch from Andrew Victor

The serial_core already manages the power state of the UARTs, and
therefore it shouldn't suspend a UART which was previously suspended.

This patch modifies serial_core only call the UART-specific
power-management function if the PM state is actually changing.
Signed-off-by: NAndrew Victor <andrew@sanpeople.com>
Signed-off-by: NRussell King <rmk+kernel@arm.linux.org.uk>

drivers/serial/serial_core.c

@@ -1907,9 +1907,12 @@ uart_set_options(struct uart_port *port, struct console *co,
 static void uart_change_pm(struct uart_state *state, int pm_state)
 {
 	struct uart_port *port = state->port;
-	if (port->ops->pm)
-		port->ops->pm(port, pm_state, state->pm_state);
-	state->pm_state = pm_state;
+
+	if (state->pm_state != pm_state) {
+		if (port->ops->pm)
+			port->ops->pm(port, pm_state, state->pm_state);
+		state->pm_state = pm_state;
+	}
 }
 
 int uart_suspend_port(struct uart_driver *drv, struct uart_port *port)