atmel_serial: Drain console TX shifter before suspending
Funny things may happen if we stop the USART clock before the shifter is
empty. Prevent this from happening by waiting until the shifter is
completely drained before allowing suspend to continue.
Signed-off-by: Haavard Skinnemoen <haavard.skinnemoen@atmel.com>
Cc: Andrew Victor <linux@maxim.org.za>
diff --git a/drivers/serial/atmel_serial.c b/drivers/serial/atmel_serial.c
index 5f0414f..6aeef22b 100644
--- a/drivers/serial/atmel_serial.c
+++ b/drivers/serial/atmel_serial.c
@@ -1454,6 +1454,12 @@
struct uart_port *port = platform_get_drvdata(pdev);
struct atmel_uart_port *atmel_port = to_atmel_uart_port(port);
+ if (atmel_is_console_port(port) && console_suspend_enabled) {
+ /* Drain the TX shifter */
+ while (!(UART_GET_CSR(port) & ATMEL_US_TXEMPTY))
+ cpu_relax();
+ }
+
if (device_may_wakeup(&pdev->dev)
&& !atmel_serial_clk_will_stop())
enable_irq_wake(port->irq);