Subject: [PATCH 2/2] atmel_serial: Implement flush_buffer() hook

Avoid dumping garbage to the serial port when the tty is flushed. This
tends to happen when rebooting from a serial console.
Signed-off-by: Haavard Skinnemoen <haavard.skinnemoen@atmel.com>
Acked-by: Alan Cox <alan@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

drivers/serial/atmel_serial.c

@@ -955,6 +955,20 @@ static void atmel_shutdown(struct uart_port *port)
 		atmel_close_hook(port);
 }
 
+/*
+ * Flush any TX data submitted for DMA. Called when the TX circular
+ * buffer is reset.
+ */
+static void atmel_flush_buffer(struct uart_port *port)
+{
+	struct atmel_uart_port *atmel_port = to_atmel_uart_port(port);
+
+	if (atmel_use_dma_tx(port)) {
+		UART_PUT_TCR(port, 0);
+		atmel_port->pdc_tx.ofs = 0;
+	}
+}
+
 /*
  * Power / Clock management.
  */
@@ -1189,6 +1203,7 @@ static struct uart_ops atmel_pops = {
 	.break_ctl	= atmel_break_ctl,
 	.startup	= atmel_startup,
 	.shutdown	= atmel_shutdown,
+	.flush_buffer	= atmel_flush_buffer,
 	.set_termios	= atmel_set_termios,
 	.type		= atmel_type,
 	.release_port	= atmel_release_port,