tty: serial: imx: allow breaks to be received when using dma

This allows me to login after sending a break when service
serial-getty@ttymxc0.service is running

The "tty_insert_flip_char(port, 0, TTY_BREAK)" in clear_rx_errors
fixes this by allowing the higher layers to see a break.

Also, call uart_handle_break to handle possible
"secure attention key."

FYI: Martin said the ROM sdma firmware works with this patch,
but external sdma firmware still does not send breaks on a
i.mx6UL
Signed-off-by: Troy Kisky <troy.kisky@boundarydevices.com>
Tested-by: Martin Hicks <mort@bork.org>
Reviewed-by: Fabio Estevam <fabio.estevam@nxp.com>
Acked-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/serial/imx.c

@@ -927,7 +927,6 @@ static void dma_rx_callback(void *data)
 	status = dmaengine_tx_status(chan, (dma_cookie_t)0, &state);
 
 	if (status == DMA_ERROR) {
-		dev_err(sport->port.dev, "DMA transaction error.\n");
 		clear_rx_errors(sport);
 		return;
 	}
@@ -1028,6 +1027,7 @@ static int start_rx_dma(struct imx_port *sport)
 
 static void clear_rx_errors(struct imx_port *sport)
 {
+	struct tty_port *port = &sport->port.state->port;
 	unsigned int status_usr1, status_usr2;
 
 	status_usr1 = readl(sport->port.membase + USR1);
@@ -1036,13 +1036,20 @@ static void clear_rx_errors(struct imx_port *sport)
 	if (status_usr2 & USR2_BRCD) {
 		sport->port.icount.brk++;
 		writel(USR2_BRCD, sport->port.membase + USR2);
-	} else if (status_usr1 & USR1_FRAMERR) {
+		uart_handle_break(&sport->port);
+		if (tty_insert_flip_char(port, 0, TTY_BREAK) == 0)
+			sport->port.icount.buf_overrun++;
+		tty_flip_buffer_push(port);
+	} else {
+		dev_err(sport->port.dev, "DMA transaction error.\n");
+		if (status_usr1 & USR1_FRAMERR) {
 			sport->port.icount.frame++;
 			writel(USR1_FRAMERR, sport->port.membase + USR1);
 		} else if (status_usr1 & USR1_PARITYERR) {
 			sport->port.icount.parity++;
 			writel(USR1_PARITYERR, sport->port.membase + USR1);
 		}
+	}
 
 	if (status_usr2 & USR2_ORE) {
 		sport->port.icount.overrun++;