Fix P0/EVT boards boot without serial cable connection.

Change-Id: I5969217e400ab494f9a74662d1d228fcf2e2d465
(cherry picked from commit 92c762e1b80b3b12852e3f766cdb16a6be3cbbf8)

1 files changed, 16 insertions, 1 deletions

diff --git a/drivers/serial/serial_mxc.c b/drivers/serial/serial_mxc.c
index 42abb96a26f..3efab1fa711 100644
--- a/drivers/serial/serial_mxc.c
+++ b/drivers/serial/serial_mxc.c
@@ -216,12 +216,27 @@ static void mxc_serial_putc(const char c)
 		WATCHDOG_RESET();
 }
 
-/* Test whether a character is in the RX buffer */
+/*
+ * Test whether a character is in the RX buffer
+ */
+static int one_time_rx_line_always_low_workaround_needed = 1;
 static int mxc_serial_tstc(void)
 {
 	/* If receive fifo is empty, return false */
 	if (readl(&mxc_base->ts) & UTS_RXEMPTY)
 		return 0;
+
+	/* Empty RX FIFO if receiver is stuck because of RXD line being low */
+	if (one_time_rx_line_always_low_workaround_needed) {
+		one_time_rx_line_always_low_workaround_needed = 0;
+		if (!(readl(&mxc_base->sr2) & USR2_RDR)) {
+			while (!(readl(&mxc_base->ts) & UTS_RXEMPTY)) {
+				(void) readl(&mxc_base->rxd);
+			}
+			return 0;
+		}
+	}
+
 	return 1;
 }