[U-Boot] [PATCH] serial: serial_sh: bugfix: autoboot fails if serial console is not connected

[Tetsuyuki Kobayashi]

On kzm9g board (rmobile SoC), autoboot fails if serial console cable is not
connected.  When serial cable is not connected, serial error occurs and
some garbage comes in data register.
sh_serial_tstc() in serial_sh.c does not check error status and misunderstand
there is some input data.  It is the reason that autoboot fails.
This patch adds checking error status in sh_serial_tstc().

This patch is based on v2013.01-rc1 tag of u-boot master git.

Signed-off-by: Tetsuyuki Kobayashi <koba at kmckk.co.jp>
---
Hello Iwamatsu-san,

I checked this patch only on kzm9g board. Other SH or rmobile SoC might
have the same problem.

 drivers/serial/serial_sh.c |   20 +++++++++++++-------
 1 file changed, 13 insertions(+), 7 deletions(-)

diff --git a/drivers/serial/serial_sh.c b/drivers/serial/serial_sh.c
index 3c931d0..ee1f2d7 100644
--- a/drivers/serial/serial_sh.c
+++ b/drivers/serial/serial_sh.c
@@ -117,6 +117,14 @@ static int serial_rx_fifo_level(void)
 	return scif_rxfill(&sh_sci);
 }
 
+static void handle_error(void)
+{
+	sci_in(&sh_sci, SCxSR);
+	sci_out(&sh_sci, SCxSR, SCxSR_ERROR_CLEAR(&sh_sci));
+	sci_in(&sh_sci, SCLSR);
+	sci_out(&sh_sci, SCLSR, 0x00);
+}
+
 void serial_raw_putc(const char c)
 {
 	while (1) {
@@ -138,16 +146,14 @@ static void sh_serial_putc(const char c)
 
 static int sh_serial_tstc(void)
 {
+	if (sci_in(&sh_sci, SCxSR) & SCIF_ERRORS) {
+		handle_error();
+		return 0;
+	}
+
 	return serial_rx_fifo_level() ? 1 : 0;
 }
 
-void handle_error(void)
-{
-	sci_in(&sh_sci, SCxSR);
-	sci_out(&sh_sci, SCxSR, SCxSR_ERROR_CLEAR(&sh_sci));
-	sci_in(&sh_sci, SCLSR);
-	sci_out(&sh_sci, SCLSR, 0x00);
-}
 
 int serial_getc_check(void)
 {
-- 
1.7.9.5