[PATCH 4.19 129/131] serial: sh-sci: Make sure status register SCxSR is read in correct sequence

[Greg Kroah-Hartman]

From: Kazuhiro Fujita <kazuhiro.fujita.jg@xxxxxxxxxxx>

commit 3dc4db3662366306e54ddcbda4804acb1258e4ba upstream.

For SCIF and HSCIF interfaces the SCxSR register holds the status of
data that is to be read next from SCxRDR register, But where as for
SCIFA and SCIFB interfaces SCxSR register holds status of data that is
previously read from SCxRDR register.

This patch makes sure the status register is read depending on the port
types so that errors are caught accordingly.

Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Kazuhiro Fujita <kazuhiro.fujita.jg@xxxxxxxxxxx>
Signed-off-by: Hao Bui <hao.bui.yg@xxxxxxxxxxx>
Signed-off-by: KAZUMI HARADA <kazumi.harada.rh@xxxxxxxxxxx>
Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@xxxxxxxxxxxxxx>
Tested-by: Geert Uytterhoeven <geert+renesas@xxxxxxxxx>
Link: https://lore.kernel.org/r/1585333048-31828-1-git-send-email-kazuhiro.fujita.jg@xxxxxxxxxxx
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 drivers/tty/serial/sh-sci.c |   11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

--- a/drivers/tty/serial/sh-sci.c
+++ b/drivers/tty/serial/sh-sci.c
@@ -873,9 +873,16 @@ static void sci_receive_chars(struct uar
 				tty_insert_flip_char(tport, c, TTY_NORMAL);
 		} else {
 			for (i = 0; i < count; i++) {
-				char c = serial_port_in(port, SCxRDR);
+				char c;
 
-				status = serial_port_in(port, SCxSR);
+				if (port->type == PORT_SCIF ||
+				    port->type == PORT_HSCIF) {
+					status = serial_port_in(port, SCxSR);
+					c = serial_port_in(port, SCxRDR);
+				} else {
+					c = serial_port_in(port, SCxRDR);
+					status = serial_port_in(port, SCxSR);
+				}
 				if (uart_handle_sysrq_char(port, c)) {
 					count--; i--;
 					continue;