serial: sh-sci: Make sure status register SCxSR is read in correct sequence

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

diff --git a/drivers/tty/serial/sh-sci.c b/drivers/tty/serial/sh-sci.c
index 333de7d3fe8668566a76dd833dad7440fa9d5e44..06cf474072d6dfe73c9c3c0e0386a09cd184836e 100644 (file)
--- a/drivers/tty/serial/sh-sci.c
+++ b/drivers/tty/serial/sh-sci.c
@@ -841,9 +841,16 @@ static void sci_receive_chars(struct uart_port *port)
                                tty_insert_flip_char(tport, c, TTY_NORMAL);
                } else {
                        for (i = 0; i < count; i++) {
-                               char c = serial_port_in(port, SCxRDR);
-
-                               status = serial_port_in(port, SCxSR);
+                               char c;
+
+                               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;