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

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 c073aa7001c4fe716a7d4caa7b92c76e7d8c7454..e1179e74a2b89d892f4c8e0edceb3378c6755e5a 100644 (file)
--- a/drivers/tty/serial/sh-sci.c
+++ b/drivers/tty/serial/sh-sci.c
@@ -870,9 +870,16 @@ 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;