[PATCH 4.4.y-cip] serial: sh-sci: Make sure status register SCxSR is read in correct sequence


Biju Das <biju.das.jz@...>
 

From: Kazuhiro Fujita <kazuhiro.fujita.jg@renesas.com>

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>
Signed-off-by: Biju Das <biju.das.jz@bp.renesas.com>
---
drivers/tty/serial/sh-sci.c | 13 ++++++++++---
1 file changed, 10 insertions(+), 3 deletions(-)

diff --git a/drivers/tty/serial/sh-sci.c b/drivers/tty/serial/sh-sci.c
index 22f7201..2b5b342 100644
--- a/drivers/tty/serial/sh-sci.c
+++ b/drivers/tty/serial/sh-sci.c
@@ -793,9 +793,16 @@ 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 defined(CONFIG_CPU_SH3)
/* Skip "chars" during break */
if (sci_port->break_flag) {
--
2.7.4

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