linux-kernel - [PATCH] serial: sh-sci: Make sure status register SCxSR is read in correct sequence

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Date:   Fri, 27 Mar 2020 18:17:28 +0000
From:   Kazuhiro Fujita <kazuhiro.fujita.jg@...esas.com>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jiri Slaby <jslaby@...e.com>
Cc:     linux-serial@...r.kernel.org, linux-renesas-soc@...r.kernel.org,
        Prabhakar <prabhakar.csengg@...il.com>,
        linux-kernel@...r.kernel.org,
        Kazuhiro Fujita <kazuhiro.fujita.jg@...esas.com>,
        stable@...r.kernel.org, Hao Bui <hao.bui.yg@...esas.com>,
        KAZUMI HARADA <kazumi.harada.rh@...esas.com>,
        Lad Prabhakar <prabhakar.mahadev-lad.rj@...renesas.com>
Subject: [PATCH] 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@...r.kernel.org>
Signed-off-by: Kazuhiro Fujita <kazuhiro.fujita.jg@...esas.com>
Signed-off-by: Hao Bui <hao.bui.yg@...esas.com>
Signed-off-by: KAZUMI HARADA <kazumi.harada.rh@...esas.com>
Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@...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 0641a72..d646bc4 100644
--- 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;
-- 
2.7.4