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


Nobuhiro Iwamatsu
 

Hi,

-----Original Message-----
From: Biju Das [mailto:biju.das.jz@bp.renesas.com]
Sent: Thursday, July 16, 2020 10:24 PM
To: cip-dev@lists.cip-project.org; iwamatsu nobuhiro(岩松 信洋 □SWC◯ACT)
<nobuhiro1.iwamatsu@toshiba.co.jp>; Pavel Machek <pavel@denx.de>
Cc: Chris Paterson <chris.paterson2@renesas.com>; Biju Das <biju.das.jz@bp.renesas.com>; Prabhakar Mahadev Lad
<prabhakar.mahadev-lad.rj@bp.renesas.com>
Subject: [PATCH 4.4.y-cip] serial: sh-sci: Make sure status register SCxSR is read in correct sequence

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>
Looks good to me.
I will merge if nothing else is mentioned.

Best regards,
Nobuhiro

---
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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