patch "serial: sh-sci: Fix HSCIF RX sampling point calculation" added to tty-linus

patch "serial: sh-sci: Fix HSCIF RX sampling point calculation" added to tty-linus

[gregkh]

This is a note to let you know that I've just added the patch titled

    serial: sh-sci: Fix HSCIF RX sampling point calculation

to my tty git tree which can be found at
    git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/tty.git
in the tty-linus branch.

The patch will show up in the next release of the linux-next tree
(usually sometime within the next 24 hours during the week.)

The patch will hopefully also be merged in Linus's tree for the
next -rc kernel release.

If you have any questions about this process, please let me know.


From ace965696da2611af759f0284e26342b7b6cec89 Mon Sep 17 00:00:00 2001
From: Geert Uytterhoeven <geert+renesas@glider.be>
Date: Mon, 1 Apr 2019 13:25:10 +0200
Subject: serial: sh-sci: Fix HSCIF RX sampling point calculation

There are several issues with the formula used for calculating the
deviation from the intended rate:
  1. While min_err and last_stop are signed, srr and baud are unsigned.
     Hence the signed values are promoted to unsigned, which will lead
     to a bogus value of deviation if min_err is negative,
  2. Srr is the register field value, which is one less than the actual
     sampling rate factor,
  3. The divisions do not use rounding.

Fix this by casting unsigned variables to int, adding one to srr, and
using a single DIV_ROUND_CLOSEST().

Fixes: 63ba1e00f178a448 ("serial: sh-sci: Support for HSCIF RX sampling point adjustment")
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: Mukesh Ojha <mojha@codeaurora.org>
Cc: stable <stable@vger.kernel.org>
Reviewed-by: Ulrich Hecht <uli+renesas@fpond.eu>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 drivers/tty/serial/sh-sci.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/tty/serial/sh-sci.c b/drivers/tty/serial/sh-sci.c
index 2d1c626312cd..55ef6e577f46 100644
--- a/drivers/tty/serial/sh-sci.c
+++ b/drivers/tty/serial/sh-sci.c
@@ -2512,7 +2512,9 @@ static void sci_set_termios(struct uart_port *port, struct ktermios *termios,
 			 * center of the last stop bit in sampling clocks.
 			 */
 			int last_stop = bits * 2 - 1;
-			int deviation = min_err * srr * last_stop / 2 / baud;
+			int deviation = DIV_ROUND_CLOSEST(min_err * last_stop *
+							  (int)(srr + 1),
+							  2 * (int)baud);
 
 			if (abs(deviation) >= 2) {
 				/* At least two sampling clocks off at the
-- 
2.21.0