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authorGeert Uytterhoeven <geert+renesas@glider.be>2019-04-01 13:25:10 +0200
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2019-04-16 15:24:38 +0200
commitace965696da2611af759f0284e26342b7b6cec89 (patch)
tree4940e55d2b2f43a43cc894e4f69e5f28689640db /drivers/tty
parent79a3aaa7b82e3106be97842dedfd8429248896e6 (diff)
downloadlinux-ace965696da2611af759f0284e26342b7b6cec89.tar.bz2
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>
Diffstat (limited to 'drivers/tty')
-rw-r--r--drivers/tty/serial/sh-sci.c4
1 files changed, 3 insertions, 1 deletions
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 @@ done:
* 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