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authorGeert Uytterhoeven <geert+renesas@glider.be>2019-04-01 13:25:10 +0200
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2019-04-27 09:36:36 +0200
commit38b7f09a9e83da3d8d786429520aace041e1d29e (patch)
treef3fa65596fb1bde51673e53eb9a139946dd0cca3
parentde6d6b8902fb2d26a46d266841364c3bfa70dc41 (diff)
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serial: sh-sci: Fix HSCIF RX sampling point calculation
commit ace965696da2611af759f0284e26342b7b6cec89 upstream. 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>
-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 3c25e9f0b579..03fe3fb4bff6 100644
--- a/drivers/tty/serial/sh-sci.c
+++ b/drivers/tty/serial/sh-sci.c
@@ -2497,7 +2497,9 @@ 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